Finite element modelling of the geodynamic processes of the Central Andes subduction zone:A Reference Model

This paper presents preliminary results of three-dimensional thermomechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central Andes （16°S-26°S） up to a depth of 400 km, the bottom of the asthenosphere. For this purpose a simulation running over c. 50,000 years will be realized based on the geometry of a generic subduction zone and an elasto-viscoplastic Drucker-Prager rheology. The kinematic and thermal boundary conditions as well as the rheological parameters represent the current state of the study area. In future works the model will be refined using a systematic study of physical parameters in order to estimate the influence of the main parameters （e.g. viscosity, fault friction, velocity, shear heating） on the results of the reference model presented here. The reference model is kept as simple as possible to be able to estimate the influence of the parameters in future studies in the best possible way, whilst minimizing comnutational time.

Microstructure-based Finite Element Modelling and Characterisation of Bovine Trabecular Bone

The mechanical behaviour of trabecular bone is dependent on both the properties of individual trabeculae as well as their three-dimensional arrangement in space. In this study, nanoindentation was used to determine trabecular stiffness of bovine bone, both dehydrated and rehydrated. Values of 18.3 GPa and 14.3 GPa were obtained for dehydrated and rehydrated trabeculae respectively. These values were then used for finite element analysis where the mesh was generated directly from an X-ray microtomography dataset. The relationship between intrinsic tissue properties and apparent stiffness was explored. Moreover, the important role of collagen in bone micromechanics was demonstrated by complementing the study with Raman spectroscopy.

Rutting Resistance of Asphalt Pavement Mixes by Finite Element Modelling and Optimisation

Asphalt pavement rtting is a major safety concem and is one of the main distress modes of asphalt pavement.Research into asphalt pavement mixes that provide strong resistance for nutting is considered of great significance as it can help provide extended pavement life and significant cost savings in pavement maintenance and rehabilitation.The objectives of this study are to develop numernical models to investigate the ntting of asphalt concrete pavements and to find optimal design of asphalt pave-ment mix for nutting resistance.Three-dimensional Finite Element mod-els were first developed to simulate both the axial compression and wheel track testing in which a visco elastic-plastic material model was used to predict the ntting of the asphalt concrete pavements.A strain hardening creep model with the material parameters developed from experimental testing was employed to model the time-dependent characteristics of the asphalt concrete pavements.The results were validated against the pre-vious experimental wheel track test results of different pavement mixes.Finally,optimisation techniques using the Design Of Experiments method were applied to the simulation rutting results by varying creep parameters to identify their effects on rutting resistance in order to obtain an optimal asphalt pavements mixes.The results of this paper clearly demonstrate an efficient and effective experimental-numerical method and tool set towards optimal design for asphalt concrete pavements for rutting resis-tance.

Interaction between encapsulated microbubbles:A finite element modelling study

Theoretical studies on the multi-bubble interaction are crucial for the in-depth understanding of the mechanism behind the applications of ultrasound contrast agents （UCAs） in clinics. A two-dimensional （2D） axisymmetric finite element model （FEM） is developed here to investigate the bubble-bubble interactions for UCAs in a fluidic environment. The effect of the driving frequency and the bubble size on the bubble interaction tendency （viz., bubbles＇ attraction and repulsion）, as well as the influences of bubble shell mechanical parameters （viz., surface tension coefficient and viscosity coefficient） are discussed. Based on FEM simulations, the temporal evolution of the bubbles＇ radii, the bubble-bubble distance, and the distribution of the velocity field in the surrounding fluid are investigated in detail. The results suggest that for the interacting bubble-bubble couple, the overall translational tendency should be determined by the relationship between the driving frequency and their resonance frequencies. When the driving frequency falls between the resonance frequencies of two bubbles with different sizes, they will repel each other, otherwise they will attract each other. For constant acoustic driving parameters used in this paper, the changing rate of the bubble radius decreases as the viscosity coefficient increases, and increases first then decreases as the bubble shell surface tension coefficient increases, which means that the strength of bubble-bubble interaction could be adjusted by changing the bubble shell visco-elasticity coefficients. The current work should provide a powerful explanation for the accumulation observations in an experiment, and provide a fundamental theoretical support for the applications of UCAs in clinics.

Joint slip investigation based on finite element modelling verified by experimental results on wind turbine lattice towers

Slippage corresponds to the relative displacement of a bolted joint subjected to shear loads since the construction clearance between the bolt shank and the bolthole at assembly can cause joint slip. Deflections of towers with joint slippage effects is up to 1.9 times greater than the displacements obtained by linear analytical methods. In this study, 8 different types of joints are modelled and studied in the finite element program, and the results are verified by the experimental results which have been done in the laboratory. Moreover, several types of joints have been modelled and studied and load-deformation curves have also been presented. Finally, joint slip data for different types of angles, bolt diameter and bolt arrangements are generated. Thereupon, damping ratios （ζ） for different types of connections are reported. The study can be useful to help in designing of wind turbine towers with a higher level of accuracy and safety.

Biomechanics of human optic chiasmal compression: ex vivo experiment and finite element modelling

The mechanism of bitemporal hemianopia arising as a result of chiasmal compression is unknown.In this study,we combined an ex vivo experiment and finite element modelling(FEM)to investigate its potential mechanism.A cadaveric human optic chiasm was scanned using micro-CT before and after deformation by inflation of Foley catheter,to simulate tumour growth from beneath.The geometry of the same chiasm was reconstructed and simulated using finite element analysis.Chiasmal deformations were extracted from the simulation and compared with those observed during micro-CT scanning.In addition,nerve fibre models examining variation in local fibre distribution patterns of the chiasm were incorporated to investigate the strain(deformation)distributions of the chiasm at an axonal level.The FEM model matched the micro-CT scans well both qualitatively and quantitatively.Compression of the chiasm induced high strains in the paracentral portions of the chiasm where the crossing optic nerve fibres are located.At an axonal level,the magnitude of strains affecting crossed fibres were greater than those affecting uncrossed fibres.The high strains in the paracentral portions of the chiasm,combined with the differences in strain between crossed and uncrossed nerve fibres,are consistent with a biomechanical explanation for the pattern of visual field loss seen in chiasmal compression.

Finite element approach for free vibration and transient response of bi-directional functionally graded sandwich porous skew-plates with variable thickness subjected to blast load

At the first time,the finite element method was used to model and analyze the free vibration and transient response of non-uniform thickness bi-directional functionally graded sandwich porous(BFGSP)skew plates.The whole BFGSP skew-plates is placed on a variable visco-elastic foundation(VEF)in the hygro-thermal environment and subjected to the blast load.The BFGSP skew-plate thickness is permitted to vary non-linearly over both the length and width of the skew-plate,thereby faithfully representing the real behavior of the structure itself.The analysis is based on a four-node planar quadrilateral element with eight degrees of freedom per node,which is approximated using Lagrange Q_(4)shape function and C^(1)level non-conforming Hermite shape function based on refined higher-order shear deformation plate theory.The forced vibration parameters of the non-uniform thickness BFGSP skew-plate are fully determined using Hamilton's principle and the Newmark-βdirect integration technique.Accuracy of the calculation program is validated by comparing its numerical results with those from reputable sources.Furthermore,a thorough assessment is conducted to determine the impact of various parameters on the free and forced vibration responses of the non-uniform thickness BFGSP skew-plate.The findings of the paper may be used in the development of civil and military structures in situations that are prone to exceptional forces,such as explosions and impacts load.

In silico optimization of actuation performance in dielectric elastomercomposites via integrated finite element modeling and deep learning

Dielectric elastomers(DEs)require balanced electric actuation performance and mechanical integrity under applied voltages.Incorporating high dielectric particles as fillers provides extensive design space to optimize concentration,morphology,and distribution for improved actuation performance and material modulus.This study presents an integrated framework combining finite element modeling(FEM)and deep learning to optimize the microstructure of DE composites.FEM first calculates actuation performance and the effective modulus across varied filler combinations,with these data used to train a convolutional neural network(CNN).Integrating the CNN into a multi-objective genetic algorithm generates designs with enhanced actuation performance and material modulus compared to the conventional optimization approach based on FEM approach within the same time.This framework harnesses artificial intelligence to navigate vast design possibilities,enabling optimized microstructures for high-performance DE composites.

Dynamic finite element model updating using meta-model and genetic algorithm

Current dynamic finite element model updating methods are not efficient or restricted to the problem of local optima. To circumvent these, a novel updating method which integrates the meta-model and the genetic algorithm is proposed. Experimental design technique is used to determine the best sampling points for the estimation of polynomial coefficients given the order and the number of independent variables. Finite element analyses are performed to generate the sampling data. Regression analysis is then used to estimate the response surface model to approximate the functional relationship between response features and design parameters on the entire design space. In the fitness evaluation of the genetic algorithm, the response surface model is used to substitute the finite element model to output features with given design parameters for the computation of fitness for the individual. Finally, the global optima that corresponds to the updated design parameter is acquired after several generations of evolution. In the application example, finite element analysis and modal testing are performed on a real chassis model. The finite element model is updated using the proposed method. After updating, root-mean-square error of modal frequencies is smaller than 2%. Furthermore, prediction ability of the updated model is validated using the testing results of the modified structure. The root-mean-square error of the prediction errors is smaller than 2%.

Compression of finite element hybrid mesh

A method for encoding and compressing finite element models is proposed. Themodel may be various non-simple topological structures and contain any combinations of beams,triangular elements and quadrilateral elements. First the model is subdivided into simple meshesthat are orientable and manifold. Based on the Edgebreaker algorithm, 13 labelled pairs areintroduced for quadrilateral meshes and five other labelled pairs are introduced for triangles. Thenthe connectivity information of mixed triangle/quadrilateral meshes is coded in a direct manner.Two other bits are used to record the wireframe information. For the pure wireframe model, Taubin'smethod is extended to compress it. The compression algorithm is implemented and evaluated.Experiments with several models show that the method achieves excellent compression ratios.

Dynamic Characteristics of Inflated Torus Using Finite Element Analysis

In recent years, inflatable structures have been a subject of interest for space applications such as communication antenna, solar thermal propulsion and entry/landing systems. The inflatable structures characterized by high strength-to-mass ratios, minimal stowage volume, which makes them suitable for cost-effective large space structures. A typical example for the inflatable structure is the inflated torus which often used in order to provide structure support. In this study, our main focus is to understand the dynamic characteristics of an inflated torus in order to formulate an accurate mathematical model suitable for active vibration control applications. A commercial finite element package, ANSYS, is used to model the inflated torus. To verify the model the obtained frequencies and mode shapes are compared with the published results, which are derived using analytical approach, the verification shows a good agreement between the FEM and the analytical results. Based on the verified model, parametric study was investigated; the material thickness increase causes the natural frequencies decrease, while the increase of the inflation pressure simply results in stiffening the ring, which means that the natural frequency increased. The FEM analysis gives an easy and fast way for the vibration analysis of the structures compared with the complicated analytical solutions.

Mechanistic insights into homogeneous electrocatalytic reaction for energy storage using finite element simulation

The application of homogeneous electrocatalytic reactions in energy storage and conversion has driven surging interests of researchers in exploring the reaction mechanisms of molecular catalysts.In this paper,homogeneous electrocatalytic reaction between hydroxymethylferrocene(HMF)and L-cysteine is intensively investigated by cyclic voltammetry and square wave voltammetry for which,the secondorder rate constant(k_(ec))of the chemical reaction between HMF^(+)and L-cysteine is determined via a 1D homogeneous electrocatalytic reaction model based on finite element simulation.The corresponding k_(ec)(1.1(mol·m^(-3))^(-1)·s^(-1))is further verified by linear sweep voltammograms under the same model.Square wave voltammetry parameters including potential frequency(f),increment(Estep)and amplitude(ESW)have been comprehensively investigated in terms of the voltammetric waveform transition of homogeneous electrocatalytic reaction.Specifically,the effect of potential frequency and increment is in accordance with the potential scan rate in cyclic voltammetry and the increase of pulsed potential amplitude results in a conspicuous split oxidative peaks phenomenon.Moreover,the proposed methodology of k_(ec)prediction is examined by hydroxyethylferrocene(HEF)and L-cysteine.The present work facilitates the understanding of homogeneous electrocatalytic reaction for energy storage purpose,especially in terms of electrochemical kinetics extraction and flow battery design.

Finite element analysis of pressure on 2024 aluminum alloy created during restricting expansion-deformation heat-treatment

Metals heat-treated under high pressure can exhibit different properties. The heat-induced pressure on 2024 aluminum alloy during restricting expansion-deformation heat-treatment was calculated by using the ABAQUS finite element software, and the effects of the mould material properties, such as coefficient of thermal expansion （CTE）, elastic modulus and yield strength, on the pressure were discussed. The simulated results show that the relatively uniform heat-induced pressure, approximately 503 MPa at 500 ℃, appears on 2024 alloy when 42CrMo steel is as the mould material. The heat-induced pressure increases with decreasing the CTE and the increases of elastic modulus and yield strength of the mould material. The influences of the CTE and elastic modulus on the heat-induced pressure are more notable.

Numerical analysis of high‑speed railway slab tracks using calibrated and validated 3D time‑domain modelling

Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance frequency.In this paper,the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus.It is then compared to the performance of a ballasted track.First,slab and ballasted track models are developed to replicate the full-scale testing of track sections.Once the models are calibrated with the experimental results,the novel slab model is developed and compared against the calibrated slab track results.The slab and ballasted track models are then extended to create linear dynamic models,considering the track geodynamics,and simulating train passages at various speeds,for which the Ledsgard documented case was used to validate the models.Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil,considering the issues associated with critical speeds.Various train loading methods are discussed,and the most practical approach is retained and described.Moreover,correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards.It is found that considering the same ground condition,the slab track deflections are considerably smaller than those of the ballasted track at high speeds,while they show similar behaviour at low speeds.

Prediction of Cross-Tension Strength of Self-Piercing Riveted Joints Using Finite Element Simulation and XGBoost Algorithm

Self-piercing riveting(SPR)has been widely used in automobile industry,and the strength prediction of SPR joints always attracts the attention of researchers.In this work,a prediction method of the cross-tension strength of SPR joints was proposed on the basis of finite element(FE)simulation and extreme gradient boosting decision tree(XGBoost)algorithm.An FE model of SPR process was established to simulate the plastic deformations of rivet and substrate materials and verified in terms of cross-sectional dimensions of SPR joints.The residual mechanical field from SPR process simulation was imported into a 2D FE model for the cross-tension testing simulation of SPR joints,and cross-tension strengths from FE simulation show a good consistence with the experiment result.Based on the verified FE model,the mechanical properties and thickness of substrate materials were varied and then used for FE simulation to obtain cross-tension strengths of a number of SPR joints,which were used to train the regression model based on the XGBoost algorithm in order to achieve prediction for cross-tension strength of SPR joints.Results show that the cross-tension strengths of SPR steel/aluminum joints could be successfully predicted by the XGBoost regression model with a respective error less than 7.6%compared to experimental values.

Finite element modeling of pore-fluid flow in the Dachang ore district,Guangxi,China:Implications for hydrothermal mineralization

Convective heat transfer associated with the circulation of porefluid in porous rocks and fractures within the upper crust of the Earth is substantial when the temperature gradient is sufficiently high. In order to understand the process of Snpolymetallic mineralization in the Dachang ore district of Guangxi, a finite element method has been used in this study to simulate both pore-fluid flow and heat transfer in this district. On the basis of related geological, tectonic and geophysical constraints, a computational model was established. It enables a computational simulation and sensitivity analysis to be carried out for investigating ore-forming pore-fluid flow and other key factors that may affect hydrothermal ore genesis in the district. The related simulation results have indicated that： （1） permeable fault zones in the Dacbang ore district can serve as preferential pathways for pore-fluid flow on a regional-scale; and （2） the pore-fluid flow can affect the salinity distribution. This latter factor is part of the reason why Sn-polymetallic mineralization has taken place in this district.

Finite element modeling assumptions impact on seismic response demands of MRF-buildings

Recent seismic events have raised concerns over the safety and vulnerability of reinforced concrete moment resisting frame ＂RC-MRF＂ buildings. The seismic response of such buildings is greatly dependent on the computational tools used and the inherent assumptions in the modelling process. Thus, it is essential to investigate the sensitivity of the response demands to the corresponding modelling assumption. Many parameters and assumptions are justified to generate effective structural finite element（FE） models of buildings to simulate lateral behaviour and evaluate seismic design demands. As such, the present study focuses on the development of reliable FE models with various levels of refinement. The effects of the FE modelling assumptions on the seismic response demands on the design of buildings are investigated. the predictive ability of a FE model is tied to the accuracy of numerical analysis; a numerical analysis is performed for a series of symmetric buildings in active seismic zones. The results of the seismic response demands are presented in a comparative format to confirm drift and strength limits requirements. A proposed model is formulated based on a simplified modeling approach, where the most refined model is used to calibrate the simplified model.

Experimental Study and Finite Element Polycrystal Model Simulation of the Cold Rolling Textures in a Powder Metallurgy Processed Pure Aluminum Plate

Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared via PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural evolution at various stages of cold rolling. In FEPM simulation, the initial hot-extruded textures were taken into account as inputs. The results showed that typical β-fiber texture formed in pure PM aluminum with the cold rolling reduction increased till 80%, and there was not much change after excessive cold rolling deformation. Homogeneous slip is not the only deformation mode in PM processed pure aluminum plate at over 80% cold rolling reduction. The experimental results were qualitatively in good agreement with the simulated ones.

An ultrasound-guided percutaneous electrical nerve stimulation regimen devised using finite element modeling promotes functional recovery after median nerve transection

Percutaneous electrical nerve stimulation of an injured nerve can promote and accelerate peripheral nerve regeneration and improve function.When performing acupuncture and moxibustion,locating the injured nerve using ultrasound before percutaneous nerve stimulation can help prevent further injury to an already injured nerve.However,stimulation parameters have not been standardized.In this study,we constructed a multi-layer human forearm model using finite element modeling.Taking current density and activated function as optimization indicators,the optimal percutaneous nerve stimulation parameters were established.The optimal parameters were parallel placement located 3 cm apart with the injury site at the midpoint between the needles.To validate the efficacy of this regimen,we performed a randomized controlled trial in 23 patients with median nerve transection who underwent neurorrhaphy.Patients who received conventional rehabilitation combined with percutaneous electrical nerve stimulation experienced greater improvement in sensory function,motor function,and grip strength than those who received conventional rehabilitation combined with transcutaneous electrical nerve stimulation.These findings suggest that the percutaneous electrical nerve stimulation regimen established in this study can improve global median nerve function in patients with median nerve transection.

Determination of the Normal Contact Stiffness and Integration Time Step for the Finite Element Modeling of Bristle-Surface Interaction

In finite element modeling of impact,it is necessary to define appropriate values of the normal contact stiffness,Kn,and the Integration Time Step(ITS).Because impacts are usually of very short duration,very small ITSs are required.Moreover,the selection of a suitable value of Kn is a critical issue,as the impact behavior depends dramatically on this parameter.In this work,a number of experimental tests and finite element analyses have been performed in order to obtain an appropriate value of Kn for the interaction between a bristle of a gutter brush for road sweeping and a concrete surface.Furthermore,a suitable ITS is determined.The experiments consist of releasing a steel bristle that is placed vertically at a certain distance from a concrete surface and tracking the impact.Similarly,in the finite element analyses,a beam is modeled in free fall and impacting a surface;contact and target elements are attached to the beam and the surface,respectively.The results of the experiments and the modeling are integrated through the principle of conservation of energy,the principle of linear impulse and momentum,and Newton’s second law.The results demonstrate that,for the case studied,Kn and the impact time tend to be independent of the velocity just before impact and that Kn has a very large variation,as concrete is a composite material with a rough surface.Also,the ratio between the largest height of the bristle after impact and the initial height tends to be constant.