Structural Engineering International (2022). pp. 1-5
Abstract
Buildair S.A. has recently designed, manufactured and built an inflatable hangar (termed H75 hangar) for the aeronautic industry in Jeddah Airport (Kingdom of Saudi Arabia). H75 hangar is the largest aircell inflated structure ever built in the world, finally erected in July 2019. The structural analysis and design of the main body of the hangar has involved complex structural concepts due to the specificity of the structural elements employed, like membranes and straps which lead to a highly non-linear mechanical problem, or the treatment of wind over the structure without a defined standard for inflatable structures. In this paper, the structural conception and specificities of the structure are presented, as well as the design procedure for the H75 hangar based in the numerical analysis, to fulfill the design requirements in terms of stresses, and deformations for the structural elements of the main body.
Abstract Buildair S.A. has recently designed, manufactured and built an inflatable hangar (termed H75 hangar) for the aeronautic industry in Jeddah Airport (Kingdom of Saudi Arabia). [...]
K. Nakajima, H. Kawai, M. Kawaguchi, T. Tamura, K. Kondo, Y. Itoh, K. Takagi
WCCM-APCOM2022.
Abstract
In this study, we investigated the influence of ground surface boundary conditions of the meteorological model on the accuracy in predicting the mean wind speed and wind speed fluctuation in the urban area. Two types of ground surface boundary conditions (Cases 1 and 2) were created. In Case 1, the roughness length for the urban area was set to 0.5 m uniformly, whereas in Case 2, the spatial distribution of roughness length for the urban area was set based on the urban geometry. We performed the wind flow simulation in the central part of Tokyo during Typhoon Lan (2017) by using WRF-LES with the created ground surface boundary conditions. By setting the roughness length based on the urban geometry, the accuracy in predicting the mean wind speed was improved significantly. However, in both cases, WRF-LES underestimated the turbulence intensity, especially near the ground surface.
Abstract In this study, we investigated the influence of ground surface boundary conditions of the meteorological model on the accuracy in predicting the mean wind speed and wind speed [...]
In an urban area where middle and high-height buildings are densely built on a complex terrain, it is important for wind-resistant design to know what kind of strong wind blows during a typhoon and the wind pressure acts on the building. In this study, we focused on the wind of the wind direction SSE observed during typhoon LAN (2017), and investigated the relationship between the topography and the flow field around the buildings, and the wall surface pressure by LES. As a result, we clarified the complicated flow due to the interference between the target building and the local terrain and surrounding buildings. In addition, the validity was shown by comparing the wind pressure coefficient of LES with that of the wind tunnel experiment.
Abstract In an urban area where middle and high-height buildings are densely built on a complex terrain, it is important for wind-resistant design to know what kind of strong wind [...]
This paper presents an AR visualization system for flow simulation based on the location-based AR using GNSS data. The accuracy of position data obtained by the GNSS receiving machine is investigated and the position correction method using two GNSS receiving machines is investigated. The present method is applied to the visualization of flow velocity in rivers. The validity and the efficiency of the present method is investigated by the comparison with the marker based AR.
Abstract This paper presents an AR visualization system for flow simulation based on the location-based AR using GNSS data. The accuracy of position data obtained by the GNSS receiving [...]
Validation and/or calibration of distinct element method (DEM) models is usually performed by comparing element test simulation results with the corresponding stress-strain relationships observed in the laboratory [1]. However, such a validation procedure performed at the macroscopic level does not ensure capturing the microscopic particle-level motion [2]. Thus, the reliability of the DEM model may be limited to some stress paths and may not hold when the material response becomes non-uniform for example when shear bands develop. In this study, the validity of the DEM is assessed by comparing the numerical result with experimental data considering both particle-scale behavior (including particle rotations) and macroscopic stress-strain characteristics observed in shearing tests on granular media. Biaxial shearing tests were conducted on bi-disperse granular assemblies composed of around 2700 circular particles under different confining pressures. Particle-level motions were detected by a novel image analysis technique. Particle rotations are observed to be a key mechanism for the deformation of granular materials. The results from this study suggest that to properly calibrate DEM models able to capture the mechanical behavior in a more realistic way particle scale motions observed in laboratory experiments along with macroscopic response are necessary.
Abstract Validation and/or calibration of distinct element method (DEM) models is usually performed by comparing element test simulation results with the corresponding stress-strain [...]
This work presents a numerical framework for long dynamic simulations of structures made of multiple thin shells undergoing large deformations. The C1-continuity requirement of the KirchhoffLove theory is met in the interior of patches by cubic NURBS approximation functions with membrane locking avoided by patch-wise reduced integration. A simple penalty approach for coupling adjacent patches, applicable also to non-smooth interfaces and non-matching discretization is adopted to impose translational and rotational continuity. A time-stepping scheme is proposed to achieve energy conservation and unconditional stability for general nonlinear strain measures and penalty coupling terms, like the nonlinear rotational one for thin shells. The method is a modified mid-point rule with the internal forces evaluated using the average value of the stress at the step end-points and an integral mean of the strain-displacement tangent operator over the step computed by time integration points.
Abstract This work presents a numerical framework for long dynamic simulations of structures made of multiple thin shells undergoing large deformations. The C1-continuity requirement [...]
Some commercial base isolators have been introduced in the last four decades to protect buildings from vibration and earthquakes. Typically, they are constituted by several alternating layers of rubber pads and steel (elastomeric isolator) interposed by two continuous pads, limiting vertical deformability. At the same time, they exhibit good deformation capacity in the horizontal direction when subjected to a seismic load. A very effective seismic isolator shall satisfy the following functions: good performance under all service loads, vertical and horizontal; provide enough horizontal flexibility to reach the target natural period for the isolated structure; recentering capability after the ground motion so that no residual horizontal displacement can downgrade the serviceability of the structure; provide an adequate level of energy dissipation (damping) to control the displacement that could damage other structural members. Steel-reinforced elastomeric isolators (SREIs) are the most used method of seismic isolation. Since these devices are generally too expensive due to the need to introduce thick steel plates for their supports and the high energy consumed for the manufacturing process, they are not suitable for ordinary residential buildings, especially in developing countries. Compared with SREIs, fiber-reinforced elastomeric isolators (FREIs) have considerably lower weight and can be installed between the structure in elevation and the foundation without any bonding or fastening in the so called unbonded application (UFREI), reducing costs hugely. Furthermore, without steel supports, the shear load is transferred through the friction generated between the isolator and the structure surfaces, improving the dissipation energy of the devices. The main feature of such a UFREIs is the large deformability thanks to the rollover deformation and the favorably lower lateral stiffness compared to the bonded isolator. In this paper, a series of experimental tests of the rubber compound and numerical analyses of UFREIs made of high damping rubbers (HDR) combined with glass fiber reinforcement have been performed. A HDR made of Natural Rubber and Ethylene Propylene Diene Monomer (NREPDM) blend has been considered. Finite Element shear test results have shown good dynamic performances of the proposed device.
Abstract Some commercial base isolators have been introduced in the last four decades to protect buildings from vibration and earthquakes. Typically, they are constituted by several [...]
For fiber reinforced polymers (FRPs), ply stacking errors and fiber waviness during manufacturing will have a great influence on the mechanical properties of composites, which requires non-destructive testing and evaluation (NDT&E) for potential structure defects. Herein, this study analyzes the ultrasonic echo signals in pulse-echo (PE) mode to assess the layered structure and sub-structure of laminates, analytically and numerically. Based on recursive stiffness matrix method and analytic-signal technology, analytical modeling is performed to investigate the propagation of ultrasound and detect the layered structure in flat laminates. In addition, a numerical finite element model is built to further study the propagation of ultrasound in wavy composites. Based on the circular variances of ply angles extracted by structure tensor analysis, the double-sided ultrasonic testing and B-scan imaging method is proposed to correct the imaging artifact areas of wavy composites. After statistical validation, this weighted sum method can indeed reduce the influence of ultrasonic beam deviation caused by out-of-plane fiber wrinkling, thereby improving the imaging effect in wavy composites.
Abstract For fiber reinforced polymers (FRPs), ply stacking errors and fiber waviness during manufacturing will have a great influence on the mechanical properties of composites, which [...]
E-vehicles and light weight structural parts in automotive and aerospace industry has led to design and development of new structures where traditional materials aluminium/steel are joined with composite laminated materials. This approach has led the engineers/researchers to reduce weight and ultimately save fuel consumption and reduce carbon footprints. Moreover, prosthetic limbs are also designed to have varying material along the length for better suitability. The above problems cannot be analysed using functionally graded theories/concepts. In theory, material properties vary linearly, exponentially, or power-law-like along x-values but for the above cases, material property does not follow a particular variation. Further even, it is not always practical to produce or manufacture components having very smooth variations along the length. Number of research articles are reported on the development of joining techniques for the dissimilar materials.1, 2Bending, free vibration and buckling analysis is also needed for theses case.3At the joining or interface point, local inplane and transverse stresses may rise sharply and may cause debonding and failure of structures. One dimensional analysis based on classical assumption or higher order can not accurately predict the stress behaviour at theses places. In this paper, an attempt is made to develop the 2D analytical solution for multi-segmented Al/ steel-composite panel under transverse loading. Extended Kantorovich method is used for developing governing equations. Continuity of displacement and stresses are satisfied at interface of each segment. Two segmented panels having aluminium/steel equal segment are considered. The deflection and stresses are compared with the finite element solution and found in good agreement.
Abstract E-vehicles and light weight structural parts in automotive and aerospace industry has led to design and development of new structures where traditional materials aluminium/steel [...]
The objective of this study is to develop a tsunami evacuation simulation system that takes into account building collapse and fire spread. Road blockage is determined by calculating the road blockage probability due to building collapse, taking into account the size of the assumed earthquake, location of buildings, and type of building. For fire spread simulation, an existing simulator based on the fire spread rate equation is used. Under average wind direction and speed conditions for the target area, arbitrary fire points are set up and fire spread is represented using fire times for each building obtained from the simulation. The applicability of this system as a scenario is extended. The present system is applied to several examples to demonstrate the validity and effectiveness of the system.
Abstract The objective of this study is to develop a tsunami evacuation simulation system that takes into account building collapse and fire spread. Road blockage is determined by [...]
The transport of logarithmic potentials provides a dynamical equilibrium that allows obtaining the lasting time estimation of a dynamical process. Bayesian rules are applied as a bridge between logarithmic potentials and the transport equation to obtain the potential associated with the interaction between systems. In this work, a data set from a chemical process is considered to test the method. Then, to enrich the analysis, an actual prediction by dynamical components is perform that illustrates how long every process and the global common process last.
Abstract The transport of logarithmic potentials provides a dynamical equilibrium that allows obtaining the lasting time estimation of a dynamical process. Bayesian rules are applied [...]
G. Gálik, V. Kutiš, J. Paulech, V. Goga, M. Uličný
WCCM-APCOM2022.
Abstract
The article describes a multistage modelling methodology proposed by the author for the modelling of emergency core cooling processes. The methodology is based on the best practice guidelines presented by the IAEA, it is applied to a specific scenario of emergency core cooling during a loss of coolant accident [1] with an effective break diameter of 20mm. A 3D thermohydraulic analysis was performed as the first step in the solution process, where the transient changes in the pressure, velocity and temperature fields within the reactor pressure vessel were studied [2]. The primary knowledge learned when processing the results of the first step, was the presence of an oscillating cold coolant stripe in close proximity to the pressure vessel wall. The next step in the methodology consisted of a three-dimensional thermomechanical analysis of the reactor pressure vessel [3]. In this step, pressure thermal shock induced critical zones of mechanical loading were identified and the influence of the oscillatory character of the cold stripe on the pressure vessel was studied. The last step of the methodology consisted of a fracture mechanics analysis of postulated defects during the pressure thermal shock. Acquired results from the final step shown, that the postulated defects' sensitivity to the oscillatory nature of the cold stripe is highly dependent on the postulated defect's orientation.
Abstract The article describes a multistage modelling methodology proposed by the author for the modelling of emergency core cooling processes. The methodology is based on the best [...]
J. Wackers, G. Deng, C. Raymond, E. Guilmineau, A. Leroyer, P. Queutey, M. Visonneau
WCCM-APCOM2022.
Abstract
Adaptive grid refinement is tested for routine, automated simulations of ship resistance in calm water. A simulation protocol for these computations is fine-tuned on one test case and then applied unchanged to three different cases. The solutions are numerically accurate and compare well with experiments. Effective numerical uncertainty estimation increases the trustworthiness of the solutions.
Abstract Adaptive grid refinement is tested for routine, automated simulations of ship resistance in calm water. A simulation protocol for these computations is fine-tuned on one test [...]
Solid structures that are light and heat conductive are significant in a variety of engineering applications. We investigated multiscale topology optimization for excessive lightweight heat-conductive porous structures and introduced a mathematical optimization model formulation for concurrently optimizing the macrostructure and the constitutive pores (microstructure) to maximize the design performance. The microscale is constructed utilizing the asymptotic homogenization approach as a representative volume element. During the optimization process, the effective heat conductivity tensor of the microstructure is assessed and utilized as the heat conductivity of the macrostructure for each iteration. To address the macro and microstructure connection, a sensitivity analysis of this concurrent optimization approach was developed. Moreover, the method of introducing initial predetermined design domain was investigated to attain fin-like design in order to despite heat efficiently. Results showed very good results for attaining excessive weight reduction with attaining high heat conductivity. Moreover, the method of predetermined design domains increased the performance significantly.
Abstract Solid structures that are light and heat conductive are significant in a variety of engineering applications. We investigated multiscale topology optimization for excessive [...]
Structures for sound attenuation have been explored in many scenarios, ranging from civil construction to automotive and aerospace industries. However, the proper multiphysics interactions of acoustic-poroelastic-elastic structures are still challenging, especially when topology optimization techniques are involved. This work entails a new topology optimization methodology based on the Bidirectional Evolutionary Structural Optimization (BESO) approach to design bidimensional structures for sound attenuation enhancements. The full modeling of poroelastic bodies is done by the mixedu/p technique. At the same time, the elastic and acoustic (air) materials are obtained by the degeneration of the latter, leading to the well-known elasto-dynamic and Helmholtz formulations, respectively. Such procedure is done in by the combination of the Finite Element Method (FEM) with the Unified Multiphase (UMP) modeling approach, which in turn contributes to the development of material interpolation schemes suited for the application. In this scenario, the topology optimization problem is established as the maximization of the time-averaged dissipative power, composed by the summation of its structural, viscous and thermal dissipative components. The numerical examples show the effectiveness of the proposed methodology since it provides well-defined topologies with generally enhanced dissipative performances.
Abstract Structures for sound attenuation have been explored in many scenarios, ranging from civil construction to automotive and aerospace industries. However, the proper multiphysics [...]
This paper presents a noise evaluation system based on acoustic wave theory. This paper utilizes two methods – the finite element method and the boundary element method using a fast multipole method, and compares the numerical results of the benchmark problem. In addition, we show the results using the analytical model of the complex shape based on standard specifications of noise barriers and discuss the difference of the numerical results and auralization results between the two methods.
Abstract This paper presents a noise evaluation system based on acoustic wave theory. This paper utilizes two methods – the finite element method and the boundary element method [...]
The time-dependent behaviour of quasi-brittle materials can have a significant effect on serviceability and ultimate failure. E.g., in the case of concrete structures, the presence of cracking can evolve, propagate and gradually widen over time, therefore significantly changing the stress state and expected structural response. The development of models that can account for the discrete nature of cracking whilst predicting time-dependent behaviour can be of interest to many practical applications. The discrete strong discontinuity approach (DSDA) has been validated as a reliable approach for simulating the cracking phenomenon by directly embedding the traction-separation constitutive relation within finite elements, therefore enriching standard finite element models with the ability to capture cracks, where material can separate without the need for remeshing. This work presents a generalisation to account for the long-term behaviour of cracked quasi-brittle materials, more specifically creep and shrinkage. To this end, a rate-type creep is first applied through a number of kelvin units; the interaction of the resulting response from the Kelvin chain system, shrinkage, and discrete cracking is developed to obtain a suitable constitutive model for the discrete crack simulations. Finally, the formulation is deployed on a finite element code where the performance of the proposed model is assessed through representative numerical examples.
Abstract The time-dependent behaviour of quasi-brittle materials can have a significant effect on serviceability and ultimate failure. E.g., in the case of concrete structures, the [...]
In future cities, micrometeorological predictions will be essential to various services such as drone operations. However, the real-time prediction is difficult even by using a super-computer. To reduce the computation cost, super-resolution (SR) techniques can be utilized, which infer high-resolution images from low-resolution ones. The present paper confirms the validity of three-dimensional (3D) SR for micrometeorology prediction in an urban city. A new neural network is proposed to simultaneously super-resolve 3D temperature and velocity fields. The network is trained using the micrometeorology simulations that incorporate the buildings and 3D radiative transfer. The error of the 3D SR is sufficiently small: 0.14 K for temperature and 0.38 m s-1for velocity. The computation time of the 3D SR is negligible, implying the feasibility of real-time predictions for the urban micrometeorology.
Abstract In future cities, micrometeorological predictions will be essential to various services such as drone operations. However, the real-time prediction is difficult even by using [...]
In this paper, advanced numerical models are used to study the progressive damage of a historic building, namely the Palazzo of Podestà and the Civic Tower of Accumoli (central Italy). The dynamic behaviour of the structure is analyzed following important seismic events such as those that occurred in 2016-2017. Discontinuous and continuous approaches are used. In the formers, the masonry response is represented both with Discrete Element Method (DEM) and the Non-Smooth Contact Dynamic (NSCD) method; in the latter the masonry non linearity is replicated using the Concrete Damage Plasticity (CDP) model. The numerical results showed a good correspondence of all the approaches with the real damage suffered by the structure after the seismic sequence.
Abstract In this paper, advanced numerical models are used to study the progressive damage of a historic building, namely the Palazzo of Podestà and the Civic Tower of Accumoli (central [...]
The effects of rock shape and initial orientation on the rockfall phenomena are studied using a two-dimensional polygonal discrete element method (DEM). In the simulation, rock particles with the same mass but different shapes are dropped from the same height onto a straight slope to investigate the variations in both translational and rotational kinetic energies and the runout distance. Parametric studies under varied angularity and aspect ratio of the rock revealed a significant effect of rock shape and initial orientation on the runout distance.
Abstract The effects of rock shape and initial orientation on the rockfall phenomena are studied using a two-dimensional polygonal discrete element method (DEM). In the simulation, [...]
In order to reduce the friction coefficient of lubricated surfaces with circular and herringbone shaped textures, an adjust variable method was introduced to optimize the shape of the oil film thickness distribution in the textured areas. The optimized oil film thickness distribution can be evolved by the shape updating formula proposed by Sasaoka et al. based on the smoothed sensitivity. For computational convenience, the objective function in the optimization is defined as the friction force, not the friction coefficient. The constraint function was also defined by the Reynolds equation. The finite element method was used in the optimization procedure. The optimization results show that the herringbone shape texture has a bowl-shaped oil film thickness distribution similar to that of the circular shape texture. Furthermore, the location of the deepest part was found to be different.
Abstract In order to reduce the friction coefficient of lubricated surfaces with circular and herringbone shaped textures, an adjust variable method was introduced to optimize the [...]
The accuracy of the numerical solution obtained by the Boundary Element Method (BEM) is directly affected by the type of interpolation function used. Meanwhile, interpolation by radial basis function augmented with polynomials has been shown to be more accurate than Lagrange interpolation for a range of different functions. Therefore, this paper is concerned with the application of such functions as the interpolation functions for all boundary values in the boundary element method for the numerical solution of two-dimensional heat transfer problems. Numerical examples with different geometries and temperature distributions are presented and comparisons with both isogeometric and classical formulation are made to demonstrate the accuracy of the proposed method.
Abstract The accuracy of the numerical solution obtained by the Boundary Element Method (BEM) is directly affected by the type of interpolation function used. Meanwhile, interpolation [...]
We propose a surrogate model for predicting in-plane nonlinear structural deformations of a compliant mechanism. Our model utilizing a 2-dimensional co-rotational beam element extracts the essential deformation degrees-of-freedoms (DOFs) of bending flexible beams. The total number of DOFs of nodes at both ends of a 2-dimensional beam is six, while the number of deformation DOFs is three, i.e., axial extension, symmetric bending, and anti-symmetric bending. Therefore, it enables us to reduce the computational cost, from six to three, associated with the models by using the essential deformation DOFs of the co-rotational beam element. Moreover, it is difficult to predict the nonlinear responses of forces derived from displacements of a compliant mechanism due to bifurcation of the deformation-path. To overcome the problem, we generate the datasets by applying external forces and use the inverse response for constructing the surrogate models. In the numerical example, large-deformation behaviors of several types of compliant mechanisms are predicted by our surrogate models constructed by three typical learning algorithms: polynomial approximation, radial basis function, and neural network. The prediction performances and computational costs are investigated for verifying that they can be beneficial tools for designing a compliant mechanism with nonlinear elastic deformation behaviors.
Abstract We propose a surrogate model for predicting in-plane nonlinear structural deformations of a compliant mechanism. Our model utilizing a 2-dimensional co-rotational beam element [...]
In the building construction above public lines such as railroads, it is necessary to assume the accident by falling objects such as column members lifted by cranes. Even if RC slabs prevent perforation caused by falling objects during construction, scattering concrete debris may cause serious damage to the public space below the slabs. This study suggests an anchoring system to control the debris scattering by folding up the end of steel deck plates which are used as permanent formworks. Impact test was performed with specimens that have an anchoring system or not with changing the drop height as parameters. As a result, the anchoring system prevents debris from scattering in the case that the falling height was twice as high as the case without the anchoring system. In addition, finite element analysis was also performed to evaluate the result of the impact test. The result showed the analysis could evaluate the debris scattering of both the specimen which has the anchoring system or not.
Abstract In the building construction above public lines such as railroads, it is necessary to assume the accident by falling objects such as column members lifted by cranes. Even [...]
This study investigates a simulation model predicting spherulite microstructure formation based on experimental observations. The crystallization process of polylactic acid is observed at different molding temperatures by in-situ observation, and the rate of spherulite formation and growth is estimated. Furthermore, according to the Turnbull-Fisher primary nucleation model and the Lauritzen-Hoffman secondary nucleation model, Monte Carlo simulations of spherulite microstructure formation are performed based on the obtained experimental results. The validity of the method is verified by a comparison of the simulated and the experimental results.
Abstract This study investigates a simulation model predicting spherulite microstructure formation based on experimental observations. The crystallization process of polylactic acid [...]
D. Wijesinghe, A. Dyson, G. You, M. Khandelwal, E. Ooi
WCCM-APCOM2022.
Abstract
Slope stability analysis is a challenging task when complex stratigraphies, complex geometries and spatially variably soil parameters are considered. Numerical methods, such as the finite element method are commonly used in slope stability analyses, however, these methods require significant user input when meshing geometries consisting of heterogeneous and spatially variable materials. This paper presents a numerical technique combining the scaled boundary finite element method and image-based meshing for slope stability analysis. The inputs for the analyses require images detailing the stratigraphy and the spatial variation of the material properties. Quadtree decomposition is applied to simultaneously generate meshes and consider the spatial variation of material properties directly from the images through a mapping technique. The stability of slopes is analysed assuming an elastoplastic Mohr-Coulomb constitutive model for the soil. The shear strength reduction technique is applied to evaluate the shear reduction factor iteratively to define the factor of safety of the slope. Coal slopes at Yallourn open-pit mine, Victoria, Australia was considered, forming the basis of a case study to demonstrate the applicability of the presented method.
Abstract Slope stability analysis is a challenging task when complex stratigraphies, complex geometries and spatially variably soil parameters are considered. Numerical methods, such [...]
Ultrasonic guided waves (GW) due to their ability to monitor large areas with few sensors, are commonly employed for structural health monitoring (SHM) in aerospace, civil, and mechanical industries. The FBG sensors in the edge filtering setup are re-emerging as a favored technique for GW sensing. The FBG sensors offer embeddability, ability to be multiplexed, small size, and immunity to electric and magnetic fields. To enhance the sensitivity of these sensors, these sensors are deployed in the so-called remote bonding configuration where the optical fiber is bonded to the structure while the FBG sensor is free. This configuration not only enhances the sensitivity but also opens up possibility of self-referencing. In this setup the GW in the structure is coupled to the fiber and converted into fiber modes. These modes propagate along the fiber and then are sensed at the FBG. The conversion of the plate modes to fiber modes is a phenomenon which is still being studied. The effect of the adhesive layer and the material properties of the adhesive on the coupling are still not known. Furthermore the directional nature of this coupling and its marked difference from the directly bonded configuration needs to be studied in detail. For this detailed study a computationally efficient model which captures the physics of the coupling is necessary. Hence, in this research we develop a numerical model based on the spectral element method (SEM) for the modeling of the remote bonded configuration of the FBG. The model comprises four meters long optical fiber bonded to the center of the plate by the adhesive layer and the piezoelectric disc (PZT) used for wave excitation. The ability of the SEM model to capture the effect of the adhesive and the remote bonding as well as the directional nature of the coupling has been studied in this paper. The model is validated with analytical and experimental results. It has been shown that the SEM model captures the physics of the coupling and is computationally more efficient than other methods using conventional finite element software.
Abstract Ultrasonic guided waves (GW) due to their ability to monitor large areas with few sensors, are commonly employed for structural health monitoring (SHM) in aerospace, civil, [...]
The end-grain bonding of timber components with the Timber Structures 3.0 technology (TS3) is an emerging construction method in timber engineering. For onsite applications at low ambient temperatures down to 0 °C, it is being investigated numerically and experimentally if it’s possible to heat the butt-joint to above 17 °C during the curing process using a heating wire. The current research results show that this is basically possible.
Abstract The end-grain bonding of timber components with the Timber Structures 3.0 technology (TS3) is an emerging construction method in timber engineering. For onsite applications [...]
In this study, we proposed a simulation method for film transverse stretching based on the finite element method using the orthogonal anisotropy plastic model. The simulation method can analyse the large deformation of film stretching and predict whether the kink band phenomenon occurs during the film transverse stretching. The validity of the simulation method was confirmed by the transverse stretching tests performed on the fluorine films with different longitudinal stretching ratios. Using the simulation method, we clarified that the plastic anisotropy index of the longitudinally stretched fluorine film has a great influence on the presence or absence of the kink band phenomenon during the film transverse stretching. The plastic anisotropy index of the longitudinally stretched fluorine film can be related to its birefringence, and the two are approximately in a linear relationship. Moreover, we revealed the change in film stretching deformation due to difference in the ratio of the stretching zone length to the width of the tenter.
Abstract In this study, we proposed a simulation method for film transverse stretching based on the finite element method using the orthogonal anisotropy plastic model. The simulation [...]
Crushable soils such as volcanic soils, carbonate sand or decomposed granites whose grains are easily break under foundation pressure, especially, large magnitude of stresses under pile tips. When the grains are crushed, particle size distribution (PSD) varies followed by higher compressibility of these soils. Pile foundation's settlement in crushable soils tends to be increased. Nonetheless, design code for bearing capacity of pile in crushable soil is still unavailable leading to a lot of difficulties for engineers to have an appropriate foundation design. This paper introduces a constitutive model for soils which takes account of the breakage mechanics including the evolutions of PSD and the compressibility due to grain crushing. The model is implemented in a finite element code to simulate pile penetration in crushable soil. Finally, the particle breakage around pile's tip is examined.
Abstract Crushable soils such as volcanic soils, carbonate sand or decomposed granites whose grains are easily break under foundation pressure, especially, large magnitude of stresses [...]
The assessment of the seismic vulnerability of built heritage is still an open issue. Regarding this topic, in recent years many researchers have worked in the development of refined numerical models to simulate the behaviour of different building typologies subjected to seismic action. To be reliable, these models require in-depth knowledge of the building object of study. In many countries, such as Italy, where the widespread historical heritage is widely present, there is the need to define quick, but reliable, evaluation procedures, which allow, in advance, to assess the vulnerability of the historical heritage of an entire area using databases already present without necessarily proceeding with detailed investigations on each building. Based on procedures in the literature, the authors have developed an assessment methodology focused on the construction of fragility curves, safety factor vs PGA and vulnerability index, which allows to formulate hypotheses on the probable behaviour of a specific type of building, to any similar actions and the probable expected damage. In the view of evaluating the seismic safety of a small historic centre in an area with a high seismic propensity, this procedure could be useful for prioritizing interventions in probabilistic terms.
Abstract The assessment of the seismic vulnerability of built heritage is still an open issue. Regarding this topic, in recent years many researchers have worked in the development [...]
The inherent uncertainty in the structural parameters directly affects the structural performance, and its variation may lead to improper designs and catastrophic consequences. When subjected to uncertainty, the structure design must be optimized to get an insensitive design using a Robust Design Optimization (RDO) technique. Such design aims to find a system design in which the structural performance is less sensitive (insensitive) to the uncertainty of the inherent structural parameter without eliminating them. This is usually achieved by simultaneously minimizing the mean and variance of the structural performance function. Various RDO approaches, such as those based on Taylor series expansion, simulation-based methods, dimension reduction, and metamodel, can effectively take into account these uncertainties. However, the computational efficiency and accuracy in evaluating the mean and variance of the performance function remain a challenging task. To obliviate this limitation, a novel stochastic simulation-based approach is proposed in the present work. The proposed approach is built on an `Augmented optimization problem,' in which design variables are artificially considered an uncertain parameters. An unconstraint Genetic algorithm (GA)based optimization approach is formulated to determine the optimal solution. As the mean and variance frequently conflict with each other, so to obtain the Pareto optimum, a linear scalarized objective function is adopted. To demonstrate the proposed approach, RDO of a four-bar structure is performed. The results obtained are compared with the conventional Monte Carlo simulation approach and confirm that the proposed approach yields accurate results. This paper allows the designers to design the insensitive structure systems by minimizing the variance of the performance function. Moreover, the proposed RDO approach is not only limited to the civil structures but can also be enforced in the design of any realistic linear/nonlinear structures and systems such as machine components (like clutches, gears, etc.), aerospace, etc., having uncertainties in their geometry or material, such as the residual strain, modulus, thickness, density, etc.
Abstract The inherent uncertainty in the structural parameters directly affects the structural performance, and its variation may lead to improper designs and catastrophic consequences. [...]
In this study, we investigate a method for accurately representing mechanical anisotropy in a crystal plasticity finite element (FE) analysis using a computational model with a small number of crystal grains to reproduce the rolling texture. We propose a method for extracting the preferred orientation of the rolling texture, construct a computational model using this method, and perform a crystal plasticity FE simulation.
Abstract In this study, we investigate a method for accurately representing mechanical anisotropy in a crystal plasticity finite element (FE) analysis using a computational model with [...]
Q. Huang, Z. Liu, A. Moni, S. Ravi, F. Tian, J. Young, J. Lai
WCCM-APCOM2022.
Abstract
The immersed boundary method (IBM) has attracted growing interest in the computational fluid dynamics (CFD) research community due to its simplicity in dealing with moving boundaries in fluid-structure interaction (FSI) systems. We present a study on streamline penetration, velocity error and consequences of a FSI solver based on an iterative feedback IBM. In the FSI, the fluid flows are solved by the lattice Boltzmann method; the solid structure deformation is solved by the finite difference method, and an iterative feedback IBM is used to realize the interaction between fluid and structure. The iteration can improve the no-slip and no-penetration boundary conditions at the fluid-solid interface. Four benchmark cases are simulated to study the reduced velocity error and its consequences: a uniform flow over a flapping foil, flow-induced vibration of a flexible plate attached behind a stationary cylinder in a channel, flow through a two-dimensional asymmetric stenosis and a one-sided collapsible channel. Results show that the iterative IBM can suppress the boundary-slip error and spurious flow penetration on the solid wall. While the iterative IBM does not have significant effect on the force production and structure deformation for external flows, it significantly improves the prediction of the force distribution and structure deformation for internal flows. The increased computational cost incurred by the iteration can be largely reduced by increasing the feedback coefficient. This study will provide a better understanding of the feedback IBM and a better option for the CFD community.
Abstract The immersed boundary method (IBM) has attracted growing interest in the computational fluid dynamics (CFD) research community due to its simplicity in dealing with moving [...]
A model order reduction technique in combination with mesh tying is used to efficiently simulate a large number of different structures that are assembled from a set of substructures. The stiffness matrices of the substructures are computed separately and assembled into a global stiffness matrix with tied contact formulation. The computational time can be further decreased by reducing the degrees of freedom of each substructure with a projection-based model order reduction technique. The precomputations to obtain the mode matrices are computationally cheap because they can be carried out on each substructure separately. For the development and optimization of new construction strategies for fiber reinforced concrete, a large number of different combinations of the modules have to be tested. The nonlinear anisotropic material behavior, like the primary directions of orthotropic materials, leads to parameter-dependent mode matrices. The precomputations can only be done for a relatively small number of parameters. For all other parameters, the mode matrices have to be adapted with interpolation methods to obtain an accurate solution .
Abstract A model order reduction technique in combination with mesh tying is used to efficiently simulate a large number of different structures that are assembled from a set of substructures. [...]
The strength evaluation of structures that requires high reliability, such as power generation facilities, is extremely important. It is necessary to ensure safety under extremely low cycle fatigue caused by earthquakes. However, a highly reliable evaluation method has not yet been developed because of variable fracture toughness due to the constraint effect with large deformation. The crack propagation criterion proposed by the previous study has needed some modification for accurate prediction. In this study, we confirmed whether the crack propagation criterion proposed by previous study can reproduce the fracture behavior of the experiment. Among then, relationship between the number of cycle and crack length, hysteresis loop, reproduction of crack shape were evaluation items.
Abstract The strength evaluation of structures that requires high reliability, such as power generation facilities, is extremely important. It is necessary to ensure safety under extremely [...]
The prediction of fracture behavior under extremely low cycle fatigue due to excessive loading is necessary for the life assessment of structures. This study evaluates the validity of the crack propagation criterion proposed in a previous study by performing generation phase and application phase analysis based on the results of fracture tests on a 1.5T-CT specimen (SGV410). The analysis show that the crack propagation criterion in the previous study predicted the experimental behavior well, however crack shape was incomplete in reproducing the crack shape.
Abstract The prediction of fracture behavior under extremely low cycle fatigue due to excessive loading is necessary for the life assessment of structures. This study evaluates the [...]
We present an analysis of the performance of some standard and optimized explicitly Runge Kutta schemes that are equipped with CFL-based and error-based time step adaptivity when they are coupled with the relaxation procedure to achieve fully-discrete entropy stability for complex compressible flow simulations. We investigate the performance of the temporal integration algorithms by simulating the flow past the NASA juncture flow model using the in-house KAUST SSDC hp-adaptive collocated entropy stable discontinuous Galerkin solver. In addition, we present a preliminary analysis of the performance of the SSDC framework on the Amazon web service cloud computing. The results indicate that SSDC scales well on the most recent and exotic computing architectures available on the Amazon cloud platform. Our findings might help select a more robust and efficient temporal integration algorithm and guide the choice of the EC2 AWS instances that give the best price and wall-clock-time performance to simulate industrially relevant turbulent flow problems.
Abstract We present an analysis of the performance of some standard and optimized explicitly Runge Kutta schemes that are equipped with CFL-based and error-based time step adaptivity [...]
A convolutional neural network, which reproduce a function by data, was used to predict the amount of warp distortion of a four-layer circuit board in a reflow soldering process. The data used for training are material properties such as Young's modulus, board thickness, and residual copper content as input data, and the predicted warp distortion data is the amount of warpage of the circuit board obtained from the measurement. Since a number of distortion data to be predicted was insufficient to be used for training, a newly proposed data augmentation method used to increase a number of data. The augmentation method is evaluated through the result of the predictions and discussed.
Abstract A convolutional neural network, which reproduce a function by data, was used to predict the amount of warp distortion of a four-layer circuit board in a reflow soldering process. [...]
Computational materials design is an active area of research which aims at predicting physical and chemical properties of various materials from first-principles electronic structure calculations. To keep the computational costs manageable, the Schr¨odinger equations are often approximated by Kohn-Sham equations within the framework of density-functional theory. These Kohn-Sham equations are solved numerically either by a basis set expansion or real-space discretization under given boundary conditions. In the case of a plane-wave basis set, it is common practice to apply periodic boundary conditions in all directions, while isolated boundary conditions are more common for the atomic basis set. However, there are many other options besides these standard boundary conditions. In this presentation, we will explore several non-standard boundary conditions which exploit the characteristics of each system, such as surfaces, interfaces, and cyclic/helical structures, to minimize the computational costs of electronic structure calculations. Most of these boundary conditions are easily implemented by minor modifications of existing electronic structure codes. Numerical examples on a few model systems are also presented for the validation of these boundary conditions.
Abstract Computational materials design is an active area of research which aims at predicting physical and chemical properties of various materials from first-principles electronic [...]
The present work is carried out in the framework of the WAS project [1] which deals with WAAM process. The process relies on an automatized welding process in which a part is built by successively deposed metal bead. We propose a physically based bead topology model using the equilibrium between the hydrostatic pressure and the capillarity force, under twodimensional hypothesis. This equilibrium can be described by the Laplace equation [2]. The proposed model is used to estimate a bead topology which is deposed on an inclined support. Moreover, a deposed melted metal volume is necessary for the bead topology model. By modelling a gas metal arc welding (GMAW) power source system [3], the volume can be estimated and be used as a physical parameter for the bead topology model. Combining the topology and the power source models, the coupling model allows to simulate the topology of a weld bead through WAAM. In addition to the modelling, experimental profiles of the beads are used to validate the model.
Abstract The present work is carried out in the framework of the WAS project [1] which deals with WAAM process. The process relies on an automatized welding process in which a part [...]
This study proposes a thermos-mechanical model for the transfusion module in the additive manufacturing process, selective thermoplastic electrophotographic process (STEP). The reduced-order method and parametric study are presented, as well.
Abstract This study proposes a thermos-mechanical model for the transfusion module in the additive manufacturing process, selective thermoplastic electrophotographic process (STEP). [...]
The paper provides a novel Lower Bound (LB) Limit Analysis (LA) Finite Element (FE) model for the study at failure of masonry walls in two-way bending by means of full 3D elements. The method of hexahedral discretization is used, while assuming infinite resistance and a quadrilateral interface where all plastic dissipation occurs. It can more accurately analyze the collapse mechanism of masonry panels in the process of two-way bending. It chose two cases to study. They are three series of panels with and without perforations tested at collapse at the University of Adelaide Australia and four series of solid and perforated panels tested at the University of Plymouth UK. The feasibility of the research method was verified. The obtained research results show that the use of the method proposed allows to provide a safe prediction of the existing LA code based on kinematics theorem, with a small computational burden, and the obtained results are more in line with the actual situation and have better practical effects.T The original abstract is titled: 'Out of Plane Lower Bound Limit Analysis'
Abstract The paper provides a novel Lower Bound (LB) Limit Analysis (LA) Finite Element (FE) model for the study at failure of masonry walls in two-way bending by means of full 3D [...]
Railway network is subject to increasing travelling loads and traffic frequency. In addition, since most of the bridges were built in the last century, they are subject to ageing and degradation. It is therefore necessary to develop proper structural health monitoring systems that can support periodical visual inspections. In this context, direct monitoring systems represent an important and promising solution for structural health monitoring purposes. This paper is the result of a numerical study performed on a 3D FE bridge model based on an existing structure: the latter is a Warren truss railway bridge, located in Northern Italy, built few years after the end of the second world war. The purpose of the study is to numerically evaluate the effectiveness in damage detection and localization of different vibration-based techniques. This analysis has been performed for a set of different damage scenarios, suggested by the infrastructure managers.
Abstract Railway network is subject to increasing travelling loads and traffic frequency. In addition, since most of the bridges were built in the last century, they are subject to [...]
H. Okawa, S. Omoto, S. Yagi, T. Miyamoto, K. Kashiyama
WCCM-APCOM2022.
Abstract
This paper presents a fast and accurate classification method for underwater objects using underwater mapping data obtained by a small Autonomous Underwater Vehicle (AUV) and autonomous surface vehicle (ASV). For the mapping data, in addition to underwater acoustic reflection intensity images, water depth data, point cloud data and backscattering reflection intensity data are employed. We propose the automatic classification and semantic segmentation method on deep learning using a convolutional neural network (CNN) and PointNet++. In order to verify the effectiveness of the present method, we applied it to the measured several underwater mapping data.
Abstract This paper presents a fast and accurate classification method for underwater objects using underwater mapping data obtained by a small Autonomous Underwater Vehicle (AUV) [...]
Exploratory studies have been carried out to identify the potential natural gas hydrate reserves for commercially producing gas. While extracting the gas from the hydrate-bearing sediments using various dissociation techniques, there will be a significant loss of strength in these sediments. It is well known that the behavior of gas hydrate sediments is governed by Thermo Hydro Mechanical Chemical THMC coupled process during the gas extraction. Thus, in this study, in order to understand the influence of depressurization at the well-bore and the permeability of the hydrate reservoir on the sediment deformation characteristics, a 2D (plane strain condition) hydrate reservoir is simulated (using a multiphase numerical schema). From the study, it is observed that the flow response, i.e., the rate of change of gas pressure near the well-bore, decreases with the increase in the duration of the extraction. The maximum settlement occurs for reservoirs having low well-bore pressure (higher amount of depressurization) and high intrinsic permeability. Additionally, these same reservoir conditions also lead to maximum cumulative gas production. Thus, the continuous gas extraction results in a highly porous medium that is stabilized primarily due to the geomechanical changes.
Abstract Exploratory studies have been carried out to identify the potential natural gas hydrate reserves for commercially producing gas. While extracting the gas from the hydrate-bearing [...]
In this study, we at first employ a nonaffine polymer chains network model to account for the irreversible structural change during the deformation of DN gels. And then, a finite element model of the DN gels under simple tension is constructed. On the other hand, neck propagation is one kind of localized instability and there will be a local transfer of strain energy from one part of the model to neighboring parts. To solve such unstable quasi-static problem, an automatic mechanism provided by Abaqus/Standard is employed. The simulation results show that the nonaffine polymer chains network model together with the stablization algorithm for localized transformation of strain energy can be employed to reproduce the phenomenon of neck propagation in DN gels very well.
Abstract In this study, we at first employ a nonaffine polymer chains network model to account for the irreversible structural change during the deformation of DN gels. And then, a [...]
One of the vertical axis wind turbines that utilize drag force is the Savonius wind turbine. Savonius wind turbines are characterized by low speed rotation and high torque, so they are rarely used for wind power generation but have possibility to apply to ocean current power generation, which has been attracting attention recently. In this report, we actually performed a numerical simulation of the flow using suitable grid, focusing mainly on the case where two wind turbines are rotating in reverse at a constant speed, and investigated the state of the flow field. Two-dimensional incompressible Navier-Stokes equations are adopted as the basic equation and solved numerically using the finite difference method. In addition, in order to enable calculation even in a high Reynolds number flow, the nonlinear term of the equations are approximated by using the third-order accuracy upstream difference method. The simulation is performed under the condition that the flow corresponds to three types of angles of 90 degrees, 45 degrees, and 0 degrees with respect to the line connecting the centers of the two wind turbines. The flow field differs greatly depending on each angle, and the interaction between the two wind turbines has been clarified.
Abstract One of the vertical axis wind turbines that utilize drag force is the Savonius wind turbine. Savonius wind turbines are characterized by low speed rotation and high torque, [...]
A new type of proportional damping models, called bell-shaped proportional damping model, has recently been proposed. This new model has not only addressed the spurious damping forces, but also maintained the same order of computational efficiency as the Rayleigh model. This model has also been further improved such that, by using the tangent stiffness approach, it becomes suitable for structures experiencing softening response with negative stiffness. The improved model allows users to have flexible control of modal damping ratio for all interested frequency intervals, including those associated with negative stiffness. In this study, the performance of bell-shaped damping model is evaluated numerically in a response history analysis of a multi-storey building under seismic loading. The results show that, compared to the Rayleigh model, the bell-shaped model performs excellently in terms of always giving desirable positive energy dissipation even when the structure is experiencing softening response.
Abstract A new type of proportional damping models, called bell-shaped proportional damping model, has recently been proposed. This new model has not only addressed the spurious damping [...]
In the fields of morphing aircraft design, flow control and broadband energy harvesting, the dynamic characteristics of the multi-stable structure provide an idea for realizing the dynamic deformation of configurations. Its unique nonlinear characteristics and local strong stability provide an important theoretical basis and application value for the investigation of morphing structures. Taking asymmetric bi-stable composite laminates as the research object, this paper analyzes the effects of boundary conditions on the stable configurations and utilizes finite element simulation software ABAQUS to research the nonlinear dynamic characteristics of each configuration and its dynamic response under different excitation levels. By comparing two boundary conditions of cantilever and clamped at the center, the dynamic snap-through phenomena of bistable laminated panels are investigated, and the morphing strategies targeting modal frequencies need to be optimized.
Abstract In the fields of morphing aircraft design, flow control and broadband energy harvesting, the dynamic characteristics of the multi-stable structure provide an idea for realizing [...]
In this paper, numerical demonstrations of a modified compressible Euler system are shown, where the bubble function element stabilization method together with adaptive mesh refinement is introduced for increasing numerical stability and numerical accuracy. For a test case, NACA0012 is selected as a domain of interest, and numerical results using finite elements of P1P1bP1 and P2P2bP2 for densityvelocitypressure were compared at AOA=1.25 and Mach number 0.8. As a result, the shock wave is not found on the upperend and the lower end of NACA0012 in the former, and on the other hand the latter is adequate numerical result and relative errors of Cl, Cd with previous study are 1.197% and 0.15376%. The mathematical model is much simpler than the compressible Euler equation, because they are advection equations for a density, a velocity, and a pressure with each external forces. Therefore, the material derivative is considered for time stepping, and the characteristic curve method can be used for decreasing calculation cost.
Abstract In this paper, numerical demonstrations of a modified compressible Euler system are shown, where the bubble function element stabilization method together with adaptive mesh [...]
Traditional computational methods face significant challenges with ever-increasing complexity in the problems of engineering interest. One category of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. One set of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. FSI simulations are traditionally time-consuming and computationally extremely expensive. Potential alternatives rely on using a surrogate model to substitute one or more systems involved. A promising approach employs artificial neural networks as the basis for such a surrogate model combined with strong physics simulations based on finite element methods (FEM). This approach requires the seamless integration of AI algorithms and packages into the simulation workflow. Such an example is the NeuralNetworkApplication developed in KratosMultiphysics. The routines related to the neural networks are executed through an interface with the Keras API. Mok's benchmark is chosen as the study case to test the capacity of the previous method applied to FSI problems. Two cases in which one of the systems is substituted by a neural network-based surrogate model are analyzed. Strong and weak coupling scenarios are considered. The results present improvements in simulation time without sacrificing accuracy, especially when compared with the original benchmark. This contribution discusses the influence of the original data and network architecture on the simulation outcome and different considerations for generating surrogate models for FSI.
Abstract Traditional computational methods face significant challenges with ever-increasing complexity in the problems of engineering interest. One category of problems that suffer [...]
R. Alhayki, E. Muttio-Zavala, W. Dettmer, D. Perić
WCCM-APCOM2022.
Abstract
Constitutive models have been utilized to study the mechanical behaviors of solid material. The formulation of constitutive relations is difficult and could be associated with limiting hypothesis. This work proposes neural network-based approaches to reproduce the complex nonlinear constitutive relations of solid materials including elastic behavior and plastic deformation. It is shown that the proposed history-based and internal variable-based strategies can represent exactly the von Mises elasto-plastic material model in uni-axial stress state. Furthermore, close investigation suggests that the internal variable-based approach is most suitable.
Abstract Constitutive models have been utilized to study the mechanical behaviors of solid material. The formulation of constitutive relations is difficult and could be associated [...]
A multiscale approach that couples the finite element method (FEM) and the discrete element method (DEM) is employed to model and analyses the earthquake fault rupture-soilfoundation interaction (FR-SFI) problem. In the approach, the soil constitutive responses are obtained from DEM solutions of representative volume elements (RVEs) embedded at the FEM integration points so as to effectively bypass the phenomenological hypotheses in conventional FEM simulations. The fault rupture surfaces and shear localization patterns under normal faults with or without foundation atop have been well captured by the multiscale approach and verified with available centrifuge experimental and numerical results. By examining the responses and microstructural evolutions of local RVE packings, it is found that the RVEs located in- or outside the shear bands (SBs) behave distinctly, and may change their stress states from initial at-rest to active in the normal fault case. The micromechanics study also sheds lights on the possible detriment of heavy foundations for the superstructure despite the rupture surface diversion.
Abstract A multiscale approach that couples the finite element method (FEM) and the discrete element method (DEM) is employed to model and analyses the earthquake fault rupture-soilfoundation [...]
H. Kuramae, T. Sugimoto, M. Matsumoro, N. Watanabe
WCCM-APCOM2022.
Abstract
To elucidate the corrosion mechanism of a hydrothermal oxidation decomposition reactor for the treatment of polychlorinated biphenyls (PCBs), a coupled thermal fluid analysis of the heat transfer between two mixtures of fluids with different physical properties and the reactor body was executed using OpenFOAM. Based on the analysis results, we propose a method to evaluate the corrosion risk at the solid-liquid interface by focusing on three factors: (1) the corrosion temperature of reactor vessel, (2) the amount of fluid deposition that causes corrosion, and (3) the wall shear stress on the solid-liquid interface. Variation of corrosion risk with operating conditions of the reactor is discussed.
Abstract To elucidate the corrosion mechanism of a hydrothermal oxidation decomposition reactor for the treatment of polychlorinated biphenyls (PCBs), a coupled thermal fluid analysis [...]
S. Li, X. Xiao, Q. Cai, Y. Zhong, R. Chen, K. Guo, W. Tian, G. Su, I. Qiu
WCCM-APCOM2022.
Abstract
In this study, an implicit algorithm and different solvers are applied to the Moving Particle Semi-Implicit (MPS) method for temperature calculation. The original MPS method uses an explicit method for temperature calculation and is limited by time increment due to diffusion number. In this paper, the heat conduction of plates with Dirichlet boundary condition and Neumann boundary condition is studied. The accuracy of explicit and implicit calculation of plate heat transfer cases are compared. In addition, different solvers are compared. Consequently, it is shown thatthe error of the implicit algorithm is not much different from the original one. And CG is still the better solver,CGS is also a superior solver. The implicit algorithm increases the size of a single time stepby a maximum of 50 times (original diffusion number is 0.2), while the calculation time of a single time step does not increase Substantially, so it has a significant effect on the acceleration of calculation.
Abstract In this study, an implicit algorithm and different solvers are applied to the Moving Particle Semi-Implicit (MPS) method for temperature calculation. The original MPS method [...]
Over the past decades, different approaches, physical and geometrical, were implemented to identify the optimal shape, reducing the internal stresses, of grid shells and vaults. As far as their original organic shape is concerned, the design of grid shell structures inspired architects and structural engineers worldwide and in any time. The method, here presented, is developed and extended, from its original formulation, employing a self-made code based on the dynamic equilibrium, ensured by the d'Alembert principle, of masses interconnected by rope elements in the space-time domain. The equilibrium corresponding the optimized shape to be defined, is obtained through an iterative process in the falling masses connected by a net for the definition of the 'catenary surface' coinciding with the best shape of the shell (form minimizing the bending moment) according to the conditions of zero velocities and accelerations of the nodes. The implementation of the method is realized in MATLAB and set up for Python in an interpreted high-level general-purpose programming language. By the use of this code as well as its object-oriented architecture the MRA Python code will be linked to the Grasshopper environment for the direct visualization of the shapes and their fastparametrization phase.
Abstract Over the past decades, different approaches, physical and geometrical, were implemented to identify the optimal shape, reducing the internal stresses, of grid shells and vaults. [...]
High-speed trains are equipped with yaw dampers to prevent the arising of hunting motion. These suspension components play an important role in improving the vehicle stability. However, the presence of yaw dampers increases the steering resistance of the bogies, especially in transient curve track segments. For this reason, passive yaw dampers are designed according to a tradeoff between improvement of high-speed stability and limitation of curving performance degradation. This paper introduces an innovative passive smart yaw damper, the Position Dependent Yaw Damper, able to overcome the typical limitations of standard passive components. The damper can variate its dynamic performances according to the operating conditions of the vehicle. In this paper, a PDYD prototype will be experimentally characterized. Then, a numerical model of the damper will be tuned on the experimental data. The model aims at predicting the influence of the PDYD on the dynamic performances of a rail vehicle, simulated with a Multibody model. A sensitivity analysis will assess the relationship between different PDYD layouts and the vehicle curving performances co-simulating damper and vehicle models. The numerical comparison will be focused on the low-speed negotiation of low radius curves. Finally, the best PDYD layout will be implemented in a numerical simulation of a high-speed high-radius curve to verify its effectiveness in reducing the arising of hunting unstable motion.
Abstract High-speed trains are equipped with yaw dampers to prevent the arising of hunting motion. These suspension components play an important role in improving the vehicle stability. [...]
In this work we present the latest advances in the Particles Finite Element Method (PFEM) for the numerical modeling of forming processes. In the recent past, very good results of the method have been shown in the simulation of 3D cutting problems. The method has very good capabilities for treating large deformations in massive volumetric parts. Now the method is applied and extended to other forming operations: forging, blanking, minting, machining, etc., for metals and other materials. One of the important aspects of these manufacturing techniques is the interaction with the molds and dies. Deformable contact interactions are needed to obtain a close correspondence between numerical and experimental results. The characterization of the thermomechanical interaction with the coatings of the tool plays an important role. Advances have been made in meshing techniques for treating threedimensional parts and for the modeling deformable contact. The characterization of friction and wear of the forming tools can be modeled considering also the lubrication on the surfaces. The purpose is to obtain the characteristics of the final shape of the workpiece, the areas that experience large plastic deformations and the residual stresses that remain in the processed material. This information is very valuable for the optimal design of the manufacturing operation. To show the virtues of the method, several examples of forming operations are presented. The capabilities of the method are discussed, as well as the accuracy of the solutions.
Abstract In this work we present the latest advances in the Particles Finite Element Method (PFEM) for the numerical modeling of forming processes. In the recent past, very good results [...]
The volume and mobility of a debris flow could increase with distance travelled as it has the potential to entrain a substantial amount of channel-bed material along its travel path. This entrainment effect renders the debris flow more devastating to downslope populations and facilities. Over the past two decades, the Geotechnical Engineering Office (GEO) of Hong Kong has expended considerable effort to develop debris mobility modelling tools for use in routine engineering practice for forward prediction purposes. Recently, GEO has completed a study to enhance an in-house debris mobility code. Physical parameters which can be estimated from the field by engineers or geologists are incorporated in the code to predict entrainment effects in a simple and rational manner. This allows the modelling of varying entrainment potential along a debris flow path. The code has been checked against simplified analytical solutions and validated against field observations in a major historical landslide event involving highmobility debris flows in Hong Kong. The numerical modelling results indicated that simulated entrainment volume and mobility characteristics are broadly consistent with geological field mapping records.
Abstract The volume and mobility of a debris flow could increase with distance travelled as it has the potential to entrain a substantial amount of channel-bed material along its travel [...]
One of the larger growing fields within additive manufacturing is the selective laser sintering process of semi-crystalline polymer powders. The powder is locally fused at certain areas, due to the energy output of a laser. This method allows for rapid production of complex parts, which are well suited for prototyping. The overall accuracy and stability of the process along with part properties are highly related to the process parameter. A better control of these parameters will therefore optimize the process even further. The current paper propos a numerical modelling approach and the model makes it possible, to analyze the influence of the laser-related input parameters concerning the temperature distribution and size of the melt pool. For the validation, certain outputs from the model are compared to the ones found from experimental single-line track data, where the melt pool geometry can be compared to the numerical measurements.
Abstract One of the larger growing fields within additive manufacturing is the selective laser sintering process of semi-crystalline polymer powders. The powder is locally fused at [...]
Flying insects are impressive creatures due in part to their small size and agile flight maneuvers. Additionally, butterflies can be highly efficient fliers, as evidenced by monarchs having the longest migration amongst insects. To begin uncovering the complex mechanisms enabling monarchs to migrate roughly 80 million times their average body length, high-fidelity modeling tools are required: These tools must consider the distinguishing features of monarchs their low flapping frequency, high Reynolds number (amongst insects), large wings relative to their body, low wing loading, flexibility of their wings, and the highly coupled interplay between the instantaneous wing aerodynamics and dynamic body response. Many butterfly flight models to date have neglected the passive wing pitching arising from butterfly's flexible wings. Here, we propose a framework that tightly couples the effects of all three physics solvers using a dynamic relaxation scheme. As such, the highly nonlinear interplay between fluid, body, and passive wing dynamics is efficiently accounted for in each time step. We apply the model to the free flight of monarch butterflies, resulting in stable motion for many periods without any controllers.
Abstract Flying insects are impressive creatures due in part to their small size and agile flight maneuvers. Additionally, butterflies can be highly efficient fliers, as evidenced [...]
We investigate the acoustic behaviour of Micro-Electro-Mechanical-Systems (MEMS) with a focus on shutter devices. These shutter devices can be used for a new method of sound generation which we call Advanced Digital Sound Reconstruction (ADSR) where a redirection mechanism for sound pulses is incorporated [1]. With the help of this redirection mechanism, sound pulses can be generated which are superimposed to form an audio signal. At MEMS-scales viscous effects can play a major role regarding sound transmission. Therefore, we utilize the linearized flow equations in time domain in order to solve for the acoustic pressure while incorporating effects caused by viscous boundary layers. Furthermore, the movement of the shutter itself contributes to the overall generated sound in a negative manner. Since the generation of the sound pulses is in the ultra sound range, the generated noise by the shutter might lead to adverse effects on the human body [2]. Hence, modeling the shutter noise and understanding its generation process can help to improve the design. To model the noise generated by the shutter, we apply the arbitrary LagrangianEulerian (ALE) framework to the linearized flow equations to be able to compute the noise generation on the moving geometry. The geometry update itself is governed by an artificial quasi-static mechanical problem which is solved in each step to get the new element deformation [3]. Assuming that the impact of the acoustic pressure is negligible, a simple forward coupling from the quasistatic mesh-smoothing to the the linearized flow equations is employed. Furthermore, we use a direct coupling approach to couple the acoustic wave equation to the linearized flow equations. The final coupled system is then used to characterize the impact of the shutter movement on the overall system behaviour of a certain embodiment.
Abstract We investigate the acoustic behaviour of Micro-Electro-Mechanical-Systems (MEMS) with a focus on shutter devices. These shutter devices can be used for a new method of sound [...]
V. Tsotoulidi, P. Karakitsios, P. Kolios, G. Mprellas
WCCM-APCOM2022.
Abstract
In this paper, the new Geomiso SEA software (www.geomiso.com) is proposed for inelastic static isogeometric analysis with shell elements and splines. Geomiso SEA offers an innovative way to merge geometric design with mesh generation, by creating, with its modern user interface, 3D models as tensor product grids. The utilization of the exact mesh for analysis eliminates geometric errors, while there is no need of repeating the geometry design for refinement purposes. In contrast, the standard finite element technique, not only cannot fully utilize the available data ofthe exact mesh, but also makes engineers unable to benefit from advanced spline techniques. Real world and industry applications on both thick (Mindlin-Reissner) and thin (KirchhoffLove) shells are demonstrated with a comparison between Geomiso SEA and FEA programs with shell and hexahedral elements.
Abstract In this paper, the new Geomiso SEA software (www.geomiso.com) is proposed for inelastic static isogeometric analysis with shell elements and splines. Geomiso SEA offers an [...]
In this paper, we propose Geomiso ISA (www.geomiso.com), a new hybrid software for applications on static isogeometric analysis with plate elements. It is based on the IGA, the powerful generalization of the traditional FEA, which, in combination with the plate theory, has attracted increasing attention in construction industry over the last decade, as it achieves efficient design-through-analysis procedures and shows superior performance. This recently developed program is not just a plug-in, but a both on-premises and cloud-based software solution, applicable to thin (Kirchhoff-Love) and thick (Mindlin-Reissner) plates. It is used to simulate spline models of slabs and analyze their strength and behavior, while it has many features in common with both FEA software and design programs. This software solution addresses the rising industrial need for seamless integration of CAD and CAE, while it appears to be more efficient to FEA software packages with major improvements, as it facilitates the geometry modeling within analysis, and achieves superior accuracy per degreeof-freedom with shortened computational cost. This is the first time ever such a cloud-based program has been developed.
Abstract In this paper, we propose Geomiso ISA (www.geomiso.com), a new hybrid software for applications on static isogeometric analysis with plate elements. It is based on the IGA, [...]
Double concave surface slider (DCSS) is considered as an effective solution for baseisolation of existing structures located in a near-fault site, because of its capacity to notably increase horizontal displacements that can be accommodated in comparison to a single concave surface slider (SCSS) of identical in-plan dimensions. However, unexpected torsional pounding of in-plan irregular adjacent structures may be induced by variability of friction force and lateral stiffness of SCSS and DCSS, depending on the axial load and friction coefficient changes during an earthquake. Effectiveness of supplemental viscous damping at the base is studied in this work with the aim to analyse its effectiveness for limiting base displacement, so avoiding too large seismic gap requirement. Structural pounding between fixed-base and baseisolated L-shaped buildings, placed adjacent to form Tand C-shaped plans, is analysed. A simulated design of the original reinforced concrete (RC) fixed-base framed structure is preliminarily carried out in accordance to a former Italian code, for a medium-risk seismic zone. Then, seismic retrofitting with SCSSs is carried out, in order to attain performance levels imposed by the current Italian code in a high-risk seismic zone, while DCSSs have radius of curvature equal to half the SCSSs and the same friction coefficient. The insertion of additional fluid viscous dampers (FVD) at the base is examined, following damping distribution inversely proportional to the distance between the stiffness centre of the base-isolation system and the plane frame where each FVD is placed. Nonlinear modelling of SCSSs and DCSSs considers variable axial load combined with friction coefficient at breakaway and stick-slip and as function of the sliding velocity, axial pressure and rising temperature at the sliding interface. Attention is focused on the pulse-type nature of near-fault earthquakes generally observed in the velocity time-histories but largely overlooked in the acceleration ones. Automated classification algorithms using wavelet analysis are adopted to compile three datasets of seismic input rotated in the range 0°-360°, with a constant step of 15°. Distinction is made between no-pulse and velocity-pulse, the latter further categorised into non-acceleration and acceleration-pulses.
Abstract Double concave surface slider (DCSS) is considered as an effective solution for baseisolation of existing structures located in a near-fault site, because of its capacity [...]
Naturally contaminated soils that contain contaminants deep within the particles may show delayed leaching. To incorporate this, a novel approach for predicting the distribution of contaminants, both in the soil particle and surrounding liquid, is achieved using the finite difference method. The approach is named the 'intraparticle pore-diffusion model' and is applied to simulate the batch leaching test of heavy metal contaminated soils. Intraparticle diffusion and sorption equilibrium are considered. The desorption phenomena of heavy metal from soil particles are considered as a one-dimensional, polar-symmetric problem in the spherical coordinate system by supposing soil particles to be porous, perfect spheres. The results indicate that soil constituted of larger particles leach more contaminants at a certain time and faster for a certain leaching amount.
Abstract Naturally contaminated soils that contain contaminants deep within the particles may show delayed leaching. To incorporate this, a novel approach for predicting the distribution [...]
Aluminum alloy is a light-weight material with excellent corrosion resistance but low rigidity. When the aluminum alloy is used to a girder bridge, it takes high costs owing to the increment of its stiffness. Therefore in order to reduce a material cost, the cost minimization problem was performed on beam string structure (BSS) made of the aluminum alloy material based on the results of the topology optimization. We focused on the layout of the BSS and diameter of the cable. The conducted simulation made clear the effectivity of the BSS to the aluminum alloy material for a reduction of material cost and increment of the beam span.
Abstract Aluminum alloy is a light-weight material with excellent corrosion resistance but low rigidity. When the aluminum alloy is used to a girder bridge, it takes high costs owing [...]
This study predicts wind pressure on high-rise buildings under typhoons by LES using CUBE and discuss the effects of turbulence fields obtained from broad region simulation and fine vortex structure around complicated facade on wind pressure. First, the computation of broad region including many high-rise building is carried out. The computation reveals that structures with streamtwise vorticity appears from the upper corner of high-rise building and remains even in 1km leeward region. Then, the computation resolving the complicated façade of two buildings is carried out and turbulent structure around the complicated façade is examined. The result shows that it is possible to show local wind pressure induced by fine structure of vortex by the computation with high spatial resolution resolving the shape of unevenness on building façade.
Abstract This study predicts wind pressure on high-rise buildings under typhoons by LES using CUBE and discuss the effects of turbulence fields obtained from broad region simulation [...]
In this study, we discuss the flow field of the realistic city block model planned according to the concept of the future city, in the case of an actual typhoon and a winter monsoon hit. This study applied BCM-LES technique, which enables large scale simulation with high efficient of parallel computing. The fluctuating inflow of the actual typhoon was created by using the method of adding the turbulent component based on WRF-LES. From the computed results, we confirmed that properties of inflow and the location of high-rise buildings affect the flow field and the pressure distribution of target high-rise building.
Abstract In this study, we discuss the flow field of the realistic city block model planned according to the concept of the future city, in the case of an actual typhoon and a winter [...]
In order to achieve desirable urban redevelopment in the near future, various transformation strategies were investigated using LES, focusing on their impact on ventilation performance and wind gust generation. This study evaluated the replacement of city blocks with high-rise buildings, replacement with mid-rise buildings lower than the surrounding area, and simple multi-building arrangements utilizing the prevailing wind direction.
Abstract In order to achieve desirable urban redevelopment in the near future, various transformation strategies were investigated using LES, focusing on their impact on ventilation [...]
Pipelines are vital means of transportation of liquids and gases over large geographical areas. Regarding buried pipes, they are submitted to thermal and mechanical loads due to their support conditions, pipe-soil friction and the surrounding soil mass. Under high compressive loads carried out by these efforts, loss of stability and buckling may occur. Then, the evaluation of soil lateral resistance that will cause a imminent breakout is important. This work aims the analysis of the soil lateral resistance by frictional limit analysis formulation, considering the soil mass as a deformable body and the pipe as a rigid one. An yield function considering material porosity and material friction angle is considered. The soil lateral resistance forces obtained from the proposed formulation are compared to a those ones considering the limit analysis lower bound found in literature. The fully bounded condition observed in most models is also discussed.
Abstract Pipelines are vital means of transportation of liquids and gases over large geographical areas. Regarding buried pipes, they are submitted to thermal and mechanical loads [...]
Anisotropy is one of the most important characteristics of 3D printed concrete. If material property is only symmetric on one plane, it is called monoclinic material, in which there are totally 13 independent elastic constants. In this paper, 3D printed concrete Timoshenko beam is analysed using isogeometric technique considering the monoclinic material property. Non-uniform Rational B-Spline(NURBS) functions are used as basis functions to integrate with computer aided design data. In addition, several numerical experiments are conducted to verify accuracy of the isogeometric analytical model. It is demonstrated that the proposed method in this paper can be widely used in analyses of 3D printed concrete monoclinic Timoshenko beams.
Abstract Anisotropy is one of the most important characteristics of 3D printed concrete. If material property is only symmetric on one plane, it is called monoclinic material, in which [...]
T. Hamada, F. Chabi, R. Chakir, D. Lejri, J. Waeytens
WCCM-APCOM2022.
Abstract
As majority of people spend 90% of their time in indoor environment, air quality has become an important scientific field in the last few decades. Indoor air quality is affected by many factors. One of the significant factors is outdoor air pollutions [1]. They enter the indoors through ventilation systems or natural ventilation and may stay indoors for a long time due to the airtightness of buildings. The present study especially focuses on nitrogen dioxide (NO2) concentration in a natural ventilating room that comes from outdoor pollutant sources such as vehicle emissions. In the present study, we have performed numerical simulations of a controlled environment in Sense-City urban area [2]. Sense-City is a unique full-scale equipment that can reproduce controlled conditions of temperature, humidity, airflow and pollution using an atypical climatic chamber. Reynolds Averaged Navier-Stokes (RANS) simulations have been carried out to calculate indoor and outdoor NO2 concentrations. RANS simulations are performed in two steps: district scale and building scale. Pressure values and pollutant concentrations are extracted from the district scale simulation and applied to the building scale simulation as boundary conditions. As expected, a sensitivity analysis study shows that the NO2 concentration in the building depends mainly on the pollutant concentration at the windows. Once opening windows, indoor pollutant concentration reached the almost same level of that of outdoor within a few minutes. Therefore, the interaction between indoor and outdoor air quality cannot be negligible for indoor air quality. This study can be useful for engineers and for local authorities to understand the importance of considering the interaction of the indoors and outdoors, the potential and limitation of RANS simulation in a natural ventilating. Considering the limitation of the number of sensors for air pollution in real applications, Computational Fluid Dynamics (CFD) is promising to obtain air pollutant distribution cartography. It can also be used as a decision-support tool for relevant urban planning such as the optimal placement of sensors and depolluting systems in urban areas.
Abstract As majority of people spend 90% of their time in indoor environment, air quality has become an important scientific field in the last few decades. Indoor air quality is affected [...]
A new inverse modeling is investigated for identifying an effective seismic force at virtual interfaces and estimating the seismic wave motions in an interior domain surrounded by a domain reduction method (DRM) boundary from limited seismic measurement data. The two-dimensional domain is truncated by the highly efficient non-convolutional second-order complex-frequency-shifted perfectly matched layers (CFS-PML), and the DRM is utilized to model seismic input motions coming from the outside domain of the CFS-PML. A partial differential equation (PDE)-constrained optimization method aims at minimizing a misfit between measured ground motions at sparsely-distributed sensors on the surface induced by surface wave-dominant incident waves (or equivalent effective forces on a DRM layer) and their estimated counterparts induced by inverted effective forces. The numerical results show that the presented full-waveform inversion of seismic input motions can identify an effective seismic force at a DRM layer and reconstruct the seismic wave responses in a near-surface domain.
Abstract A new inverse modeling is investigated for identifying an effective seismic force at virtual interfaces and estimating the seismic wave motions in an interior domain surrounded [...]
J. Schultz, K. Springer, J. Roberson, J. Carroll, M. Hegbloom
WCCM-APCOM2022.
Abstract
When completed in 1961, the roof of St. Charles Church became the largest unbalanced hyperbolic paraboloid structure in the world and the only shell structure in Spokane, WA. Situated on an 8-acre site on the north side of the city, St. Charles is a modernist structure designed through partnership of Funk, Molander & Johnson and architect William C. James. This asymmetric structure is over 45.72m (150ft) and utilizes folded edge beams that taper from 1067mm (42in) at the base to a 76.2mm (3in) thickness at the topmost edge using regular strength reinforcing steel and concrete. The novelty of the shell structure serves both architectural and structural design criteria by delivering a large, uninterrupted interior sanctuary space in materially and economically efficient manner. Having previously completed an initial analysis of the structure, now, 60 years later, a complete structural forensic evaluation of the shell has been conducted using full point cloud laser scanning to generate a complete in-situ model. The in-situ geometry and historic loads are described and deflections as first steps in a full structural forensic study. Results of the current in-situ geometry are compared to the design geometry of original construction documents.
Abstract When completed in 1961, the roof of St. Charles Church became the largest unbalanced hyperbolic paraboloid structure in the world and the only shell structure in Spokane, [...]
This work presents a novel force method for multiphase flow in which displacements and forces progress while strains terminate on surfaces between two different phases, such as the surface between air and liquid. This report is part of a research project to apply Helmholtz decomposition (H-d) to the finite element method. State vectors continues to exist on the surface of multiphase. The conventional scheme uses displacement method and applies a model to set Dirichlet boundary conditions for air on the air-liquid interface. The proposed scheme allows simulating it without such modeling.
Abstract This work presents a novel force method for multiphase flow in which displacements and forces progress while strains terminate on surfaces between two different phases, such [...]
In the past two decades, finite element method (FEM) has been widely used to study mechanics of solids, fluid–structure interactions, and building construction strategies. FEM has been rapidly grown all over the world due to development of computer technology. Computer has much more powerful computing capability than humans. However, structural engineering education not only focused on teaching engineers to use FEM as computation tool, but also concentrated on cultivating engineers’ capability of experience-based qualitative analysis. In addition, artificial intelligence techniques have been rapidly developed in recent years. It is demonstrated that human experience-based capabilities might also be replaced by deep learning methods in various game-playing areas. Thus, this study aims at exploring what role artificial intelligence techniques will play in the futural structural analysis area. In this paper, several finite element analyses are carried out for three representative boundary value problems, such as tightly stretched wires under loading, soil seepage, and plane stress. Corresponding deep neural networks are trained using FEM simulation data to quickly and accurately predict results of relevant problems. It is indicated that to some extent artificial intelligence technique might replace human experience-based qualitative analysis as a surrogate of FEM.
Abstract In the past two decades, finite element method (FEM) has been widely used to study mechanics of solids, fluid–structure interactions, and building construction strategies. [...]
In recent years, heavy rain which frequently occurred in various places in Japan have been caused severe damage. It is important to identify the damaged area for disaster recovery and reconstruction. In this study, we focus on the optical satellite images that are easy to process and interpret, and extract the damaged area by combining a land cover classification method using machine learning and an additive color mixture method. As the results, it is possible to visually express the land cover changes before and after the disasters in a specific category and to extract the damaged area from the optical satellite image.
Abstract In recent years, heavy rain which frequently occurred in various places in Japan have been caused severe damage. It is important to identify the damaged area for disaster [...]
R. Cucuzza, A. Cardoni, A. Manuello, M. Domaneschi, G. Cimellaro, G. Marano
WCCM-APCOM2022.
Abstract
Over the last years, several optimization strategies were conducted to find the optimal shape minimazing internal stress or total weight (volume) of shell structures. In recent times, this structure typology gained a great importance among researchers and the scientific community for the renowed interest in the form-findind optimization of column-free space solution for large span roofing constructions. In the present paper, a form-finding of a shallow grid shells was introduced basing on the multy-body rope approach (MRA) for the definitions of vault shapes and different hole percentage. In order to obtain an experimental validation, a physical model was reproduced at the laboratory scale performing ad hoc measurements to compare the observed respect to the simulated behaviour. A 3D printing procedure based on the Fuse Deposition Modeling (FDM) technique in polylactide (PLA) material was used to realise form-works of the cement based blocks of the scaled prototype. Several static and dynamic load configurations are investigated, collecting into a sensitivity analysis the parameters which mainly affect the structural behaviour. To simulate earthquake ground motion an assigned frequency range as dynamic input to the structure was provided by a shaking table. Finally, some preliminary considerations of the dynamic response of the model were provided testing the robustness of the form-finding approach when horizontal load are taken into account.
Abstract Over the last years, several optimization strategies were conducted to find the optimal shape minimazing internal stress or total weight (volume) of shell structures. In recent [...]
Nowadays, the need to deal with limited resources together with the newly discovered awareness of the human over-exploitation of the environment, has made the optimization a cutting edge topic both in scientific research and in the different professional fields. In this paper, a particular evolutionary optimization algorithm is presented: The Estimation of Distribution Algorithm (EDA). This type of algorithm has been developed to be used in search-based constrained optimization problems which are difficult and time-consuming to be solved by other general algorithms. Being an evolutionary algorithm, the main idea is to generate a population of solutions and evaluate the objective function of each one of them. Then, using the information obtained from the previous generations, the algorithm step-by-step will generate new populations that will tend to the best value of the objective function. In EDA, the population of solutions defines a probability density function (PDF) and, by integration, a cumulative density function (CDF), which is used for the generation of the next generation. In structural design optimization problems, it is very common that the best solution is very close to the constraint function. The main advantage of applying the EDA for constrained optimization problems is that each generation of solutions is obtained starting from a PDF that is defined on the whole domain. This means that, for each generation, the solutions have a probability to be on the unfeasible domain space, maintaining the information about the objective function in the evolution process. In the present research, an original EDA and related self-made code are presented together with a specific application to structural optimization problems, in order to show the effectiveness of the obtained results and to make a comparison with other evolutionary optimization algorithms.
Abstract Nowadays, the need to deal with limited resources together with the newly discovered awareness of the human over-exploitation of the environment, has made the optimization [...]
The report examines the results of a 3D-survey of the relief in young impact craters based on high-resolution images obtained from lunar orbits. The craters examined included: the Tsiolkovsky and Aitken craters on the far side of the Moon, the Ticho and Ina craters of the visible hemisphere, as well as the Orientale Mare in the marginal zone of the Moon. To build 3D-models, orbital images of the Soviet spacecraft'Zond-6,-8' and the American spacecraft 'Apollo-17' delivered to Earth, as well as images transmitted to Earth from the Lunar Reconnaissance Orbiter (LRO) were used.
Abstract The report examines the results of a 3D-survey of the relief in young impact craters based on high-resolution images obtained from lunar orbits. The craters examined included: [...]
M. Bosch, M. Nitzlader, T. Burghardt, M. Bachmann, H. Binz, L. Blandini, M. Kreimeyer
WCCM-APCOM2022.
Abstract
High demand for living and working space as well as the corresponding infrastructure, caused by a growing population and increasing prosperity worldwide, leads to increased consumption of mineral resources. This is accompanied by high usage of grey energy and a high output of greenhouse gas emissions. Adaptive structures represent a promising approach for mass and resource savings. Through the interaction of actuators, sensors and control units, the structure can adapt to the external loads to reduce stresses and deformations. As a result, the building material required can be reduced. For actuators integrated into slabs, new challenges arise due to the multi-axial load transfer. In particular, the aim is to achieve the largest possible effective range of the applied moment to reduce the number of actuators required. One approach is to optimize the geometry of the force-introducing surfaces inside the structural element. This paper presents a study about the correlations of the geometric parameters using numerical simulations. This enables the pre-dimensioning of the actuator and is thus a first step in its design.
Abstract High demand for living and working space as well as the corresponding infrastructure, caused by a growing population and increasing prosperity worldwide, leads to increased [...]
Gas entrainment is one of the major defects caused in the casting filling process. Since the particle method is a Lagrangian method that does not use a lattice, it can easily analyze large deformations and boundary movements, so it has the potential to be applied to gas defect prediction as a methodology. However, in the two-phase flow simulation including gas entrainment, the analysis fails when the gas / liquid density ratio becomes smaller than about 1/10 in the conventional SPH. Therefore, two dimensional two-phase flow SPH methodology was developed. Then, authors extended the methodology to three dimensions that can be applied to gas entrainent during a die cast filling process.
Abstract Gas entrainment is one of the major defects caused in the casting filling process. Since the particle method is a Lagrangian method that does not use a lattice, it can easily [...]
Die-casting is a casting method suitable for mass production because it can accurately form complicated shapes. However, when the mold is filled with the molten metal, casting cavities (gas porosity) are generated due to air entrainment, and the strength of the product varies. In this study, the mold filling process considering air entrainment in the die cast are simulated using the two-phase flow SPH method. And then, the behavior of air entrainment due to the filling of molten metal (Aluminum alloy), especially the efect of injection speeds are investigated. In concluson, it is possible to investigate the air entrainment behavior at the time of filling the molten metal and the flow behavior due to different filling speeds. In addition, to speed up the two-phase flow program by SPH method, a parallel algorithm using OpenMP is implemented.
Abstract Die-casting is a casting method suitable for mass production because it can accurately form complicated shapes. However, when the mold is filled with the molten metal, casting [...]
In industrial numerical simulation of the complex and/or large-scale fluid flow, the computation cost must be reduced. In order to develop numerical low-cost solver for incompressible fluid flow problems based on BEM an effective scheme of DRM is proposed.
Abstract In industrial numerical simulation of the complex and/or large-scale fluid flow, the computation cost must be reduced. In order to develop numerical low-cost solver for incompressible [...]
A new discretization analysis method named the isolated element method, that differ from conventional FEM, for solid mechanical problems is proposed. An object to be analyzed is divided into the elements that are separated from each other. A set of displacement functions providing arbitrary number of degrees of freedom is used for each isolated element which expresses the translation and rotation of a rigid body. The extended principle of minimum potential energy is applied to satisfy the continuity of the displacement of isolated elements adjoining to each other. Any node or spring, penalty functions and Lagrange multipliers are not used in this method. The displacement functions of the power series are used to describe the mechanical state of the isolated element and finally, the coefficients of series are determined by a variational principle derived from the extended principle of minimum potential energy. Furthermore, a new mixed and hybrid variational principle which is composed from the potential and the complemental energy functional is proposed. The pair of these energy are constrained by a formula. Using this new principle, in which stress and displacement can be used as independent variables, the stress and displacement are computed at the same time. Besides, upper and lower bounds solutions are analyzed using the new principle and the isolated element method. Some computed examples of the plane stress problems are presented. We show the good convergency of the numerical results, and also present the upper and lower bound results of stress and displacement by the new mixed and hybrid variational principle using the isolated element method.
Abstract A new discretization analysis method named the isolated element method, that differ from conventional FEM, for solid mechanical problems is proposed. An object to be analyzed [...]
LFW(Linear Friction Welding) is the one of the smart industrial method matching to SDGs concept. It only needs a pair of blanks with no other assisting materials. This technique is now widely used in the Aeronautical, Automobile and other mechanical industries. In this paper we introduce an efficient LFW analysis method with 2D FEM model of LS-DYNA. In conclusion, analysis showed good correlation to the experimental results of the LFW process.
Abstract LFW(Linear Friction Welding) is the one of the smart industrial method matching to SDGs concept. It only needs a pair of blanks with no other assisting materials. This technique [...]
Large plants in the process industry are monitored and maintained at regular intervals and repeatedly maintenance is either too early or too late. This causes unnecessary costs due to technicians, spare parts procurement as well as delivery issues and to high downtime costs due to unexpected shutdowns. In this context, the Remaining Useful Life (RUL) plays a major role, as it is an indicator of how long a machine or component can run without breakdown, repair or replacement. By predicting RUL using predictive maintenance, maintenance can be better planned, operational efficiency optimized, and unplanned downtime avoided. Optimizing the prediction accuracy should therefore always be in the foreground and is therefore the topic of this paper.
Abstract Large plants in the process industry are monitored and maintained at regular intervals and repeatedly maintenance is either too early or too late. This causes unnecessary [...]
The purpose of this study is to develop a fluid-structure interaction analysis method using IGA. For fluid analysis, the numerical method based on the VOF method is employed. The stabilized finite element method with IGA is applied as the spatial discretization method and the Crank-Nicolson method as the temporal discretization method. Several numerical examples are presented to demonstrate the promise and potential of the present method to solve the solid-fluid interaction problems with free surface(WCCM-APCOM 2022).
Abstract The purpose of this study is to develop a fluid-structure interaction analysis method using IGA. For fluid analysis, the numerical method based on the VOF method is employed. [...]
The most commonly used coupling schemes in partitioned multiphysics simulations suffer from a decrease in the order of convergence, specifically in the time domain; a phenomenon we call order degradation. This paper discusses when this issue arises and how it can be studied with a simple example. We present a simple mass-spring system of ordinary differential equations (ODEs) to analyze accuracy and energy conservation of different coupling schemes. The ability to restore higher order of convergence by using Strang splitting or waveform iterations is verified in the context of the presented example. This paper provides details on some aspects of the talk titled 'Design and evaluation of a waveform iterationbased approach for coupling heterogeneous time stepping methods via preCICE' given at WCCM-APCOM 2022.
Abstract The most commonly used coupling schemes in partitioned multiphysics simulations suffer from a decrease in the order of convergence, specifically in the time domain; a phenomenon [...]
Multi-objective Topology Optimization has been receiving more and more attention in structural design recently. It attempts to maximize several performance objectives by redistributing the material in a design space for a given set of boundary conditions and constraints, yielding many Paretooptimal solutions. However, the high number of solutions makes it difficult to identify preferred designs. Therefore, an automatic way of summarizing solutions is needed for selecting interesting designs according to certain criteria, such as crashworthiness, deformation, and stress state. One approach for summarization is to cluster similar designs and obtain design representatives based on a suitable metric. For example, with Euclidean distance of the objective functions as the metric, design groups with similar performance can be identified and only the representative designs from different clusters may be analyzed. However, previous research has not dealt with the deformation-related time-series data of structures with different topologies. Since the non-linear dynamic behavior of designs is important in various fields such as vehicular crashworthiness, a clustering method based on time-dependent behavior of structures is proposed here. To compare the time-series displacement data of selected nodes in the structure and to create similarity matrices of those datasets, euclidean metrics and Dynamic Time Warping (DTW) are introduced. This is combined with clustering techniques such as k-medoids and Ordering Points To Identify the Clustering Structure (OPTICS), and we investigate the use of unsupervised learning methods to identify and group similar designs using the time series of nodal displacement data. In the first part, we create simple time-series datasets using a mass-spring system to validate the proposed methods. Each dataset has predefined clusters of data with distinct behavior such as different periods or modes. Then, we demonstrate that the combination of metrics for comparison of time series (Euclidean and DTW) and the clustering method (k-medoids and OPTICS) can identify the clusters of similar behavior accurately. In the second part, we apply these methods to a more realistic, engineering dataset of nodal displacement time series describing the crash behavior of topologically-optimized designs. We identify similar structures and obtain representative designs from each cluster. This reveals that the suggested method is useful in analyzing dynamic crash behavior and supports the designers in selecting representative structures based on deformation data at the early stages of the design process.
Abstract Multi-objective Topology Optimization has been receiving more and more attention in structural design recently. It attempts to maximize several performance objectives by redistributing [...]
The objective of this study is to predict the degree of danger to the human body from motion information such as acceleration, velocity and displacement during a collision between a car and a human body. As a preliminary step, the maximum bending moment that occurs in the leg was predicted using a convolutional neural network. The responses which are represented by learning data generated by 1D-CAE system. A number of training data sets are varied in order to show the enough number to predict. The predictor's accuracy is evaluated by the test data sets. We'd like to discuss necessisty of a total number of training data sets and effectiveness of data augmentation technique. In addition, the technique to utilize classification by the t-SNE method to improve accuracy is also examined. t-SNE is based on classification algorithm, however an engineering interpolation should be computed based on physical meanings and influential parameters.
Abstract The objective of this study is to predict the degree of danger to the human body from motion information such as acceleration, velocity and displacement during a collision [...]
Arch structure is a widely used and important structure type all over the World. Due to its beautiful form and large spanning capacity, arch structure is widely used in bridges, tunnels and other buildings. Recently, the large span space arch structure has a stage of development. The defects of arch structure, such as connection, material, fatigue, stress concentration and welding, will directly affect the safety of these kind of structures. The study of the evolution of the damage in arches is a topic of interest since the antiquity. A well-done structural design should always account for the evolution of the damage in time, in particular if it can bring to a change in the static behaviour of the structure itself under different loading conditions. In this paper, a model for the calculation of localized damaged in arch structures is presented. In particular, using an analytical solution for the computation of the displacements field and the consequent internal actions of very general shapes with variable curvature and tapered cross-section, the damage is modelled by localized depletion of the cross-sectional properties (inertia) in the different points along the arch axis. Moreover, the depleted parameters are the crosssection and the bending stiffness of the arch. The model is applied to the study different configurations of the damage (localization of plastic hinges or different pattern of defects) and to consider the evolution of the damage in time.
Abstract Arch structure is a widely used and important structure type all over the World. Due to its beautiful form and large spanning capacity, arch structure is widely used in bridges, [...]
J. Sharma, P. Fiborek, R. Soman, P. Kudela, K. Agathos, E. Chatzi, W. Ostachowicz
WCCM-APCOM2022.
Abstract
Guided wave-based Structural Health Monitoring (SHM) tools utilize the guided wave responses to interrogate damage in structures. This research demonstrates the use of various objective functions in single (mono) objective and multi-objective genetic algorithms for damage identification in isotropic 1D structures. The time domain spectral element method and a deep-learning-based surrogate is utilized for simulating wave propagation in an isotropic cracked rod. The genetic algorithms employ results ('numerical experiment') obtained from the spectral element model and the deep-learning-based surrogate to determine the optimized crack locations and crack depths as output parameters. The obtained optimized parameters from genetic algorithms are compared in terms of errors for various objective functions.
Abstract Guided wave-based Structural Health Monitoring (SHM) tools utilize the guided wave responses to interrogate damage in structures. This research demonstrates the use of various [...]
In this contribution, a new form of semianalytical results related to inertial objects that are traversing homogeneous infinite structures, introduced in previous author's work, is used to analyze one-, twoand three-layer models of the railway track. The aim of these analyses is determination of the critical velocity of a moving force and of the onset of instability of moving masses or oscillators. As one of the most important conclusions, it will be shown that in the case of two moving proximate masses, damping can act in the opposite direction than expected and owing to the dynamic interaction, the onset of instability can be shifted deeply into the subcritical velocity range.
Abstract In this contribution, a new form of semianalytical results related to inertial objects that are traversing homogeneous infinite structures, introduced in previous author's [...]
The vibrations and the sound field around the body of an old violin made by Stradivari are studied in this paper, in which this violin is scanned using a micro-CT scanner to generate a highly precise geometric image. After the noise in the scanned data is eliminated using a computer-assisted design (CAD) software for post-processing, the geometric data are saved in the simulation software. Assuming the orthotropic properties of woods (spruce and maple), the major vibration modes of the violin, such as A0, center bout rotation, B1-, B1+, and the acoustic pressure level at the surface of the violin body are calculated using the finite element method. Next, using the sound pressure distribution at the surface of the instrument, the sound pressure spreading in a rectangular box simulating a concert hall is calculated with the open-source parallel acoustic analysis software: ADVENTURE Sound. It is concluded that the sound pressure from the violin is successfully simulated.
Abstract The vibrations and the sound field around the body of an old violin made by Stradivari are studied in this paper, in which this violin is scanned using a micro-CT scanner [...]
The structural strength evaluation of crash boxes is predicted by machine learning in this study. The training data was obtained from the dynamic elastic plastic analysis of the crash box. The input physical quantities are barrier angle, box thickness, material properties and mass equivalent to vehicle weight. The output physical quantity is the reaction force. Buckling occurs in the analysis and different directions of corruptions are one of the most interesting phenomenon from a point of engineering view.
Abstract The structural strength evaluation of crash boxes is predicted by machine learning in this study. The training data was obtained from the dynamic elastic plastic analysis [...]
Structural analysis and design of a large inflatable hangar for aircrafts (preprint) 