Macro Finite Element Research Articles

Structural Static Evaluation of Historic Stone Building (Case Study: Zahdeh Building in Hebron Old City)

The historical buildings are of great importance, as they represent the architectural heritage and the image of history.Accurate structural analysis of stone buildings is a real challenge, as the mechanical properties of stone and mortarunits are different and unavailable. The aim of the research is assessment historical stone buildings. An experimentalstudy was conducted to determine the mechanical properties of stone building materials and to modelling validation.A numerical modelling was carried out through a non-linear static analysis based on a macro finite element model,using ANSYS. The result obtained of the model of Zahdeh building is that building can bear its loads in its currentcondition, and it also has the ability to bear loads equivalent to two floors. The proposed methods, are suitable forstructural assessment process and can be applied to similar building models to preserve, both architectural heritageand historic buildings.

Fracture behavior of composite piezoelectric intelligent structures formed by pasting MFC based on serial multi-scale method

The composite piezoelectric intelligent structures formed by combining piezoelectric materials with composite materials can achieve state perception and deformation control of the structure. Based on the molecular dynamics method, the continuum finite element method and the cohesive force model, the serial multi-scale research on the bonded composite piezoelectric intelligent structure was carried out from the micro, meso and macro scales. Molecular models of adhesive, macro fiber composite (MFC) surface and composite surface were established. The effects of temperature and pressure on the surface interaction energy of adhesive/MFC and adhesive/composite materials were analyzed. The traction-separation (T-S) relationship of cohesive region was obtained by virtual stretching method. Combined with the microscopic observation of the mesoscopic adhesive layer, the representative volume element (RVE) model of the mesoscopic adhesive layer considering the bubble defect was established, and the cohesive relationship curve of the adhesive layer was obtained. A double cantilever beam (DCB) macro finite element model was established to simulate the crack propagation behavior of the adhesive layer, and compared with the experimental results.

Micro–macro finite element modeling method for rub response in abradable coating materials

Micro–macro finite element modeling method for rub response in abradable coating materials

Correlation between Surface Integrity and Low Cycle Fatigue Life of Machined Inconel 718

This work aims to improve the surface integrity and LCF life of machined Inconel 718. The correlation between the LCF life of Inconel 718 and various states of machined surface integrity is explored. In this paper, the surface integrity of Inconel 718 specimens is enhanced by low-plasticity burnishing (LPB). The LCF life of specimens with different surface integrity is predicted using a micro–macro finite element method (FEM). Firstly, the LCF specimens with different surface integrity are machined by turning (turned specimen), polishing (matrix specimen), and LPB process (LPBed specimen). Secondly, the LCF experiment is carried out to reveal the effect of surface integrity on LCF life. Finally, the LCF micro–macro FEM model is proposed to predict the LCF of machined Inconel 718 specimens. The representative volume element (RVE) model is established based on the measured surface integrity and microstructure of Inconel 718 specimens. The effect of surface integrity on LCF life is transformed to equivalent load. The micro–macro FEM model combined with Tanaka–Mura dislocation crack initiation theory and extended finite element method (XFEM) is applied to predict the LCF life of the machined specimens. The study results show that the LCF life of LPBed specimens can be improved by 90.5% and 36.1% compared with that of turned specimens and polished matrix specimens, respectively. The errors between FEM prediction results and experimental results are 13.1%, 9.2%, and 12.2%, respectively. The proposed micro–macro FEM model could be utilized to predict the LCF life of Inconel 718 with different surface integrities, and to apply the LCF life prediction further in industry.

Multi-objective optimization-based model calibration of masonry bridges

Multi-objective optimization-based model calibration can be an intermediate solution between the computationally expensive probabilistic approaches and the single-objective optimization strategies that do not allow uncertainty quantification of the obtained solutions. This work addresses the multi-objective model calibration of two historic stone arch bridges using high-fidelity computational FE models. To implement the methodology, a five-step approach is proposed: experimental characterization through non-destructive testing techniques, non-parametric as-built geometric modeling, macro-finite element modeling, sensitivity analysis, and multi-objective optimization. The preferred solution among the Pareto front solutions is selected based on two different classical criteria, and the set of optimal solutions is further statistically analyzed to assess the validity of the identification process. The results show an average frequency error of 0.97 % and 0.70 % and an average MAC of 0.97 and 0.96 for each case study, respectively, thus highlighting the adequacy of the proposed methodology.

Accelerated offline setup of homogenized microscopic model for multi‐scale analyses using neural network with knowledge transfer

AbstractThe FE computational homogenization method is a predictive multi‐scale method without the need for constitutive assumptions and/or potential function postulates at the macro engineering scale. Instead, the effective micro‐structural responses are extracted directly from a representative volume element (RVE) underlying each macro point. However, the FE method is still computationally too expensive for most practical uses, since the micro‐macro FE coupling is done at each loading step/iteration for the entire domain. To this end, the machine learning method has been utilized in the literature for the offline training of a surrogate model to predict the RVE homogenized response for general loading conditions. In this contribution, the neural network (NN) is incorporated into the macro finite element framework in a non‐intrusive manner. This is termed as the FE‐NN framework, in analogy to the FE method. In general, online simulations in the FE‐NN method is very efficient, with predictions matching closely to those obtained from reference direct numerical simulations (DNS). A bottleneck with the FE‐NN framework, however, is the high computational cost associated with the data generation for offline NN model setup. In this paper, focusing on the FE‐NN multi‐scale framework for non‐linear elastic deformation of heterogeneous materials, a sequential training strategy with knowledge transfer is proposed, to enable an efficient offline microscopic NN model setup. For a given target RVE, we first consider a simplified source RVE, where data can be generated rapidly, for the NN pre‐training of surrogate model. The pre‐trained network parameters are next downloaded to initialize the target NN surrogate model, followed by a fine‐tuning training process, using only a small dataset generated by the computationally expensive high‐fidelity RVE. The efficiency of the proposed sequential learning method over the conventional NN training, as well as, its excellent predictive capability for multi‐scale analyses, are demonstrated for a multi‐phase composite material. The proposed FE‐NN‐KT approach can be implemented easily without complicated pre‐processing procedures, since the data generation only involves the standard extraction of effective responses from RVEs, together with a standard NN architecture.

Plastic Deformation Mechanism of High Strength and Toughness ZK61 Magnesium Alloy Plate by Multipass Horizontal Continuous Rolling.

ZK61 magnesium-alloy plate with high tensile strength and elongation is obtained by combined multipass symmetric hot rolling and asymmetric warm rolling. Deformation history considering varying strain rate obtained from the macro-finite element analysis of the selected passes are introduced into the viscoplastic self-consistent model (VPSC) as initial boundary conditions for macro- multiscale and micro-multiscale coupling analysis. VPSC simulation results show that in the initial stage of rolling deformation, the basal <a> slip is the dominated deformation mode, supplemented by prismatic <a> slip and pyramidal <c+a> slip. With increased rolling strain, the pyramidal <c+a> slip presents competitive relationship with basal <a> slip, and the activation amount of {101-1} compression twins is limited. During asymmetric rolling, the basal <a> slip is dominant, followed by the pyramidal <c+a> slip. Experimental results show that the basal texture is gradually strengthened after symmetric rolling, and grain size is refined due to the activation and recrystallization of twins. Asymmetric rolling makes the basal texture deflect 10° to the rolling direction and further refine the grain size. With the ongoing of symmetric rolling, the mechanical anisotropy of the plate weakens, and the yield strength, tensile strength, and plasticity of the material improves. In particular, after asymmetric rolling, the tensile strength in the RD and TD directions of the plate reaches 391.2 MPa and 398.9 MPa, whereas the elongation reaches 19.8% and 25.5%.

3D structure-soil-structure interaction in an arbitrary layered half-space

The aim of the study is to evaluate the 3D dynamic response of a finite geological region containing two structures and rested on a semi-infinite elastic layered half-space with a dynamic source radiating transient waves. The hybrid modelling approach is applied. It is based on the decomposition of the whole domain under consideration into two sub-regions: a finite-sized near-field elastic isotropic zone with two containment structures and the open semi-infinite far-field layered region. The far-field zone is a semi-infinite elastic isotropic arbitrary layered medium where the near-field finite geological region is located on. The 3D hybrid computational tool is based on the boundary element method (BEM) for the far-field layered zone and the finite element method (FEM) for the finite near-field domain. The model for the semi-infinite layered zone is further extended by the incorporation of a new condensation algorithm which makes it possible to handle 3D wave propagation through arbitrary layered half-space. The condensation algorithm is developed to avoid high computational memory cost while retaining the compatibility with the hybrid FEM-hosted procedure which facilitates the useful solution for the practical three-dimensional engineering problems. The BEM model of the dynamically active far-field zone is inserted as a macro-finite element (MFE) in the FEM commercial program ABAQUS. The accuracy and convergence study of the hybrid numerical scheme is presented. Numerical simulations convincingly illustrate that the dynamic response of structure-soil-structure system depends on different key factors and their mutual interplay. These factors are arbitrary layering of the far-field geological zone, the characteristics of the dynamic source, the site effects phenomena, the structure-soil-structure dynamic interaction, the type and geometrical disposition of foundations and structures and the 3D features of the dynamic motion.

Structural performance of novel aluminium alloy gusset joints for connecting four I-section beam members

This paper presents the seismic behaviour of an aluminium alloy grid shell structure with due consideration of the rotation performance of its two novel gusset joints. The two novel aluminium alloy gusset joints were designed for connecting cross-arranged I-section beam members by stainless steel swage-locking pins and stainless steel bolts. One full-scale gusset joint was tested under monotonic loading, with the failure mode, load-displacement response and stiffness classification fully reported. The solid-based refined finite element (FE) model of the joint was developed by using Abaqus program and validated against test results. Based on the validated FE model, parametric studies were performed to investigate the effect of key parameters, including the shape of gusset plates, the preload of fasteners, angle shear connector configurations, and the number and layout of pins, on the structural performance of the novel gusset joints. The failure modes, moment-rotation curves, initial stiffness and ultimate design resistance were identified and compared in groups for joint design optimization. The cyclic behaviour of two optimal gusset joints was numerically analysed, and then incorporated in the fibre-based macro FE model of the aluminium alloy grid shell structure developed by using OpenSees program. The seismic performance of the grid shell structure subjected to different earthquake hazard levels, including the displacement, joint rotation, beam stress and shear base responses, was comprehensively evaluated. Sound earthquake resistance of the aluminium alloy grid shell structure is demonstrated, with safety and reliability of the novel gusset joints used in it.

Evaluation of seismic performance and effective lateral stiffness for corrugated steel-plate concrete composite structural walls repaired using bottom corner dampers

The plastic hinge regions of conventional structural walls often experience severe damage after earthquakes. In this study, a new repair method is proposed for corrugated steel-plate concrete composite structural walls based on corner failure. The proposed method involves installing a tension–compression dampers at the damage corners. The seismic performance of the retrofitted composite structural walls was evaluated by quasi-static test. The results demonstrated that the retrofitted walls had full hysteresis loops and large lateral displacement. The damage of retrofitted walls was primarily concentrated at the corner dampers. And the bottom corner dampers can be easily replaced after earthquakes. However, there was a substantial loss in the effective lateral stiffness of the retrofitted walls. Macro finite element models were then implemented to investigate the effective lateral stiffness of the retrofit walls using OpenSees. Lastly, an effective lateral stiffness equation for retrofit walls was suggested using a parametric regression analysis.

A Multi-Scale Submodel Method for Fatigue Analysis of Braided Composite Structures.

A multi-scale fatigue analysis method for braided ceramic matrix composites (CMCs) based on sub-models is developed in this paper. The finite element shape function is used as the interpolation function for transferring the displacement information between the macro-scale and meso-scale models. The fatigue failure criterion based on the shear lag theory is used to implement the coupling calculation of the meso-scale and micro-scale. Combining the meso-scale cell model and the fatigue failure criterion based on the shear lag theory, the fatigue life of 2D SiC/SiC is analyzed. The analysis results are in good agreement with the experimental results, which proves the accuracy of the meso-scale cell model and the fatigue life calculation method. A multi-scale sub-model fatigue analysis method is used to study the fatigue damage of 2D SiC/SiC stiffened plates under random tension–tension loads. The influence of the sub-models at different positions in the macro-model element on the analysis results was analyzed. The results shows that the fatigue analysis method proposed in this paper takes into account the damage condition of the meso-structured of composite material, and at the same time has high calculation efficiency, and has low requirements for modeling of the macro finite element model, which can be better applied to the fatigue analysis of CMCs structure.

Effects of infill walls on load resistance of multi-story RC frames to mitigate progressive collapse

To study the effects of infill wall on progressive collapse resistance of reinforced concrete (RC) frames with slabs, a macro finite element (FE) model was built using general purpose software OpenSees. The FE model was validated by existing test results. Then, the model was subsequently used to predict the progressive collapse potential of eight-story RC frame including slabs and infill walls. The numerical studies demonstrated that the inclusion of the slabs and infill walls could increase the ultimate load and initial stiffness by 70% and 169%, respectively, compared with the bare frame. The infill walls not only changed the load resisting path but also effectively improved the load redistribution ability of the frame. To evaluate the reliability of using a two-story sub-structure to investigate the progressive collapse behavior of a multi-story building, the resistance of each story of a multi-story building in case of column missing is compared. It was found that the resistance of each story was similar, except the first story. Finally, a series of parameter studies were carried out to quantify the effects of opening ratio, thickness and compressive strength of the infill walls on the progressive collapse performance of RC frame.

Methodology for Developing a Macro Finite Element Model of Lithium-Ion Pouch Cells for Predicting Mechanical Behaviour under Multiple Loading Conditions

To assist in light weighting of electric vehicles by improving the volumetric and gravimetric energy density and the structural performance of the battery pack, a modelling methodology based on a macro finite element model of a pouch cell has been developed. This model treats the core cell structure as a homogeneous orthotropic honeycomb block with the pouch material being defined as an orthotropic fabric with compressive stress elimination. The model considers five compression and bending load cases simultaneously and allows a level of element discretisation that is computationally efficient and appropriate for inclusion in full vehicle and sub-system simulations. The methodology is scalable in that it can be applied to a range of chemistries, external geometries and internal cell constructions. When considering stacks of cells, the model is predictive for both lateral compression and three-point bend, but further work is required to improve the confined compression response.

3D Finite Element Model on Drilling of CFRP with Numerical Optimization and Experimental Validation.

When drilling Carbon Fibre-Reinforced Plastic (CFRP) materials, achieving acceptable hole quality is challenging while balancing productivity and tool wear. Numerical models are important tools for the optimization of drilling CFRP materials in terms of material removal rate and hole quality. In this research, a macro-Finite Element (FE) model was developed to accurately predict the effect of drill tip geometry on hole entry and exit quality. The macro-mechanical material model was developed treating the Fiber-Reinforced Plastic (FRP) as an Equivalent Homogeneous Material (EHM). To reduce computational time, a numerical analysis was performed to investigate the influence of mass scaling, bulk viscosity, friction, strain rate strengthening, and cohesive surface modelling. A consideration must be made to minimize the dynamic effects in the FE prediction. The experimental work was carried out to investigate the effect of drill tip geometry on drilling forces and hole quality and to validate the FE results. The geometry of the drills used were either double-point angle or a “candle-stick” profile. The 3D drilling model accurately predicts the thrust force and hole quality generated by the two different drills. The results highlight the improvement in predicted results with the inclusion of cohesive surface modelling. The force signature profiles between the simulated and experimental results were similar. Furthermore, the difference between the predicted thrust force and those measured were less than 9%. When drilling with a double-angle drill tip, the inter-ply damage was reduced. This trend was observed in FE prediction.

Nonlinear dynamic simulation of cable based structures interacting with sliding objects using the concept of macro element

This paper presents the formulation of a finite element enclosing a specific internal mechanical equilibrium in order to model cable-based structures in dynamics conditions. It is based on the concept of macro finite element which allows embedding complex mechanical systems solved inside the element boundaries. A significant advantage is to allow an easy implementation within classical commercial codes. The proposed macro finite element describes a cable interacting with a sliding object assimilated to a punctual mass where friction can be accounted for. The dynamic response is described by a model developed within the framework of the DEM (Discrete Element Method) where geometrical nonlinearity (large displacements) is considered. A model combining the proposed macro finite element and a classical linear truss finite element is presented in order to validate its implementation. Finally, illustrative examples are presented. First, a cable yarning system is considered. The effect of friction and of the bending stiffness of the posts on the overall kinematics and force within the system are explored. Then the vulnerability of a cable-stayed bridge to earthquake is explored accounting for guy ropes failure.

Crystal Plasticity Finite Element Simulation of Aluminium Deformation

Crystal plasticity deformation of aluminium plays an important role on the investigation of macro deformation. In this paper, to discuss the effect ot crystal plasticity on the aluminium material behavior, crystal plasticity theory and macro finite element was combined together. The basic theory of crystal plasticity and finite element was introduce and the simulation result of aluminium was given. The stress and strain distribution was discussed and the efficient of the method was shown. It is shown that the orientation of the material and other micro character of the materials all influence the plasticity behavior of the material greatly.

Behavior and design of reinforced concrete frames retrofitted with steel bracing against progressive collapse

SummarySteel bracing is able to improve progressive collapse resistance of reinforced concrete (RC) frames, but the bracing design is typically based on seismic retrofitting or lateral stability. There is no approach for design of steel bracing against progressive collapse. To this end, a retrofitting approach with steel braces is proposed based on analysis of macro finite element (FE) models with fiber beam elements. The FE models were initially validated through the experimental results of a braced frame and then used to investigate the effects of pertinent parameters on the progressive collapse resistance of planar frames. The results suggest the braces should be placed at the top story. Thereafter, macro FE models are built to investigate the dynamic responses of the three‐dimensional prototype RC frames under different column removal scenarios (CRS) and show the necessity of retrofitting. Accordingly, the design approach of steel bracing is proposed with incremental dynamic analysis (IDA) and assuming independent contribution of braces and frames to resistance. Finally, the fragility analysis of the frames under a corner‐penultimate‐exterior CRS is conducted through IDA and Monte Carlo simulation, and the results confirm the validity of the proposed design approach for retrofitting RC frames.

Hybrid modelling of multi-layered geological structure under seismic excitation

This paper deals with seismic response evaluation of a finite multilayered geological structure with non-parallel boundaries rested on semi-infinite elastic half-plane subjected to transient seismic wave. The hybrid modelling approach is applied. It is based on the decomposition of the whole domain under consideration into two subregions: a finite-sized near-field zone and the open semi-infinite far-field region. The near-field range is presented by a finite geological profile, which is heterogeneous due to non-parallel layering. The far-field region is semi-infinite elastic isotropic homogeneous medium where the finite layered structure is located. An efficient 2D hybrid computational tool based on the boundary element method (BEM) for the far-field zone and the finite element method (FEM) for the finite layered domain is developed and verified in frequency domain. The BEM model of the seismically active far-field zone is inserted as a macro-finite element (MFE) in the FEM commercial program ANSYS. The hybrid model is of the FEM hosted type, where the boundary element domain (BED) is converted into macro-finite element, the nodal forces along the interface between two zones are expressed through the BED nodal tractions and the entire BEM formulation is converted to FEM-like approach. This hybrid model is applied for modelling of a real geological profile of the main wall of the “Liulyakovitsa” tailing pond, near Panagyurishte town, Bulgaria. Simulation results are given in the form of free surface synthetic seismograms stemming from the real seismic signals recorded at bedrock so as to establish the tailing pond’s seismic response.

Experimental and macro finite element modeling studies on conformability behavior of woven nylon 66 composite reinforcement

In this study, 3D hemispherical forming experiments are conducted to analyze the conformability behavior of nylon 66 plain woven reinforcements with different weft densities. To make insight into the forming process, a macro finite element model is also proposed for 3D forming of a specific woven reinforcement by using the defined ‘Fabric’ material. The results show that the proposed FEM modelling is highly correlated with experimental findings in terms of forming energy values with small and insignificant errors values, which confirm well model validity. It shows that the nylon 66 composite woven reinforcement with a lower weft density exhibits a lower forming energy (toughness) and hence a higher conformability over a hemispherical surface. On the other hand, modeling outputs clearly indicate that more wrinkling intensity appear for woven reinforcement with a higher weft density.

Numerical modeling of reinforced masonry walls under lateral loading at the component level response as opposed to system level response

Many experimental and analytical investigations were carried out on fully-grouted reinforced masonry shear walls types (rectangular, flanged or end-confined) to investigate their behavior under lateral loads. These studies mainly focused on evaluating the seismic response parameters for reinforced masonry shear walls (RMSW) such as ductility capacity, energy dissipation, stiffness degradation and strength. Yet, most of the research was conducted on studying each wall individually (component level response) and quite few investigations were carried out considering the system level response when different wall types are combined in a single building/system. In this paper, a simple numerical macro finite element model for walls is verified and used to simulate the in-plane response of a structure composed of ten RMSW having different ductility capacities but designed to have the same ultimate strength. The model was initially verified against available experimental data in the literature, then a parametric study was introduced to represent the effect of reinforcement ratio and axial compression on wall behavior prior to modeling structures composed of several walls. The current investigation intended to introduce how the structure ductility is affected when walls, having different ductility capacity, are interacting within one lateral load resisting system in the structure. Three methods were proposed to measure the yield displacement of the entire system to determine the value of displacement ductility for the structure and compared it to that of the individual walls within the system. Finally, a set of fragility curves were represented to illustrate the enhancement of seismic performance of masonry structures through adding end confined and flanged walls inside the structure. The results of this study showed that the displacement ductility of a structure could be significantly improved when flanged and end-confined boundary walls are included in the system as opposed to that constructed using only rectangular walls. The effect of adding end-confined masonry walls in improving structure displacement ductility is found to be more significant compared to adding flanged ones. Using fragility curves, the effect of end confined and flanged wall in the enhancement of the structure performance and delaying the damage state appears clearly in third and fourth damage states but did not have any contribution in enhancement of the first and second damage states.