Macro-scale Finite Element Analysis Research Articles

Multiscale modeling of lignocellulosic foams under compression

Biodegradable lignocellulosic foams have the potential to replace foams produced from petroleum sources that have environmental issues. These lignocellulosic foams contain randomly oriented fibers or particles bonded by cellulose nanofibrils (CNFs). In this work, effort was focused on the production of lignocellulosic foams using wood flour or thermomechanical pulp (TMP) fibers bound with CNFs. Multiscale modeling is proposed to predict the mechanical properties. Microwave drying was employed to produce the low-density porous foam structures. Compression tests conducted on the foams exhibited elastic–plastic responses. Finite element analysis (FEA), a numerical method to determine the elastic–plastic mechanical properties was utilized. The Young’s modulus of lignocellulosic foams calculated from fiber-scale modeling methods exhibits strong agreement with experimental results for strains up to 10%. Meso-scale modeling indicates an FEA approach to determine Young’s modulus considering cellulose as matrix and porosity inclusions to create different porous structures. Macro-scale FEA was performed using crushable foam material model to determine the elastic–plastic behavior of the foams for strains up to 20% reveals a solid agreement with the experimental results. Modeling results at different scales promise a robust numerical framework to predict mechanical behavior of these novel lignocellulosic foams.

A hybrid approach to predict vertical temperature gradient of ballastless track caused by solar radiation

• A hybrid approach combining the field test and FEM with ML technique is proposed. • Six ML techniques are used to predict spatial and temporal temperature gradient. • The key features of hybrid approach to predict temperature gradient are analyzed. • The proposed hybrid approach has excellent performance and transferability. The spatial and temporal temperature evolution of ballastless track is difficult to be determined, due to its complex thermal conditions. Accurate acquisition of vertical temperature gradient (VTG) of ballastless track is of great significance for its design, maintenance and damage control. However, few researchers have studied the predictive approach of spatial and temporal VTG evolution. In this study, a hybrid approach that combines experimental and finite element analysis with machine learning (ML) technique is proposed to automatically predict VTG of ballastless track induced by solar radiation. Six different ML techniques, i.e., multiple linear regression (MLR), polynomial regression (PR), support vector regression (SVR), random forest (RF), extreme gradient boosting (XGBOOST), and categorical boosting (CATBOOST) with fine-tuned hyperparameters are trained and validated by a dataset of 1000 cases retrieved from macroscale finite element analysis. The maximum and minimum air temperatures, latitude, average wind speed, etc., considering spatial and temporal environment actions are used as input variables to estimate the VTG of ballastless track. The results indicate that the CATBOOST-based hybrid approach demonstrates the most appropriate method for determining VTG of ballastless track among the above ML techniques. The proposed feasible and efficient hybrid approach is expected to be widely used for the identification of temperature evolution in structural engineering.

Elucidating the Interfacial Bonding Behavior of Over-Molded Hybrid Fiber Reinforced Polymer Composites: Experiment and Multiscale Numerical Simulation.

This paper implements molecular dynamics (MD) simulation using reactive force field (ReaxFF) to evaluate the atomistic origin of the interfacial behavior in the overmolded hybrid unidirectional continuous carbon fiber low-melt PAEK (CFR-LMPAEK)-short carbon fiber reinforced PEEK (SFR-PEEK) polymer composites. From the MD simulation, it was observed that the interfacial properties improve with increasing maximum processing temperature and injection pressure although such an improving trajectory gets saturated beyond specific limits. The interfacial strength and fracture response of the hybrid polymer system at the interface are also evaluated. The mechanical responses obtained from MD simulation are used as adhesive properties in the macroscale finite element analysis (FEA)-based single lap joint (SLJ) model where the interfacial behavior between the adherends (CFR-LMPAEK and SFR-PEEK) is implemented using cohesive zone model (CZM). The simulated FE results show a good correlation with the SLJ experimental data. Thus, by linking the interfacial properties at the molecular scale to the performance of the interfacial bond at the macroscale, the comprehensive approach presented here opens up various efficient avenues toward atomistically engineered performance tuning in hybrid overmolded fiber-reinforced polymer composites to meet desired large-scale performance needs.

Meso–Macro Coupled Analysis of Pressure-Dependent Friction of Rubber

To deepen the understanding of the frictional sliding phenomena of rough surfaces, advances are required in numerical analysis methods at various spatial scales. In this study, to examine the microscopic behavior of a rough asperity contact corresponding to a bulk contact on the macroscopic scale, a loop-type meso–macro coupled analysis scheme is proposed. A mesoscale numerical model and a macroscopic friction model are required for the proposed multi-scale analysis. A friction model was adopted based on the multipoint contact model for the mesoscale model, and the pressure- and state-dependent elastoplastic analogy friction model was used for the macroscale model. In the proposed meso¬¬–macro coupled analysis, the parameter set for the elastoplastic analogy friction model was first identified via a numerical friction test using the mesoscale multipoint contact model assuming various conditions. Then, a macroscale finite element analysis incorporating the elastoplastic analogy friction model was performed for the macroscopic analysis of contact between a rough rubber hemisphere and a smooth plate. Here, the information from the mesoscale rough surfaces were reflected in the macroscale finite element analysis. Finally, a mesoscale localization analysis was performed in which the macroscopic histories of several typical locations were obtained by finite element analysis and used as boundary conditions for the mesoscale model. It is suggested that the microscopic sliding process of rough surfaces represented by the finite element analysis can be examined using the proposed method.

Digital material representation concept applied to investigation of local inhomogeneities during manufacturing of magnesium components for automotive applications

AbstractMulti-scale computer aided design of manufacturing processes of a magnesium bracket for the automotive industry is the main goal of the present paper. Tensile tests at various deformation conditions (temperatures, strain rates etc.) were performed to obtain flow stress data necessary for the macro-scale finite element analysis. The digital material representation concept was used to create a micro-scale model and to evaluate the influence of local microstructural features in the form of twins on material behaviour. An algorithm based on the cellular automata method capable of replicating microstructural morphology with twins was proposed to provide the digital material representation model. The bracket made of AZ31 magnesium alloy was formed at an elevated temperature of 200 °C. Description of the study as well as results obtained at two length scales are presented in the paper.

Two-Scale Finite Element Analysis of Equaled Channeling Angular Extrusion of Polycrystalline Metal

A two-scale finite element analysis method based on a micro-macro decoupled scheme is applied to an equaled channeling angular extrusion. At first, the macro-scale finite element analysis for one process of an equaled channeling angular extrusion is carried out with a non-liner explicit method to handle the contact and friction between die and bullet. Using the deformation history at a macroscopic material point in this process, the micro-scale finite element analysis is conducted for the multiple processes with a single crystal plasticity and a nonlinear implicit method. As the results, the deformation process of the polycrystalline aggregate during the equaled channeling angular extrusion is numerically reproduced.

Multiscale finite element modeling of failure process of composite laminates

A multiscale nonlinear finite element modeling technique is developed in this paper to predict the progressive failure process for composite laminates. A micromechanical elastic–plastic bridging constitutive model, which considers the nonlinear material properties of the constituent fiber and matrix materials and their interaction and the damage and failure in fibrous composites at the fiber and matrix level, is proposed to represent the material behavior of fiber-reinforced composite laminates. The micromechanics constitutive model is employed in the macroscale finite element analysis of structural behavior especially progressive failure process of the fiber-reinforced composites based on a 4-node 24-DOF shear-locking free rectangular composite plate element.

Coupled mesoscopic constitutive modelling and finite element simulation for plastic flow and microstructure of two-phase alloys

A mesoscopic dislocation-based model was coupled with macro-scale finite element analysis for concurrent study of local plastic flow and microstructure of two-phase alloys during thermomechanical deformation. The model was implemented in the ABAQUS code to simulate the thermomechanical processing of a Ti–6Al–4V alloy in the (α + β) phase field, with consideration of the effects of local dislocation density variation, deformation heating and phase volume fraction. The simulation show that the intergranular interaction results in non-uniform distribution of dislocations within each grain, particularly in the initial stages of deformation. Phase boundaries pose stronger influence on deformation than grain boundaries. The onset of shear localization was strongly influenced by the strain rate sensitivity parameter, deformation heating, phase volume fraction, and the die/sample friction coefficient. Both deformation heating and phase transformation in the shear-localized region contributes to the flow-stress variation during processing. The phase volume fraction largely affects the microstructure, distribution of the equivalent stress, but not the equivalent strain.