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• A microstructure-integrated acoustoplastic constitutive model for ultrasonic-assisted machining of Ti6Al4V alloy

  H. Bakhshan, E. Oñate, J. Puigbó

  CIRP Journal of Manufacturing Science and Technology (2025). Vol. 57, 14-31

  
  

  Abstract

  The ultrasonic-assisted machining (UAM) technology, compared to conventional machining (CM), has been proven to be an effective method for machining the difficult-to-cut Ti6Al4V alloy (TC4). In the UAM process, the evolution mechanism of microstructure and hardness directly influences the material behavior and consequently, mechanical response, which remains unrevealed from a computational perspective. To address this, in this study, we present a developed modeling technique that combines the Particle Finite Element Method (PFEM) with incremental homogeneous field distributions in a coupled manner to effectively predict the macro and micro response of the material in both CM and UAM processes. First, the evolution of microstructural parameters, including immobile dislocation density (IDD) and mobile dislocation density (MDD), dynamic recrystallization (DRx) grain size, and hardness, is incrementally developed and incorporated into the PFEM using internal state variables. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) model and Hall–Petch equation are employed for predicting grain size and hardness, respectively. Second, A microstructure-integrated acoustoplastic constitutive model is developed based on a modified Johnson–Cook (JC) model and average grain size (AGS) predictions dependent on ultrasonic vibration (UV) parameters. The proposed model is embedded into the PFEM to conduct a thermo-mechanical analysis capable of capturing the TC4 response, particularly in terms of serrated chip formation during CM and UAM processes. The model’s validity is checked through comparison with available experimental results in terms of chip shapes. Lastly, the predicted AGS and hardness in serrated chips and machined surface are compared with experimental data, showing good agreement. This suggests that the proposed acoustoplastic constitutive model, coupled with microstructure and UV parameters, can reliably analyze the CM and UAM processes of the TC4.

  Abstract
  The ultrasonic-assisted machining (UAM) technology, compared to conventional machining (CM), has been proven to be an effective method for machining the difficult-to-cut Ti6Al4V [...]

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• A modified Johnson–Cook model for the plastic behavior of metals in ultrasonic vibration-assisted upsetting processes

  H. Bakhshan, J. Puigbó, E. Oñate

  Journal of Manufacturing Processes (2024). Vol. 121, pp. 361-373

  
  

  Abstract

  In this work, we present a constitutive description of the plastic behavior of the metals and alloys under Ultrasonic Vibration (UV). When UV is imposed, it induces a softening effect on the plastic deformation of metals and alloys, referred to as the acoustoplastic phenomenon. The volumetric softening mechanism of the acoustoplasticity must consider stress superposition and acoustic softening. Taking the Johnson–Cook (JC) constitutive model as the reference for metal thermo-plasticity, the flow stress reduction due to UV is introduced by three types of softening terms: subtractive, multiplicative, and coupled. Those different configurations will be quantified via physical and phenomenological assumptions. For the study and validation of the proposed constitutive models, we focus on a well-known material, 6063 aluminum alloy. The ultrasonic vibration is modeled by an assisted upsetting process of an aluminum billet and compared with experiments. The impact of variations of the strain rate, ultrasonic amplitude, and frequency on the softening behavior of the models are analyzed and compared with available experimental results. We find out that the subtractive and coupled models agreed well with the experimental results showing the errors ranging from 2.4–4.8% and 4.4%–8%, respectively. However, the predictive ability of the multiplicative model exhibits large discrepancies at the low stage of strains following the acceptable predictions at high stains. By understanding the impact of the UV on the acoustoplastic deformation of the metals and alloys we can establish a reliable theoretical framework for prospective numerical studies of the UV-assisted manufacturing processes which is the goal of the current research presented here.

  Abstract
  In this work, we present a constitutive description of the plastic behavior of the metals and alloys under Ultrasonic Vibration (UV). When UV is imposed, it induces [...]

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• Microstructure evolution modeling of Ti6Al4V alloy during cutting using the Particle Finite Element Method and homogeneous field distributions

  H. Bakhshan, E. Oñate, J. Puigbó

  Journal of Manufacturing Processes (2024). Vol. 131, pp. 73-92

  
  

  Abstract

  This paper aims to explore the evolution of microstructural parameters induced during the cutting of Ti6Al4V alloy (TC4). The microstructure characteristics of the workpiece material is directly tied to its mechanical response during machining. During TC4 cutting, microstructure evolution is observed as a result of severe plastic deformations. The characterization of this phenomenon has significant interest from both academia and industry. In this work we present a developed modeling technique which combines the Particle Finite Element Method (PFEM) with incremental homogeneous field distributions. First, the PFEM is extended to perform a thermo-mechanical analysis capable of capturing the material responses of TC4 during orthogonal cutting. To generate serrated chips, an appropriate strain softening-based constitutive plasticity model i.e., TANH (Hyperbolic TANgent) is utilized. The PFEM’s validity is checked through comparison with available experimental results in terms of chip shapes and cutting forces. Second, the evolution of microstructural parameters such as dislocation density, vacancy concentration, dynamic recrystallization (DRx) grain size, and hardness is incrementally developed and incorporated into the PFEM using internal state variables as homogeneous field distributions. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) model and Hall–Petch equation are applied for predicting grain size and hardness, respectively. The parameters of the corresponding models are modified for TC4 to accurately capture their alterations. Lastly, the predicted results of the microstructure evolution in serrated chips and machined surfaces, including average grain size and hardness, are compared with experiments, demonstrating good agreement. This implies that the PFEM combined with microscale schemes can reliably simulate the machining process of the TC4.

  Abstract
  This paper aims to explore the evolution of microstructural parameters induced during the cutting of Ti6Al4V alloy (TC4). The microstructure characteristics of the workpiece [...]

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• Modeling of ultrasonic vibration-assisted micromachining using the particle finite element method

  H. Bakhshan, E. Oñate, J. Puigbó

  Computational Particle Mechanics (2024). Vol. 11, pp. 2267–2290

  
  

  Abstract

  When metals and alloys are exposed to ultrasonic vibrations (UV), a softening behavior occurs, caused by the phenomenon of acousto-plasticity. To obtain accurate results in a deformation analysis, this phenomenon must be included in the formulation of the constitutive material model. In this work, an acoustic-plastic model is proposed to capture the effects of ultrasonic vibrations during machining. The desired effect is to modify the chip morphology to reduce the magnitude of the cutting forces and thus reduce the energy consumption of the process. The study focuses on the modeling of ultrasonic vibration-assisted micromachining (VAMM). The particle finite element method is used and extended to perform a thermo-mechanical analysis capable of capturing the responses of conventional micromachining (CMM) and VAMM operations of 32 HRC stainless steel. The cutting speed and UV parameters, including amplitude and frequency, are integrated into the Johnson–Cook constitutive model to account for the effects of acoustic softening on the machining characteristics. The results show that the influence of UV on microcutting leads to thinner chips and lower cutting force. In the VAMM operations, an average reduction in cutting forces of 20% is achieved at five different cutting speeds. In addition, the contact length between the tool and chip decreases at different cutting speeds from 29% to a maximum of 44%. Furthermore, the thermal analysis results show that there is a negligible temperature change during the CMM and VAMM simulations, indicating that the study of the machining process can focus exclusively on its mechanical aspects when performed at the microscale. The predicted average chip thickness and effective shear angle of the workpiece material are in strong agreement with the experimental results, emphasizing the importance of considering acoustic softening in VAMM studies.

  Abstract
  When metals and alloys are exposed to ultrasonic vibrations (UV), a softening behavior occurs, caused by the phenomenon of acousto-plasticity. To obtain accurate results in [...]

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• Modelling 3D metal cutting problems with the particle finite element method

  J. Puigbó, . J.M.Rodríguez, E. Oñate

  Computational Mechanics (2020). Vol. 66, pp. 603–624, 2020

  
  

  Abstract

  This work presents the development of the Particle Finite Element Method (PFEM) for the modelling of 3D solid mechanics problems under cutting conditions. The study and analysis of numerical models reproducing the cut of a material is a matter of interest in several areas; namely, the improvement of the material properties, the optimization of the process and tool geometries and the prediction of unexpected failures. The analysis of bi-dimensional (2D) models is the most common approach for different reasons. Just focusing on the simulation point of view, it is the simplest procedure, the cheapest in terms of computational cost and sometimes the only feasible numerical solution. However, many industrial machining processes, such as cutting, blanking, milling and drilling have not a possible simplification to 2D models. Actually even a simple turning processes for non-orthogonal cuts can not be simplified to 2D. This work present an upgrade of the PFEM techniques in order to deal with the 3D machining problems. We present recent improvements in the finite element formulation, the meshing re-connections and the contact detection. By applying these developments the PFEM has the capability for modelling a wide range of practical machining processes. In this paper the capacity of the formulation and the accuracy of the results are analyzed and validated with some representative examples.

  Abstract
  This work presents the development of the Particle Finite Element Method (PFEM) for the modelling of 3D solid mechanics problems under cutting conditions. The study and analysis [...]

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• Explicit finite deformation stress integration of the elasto-plastic constitutive equations

  L. Monforte, M. Arroyo, A. Gens, J. Puigbó

  (2014). Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014". Kyoto: CRC Press Taylor & Francis Group, p. 267-272.

  
  

  Abstract

  In this work, an explicit integration scheme for hyperelastic-based finite strains elasto-plasticity is presented. One step update equations are obtained from the large deformation multiplicative elasto-plasticity theory, where an exponential variation of the plastic deformation gradient is assumed. In addition, the material tangent matrix is presented and has the same formal structure as the usual small strains elasto-plastic tangent matrix. In purely elastic regime, the proposal reduces to the usual large deformation elasticity equations. Routines to alleviate the main drawbacks of explicit methods are outlined, such as a yield surface drift correction scheme and an adaptive substepping method. Several examples of typical geotechnical tests using the Houlsby hyperelastic model along with the Modified Cam Clay plastic model are discussed. Results from a convergence test suggest that, using an adaptive substepping scheme, the error of the local problem is independent of the step size.

  Abstract
  In this work, an explicit integration scheme for hyperelastic-based finite strains elasto-plasticity is presented. One step update equations are obtained from the large deformation [...]

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• Evaluation of Multilayer Pavement Viscoelastic Properties from Falling Weight Deflectometer using Neural Networks

  J. González, J. Puigbó, W. Bijsterveld

  (2016). Chapters 16. In Materials and Infrastructures 1 (eds J.‐M. Torrenti and F. La Torre).

  
  

  Abstract

  The surface deflection caused by the falling weight deflectometer (FWD) is a dynamic problem usually treated as a static problem. This chapter presents a dynamic solution of the backcalculation problem using a viscoelastic model, introducing a viscosity variable. The calibration process is based on the numerical simulation of the FWD test to approximate the deflection curves obtained in the road track. Description of the experimental curves and the hypothesis of the numerical problem assumed are also described. The samples used to train and validate the artificial neural network (ANN) are conformed by four values per curve times the number of geophones, the input data, while the output data are five Young moduli and five viscosities. The backcalculation process is based on experimental tests from the FWD and calibrated using an FEM simulation of the problem.

  Abstract
  The surface deflection caused by the falling weight deflectometer (FWD) is a dynamic problem usually treated as a static problem. This chapter presents a dynamic solution [...]

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• The particle finite element method (PFEM) in thermo‐mechanical problems

  J. Rodríguez, J. Puigbó, J. Cante, J. Oliver

  Int. J. Numer. Meth. Engng. (2015). (preprint) Vol. 107 (9), pp. 733-785

  
  

  Abstract

  The aim of this work is to develop a numerical framework for accurately and robustly simulating the different conditions exhibited by thermo‐mechanical problems. In particular, the work will focus on the analysis of problems involving large strains, rotations, multiple contacts, large boundary surface changes, and thermal effects. The framework of the numerical scheme is based on the particle finite element method (PFEM) in which the spatial domain is continuously redefined by a distinct nodal reconnection, generated by a Delaunay triangulation. In contrast to classical PFEM calculations, in which the free boundary is obtained by a geometrical procedure (α − shape method), in this work, the boundary is considered as a material surface, and the boundary nodes are removed or inserted by means of an error function. The description of the thermo‐mechanical constitutive model is based on the concepts of large strains plasticity. The plastic flow condition is assumed nearly incompressible, so a u‐p mixed formulation, with a stabilization of the pressure term via the polynomial pressure projection, is proposed. One of the novelties of this work is the use of a combination between the isothermal split and the so‐called IMPL‐EX hybrid integration technique to enhance the robustness and reduce the typical iteration number of the fully implicit Newton–Raphson solution algorithm. The new set of numerical tools implemented in the PFEM algorithm, including new discretization techniques, the use of a projection of the variables between meshes, and the insertion and removal of points allows us to eliminate the negative Jacobians present during large deformation problems, which is one of the drawbacks in the simulation of coupled thermo‐mechanical problems. Finally, two sets of numerical results in 2D are stated. In the first one, the behavior of the proposed locking‐free element type and different time integration schemes for thermo‐mechanical problems is analyzed. The potential of the method for modeling more complex coupled problems as metal cutting and metal forming processes is explored in the last example.

  Abstract
  The aim of this work is to develop a numerical framework for accurately and robustly simulating the different conditions exhibited by thermo‐mechanical problems. In particular, [...]

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• Numerical simulation of undrained insertion problems in geotechnical engineering with the Particle Finite Element Method (PFEM)

  L. Monforte, M. Arroyo, J. Puigbó, A. Gens

  Computers and Geotechnics (2017). (preprint)Vol. 82, pp. 144-156

  
  

  Abstract

  The paper presents total-stress numerical analyses of large-displacement soil-structure interaction problems in geomechanics using the Particle Finite Element Method (PFEM). This method is characterized by frequent remeshing and the use of low order finite elements to evaluate the solution. Several important features of the method are: (i) a mixed formulation (displacement-mean pressure) stabilized numerically to alleviate the volumetric locking effects that are characteristic of low order elements when the medium is incompressible, (ii) a penalty method to prescribe the contact constraints between a rigid body and a deformable media combined with an implicit scheme to solve the tangential contact constraint, (iii) an explicit algorithm with adaptive substepping and correction of the yield surface drift to integrate the finite-strain multiplicative elasto-plastic constitutive relationship, and (iv) the mapping schemes to transfer information between successive discretizations. The performance of the method is demonstrated by several numerical examples, of increasing complexity, ranging from the insertion of a rigid strip footing to a rough cone penetration test. It is shown that the proposed method requires fewer computational resources than other numerical approaches addressing the same type of problems.

  Abstract
  The paper presents total-stress numerical analyses of large-displacement soil-structure interaction problems in geomechanics using the Particle Finite [...]

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• Damage analysis of masonry structures subjected to rockfalls

  O. Mavrouli, P. Giannopoulos, J. Puigbó, C. Syrmakezis

  Landslides (2017). (preprint) Vol. 14 (3), pp. 891-904

  
  

  Abstract

  Masonry structures present substantial vulnerability to rockfalls. The methodologies for the damage quantification of masonry structures subjected to rockfalls are scarce. An analytical procedure for the damage assessment of masonry structures is presented. The procedure comprises three stages: (1) determination of the rockfall impact actions which are applied to a masonry structure, in terms of external forces, using the particle finite element method (PFEM), (2) evaluation of the mechanical properties, modelling of the masonry structure, and calculation of the internal stresses, using the finite element method (FEM), (3) assessment of the damage due to the rockfall actions, applying a failure criterion adapted to masonries, and calculation of the damage in terms of the percentage of the damaged wall surface. Three real rockfall events and their impact on buildings are analysed. A sensitivity analysis of the proposed procedure is then used to identify the variables that mostly affect the extent of the wall damage, which are the masonry width, the tensile strength, the block diameter and lastly, velocity.

  Abstract
  Masonry structures present substantial vulnerability to rockfalls. The methodologies for the damage quantification of masonry structures subjected to rockfalls are scarce. [...]

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Articles (Documents not available in Scipedia)

• Generation of segmental chips in metal cutting modeled with the PFEM

  JMR Prieto, JM Carbonell, JC Cante, J Oliver, P Jonsén

  Computational Mechanics, 1-17, 2017

• Continuous chip formation in metal cutting processes using the Particle Finite Element Method (PFEM)

  JM Rodríguez, JM Carbonell, JC Cante, J Oliver

  International Journal of Solids and Structures 120, 81-102, 2017

• PFEM formulation for thermo-coupled FSI analysis. Application to nuclear core melt accident

  A Franci, E Oñate, JM Carbonell, M Chiumenti

  Computer Methods in Applied Mechanics and Engineering 325, 711-732, 2017

• Performance of mixed formulations for the particle finite element method in soil mechanics problems

  L Monforte, JM Carbonell, M Arroyo, A Gens

  Computational Particle Mechanics 4 (3), 269-284, 2017

• Damage analysis of masonry structures subjected to rockfalls

  O Mavrouli, PG Giannopoulos, JM Carbonell, C Syrmakezis

  Landslides 14 (3), 891-904, 2017

• Numerical simulation of undrained insertion problems in geotechnical engineering with the Particle Finite Element Method (PFEM)

  L Monforte, M Arroyo, JM Carbonell, A Gens

  Computers and Geotechnics 82, 144-156, 2017

• Simulation of the cone penetration test: discrete and continuum approaches

  A Gens Solé, M Arroyo Alvarez de Toledo, J Butlanska, L Monforte Vila, ...

  Geotechnical and geophysical site characterisation 5: Proceedings of the …, 2016

• Simulation of the cone penetration test: discrete and continuum approaches

  A Gens, M Arroyo, J Butlanska, JM Carbonell, M Ciantia, L Monforte, ...

  Aust. Geomech 51 (4), 169-182, 2016

• Velocity‐based formulations for standard and quasi‐incompressible hypoelastic‐plastic solids

  A Franci, E Oñate, JM Carbonell

  International Journal for Numerical Methods in Engineering 107 (11), 970-990, 2016

• The Double Hierarchy Method. A parallel 3D contact method for the interaction of spherical particles with rigid FE boundaries using the DEM

  M Santasusana, J Irazábal, E Oñate, JM Carbonell

  Computational Particle Mechanics 3 (3), 407-428, 2016

• The particle finite element method (PFEM) in thermo‐mechanical problems

  JM Rodriguez, JM Carbonell, JC Cante, J Oliver

  International Journal for Numerical Methods in Engineering 107 (9), 733-785, 2016

• Numerical simulation of penetration problems in geotechnical engineering with the particle finite element method (PFEM)

  L Monforte Vila, JM Carbonell Puigbó, M Arroyo Alvarez de Toledo, ...

  Proceedings of the IV International Conference on Particle-Based Methods …, 2015

• Explicit finite deformation stress integration of the elasto-plastic constitutive equations

  L Monforte, M Arroyo, A Gens, JM Carbonell

  Computer Methods and Advances in Geomechanics, 267-272, 2015

• On the effect of the bulk tangent matrix in partitioned solution schemes for nearly incompressible fluids

  A Franci, E Oñate, JM Carbonell

  International Journal for Numerical Methods in Engineering 102 (3-4), 257-277, 2015

• Evaluation of multilayer pavement viscoelastic properties from falling weight deflectometer using neural networks

  JM Gonzalez, JM Carbonell, W van Bijsterveld

  Materials and Infrastructures 1, 211-225, 2014

• A particle finite element method (PFEM) for coupled thermal analysis of quasi and fully incompressible flows and fluid-structure interaction problems

  E Oñate, A Franci, JM Carbonell

  Numerical Simulations of Coupled Problems in Engineering, 129-156, 2014

• On the effect of the tangent bulk stiffness matrix in the analysis of free surface Lagrangian flows using PFEM

  A Franci, E Oñate, JM Carbonell

  Research Report CIMNE PI402, 2013

• Modelling of tunnelling processes and rock cutting tool wear with the particle finite element method

  JM Carbonell, E Oñate, B Suárez

  Computational Mechanics 52 (3), 607-629, 2013

• Advances in the particle finite element method (PFEM) for solving coupled problems in engineering

  E Oñate, SR Idelsohn, MA Celigueta, R Rossi, J Marti, JM Carbonell, ...

  Particle-Based Methods, 1-49, 2011

• Análisis numérico de los fenómenos hidrodinámicos en escolleras con aplicaciones a presas de materiales sueltos

  RJ Hernández, E Oñate, SR Idelsohn, MA Celigüeta, R Rossi, J Marti, ...

  Universitat Politècnica de Catalunya. Escola Tècnica Superior d'Enginyers de …, 2010

• Modeling of surface wear by the particle finite element method: application to tunneling processes

  JM Carbonell Puigbó, B Suárez Arroyo, E Oñate Ibáñez de Navarra

  Computational Plasticity X-Fundamentals and Applications, 1-4, 2009