In this article,a high-order scheme,which is formulated by combining the quadratic finite element method in space with a second-order time discrete scheme,is developed for looking for the numerical solution of a two-d...In this article,a high-order scheme,which is formulated by combining the quadratic finite element method in space with a second-order time discrete scheme,is developed for looking for the numerical solution of a two-dimensional nonlinear time fractional thermal diffusion model.The time Caputo fractional derivative is approximated by using the L2-1formula,the first-order derivative and nonlinear term are discretized by some second-order approximation formulas,and the quadratic finite element is used to approximate the spatial direction.The error accuracy O(h3+t2)is obtained,which is verified by the numerical results.展开更多
This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens ...This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.展开更多
The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of...The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of roughly parallel anticlines.Geological observations predicted that averaged over last^1 Ma time scale,the shortening rates of these anticlines are about2.1–5.5 mm/a;However by averaged over about 10±2 kyr,their shortening rates reduce to merely about 1.25±0.5 mm/a.The slow shortening of the anticlines in the last^10±2 kyr is coarsely concurrent in time with the last global deglaciation.Here,we use a two-dimensional finite element model to explore crustal deformation across north piedmont of the Tianshan Mountains under various erosion-sedimentation conditions that are assumed to represent the climate-controlled surface process.Numerical experiments show that with a relatively weak erosion-sedimentation strength,the crustal shortening is accommodated mainly by north piedmont of the Tianshan Mountains,similar to the high shortening rate of anticlines averaged over the last^1Ma.By increasing erosion-sedimentation strength,the resultant crustal shortening is transformed gradually toward the Tianshan Mountains,resulting in the shortening rate in its north piedmont being decelerated to what is observed as averaged over the last^10±2 kyr.This result suggests that erosion and sedimentation could play an important role mechanically on strain localization across an intra-continent active tectonic belt.Hence,if the climate change around the last global deglaciation could be simply representative to the enhancement of surface erosion and sedimentation across the pre-existed Tianshan Mountains and its foreland,our models indicate that the observed shortening-rate variations averaged over^1 Ma and^10±2kyr time scales around north piedmont of the Tianshan Mountains should be resulted from climate changes.展开更多
Geared-rotor systems are critical components in mechanical applications,and their performance can be severely affected by faults,such as profile errors,wear,pitting,spalling,flaking,and cracks.Profile errors in gear t...Geared-rotor systems are critical components in mechanical applications,and their performance can be severely affected by faults,such as profile errors,wear,pitting,spalling,flaking,and cracks.Profile errors in gear teeth are inevitable in manufacturing and subsequently accumulate during operations.This work aims to predict the status of gear profile deviations based on gear dynamics response using the digital model of an experimental rig setup.The digital model comprises detailed CAD models and has been validated against the expected physical behavior using commercial finite element analysis software.The different profile deviations are then modeled using gear charts,and the dynamic response is captured through simulations.The various features are then obtained by signal processing,and various ML models are then evaluated to predict the fault/no-fault condition for the gear.The best performance is achieved by an artificial neural network with a prediction accuracy of 97.5%,which concludes a strong influence on the dynamics of the gear rotor system due to profile deviations.展开更多
In this study,an alternative modelling approach for absorbed hydrogen stress corrosion cracking(SCC)is proposed,with hydrogen-enhanced decohesion(HEDE)identified as the key failure mechanism.All analyses have been per...In this study,an alternative modelling approach for absorbed hydrogen stress corrosion cracking(SCC)is proposed,with hydrogen-enhanced decohesion(HEDE)identified as the key failure mechanism.All analyses have been performed by utilising only ABAQUS standard elements,COH2D4T and CPE4T,already available within the software and without the need to develop external subroutines.The study also tends to highlight the criticality of implementing a correct Traction Separation Law(TSL)curve to simulate the hydrogen diffusion within the specimen and using the concept of dynamic hydrogen penetration by continuously updating the hydrogen concentration boundary conditions as the crack propagates.In conclusion,this study successfully demonstrated that standard software elements(COH2D4T and CPE4T)can effectively model physical problems and crack velocity propagation without custom subroutines.It emphasized that while the specific shape of the Traction-Separation Law(TSL)is less critical,its correct implementation is vital for simulating dynamic hydrogen coverage.Crucially,excluding this dynamic coverage—a common practice—risks significantly underestimating crack propagation speed.Although results incorporating dynamic coverage aligned well with experimental data,minor discrepancies are likely due to unmodeled factors like material property variations,hydrogen trapping,temperature,and granular microstructure,which are proposed for future research.展开更多
In this work,the microstructure evolution and mechanical behavior of extruded SiC/ZA63 Mg matrix composites are investigated via combined experimental study and three-dimensionalfinite element modelling(3D FEM)based on...In this work,the microstructure evolution and mechanical behavior of extruded SiC/ZA63 Mg matrix composites are investigated via combined experimental study and three-dimensionalfinite element modelling(3D FEM)based on the actual 3D microstructure achieved by synchrotron tomography.The results show that the average grain size of composite increases from 0.57μm of 8μm-SiC/ZA63 to 8.73μm of 50μm-SiC/ZA63.The type of texture transforms from the typicalfiber texture in 8μm-SiC/ZA63 to intense basal texture in 50μm-SiC/ZA63 composite and the intensity of texture increases sharply with increase of SiC particle size.The dynamic recrystallization(DRX)mechanism is also changed with increasing SiC particle size.Experimental and simulation results verify that the strength and elongation both decrease with increase of SiC particle size.The 8μm-SiC/ZA63 composite possesses the optimal mechanical property with yield strength(YS)of 383 MPa,ultimate tensile strength(UTS)of 424 MPa and elongation of 6.3%.The outstanding mechanical property is attributed to the ultrafine grain size,high-density precipitates and dislocation,good loading transfer effect and the interface bonding between SiC and matrix,as well as the weakened basal texture.The simulation results reveal that the micro-cracks tend to initiate at the interface between SiC and matrix,and then propagate along the interface between particle and Mg matrix or at the high strain and stress regions,and further connect with other micro-cracks.The main fracture mechanism in 8μm-SiC/ZA63 composite is ductile damage of matrix and interfacial debonding.With the increase of particle size,interface strength and particle strength decrease,and interface debonding and particle rupture become the main fracture mechanism in the 30μm-and 50μm-SiC/ZA63 composites.展开更多
In this paper,we propose a multiphysics finite element method for a nonlinear poroelasticity model with nonlinear stress-strain relation.Firstly,we reformulate the original problem into a new coupled fluid system-a ge...In this paper,we propose a multiphysics finite element method for a nonlinear poroelasticity model with nonlinear stress-strain relation.Firstly,we reformulate the original problem into a new coupled fluid system-a generalized nonlinear Stokes problem of displacement vector field related to pseudo pressure and a diffusion problem of other pseudo pressure fields.Secondly,a fully discrete multiphysics finite element method is performed to solve the reformulated system numerically.Thirdly,existence and uniqueness of the weak solution of the reformulated model and stability analysis and optimal convergence order for the multiphysics finite element method are proven theoretically.Lastly,numerical tests are given to verify the theoretical results.展开更多
A two-dimensional nonlinear sloshing problem is analyzed by means of the fully nonlinear theory and time domain second order theory of water waves. Liquid sloshing in a rectangular container Subjected to a horizontal ...A two-dimensional nonlinear sloshing problem is analyzed by means of the fully nonlinear theory and time domain second order theory of water waves. Liquid sloshing in a rectangular container Subjected to a horizontal excitation is simulated by the finite element method. Comparisons between the two theories are made based on their numerical results. It is found that good agreement is obtained for the case of small amplitude oscillation and obvious differences occur for large amplitude excitation. Even though, the second order solution can still exhibit typical nonlinear features of nonlinear wave and can be used instead of the fully nonlinear theory.展开更多
The effect of various process variables on the law of metal flow for semi-solid rolling 60Si2Mn was studied by finite element method. Semi-solid 60Si2Mn can be described as compressible rigid visco-plastic porous mate...The effect of various process variables on the law of metal flow for semi-solid rolling 60Si2Mn was studied by finite element method. Semi-solid 60Si2Mn can be described as compressible rigid visco-plastic porous material saturated with liquid. In terms of ther-mo-mechanical coupling condition, the distributions of stress, velocity and temperature were studied using software MARC. The simulation results show that the rigid visco-plastic model can accurately describe the semi-solid 60Si2Mn rolling process. The great deformation can achieve completely in view of low flow stress of semi-solid slurry.展开更多
Based on the finite element （FE） program ANSYS, a three-dimensional model for the Runyang Suspension Bridge （RSB） is established. The structural natural frequency, vibration mode, stress and displacement response ...Based on the finite element （FE） program ANSYS, a three-dimensional model for the Runyang Suspension Bridge （RSB） is established. The structural natural frequency, vibration mode, stress and displacement response under various load cases are given. A new method of FE model updating is presented based on the physical meaning of sensitivity and the penalty function concept. In this method, the structural model is updated by modifying the parameters of design, and validated by structural natural vibration characteristics, stress response as well as displacement response. The design parameters used for updating are bounded according to measured static response and engineering judgment. The FE model of RSB is updated and validated by the measurements coming from the structural health monitoring system （SHMS）, and the FE baseline model reflecting the current state of RSB is achieved. Both the dynamic and static results show that the method is effective in updating the FE model of long span suspension bridges. The results obtained provide an important research basis for damage alarming and health monitoring of the RSB.展开更多
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 algori...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%.展开更多
A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic gr...A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic growth was simulated from undercooled nickel melt under the forced flow. The simulation results show that the asymmetry behavior of the dendritic growth is caused by the forced flow. When the flow velocity is less than the critical value, the asymmetry of dendrite is little influenced by the forced flow. Once the flow velocity reaches or exceeds the critical value, the controlling factor of dendrite growth gradually changes from thermal diffusion to convection. With the increase of the flow velocity, the deflection angle towards upstream direction of the primary dendrite stem becomes larger. The effect of the dendrite growth on the flow field of the melt is apparent. With the increase of the dendrite size, the vortex is present in the downstream regions, and the vortex region is gradually enlarged. Dendrite tips appear to remelt. In addition, the adaptive finite element method can reduce CPU running time by one order of magnitude compared with uniform grid method, and the speed-up ratio is proportional to the size of computational domain.展开更多
The difficulty in establishing the finite element model of head and cervical spine is interpreted in the study. A head-neck 3D model is constructed accurately and quickly by the technology of CT scan,the automatically...The difficulty in establishing the finite element model of head and cervical spine is interpreted in the study. A head-neck 3D model is constructed accurately and quickly by the technology of CT scan,the automatically modeling of Mimics software and the RE technology of Geomagic software. Then the finite element model of the head-neck which is close to the real one is set up by the preprocessor of the FEM soft ware ANSYS. After the transient finite element analysis is performed on the model,the historical response of the displacement of the head is obtained. The result is validated by the result of the existed experiment. The stress,as well as the deformation,of nodes in the head and the cervical spine at any time benefits a lot to the clinic study on the injure to the head and neck caused by the impacts. And all the analysis is done by limited computer available.展开更多
3D free bending process,an advanced metal forming technology,has attracted much attention due to its unique geometrical flexibility and efficiency.Filling tubes with materials may effectively reduce the distortion in ...3D free bending process,an advanced metal forming technology,has attracted much attention due to its unique geometrical flexibility and efficiency.Filling tubes with materials may effectively reduce the distortion in the cross-section area and restrain wrinkling and collapse of tube wall.In the present study,the impacts of filling different materials on the copper tubes during 3D free bending process were investigated.We have found that copper tubes filled with low melting point alloys could induce the most uniform stress distribution,which result in better formability and moderate thickness changing rates when compared to SS304 steel balls and PU rubbers.The lowest ellipticity reached to 1.467%.展开更多
This study proposes an algorithm of embedding cohesive elements in Abaqus and develops the computer code to model 3D complex cragk propagation in quasi-brittle materials in a relatively easy and efficient manner. The ...This study proposes an algorithm of embedding cohesive elements in Abaqus and develops the computer code to model 3D complex cragk propagation in quasi-brittle materials in a relatively easy and efficient manner. The cohesive elements with softening traction-separation relations and damage initiation and evolution laws are embedded between solid elements in regions of interest in the initial mesh to model potential cracks. The initial mesh can consist of tetrahedrons, wedges, bricks or a mixture of these elements. Neither remeshing nor objective crack propagation criteria are needed. Four examples of concrete specimens, including a wedgesplitting test, a notched beam under torsion, a pull-out test of an anchored cylinder and a notched beam under impact, were modelled and analysed. The simulated crack propagation processes and load-displacement curves agreed well with test results or other numerical simulations for all the examples using initial meshes with reasonable densities. Making use of Abaqus＇s rich pre/post- processing functionalities and powerful standard/explicit solvers, the developed method offers a practical tool for engineering analysts to model complex 3D fracture problems.展开更多
Hydraulic fracturing is a powerful technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to the efficient applicat...Hydraulic fracturing is a powerful technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to the efficient application of this technology, but is also a great challenge because of the strong nonlinear coupling between the viscous flow of fluid and fracture propagation. By taking advantage of a cohesive zone method to simulate the fracture process, a finite element model based on the existing pore pressure cohesive finite elements has been established to investigate the propagation of a penny-shaped hydraulic fracture in an infinite elastic medium. The effect of cohesive material parameters and fluid viscosity on the hydraulic fracture behaviour has been investigated. Excellent agreement between the finite element results and analytical solutions for the limiting case where the fracture process is dominated by rock fracture toughness demonstrates the ability of the cohesive zone finite element model in simulating the hydraulic fracture growth for this case.展开更多
Functionally Graded Materials(FGMs)are innovative advanced quality materials in the field of composites concerning their strength,mechanical,and thermal properties.Nowadays,the modern requirement of the industry in th...Functionally Graded Materials(FGMs)are innovative advanced quality materials in the field of composites concerning their strength,mechanical,and thermal properties.Nowadays,the modern requirement of the industry in the fields of health care,aerospace,and power sectors needs the rapid evolution of new components,which allows researchers to invent new materials to satisfy the functional requirements of modern technology.Tissue engineering is one of the most concerned areas of the application of FGM in the healthcare sector,where the tailored properties of FGM play a significant role in building and growing an artificial structure that heals the damaged tissue of the body parts and meets the desired application that the part needs to perform.This paper highlights the suitability of the combination of a nano⁃structure enhanced epoxy functionally graded material,its properties,and applicability in the design of a prosthetic foot where it provides the mobility and comfort of the body part like natural tissue.The analytical study is done by designing an ANSYS model and simulating the results of equivalent stress and directional deformation.The Finite Element(FE)approach is used to optimize the output results of stress⁃strain analysis,different weight percentages of nano⁃filler are taken for performance enhancement.A comparative analysis is done with the previously established results taking carbon fiber⁃reinforced composites that offer a successful validation of the present results obtained.Furthermore,this study also provides a clear understanding of the justification of the composition considered for the effective application in the field of prosthetics field.展开更多
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 un...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.展开更多
The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cart...The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.展开更多
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 compu...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.展开更多
基金the National Natural Science Fund(11661058,11761053)Natural Science Fund of Inner Mongolia Autonomous Region(2016MS0102,2017MS0107)+1 种基金Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(NJYT-17-A07)National Undergraduate Innovative Training Project of Inner Mongolia University(201710126026).
文摘In this article,a high-order scheme,which is formulated by combining the quadratic finite element method in space with a second-order time discrete scheme,is developed for looking for the numerical solution of a two-dimensional nonlinear time fractional thermal diffusion model.The time Caputo fractional derivative is approximated by using the L2-1formula,the first-order derivative and nonlinear term are discretized by some second-order approximation formulas,and the quadratic finite element is used to approximate the spatial direction.The error accuracy O(h3+t2)is obtained,which is verified by the numerical results.
文摘This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.
基金supported by National Natural Science Foundation of China(Grant Nos.40474039,41030320)Chinese Academy of Sciences(Grant No.XDB030105)
文摘The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of roughly parallel anticlines.Geological observations predicted that averaged over last^1 Ma time scale,the shortening rates of these anticlines are about2.1–5.5 mm/a;However by averaged over about 10±2 kyr,their shortening rates reduce to merely about 1.25±0.5 mm/a.The slow shortening of the anticlines in the last^10±2 kyr is coarsely concurrent in time with the last global deglaciation.Here,we use a two-dimensional finite element model to explore crustal deformation across north piedmont of the Tianshan Mountains under various erosion-sedimentation conditions that are assumed to represent the climate-controlled surface process.Numerical experiments show that with a relatively weak erosion-sedimentation strength,the crustal shortening is accommodated mainly by north piedmont of the Tianshan Mountains,similar to the high shortening rate of anticlines averaged over the last^1Ma.By increasing erosion-sedimentation strength,the resultant crustal shortening is transformed gradually toward the Tianshan Mountains,resulting in the shortening rate in its north piedmont being decelerated to what is observed as averaged over the last^10±2 kyr.This result suggests that erosion and sedimentation could play an important role mechanically on strain localization across an intra-continent active tectonic belt.Hence,if the climate change around the last global deglaciation could be simply representative to the enhancement of surface erosion and sedimentation across the pre-existed Tianshan Mountains and its foreland,our models indicate that the observed shortening-rate variations averaged over^1 Ma and^10±2kyr time scales around north piedmont of the Tianshan Mountains should be resulted from climate changes.
文摘Geared-rotor systems are critical components in mechanical applications,and their performance can be severely affected by faults,such as profile errors,wear,pitting,spalling,flaking,and cracks.Profile errors in gear teeth are inevitable in manufacturing and subsequently accumulate during operations.This work aims to predict the status of gear profile deviations based on gear dynamics response using the digital model of an experimental rig setup.The digital model comprises detailed CAD models and has been validated against the expected physical behavior using commercial finite element analysis software.The different profile deviations are then modeled using gear charts,and the dynamic response is captured through simulations.The various features are then obtained by signal processing,and various ML models are then evaluated to predict the fault/no-fault condition for the gear.The best performance is achieved by an artificial neural network with a prediction accuracy of 97.5%,which concludes a strong influence on the dynamics of the gear rotor system due to profile deviations.
文摘In this study,an alternative modelling approach for absorbed hydrogen stress corrosion cracking(SCC)is proposed,with hydrogen-enhanced decohesion(HEDE)identified as the key failure mechanism.All analyses have been performed by utilising only ABAQUS standard elements,COH2D4T and CPE4T,already available within the software and without the need to develop external subroutines.The study also tends to highlight the criticality of implementing a correct Traction Separation Law(TSL)curve to simulate the hydrogen diffusion within the specimen and using the concept of dynamic hydrogen penetration by continuously updating the hydrogen concentration boundary conditions as the crack propagates.In conclusion,this study successfully demonstrated that standard software elements(COH2D4T and CPE4T)can effectively model physical problems and crack velocity propagation without custom subroutines.It emphasized that while the specific shape of the Traction-Separation Law(TSL)is less critical,its correct implementation is vital for simulating dynamic hydrogen coverage.Crucially,excluding this dynamic coverage—a common practice—risks significantly underestimating crack propagation speed.Although results incorporating dynamic coverage aligned well with experimental data,minor discrepancies are likely due to unmodeled factors like material property variations,hydrogen trapping,temperature,and granular microstructure,which are proposed for future research.
基金supported by the National Natural Science Foundation of China[51974058,52371005,52022017,51927801]the Fundamental Research Funds for the Central Universities(DUT23YG104).
文摘In this work,the microstructure evolution and mechanical behavior of extruded SiC/ZA63 Mg matrix composites are investigated via combined experimental study and three-dimensionalfinite element modelling(3D FEM)based on the actual 3D microstructure achieved by synchrotron tomography.The results show that the average grain size of composite increases from 0.57μm of 8μm-SiC/ZA63 to 8.73μm of 50μm-SiC/ZA63.The type of texture transforms from the typicalfiber texture in 8μm-SiC/ZA63 to intense basal texture in 50μm-SiC/ZA63 composite and the intensity of texture increases sharply with increase of SiC particle size.The dynamic recrystallization(DRX)mechanism is also changed with increasing SiC particle size.Experimental and simulation results verify that the strength and elongation both decrease with increase of SiC particle size.The 8μm-SiC/ZA63 composite possesses the optimal mechanical property with yield strength(YS)of 383 MPa,ultimate tensile strength(UTS)of 424 MPa and elongation of 6.3%.The outstanding mechanical property is attributed to the ultrafine grain size,high-density precipitates and dislocation,good loading transfer effect and the interface bonding between SiC and matrix,as well as the weakened basal texture.The simulation results reveal that the micro-cracks tend to initiate at the interface between SiC and matrix,and then propagate along the interface between particle and Mg matrix or at the high strain and stress regions,and further connect with other micro-cracks.The main fracture mechanism in 8μm-SiC/ZA63 composite is ductile damage of matrix and interfacial debonding.With the increase of particle size,interface strength and particle strength decrease,and interface debonding and particle rupture become the main fracture mechanism in the 30μm-and 50μm-SiC/ZA63 composites.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12371393,11971150 and 11801143)Natural Science Foundation of Henan Province(Grant No.242300421047).
文摘In this paper,we propose a multiphysics finite element method for a nonlinear poroelasticity model with nonlinear stress-strain relation.Firstly,we reformulate the original problem into a new coupled fluid system-a generalized nonlinear Stokes problem of displacement vector field related to pseudo pressure and a diffusion problem of other pseudo pressure fields.Secondly,a fully discrete multiphysics finite element method is performed to solve the reformulated system numerically.Thirdly,existence and uniqueness of the weak solution of the reformulated model and stability analysis and optimal convergence order for the multiphysics finite element method are proven theoretically.Lastly,numerical tests are given to verify the theoretical results.
文摘A two-dimensional nonlinear sloshing problem is analyzed by means of the fully nonlinear theory and time domain second order theory of water waves. Liquid sloshing in a rectangular container Subjected to a horizontal excitation is simulated by the finite element method. Comparisons between the two theories are made based on their numerical results. It is found that good agreement is obtained for the case of small amplitude oscillation and obvious differences occur for large amplitude excitation. Even though, the second order solution can still exhibit typical nonlinear features of nonlinear wave and can be used instead of the fully nonlinear theory.
基金the National Natural Science Foundation of China (No.59995440).
文摘The effect of various process variables on the law of metal flow for semi-solid rolling 60Si2Mn was studied by finite element method. Semi-solid 60Si2Mn can be described as compressible rigid visco-plastic porous material saturated with liquid. In terms of ther-mo-mechanical coupling condition, the distributions of stress, velocity and temperature were studied using software MARC. The simulation results show that the rigid visco-plastic model can accurately describe the semi-solid 60Si2Mn rolling process. The great deformation can achieve completely in view of low flow stress of semi-solid slurry.
文摘Based on the finite element （FE） program ANSYS, a three-dimensional model for the Runyang Suspension Bridge （RSB） is established. The structural natural frequency, vibration mode, stress and displacement response under various load cases are given. A new method of FE model updating is presented based on the physical meaning of sensitivity and the penalty function concept. In this method, the structural model is updated by modifying the parameters of design, and validated by structural natural vibration characteristics, stress response as well as displacement response. The design parameters used for updating are bounded according to measured static response and engineering judgment. The FE model of RSB is updated and validated by the measurements coming from the structural health monitoring system （SHMS）, and the FE baseline model reflecting the current state of RSB is achieved. Both the dynamic and static results show that the method is effective in updating the FE model of long span suspension bridges. The results obtained provide an important research basis for damage alarming and health monitoring of the RSB.
文摘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%.
基金Projects(51161011,11364024)supported by the National Natural Science Foundation of ChinaProject(1204GKCA065)supported by the Key Technology R&D Program of Gansu Province,China+1 种基金Project(201210)supported by the Fundamental Research Funds for the Universities of Gansu Province,ChinaProject(J201304)supported by the Funds for Distinguished Young Scientists of Lanzhou University of Technology,China
文摘A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic growth was simulated from undercooled nickel melt under the forced flow. The simulation results show that the asymmetry behavior of the dendritic growth is caused by the forced flow. When the flow velocity is less than the critical value, the asymmetry of dendrite is little influenced by the forced flow. Once the flow velocity reaches or exceeds the critical value, the controlling factor of dendrite growth gradually changes from thermal diffusion to convection. With the increase of the flow velocity, the deflection angle towards upstream direction of the primary dendrite stem becomes larger. The effect of the dendrite growth on the flow field of the melt is apparent. With the increase of the dendrite size, the vortex is present in the downstream regions, and the vortex region is gradually enlarged. Dendrite tips appear to remelt. In addition, the adaptive finite element method can reduce CPU running time by one order of magnitude compared with uniform grid method, and the speed-up ratio is proportional to the size of computational domain.
文摘The difficulty in establishing the finite element model of head and cervical spine is interpreted in the study. A head-neck 3D model is constructed accurately and quickly by the technology of CT scan,the automatically modeling of Mimics software and the RE technology of Geomagic software. Then the finite element model of the head-neck which is close to the real one is set up by the preprocessor of the FEM soft ware ANSYS. After the transient finite element analysis is performed on the model,the historical response of the displacement of the head is obtained. The result is validated by the result of the existed experiment. The stress,as well as the deformation,of nodes in the head and the cervical spine at any time benefits a lot to the clinic study on the injure to the head and neck caused by the impacts. And all the analysis is done by limited computer available.
基金financial support from the Open Research Funds of the Jiangsu Key Laboratory of Nuclear Energy Equipment Materials Engineering of China(No.NJ20170012)the China Aviation Science Foundation(No.2016ZE52047)the Jiangsu Province Science and Technology Program of China(No.BE2016156).
文摘3D free bending process,an advanced metal forming technology,has attracted much attention due to its unique geometrical flexibility and efficiency.Filling tubes with materials may effectively reduce the distortion in the cross-section area and restrain wrinkling and collapse of tube wall.In the present study,the impacts of filling different materials on the copper tubes during 3D free bending process were investigated.We have found that copper tubes filled with low melting point alloys could induce the most uniform stress distribution,which result in better formability and moderate thickness changing rates when compared to SS304 steel balls and PU rubbers.The lowest ellipticity reached to 1.467%.
基金supported by EPSRC UK(No.EP/F00656X/1)Xiangting Su's one-year visit to the University of Liverpoosupported by the China Scholarship Council and the National Natural Science Foundation of China(No.50579081).
文摘This study proposes an algorithm of embedding cohesive elements in Abaqus and develops the computer code to model 3D complex cragk propagation in quasi-brittle materials in a relatively easy and efficient manner. The cohesive elements with softening traction-separation relations and damage initiation and evolution laws are embedded between solid elements in regions of interest in the initial mesh to model potential cracks. The initial mesh can consist of tetrahedrons, wedges, bricks or a mixture of these elements. Neither remeshing nor objective crack propagation criteria are needed. Four examples of concrete specimens, including a wedgesplitting test, a notched beam under torsion, a pull-out test of an anchored cylinder and a notched beam under impact, were modelled and analysed. The simulated crack propagation processes and load-displacement curves agreed well with test results or other numerical simulations for all the examples using initial meshes with reasonable densities. Making use of Abaqus＇s rich pre/post- processing functionalities and powerful standard/explicit solvers, the developed method offers a practical tool for engineering analysts to model complex 3D fracture problems.
文摘Hydraulic fracturing is a powerful technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to the efficient application of this technology, but is also a great challenge because of the strong nonlinear coupling between the viscous flow of fluid and fracture propagation. By taking advantage of a cohesive zone method to simulate the fracture process, a finite element model based on the existing pore pressure cohesive finite elements has been established to investigate the propagation of a penny-shaped hydraulic fracture in an infinite elastic medium. The effect of cohesive material parameters and fluid viscosity on the hydraulic fracture behaviour has been investigated. Excellent agreement between the finite element results and analytical solutions for the limiting case where the fracture process is dominated by rock fracture toughness demonstrates the ability of the cohesive zone finite element model in simulating the hydraulic fracture growth for this case.
基金Sponsored by the Science and Technology Department,Government of Ddisha(Grant No.3724/ST,Bhubaneswar,dt.14.09.2022).
文摘Functionally Graded Materials(FGMs)are innovative advanced quality materials in the field of composites concerning their strength,mechanical,and thermal properties.Nowadays,the modern requirement of the industry in the fields of health care,aerospace,and power sectors needs the rapid evolution of new components,which allows researchers to invent new materials to satisfy the functional requirements of modern technology.Tissue engineering is one of the most concerned areas of the application of FGM in the healthcare sector,where the tailored properties of FGM play a significant role in building and growing an artificial structure that heals the damaged tissue of the body parts and meets the desired application that the part needs to perform.This paper highlights the suitability of the combination of a nano⁃structure enhanced epoxy functionally graded material,its properties,and applicability in the design of a prosthetic foot where it provides the mobility and comfort of the body part like natural tissue.The analytical study is done by designing an ANSYS model and simulating the results of equivalent stress and directional deformation.The Finite Element(FE)approach is used to optimize the output results of stress⁃strain analysis,different weight percentages of nano⁃filler are taken for performance enhancement.A comparative analysis is done with the previously established results taking carbon fiber⁃reinforced composites that offer a successful validation of the present results obtained.Furthermore,this study also provides a clear understanding of the justification of the composition considered for the effective application in the field of prosthetics field.
基金financially supported by the Natural Science Foundation of China(Grant No:10872219)
文摘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.
基金the National Natural Science Foundation of China (No. 81071235)the Medicine and Engineering Interdisciplinary Fund of Shanghai Jiaotong University (No. YG2010MS26)
文摘The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.
基金Scientific Research Deanship,Taibah University Grant No.6363/436
文摘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.
