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.

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.

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.

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.

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.

Proper orthogonal decomposition based seismic source wavefield reconstruction for finite element reverse time migration

The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The boundary value method(BVM),based on the finite difference method(FDM),can be used to reconstruct the source wavefield in the reverse time propagation in the same way as the receiver wavefield,which can reduce the storage burden of the RTM data.Considering that the FDM cannot well handle models with discontinuous material properties and rough interfaces,we develop a source wavefield reconstruction strategy based on the finite element method(FEM),using proper orthogonal decomposition(POD)to enhance computational efficiency.In this method,we divide the whole time period into several segments,and construct the POD basis functions to get a reduced order model(ROM)for the source wavefield reconstruction in each segment.We show the corresponding quantitative analysis of the storage requirement of the POD-FEM.Numerical tests on the homogeneous model show the effectiveness of the proposed method,while the layered model and part of the Marmousi model tests indicate that the POD-FEM can keep an excellent balance between computational efficiency and memory usage compared with the full-stored method(FSM)and the BVM,and can be effectively applied in imaging.

Torsional Response Analysis of Flexible Pipe Based on Theory and Finite Element Method

As key components connecting offshore floating production platforms and subsea imports, offshore flexible pipes play significant roles in oil, natural gas, and water injection. It is found that torsional failure is one of the failure modes of flexible pipes during transportation and laying. In this paper, a theoretical model(TM) of a flexible pipe section mechanics is established, in which the carcass layer and the pressure armor layer are equivalent to the orthogonal anisotropic layers due to its complex cross-section structure. The calculation results of the TM are consistent with those of a finite element model(FEM), which can accurately describe the torsional response of the flexible pipe.Subsequently, the TM and FEM are used to discuss the influence of boundary conditions on the torsional response.The structure of the flexible pipe is stable when twisted counterclockwise. However, limiting the top axial displacement can improve the axial and radial instability of the tensile armor layer when twisted clockwise. Finally, it is recommended that the flexible pipe can be kept under top fixation during service or installation to avoid torsional failure.

A rigid-flexible coupling finite element model of coupler for analyzing train instability behavior during collision

Rail vehicles generate huge longitudinal impact loads in collisions.If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body,the risk of car body structure damage and train derailment will increase.Herein,a four-stage rigid-flexible coupling finite element model of the coupler is established considering the coupler buckling load.The influence of the coupler buckling load on the train longitudinal-vertical-hori-zontal buckling behavior was studied,and the mechanism of the train horizontal buckling instability in train collisions was revealed.Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically.The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision.If the strength of the two sides of the car body structure in the lateral direction is asymmetrical,the deformation on the weaker side will be larger,and the end of the car body will begin to deflect under the action of the coupler force,which in turn causes the train to undergo sawtooth buckling.

Behaviour of non-ballast pre-stressed and precast track structures in high speed railway based on multiscale finite element model

In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditional FEM of slab non-ballast track structures was improved.The multiscale FEM of CRTSII type slab nonballast track structures was established based on the general finite element program ABAQUs.Then the comparative calculation was made between various FEMs,showing that the high solution precision,fast modelling speed and high solution efficiency could be obtained.Therefore,the multiscale FEM was suitable for the parametric study on mechanical behaviour of CRTSII type slab non-ballast track structures,and then the key influence factor and constructions could be optimized.

Constitutive modelling of fabric effect on sand liquefaction

Sand liquefaction under static and dynamic loading can cause failure of embankments,slopes,bridges and other important infrastructure.Sand liquefaction in the seabed can also cause submarine landslides and tsunamis.Fabric anisotropy related to the internal soil structure such as particle orientation,force network and void space is found to have profound influence on sand liquefaction.A constitutive model accounting for the effect of anisotropy on sand liquefaction is proposed.Evolution of fabric anisotropy during loading is considered according to the anisotropic critical state theory for sand.The model has been validated by extensive test results on Toyoura sand with different initial densities and stress states.The effect of sample preparation method on sand liquefaction is qualitatively analysed.The model has been used to investigate the response of a sand ground under earthquake loading.It is shown that sand with horizontal bedding plane has the highest resistance to liquefaction when the sand deposit is anisotropic,which is consistent with the centrifuge test results.The initial degree of fabric anisotropy has a more significant influence on the liquefaction resistance.Sand with more anisotropic fabric that can be caused by previous loading history or compaction methods has lower liquefaction resistance.

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.

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.