Documents published in Scipedia

• Study of the dynamic behavior of cellular structures for the absorption of mechanical vibrations

  M. Silva, L. Ramos

  WCCM2024.

  
  

  Abstract

  Vibration is a prevalent issue in structural engineering, encompassing a wide array of problems that, if left unaddressed, can lead to severe consequences. These consequences can vary from causing discomfort for pedestrians traversing a perceptibly moving bridge to inducing premature fatigue in aeronautical structural components, ultimately resulting in catastrophic failures and loss of human life. Various sources can induce vibration in structural components, such as misalignment of rotating systems, seismic excitations, road loads on vehicles, and aerodynamic loads. To address these phenomena, in addition to appropriate structural design, various mechanisms, which can operate actively or passively, are used to attenuate oscillatory effects and minimize their impact. Active systems use electronic controllers to generate a response via actuators, reducing the signal transmissibility level based on specific oscillatory signals. Passive systems, on the other hand, mainly rely on viscoelastic polymeric materials, utilizing the reduction of the natural frequency associated with their use and a characteristic phenomenon of these materials for energy dissipation, hysteresis [1]. Hysteresis is a phenomenon where mechanical deformation energy is dissipated in the form of heat. In other words, part of the energy that would be transmitted to the structure is dissipated, thereby increasing the system's damping. Active systems are extremely efficient in their purpose, as they can isolate vibrations across a wide frequency spectrum and can be applied to structures of different magnitudes, from small and lightweight systems using piezoelectric actuators to large structures using hydraulic actuators, such as in active stabilization systems for reducing vibrations caused by seismic activities in buildings. However, they tend to be quite costly and imply an additional layer of systems, which, if not properly designed, can reduce the structure's reliability [2].

  Abstract
  Vibration is a prevalent issue in structural engineering, encompassing a wide array of problems that, if left unaddressed, can lead to severe consequences. These consequences [...]

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• Investigating the domain of attraction of SDRE applied to a CubeSat attitude control system during launch orbit phase based on cold gas thrusters

  L. Souza, A. Romero

  WCCM2024.

  
  

  Abstract

  The precision of controlling the attitude of a CubeSat during the injection phase in orbit is of fundamental importance for the success of the mission. In general, the CubeSat starts this phase with high angular velocity, and then the controller needs to maneuver the CubeSat to its nominal mode of operation, which is characterized by an attitude of small angles. One way to achieve such a transition between these two modes is by using cold gas thrusters. In this paper, we investigate the region of attraction (ROA) of the State-Dependent Riccati Equation (SDRE) applied to the Attitude Control System (ACS) algorithm during the Launch and Early Orbit Phase which has nonlinear dynamics due to the high angular velocities and perturbations. The SDRE controller is based on cold gas thruster torques to reduce the high angular velocities. The main result of this investigation is the approach to numerically approximate the ROA.

  Abstract
  The precision of controlling the attitude of a CubeSat during the injection phase in orbit is of fundamental importance for the success of the mission. In general, the CubeSat [...]

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• Minimization of vibrations in aeronautical wing spars under flutter situation

  L. Santos, M. Silva, R. Brasil

  WCCM2024.

  
  

  Abstract

  This research project aims to investigate the mitigation of vibrations in the spars of aeronautical wings during flutter occurrences. The study will delve into aeroelastic phenomena, particularly focusing on flutter, defined as the self-excited interaction of vibration modes within a modified system, which can potentially lead to catastrophic failures. An analytical method has been developed to compute the flutter velocity, considering the stiffness and mass matrices, and the utilization of a Tuned Mass Damper (TMD) has been proposed to enhance the flutter velocity, thereby extending the aircraft's operational range. Suggestions for future research directions have been provided.

  Abstract
  This research project aims to investigate the mitigation of vibrations in the spars of aeronautical wings during flutter occurrences. The study will delve into aeroelastic [...]

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• Evaluation of effectiveness of traffic jam absorption driving using computer simulation

  S. Yamada, E. Kita

  WCCM2024.

  
  

  Abstract

  Traffic congestion absorbing driving is a method of driving at low speed with a larger inter-vehicle distance than surrounding vehicles. This makes it possible to reduce excessive acceleration and deceleration, which is effective in alleviating traffic congestion. The traffic simulation in the sag section confirmed that the traffic congestion absorption driving is effective for traffic congestion mitigation. It was shown that it is possible to increase the average speed in congested sections by means of congestion absorption driving.

  Abstract
  Traffic congestion absorbing driving is a method of driving at low speed with a larger inter-vehicle distance than surrounding vehicles. This makes it possible to reduce excessive [...]

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• Enhanced mechanical behavior of nickel-coated graphene graphene reinforced CoCrFeMnNi nanolayered composites

  J. Guan, X. Zhou, G. Qu, G. Bao

  WCCM2024.

  
  

  Abstract

  High entropy alloys (HEAs) especially CoCrFeMnNi HEAs have drawn more and more attention due to their excellent combination performance. However, the mechanical properties of CoCrFeMnNi HEAs still remain to be improved due to the single-phase FCC crystal structure. Although many efforts have been made on strengthening methods by grain refinement or nitriding the improvement of the mechanical properties is still unsatisfactory. To improve the mechanical properties of CoCrFeMnNi HEAs and broaden their application fields, we proposed that adding functionalized graphene in CoCrFeMnNi HEAs and investigated nanoscale mechanical properties and the strengthening mechanism using molecular dynamics (MD) simulation in this paper. The mechanical properties of pristine single-layer graphene nanoplatelets (GNPs) and double-side nickel-coated GNP (Ni-GNP-Ni) reinforced CoCrFeMnNi composites (Ni-GNP-Ni/CoCrFeMnNi) are studied under uniaxial tension by molecular dynamics (MD) simulations. The simulated results show that the mechanical properties of Ni-GNP-Ni/CoCrFeMnNi composites are improved significantly by the addition of Ni coated GNPs. The mechanical properties of Ni-GNP-Ni/CoCrFeMnNi composites exhibit temperature softening and strain rate strengthening effect, and their tensile mechanical properties such as the tensile strength, fracture strain decrease with increasing temperature and enhance with increasing strain rate. It is concluded that the main strengthening mechanisms for Ni-GNP-Ni/CoCrFeMnNi composites are strong interface bonding, effective load transfer from the CoCrFeMnNi matrix to the Ni-GNP-Ni and dislocation/twin strengthening by analysis of the evolution of atomic structure.

  Abstract
  High entropy alloys (HEAs) especially CoCrFeMnNi HEAs have drawn more and more attention due to their excellent combination performance. However, the mechanical properties [...]

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• Modeling the effect of backbone instabilities and guest occupancies on interfacial and structural processes and dynamics of sII gas hydrate systems using molecular dynamics

  S. Mathews, P. Servio, A. Rey

  WCCM2024.

  
  

  Abstract

  Gas hydrates are inclusion compounds that form in conditions of low temperature and high-pressure systems with water and gaseous molecules. Their potential use in carbon capture and storage, energy exploitation, and flue gas extraction makes them prime candidates for various engineering applications and climate change mitigation technologies. However, their nucleation is poorly understood and the effect of guest molecule interactions with the host on macroscale properties has yet to be elucidated. Herein we study the optimal positions of a point mass, linear molecule, and planar triangular guest molecule using a distance minimization technique that can replicate preliminary density functional theory results. The linear molecule shows strong alignment to hexagonal phases of cages, while the triangular guest molecule shows very distinct positions. These positions indicate a lower number of degrees of freedom, which in turn affect the molecules’ ability to move and vibrate in heat absorption, for example. Additionally, it shows that hydrate formation may only be possible when the guest is oriented a certain way, providing an avenue to control nucleation by adjusting guest molecule position with external fields.

  Abstract
  Gas hydrates are inclusion compounds that form in conditions of low temperature and high-pressure systems with water and gaseous molecules. Their potential use in carbon capture [...]

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• Beyond lubrication flow for thin-film manufacturing

  R. Secor, R. Rao, W. Ortiz

  WCCM2024.

  
  

  Abstract

  Reynolds’ hydrodynamic lubrication theory has been used extensively to analyze and quantify thin film manufacturing1 . Applications span liquid flows in bearings, coatings, and molds, and gas flows between rigid or elastic surfaces. To enable further applications of efficient, reduced-order modelling, we pursue streamlined algorithms for non-Newtonian liquids in marginally “thin” geometries with multiple phases and capillarity. The goal is expanded use of “modified”, non-traditional lubrication methods to bring physics-based knowledge to bear in process design, optimization, and control methods.

  Abstract
  Reynolds’ hydrodynamic lubrication theory has been used extensively to analyze and quantify thin film manufacturing1 . Applications span liquid flows in bearings, coatings, [...]

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• Towards a multiscale computational framework for simulating flow-mediated crystallization based on phase-field crystal formalisms

  L. Willis, R. Rao, L. Liu

  WCCM2024.

  
  

  Abstract

  We lay the foundation and framework for a multiscale approach for studying crystallization in the presence of flow by coupling the Structural Phase Field Crystal (XPFC) formalism with the Navier-Stokes equations. We discuss the numerical techniques and verify the formalism against previous attempts with the vanilla Phase Field Crystal (PFC) formalism. Moreover, with this new Hydrodynamically coupled Structural Phase Field Crystal (HXPFC) method, we discuss unreported global and local crystal microstructural transformation induced by the flow. The HXPFC method establishes a framework to predict more complex crystal structures while incorporating physics relevant to film coating flows.

  Abstract
  We lay the foundation and framework for a multiscale approach for studying crystallization in the presence of flow by coupling the Structural Phase Field Crystal (XPFC) formalism [...]

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• Design of in-mold decoration mold for complex thin-walled parts

  J. Dong, D. Shi, J. Wang

  WCCM2024.

  
  

  Abstract

  In order to address the issues of warping deformation and long-term production of complex thin-walled parts during In-Mold Decoration (IMD) production, the structure design of the IMD mold was carried out with the humidifier top cover as the production object. To ensure the flow characteristics of molten plastic in the mold during the injection molding process, based on the technical contradiction analysis of TRIZ theory, the hot runner mold is improved to mix cold and hot runner, that is, the sprue is set as a hot runner, the branch runner is set as a cold runner, and use a multi-point injection cold gate solution. And construct a complex structure numbering method to arrange and design various complex structure undercut-forming side insert mechanism, design of special structure lifters along the same direction of motion the two inverted buckle at the same time undercut-forming. The lifter mechanisms are used to complete the molding, parting, demolding and ejection of plastic parts, multiple uses for one mechanism. In order to optimize product quality and improve production efficiency, providing theoretical and empirical support for the production of complex thin walled parts with IMD molds. Then design the cooling system and demolding mechanism separately. Finally, based on Moldflow software, the final flow of plastic part warpage analyzed. The maximum warping deformation of the product is 0.7055mm, while the maximum warping deformation of the traditional cold runner mold is 0.8519mm, reducing the warping deformation of the humidifier top cover.

  Abstract
  In order to address the issues of warping deformation and long-term production of complex thin-walled parts during In-Mold Decoration (IMD) production, the structure design [...]

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• Numerical simulations of origami-based folded carbon-reinforced concrete shells

  H. Spartali, L. Mester, G. Kikis, S. Klarmann

  WCCM2024.

  
  

  Abstract

  The advantages of carbon-reinforced concrete (CRC) over traditional concrete elements reinforced with steel, including high strength, low weight, and corrosion resistance, make it a promising material for thin, efficient, and more sustainable designs. As the demand for less CO2-intensive materials such as concrete grows, a shift from simple massive elements to thin-walled elements with complex geometries is becoming increasingly necessary. However, to seek optimal design variants, efficient nonlinear numerical calculations that provide reasonable predictions of the structural behavior, including the stress-redistribution process and the failure mechanisms are essential. This paper presents FEM simulations of origami-based folded CRC shells that were experimentally investigated in a previous study. Two FEM modeling approaches were used, employing a smeared and a discrete representation of the carbon reinforcement. For both approaches a damage plasticity model for the concrete has been used. The load-deflection response from the discrete approach closely matches the experimentally obtained curves. Despite an overestimation of the load capacity, the computationally less expensive smeared FEM model qualitatively reproduces the structural response and the correct failure mechanism. Therefore, the quality of the results obtained from the smeared model is sufficient to determine preferable design variants in a typical design scenario. This is necessary to provide a deeper understanding of the structural behavior of these folded elements and to facilitate the sustainable design and application of thin-walled CRC elements in the future.

  Abstract
  The advantages of carbon-reinforced concrete (CRC) over traditional concrete elements reinforced with steel, including high strength, low weight, and corrosion resistance, [...]

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