A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, ...A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.展开更多
The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite elemen...The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.展开更多
In this research,a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles.The numerical model is based on thermal effects,mechanical st...In this research,a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles.The numerical model is based on thermal effects,mechanical stress fields and fatigue crack mechanics.Elastic-plastic material data of modified AISI 4340 at temperatures ranging from 25 to 1200℃and at strain rates of 4,16,32 and 48 s^(-1) was acquired from high-temperature compression tests.This was used as material property data in the simulation model.The boundary conditions applied are kept similar to the working gun barrel during continuous firing.A methodology has been provided to define thermo-mechanically active surface-to-surface type interface between the crack faces for a better approximation of stresses at the crack tip.Comparison of results from non-autofrettaged and autofrettaged simulation models provide useful information about the evolution of strains and stresses in the barrel at different points under combined thermo-mechanical loading cycles in both cases.The effect of thermal fatigue under already induced compressive yield due to autofrettage and the progressive degradation of the accumulated stresses due to thermo-mechanical cyclic loads on the internal surface of the gun barrel(mimicking the continuous firing scenario)has been analyzed.Comparison between energy release rate at tips of varying crack lengths due to cyclic thermo-mechanical loading in the non-autofrettaged and autofrettaged gun has been carried out.展开更多
In this paper, a two dimensional Voronoi cell element, formulated with creep, thermal and plastic strain, is applied for the numerical simulation of thermo-mechanical fatigue behavior for particulate reinforced compos...In this paper, a two dimensional Voronoi cell element, formulated with creep, thermal and plastic strain, is applied for the numerical simulation of thermo-mechanical fatigue behavior for particulate reinforced composites. The relation between mechanical fatigue phases and thermal fatigue phases influences the thermo-mechanical fatigue behavior and cyclic creep damage. The topological features of micro-structure in particulate reinforced composites, such as the orientation, depth-width ratio, distribution and volume fraction of inclusions, have a great influence on thermo-mechanical behavior. Some related conclusions are obtained by examples of numerical simulation.展开更多
Theory of metallo-thermo-mechamics and the developed CAE code offer a powerful tool to simulate residual stresses and distortion during heat treatment processes, in which the transformation plasticity is one of factor...Theory of metallo-thermo-mechamics and the developed CAE code offer a powerful tool to simulate residual stresses and distortion during heat treatment processes, in which the transformation plasticity is one of factors to be considered being coupled with stress/strain and metallic structure. It is pointed out in this paper that, especially in the case of carburized quenching, transformation plasticity plays very important role on the distortion, which is verified by axisymmetric finite element, employing heat treatment simulation code "HEARTS". Simulated results with the careful consideration on the effect of transformation plasticity reveal to improve remarkably the accuracy of prediction of the displacement and the mode of distortion, compensating the discrepancy between experimental and calculated results. Attention is also paid on the difference in transformation plasticity and conventional plasticity in simulating the volume fraction, stress and strain in ring-shaped specimen during quenching. Moreover some discussions are made on practical use of the effect, and recent experimental results on the coefficient of transformation plasticity are presented.展开更多
A novel modeling technique based on the coupled Eulerian-Lagrangian(CEL) method is provided to solve the geotechnical problems with large deformations. The technique is intended to solve the update problem of soil mec...A novel modeling technique based on the coupled Eulerian-Lagrangian(CEL) method is provided to solve the geotechnical problems with large deformations. The technique is intended to solve the update problem of soil mechanical properties during spudcan penetration in normally consolidated clay soil. In the CEL model, the normal method of assigning an increasing shear strength profile with depth(NA) is defective due to its Eulerian framework. In this paper, a new technique is proposed to update soil material properties by introducing thermo-mechanical coupled analysis(TMCA) to the CEL models. During establishment of the CEL models, the optimal penetration velocity and minimum mesh size are determined through parametric studies. Reasonability and accuracy are then verified through comparison of the preliminary results with the soil flow configuration and penetration resistance(Fv) of a centrifuge test, and the results of the proposed method are compared with those of the remeshing and interpolation technique with small strain(RITSS) method. To achieve a CEL model with satisfactory accuracy, the NA and TMCA methods implemented in the CEL models and the RITSS method are first adopted in weightless soil. Comparison of the findings with those obtained in previous studies shows that the TMCA method can update material properties and predict Fv. The TMCA method is then applied to soils with self-weight and different shear strength profiles. Results show that the proposed method is capable of accurately modeling the large deformation problem of spudcan penetration in non-homogeneous clay.展开更多
3D thermo-meehanical coupled simulation of whole rolling process for 60 kg/m heavy rail was accomplished by FEM method. The finite element model, physical parameters of U75V and parameter setting of simulation were in...3D thermo-meehanical coupled simulation of whole rolling process for 60 kg/m heavy rail was accomplished by FEM method. The finite element model, physical parameters of U75V and parameter setting of simulation were introduced in detail. The whole rolling process of 60 kg/m heavy rail was divided into 27 time cells to simulate respectively, and the model rebuilding and temperature inheritance method in intermediate pass were proceeded. Then, based on simulation results, the workpiece deformation result, metal flow, stress and strain of 60 kg/m heavy rail for typical passes were obtained. The temperature variation curves of whole rolling process for section key points of 60 kg/m heavy rail were plotted, and the temperature falling law of whole rolling process for 60 kg/m heavy rail was studied. In addition, temperature distribution of 60 kg/m heavy rail after whole rolling process was analyzed, and the results showed that temperature was highest at center of rail head and lowest at fringe of rail base. Moreover, the simulation results and measured results of rolling force for 60 kg/m heavy rail were compared, and the regularity was in good agreement.展开更多
Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth o...Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth oxides.Hollow N-doped carbon nano-spheres loaded ceria composites(H-NC@CeO_(2))were designed and prepared by the template method,combined with in-situ coating,pyrolysis and chemical etching.By controlling the loading content of H-NC@CeO_(2)and adjusting the impedance matching of the material,the H-NC@CeO_(2)/PS(polystyrene)composite exhibited a minimum reflection loss(RL)of-50.8 dB and an effective absorption band-width(EAB)of 4.64 GHz at a filler ratio of 20wt%and a thickness of 2 mm.In accordance with measured electromagnetic parameters,simulations using the high frequency structure simulator(HFSS)software were conducted to investigate the impact of the honeycomb structure on the electromagnetic wave performance of H-NC@CeO_(2)/PS.By calculating the surface electric field and the material’s bulk loss density,the mechanism of electromagnetic loss for the honeycomb structure was elaborated.A method for structural design and man-ufacturing of broadband absorbing devices was proposed and a broadband absorber with an EAB of 11.9 GHz was prepared.This study presents an innovative approach to designing advanced electromagnetic(EM)wave absorbing materials with broad absorption band-widths.展开更多
A finite volume method is applied to simulate a closed die hot forging process of a cylinder billet. Since variation and distribution of temperature play very important role in hot forging, the code involves a methodo...A finite volume method is applied to simulate a closed die hot forging process of a cylinder billet. Since variation and distribution of temperature play very important role in hot forging, the code involves a methodology of a coupled system of mechanical and thermal equations. The simulated results are compared with the experimental ones. The distribution of temperature in the billet obtained from the simulation is also discussed.展开更多
This paper presents an improved level set method for topology optimization of geometrically nonlinear structures accounting for the effect of thermo-mechanical couplings.It derives a new expression for element couplin...This paper presents an improved level set method for topology optimization of geometrically nonlinear structures accounting for the effect of thermo-mechanical couplings.It derives a new expression for element coupling stress resulting from the combination of mechanical and thermal loading,using geometric nonlinear finite element analysis.A topological model is then developed to minimize compliance while meeting displacement and frequency constraints to fulfill design requirements of structural members.Since the conventional Lagrange multiplier search method is unable to handle convergence instability arising from large deformation,a novel Lagrange multiplier search method is proposed.Additionally,the proposed method can be extended to multi-constrained geometrically nonlinear topology optimization,accommodating multiple physical field couplings.展开更多
In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,th...In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials.展开更多
Compared with traditional open surgery,laparoscopic surgery significantly reduces bodily trauma,postoperative pain,and hospitalization duration.However,owing to the small size of incisions and the counterintuitive mot...Compared with traditional open surgery,laparoscopic surgery significantly reduces bodily trauma,postoperative pain,and hospitalization duration.However,owing to the small size of incisions and the counterintuitive motion of surgical tools,longer training cycles are required for surgeons to achieve fine operational skills.This paper presents a laparoscopic surgery simulator with haptic-feedback control(LSHC-6)that provides a reliable and cost-effective training alternative for surgeons.In addition to the structural diagram,kinematic analysis,and gravity compensation algorithm,a particle swarm optimization algorithm(PSO)is applied to optimize the structural parameters of the simulator by evaluating its workspace,global dexterity,and gravity compensation ability.A prototype system was developed and evaluated using two training experiments.The results demonstrate that the simulator exhibits good operational fluidity,workspace,and stable force output,effectively meeting the needs of laparoscopic surgical training.展开更多
BACKGROUND Although exposure therapy is a proven treatment for post-traumatic stress disorder(PTSD),empirical research is difficult due to ethical issues.Recently,virtual reality-based content that can provide space a...BACKGROUND Although exposure therapy is a proven treatment for post-traumatic stress disorder(PTSD),empirical research is difficult due to ethical issues.Recently,virtual reality-based content that can provide space and time similar to reality for exposure therapy techniques is increasing.AIM To examine exposure therapy using driving simulations in patients with PTSD due to traffic accidents with PTSD symptoms.METHODS The intervention was provided to two individuals who experienced PTSD symptoms after a traffic accident using a driving simulator.Among the singlesubject experimental designs,the ABA(baseline-intervention-baseline)design was used,and the PTSD checklist and brain wave frequency were used to measure the results.RESULTS In all participants,the standard category departure time of the electroencephalogram decreased from baseline,and PTSD symptoms decreased after the intervention.CONCLUSION These results suggest the potential use of a driving simulator as an exposure treatment tool for PTSD.展开更多
The ground-based experimental tests are crucial to verify the related technologies of the drag-free satellite.This work presents a design method of the ground simulator testbed for emulating the planar dynamics of the...The ground-based experimental tests are crucial to verify the related technologies of the drag-free satellite.This work presents a design method of the ground simulator testbed for emulating the planar dynamics of the space drag-free systems.In this paper,the planar dynamic characteristics of the drag-free satellite with double test masses are analyzed and nondimensionalized.A simulator vehicle composed of an air bearing testbed and two inverted pendulums is devised on the basic of equivalent mass and equivalent stiffness proposed firstly in this paper.And the dynamic model of the simulator equivalent to the sensitive axis motion of the test mass and the planar motion of the satellite is derived from the Euler-Lagrange method.Then,the dynamic equivalence conditions between the space prototype system and the ground model system are derived from Pi theorem.To satisfy these conditions,the scaling laws of two systems and requirements for the inverted pendulum are put forward.Besides,the corresponding control scaling laws and a closed-loop control strategy are deduced and applied to establishing the numerical simulation experiments of underactuated system.Subsequently,the comparative simulation results demonstrate the similarity of dynamical behavior between the scaled-down ground model and the space prototype.As a result,the rationality and effectiveness of the design method are proved,facilitating the ground simulation of future gravitational wave detection satellites.展开更多
In this paper,the degradation of mechanical properties of engineering cementitious composites(ECCs)at elevated temperatures and the failure of fiber are considered.A failure model under coupled thermo-mechanical loads...In this paper,the degradation of mechanical properties of engineering cementitious composites(ECCs)at elevated temperatures and the failure of fiber are considered.A failure model under coupled thermo-mechanical loads for ECC is developed based on bond-based peridynamics.A semi-discrete model is constructed to describe fiber–matrix interactions and simulate thermal failure in ECC.The peridynamic differential operator(PDDO)is utilized for non-local modeling of thermal fluid flow and heat transfer.A multi-rate explicit time integration method is adopted to address thermo-mechanical coupling over different time scales.Model validation is achieved through simulating transient heat transfer in a homogeneous plate,with results aligning with analytical solutions.The damage behavior of a heated ECC plate in a borehole and under a fire scenario is analyzed,providing insights for enhancing fire resistance and high-temperature performance of ECC materials and structures.展开更多
Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing addit...Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.展开更多
The size and shape effect(SSE)of components has become a critical issue for mechanical properties,application reliability,and processing.In this study,the creep rupture life(CRL)of components with different wall thick...The size and shape effect(SSE)of components has become a critical issue for mechanical properties,application reliability,and processing.In this study,the creep rupture life(CRL)of components with different wall thicknesses and positions in a combustion chamber casing simulator made of K439B superalloy was investigated.The intrinsic mechanisms of the SSE were explored from the dendrite structure,volume fraction and size of theγ'phase,and element segregation,etc.It is shown that this casting exhibits a strong SSE of creep rupture life,characterized by a significant difference in the CRL values up to 60%with the variation of wall thickness and position in the casing.In terms of casting technology,the influence of SSE on CRL is actually determined by the cooling rate.The SSE on the creep rupture life originates from the dendrite structure(such as the secondary dendrite arm spacing),volume fraction size of theγ'phase in the dendrite trunk,and elements segregation rate.This work may have implications for the design and application of engineering components with large sizes and complex structures.展开更多
BACKGROUND Orthopaedic surgical education has traditionally depended on the apprenticeship model of“see one,do one,teach one”.However,reduced operative exposure,stricter work-hour regulations,medicolegal constraints...BACKGROUND Orthopaedic surgical education has traditionally depended on the apprenticeship model of“see one,do one,teach one”.However,reduced operative exposure,stricter work-hour regulations,medicolegal constraints,and patient safety concerns have constrained its practicality.Simulation-based training has become a reliable,safe,and cost-efficient alternative.Dry lab techniques,especially virtual and augmented reality,make up 78%of current dry lab research,whereas wet labs still set the standard for anatomical realism.AIM To evaluate the effectiveness,limitations,and future directions of wet and dry lab simulation in orthopaedic training.METHODS A scoping review was carried out across four databases-PubMed,Cochrane Library,Web of Science,and EBSCOhost-up to 2025.Medical Subject Headings included:"Orthopaedic Education","Wet Lab","Dry Lab","Simulation Training","Virtual Reality",and"Surgical Procedure".Eligible studies focused on orthopaedic or spinal surgical education,employed wet or dry lab techniques,and assessed training effectiveness.Exclusion criteria consisted of non-English publications,abstracts only,non-orthopaedic research,and studies unrelated to simulation.Two reviewers independently screened titles,abstracts,and full texts,resolving discrepancies with a third reviewer.RESULTS From 1851 records,101 studies met inclusion:78 on dry labs,7 on wet labs,4 on both.Virtual reality(VR)simulations were most common,with AI increasingly used for feedback and assessment.Cadaveric training remains the gold standard for accuracy and tactile feedback,while dry labs-especially VR-offer scalability,lower cost(40%-60%savings in five studies),and accessibility for novices.Senior residents prefer wet labs for complex tasks;juniors favour dry labs for basics.Challenges include limited transferability data,lack of standard outcome metrics,and ethical concerns about cadaver use and AI assessment.CONCLUSION Wet and dry labs each have unique strengths in orthopaedic training.A hybrid approach combining both,supported by standardised assessments and outcome studies,is most effective.Future efforts should aim for uniform reporting,integrating new technologies,and policy support for hybrid curricula to enhance skills and patient care.展开更多
基金supported by the National Natural Science Foundation of China(No.50227401)
文摘A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.
基金supported by the Hebei Provincial Natural Science Foundation of China(No.E2007000591).
文摘The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.
基金the DAAD Faculty Development for Ph.D.Candidates(Balochistan)2016(57245990)-HRDI-UESTP’s/UET’s funding scheme in cooperation with the Higher Education Commission of Pakistan(HEC)for sponsoring the stay at IMF TU Freiberg,Germany.
文摘In this research,a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles.The numerical model is based on thermal effects,mechanical stress fields and fatigue crack mechanics.Elastic-plastic material data of modified AISI 4340 at temperatures ranging from 25 to 1200℃and at strain rates of 4,16,32 and 48 s^(-1) was acquired from high-temperature compression tests.This was used as material property data in the simulation model.The boundary conditions applied are kept similar to the working gun barrel during continuous firing.A methodology has been provided to define thermo-mechanically active surface-to-surface type interface between the crack faces for a better approximation of stresses at the crack tip.Comparison of results from non-autofrettaged and autofrettaged simulation models provide useful information about the evolution of strains and stresses in the barrel at different points under combined thermo-mechanical loading cycles in both cases.The effect of thermal fatigue under already induced compressive yield due to autofrettage and the progressive degradation of the accumulated stresses due to thermo-mechanical cyclic loads on the internal surface of the gun barrel(mimicking the continuous firing scenario)has been analyzed.Comparison between energy release rate at tips of varying crack lengths due to cyclic thermo-mechanical loading in the non-autofrettaged and autofrettaged gun has been carried out.
基金The project supported by the Special Funds for the National Major Fundamental Research Projects(2004CB619304)the National Natural Science Foundation of China(10276020 and 50371042)the Key Grant Project of Chinese Ministry of Education(0306)
文摘In this paper, a two dimensional Voronoi cell element, formulated with creep, thermal and plastic strain, is applied for the numerical simulation of thermo-mechanical fatigue behavior for particulate reinforced composites. The relation between mechanical fatigue phases and thermal fatigue phases influences the thermo-mechanical fatigue behavior and cyclic creep damage. The topological features of micro-structure in particulate reinforced composites, such as the orientation, depth-width ratio, distribution and volume fraction of inclusions, have a great influence on thermo-mechanical behavior. Some related conclusions are obtained by examples of numerical simulation.
文摘Theory of metallo-thermo-mechamics and the developed CAE code offer a powerful tool to simulate residual stresses and distortion during heat treatment processes, in which the transformation plasticity is one of factors to be considered being coupled with stress/strain and metallic structure. It is pointed out in this paper that, especially in the case of carburized quenching, transformation plasticity plays very important role on the distortion, which is verified by axisymmetric finite element, employing heat treatment simulation code "HEARTS". Simulated results with the careful consideration on the effect of transformation plasticity reveal to improve remarkably the accuracy of prediction of the displacement and the mode of distortion, compensating the discrepancy between experimental and calculated results. Attention is also paid on the difference in transformation plasticity and conventional plasticity in simulating the volume fraction, stress and strain in ring-shaped specimen during quenching. Moreover some discussions are made on practical use of the effect, and recent experimental results on the coefficient of transformation plasticity are presented.
基金supported by the National Natural Science Foundation of China (No. 51779236)the NSFC-Shandong Joint Fund Project (No. U1706226)funded by the China Scholarship Council (No. 201606330049)
文摘A novel modeling technique based on the coupled Eulerian-Lagrangian(CEL) method is provided to solve the geotechnical problems with large deformations. The technique is intended to solve the update problem of soil mechanical properties during spudcan penetration in normally consolidated clay soil. In the CEL model, the normal method of assigning an increasing shear strength profile with depth(NA) is defective due to its Eulerian framework. In this paper, a new technique is proposed to update soil material properties by introducing thermo-mechanical coupled analysis(TMCA) to the CEL models. During establishment of the CEL models, the optimal penetration velocity and minimum mesh size are determined through parametric studies. Reasonability and accuracy are then verified through comparison of the preliminary results with the soil flow configuration and penetration resistance(Fv) of a centrifuge test, and the results of the proposed method are compared with those of the remeshing and interpolation technique with small strain(RITSS) method. To achieve a CEL model with satisfactory accuracy, the NA and TMCA methods implemented in the CEL models and the RITSS method are first adopted in weightless soil. Comparison of the findings with those obtained in previous studies shows that the TMCA method can update material properties and predict Fv. The TMCA method is then applied to soils with self-weight and different shear strength profiles. Results show that the proposed method is capable of accurately modeling the large deformation problem of spudcan penetration in non-homogeneous clay.
文摘3D thermo-meehanical coupled simulation of whole rolling process for 60 kg/m heavy rail was accomplished by FEM method. The finite element model, physical parameters of U75V and parameter setting of simulation were introduced in detail. The whole rolling process of 60 kg/m heavy rail was divided into 27 time cells to simulate respectively, and the model rebuilding and temperature inheritance method in intermediate pass were proceeded. Then, based on simulation results, the workpiece deformation result, metal flow, stress and strain of 60 kg/m heavy rail for typical passes were obtained. The temperature variation curves of whole rolling process for section key points of 60 kg/m heavy rail were plotted, and the temperature falling law of whole rolling process for 60 kg/m heavy rail was studied. In addition, temperature distribution of 60 kg/m heavy rail after whole rolling process was analyzed, and the results showed that temperature was highest at center of rail head and lowest at fringe of rail base. Moreover, the simulation results and measured results of rolling force for 60 kg/m heavy rail were compared, and the regularity was in good agreement.
基金supported by the Research Funding of Hangzhou International Innovation Institute of Beihang Uni-versity,China(No.2024KQ130)the National Natural Science Foundation of China(Nos.52073010 and 52373259).
文摘Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth oxides.Hollow N-doped carbon nano-spheres loaded ceria composites(H-NC@CeO_(2))were designed and prepared by the template method,combined with in-situ coating,pyrolysis and chemical etching.By controlling the loading content of H-NC@CeO_(2)and adjusting the impedance matching of the material,the H-NC@CeO_(2)/PS(polystyrene)composite exhibited a minimum reflection loss(RL)of-50.8 dB and an effective absorption band-width(EAB)of 4.64 GHz at a filler ratio of 20wt%and a thickness of 2 mm.In accordance with measured electromagnetic parameters,simulations using the high frequency structure simulator(HFSS)software were conducted to investigate the impact of the honeycomb structure on the electromagnetic wave performance of H-NC@CeO_(2)/PS.By calculating the surface electric field and the material’s bulk loss density,the mechanism of electromagnetic loss for the honeycomb structure was elaborated.A method for structural design and man-ufacturing of broadband absorbing devices was proposed and a broadband absorber with an EAB of 11.9 GHz was prepared.This study presents an innovative approach to designing advanced electromagnetic(EM)wave absorbing materials with broad absorption band-widths.
文摘A finite volume method is applied to simulate a closed die hot forging process of a cylinder billet. Since variation and distribution of temperature play very important role in hot forging, the code involves a methodology of a coupled system of mechanical and thermal equations. The simulated results are compared with the experimental ones. The distribution of temperature in the billet obtained from the simulation is also discussed.
基金supported by grants from the National Natural Science Foundation of China (51478130)the Guangzhou Municipal Education Bureau’s Scientific Research Project, China (2024312217)+1 种基金the China Scholarship Council (201808440070)the 111 Project of China (D21021).
文摘This paper presents an improved level set method for topology optimization of geometrically nonlinear structures accounting for the effect of thermo-mechanical couplings.It derives a new expression for element coupling stress resulting from the combination of mechanical and thermal loading,using geometric nonlinear finite element analysis.A topological model is then developed to minimize compliance while meeting displacement and frequency constraints to fulfill design requirements of structural members.Since the conventional Lagrange multiplier search method is unable to handle convergence instability arising from large deformation,a novel Lagrange multiplier search method is proposed.Additionally,the proposed method can be extended to multi-constrained geometrically nonlinear topology optimization,accommodating multiple physical field couplings.
基金supported by the National Natural Science Foundation of China(Grants 11471262,11202032)the Basic Research Project of National Defense(Grant B 1520132013)supported by the State Key Laboratory of Science and Engineering Computing and Center for high performance computing of Northwestem Polytechnical University
文摘In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials.
基金Supported by the National Key Research and Development Program of China(Grant No.2022YFB4500604)in part by the Natural Science Foundation of Guangdong Province,China(Grant No.2022A1515010100 and 2024A1515010140).
文摘Compared with traditional open surgery,laparoscopic surgery significantly reduces bodily trauma,postoperative pain,and hospitalization duration.However,owing to the small size of incisions and the counterintuitive motion of surgical tools,longer training cycles are required for surgeons to achieve fine operational skills.This paper presents a laparoscopic surgery simulator with haptic-feedback control(LSHC-6)that provides a reliable and cost-effective training alternative for surgeons.In addition to the structural diagram,kinematic analysis,and gravity compensation algorithm,a particle swarm optimization algorithm(PSO)is applied to optimize the structural parameters of the simulator by evaluating its workspace,global dexterity,and gravity compensation ability.A prototype system was developed and evaluated using two training experiments.The results demonstrate that the simulator exhibits good operational fluidity,workspace,and stable force output,effectively meeting the needs of laparoscopic surgical training.
文摘BACKGROUND Although exposure therapy is a proven treatment for post-traumatic stress disorder(PTSD),empirical research is difficult due to ethical issues.Recently,virtual reality-based content that can provide space and time similar to reality for exposure therapy techniques is increasing.AIM To examine exposure therapy using driving simulations in patients with PTSD due to traffic accidents with PTSD symptoms.METHODS The intervention was provided to two individuals who experienced PTSD symptoms after a traffic accident using a driving simulator.Among the singlesubject experimental designs,the ABA(baseline-intervention-baseline)design was used,and the PTSD checklist and brain wave frequency were used to measure the results.RESULTS In all participants,the standard category departure time of the electroencephalogram decreased from baseline,and PTSD symptoms decreased after the intervention.CONCLUSION These results suggest the potential use of a driving simulator as an exposure treatment tool for PTSD.
基金supported by the National Key Research and Development Program of China (Grant No.2021YFC2202604)the Strategy Priority Research Program of Chinese Academy of Sciences (Grant No.XDA1502110101).
文摘The ground-based experimental tests are crucial to verify the related technologies of the drag-free satellite.This work presents a design method of the ground simulator testbed for emulating the planar dynamics of the space drag-free systems.In this paper,the planar dynamic characteristics of the drag-free satellite with double test masses are analyzed and nondimensionalized.A simulator vehicle composed of an air bearing testbed and two inverted pendulums is devised on the basic of equivalent mass and equivalent stiffness proposed firstly in this paper.And the dynamic model of the simulator equivalent to the sensitive axis motion of the test mass and the planar motion of the satellite is derived from the Euler-Lagrange method.Then,the dynamic equivalence conditions between the space prototype system and the ground model system are derived from Pi theorem.To satisfy these conditions,the scaling laws of two systems and requirements for the inverted pendulum are put forward.Besides,the corresponding control scaling laws and a closed-loop control strategy are deduced and applied to establishing the numerical simulation experiments of underactuated system.Subsequently,the comparative simulation results demonstrate the similarity of dynamical behavior between the scaled-down ground model and the space prototype.As a result,the rationality and effectiveness of the design method are proved,facilitating the ground simulation of future gravitational wave detection satellites.
基金supported by National Natural Science Foundation of China(Grant Numbers 11872339,11472248).
文摘In this paper,the degradation of mechanical properties of engineering cementitious composites(ECCs)at elevated temperatures and the failure of fiber are considered.A failure model under coupled thermo-mechanical loads for ECC is developed based on bond-based peridynamics.A semi-discrete model is constructed to describe fiber–matrix interactions and simulate thermal failure in ECC.The peridynamic differential operator(PDDO)is utilized for non-local modeling of thermal fluid flow and heat transfer.A multi-rate explicit time integration method is adopted to address thermo-mechanical coupling over different time scales.Model validation is achieved through simulating transient heat transfer in a homogeneous plate,with results aligning with analytical solutions.The damage behavior of a heated ECC plate in a borehole and under a fire scenario is analyzed,providing insights for enhancing fire resistance and high-temperature performance of ECC materials and structures.
基金National Key Research and Development Program of China(2022YFB4600902)Shandong Provincial Science Foundation for Outstanding Young Scholars(ZR2024YQ020)。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.
基金financially supported by the National Science and Technology Major Project of China (No.J2019-VI-0004-0117)a Laboratory Fund Project (6142903220101)。
文摘The size and shape effect(SSE)of components has become a critical issue for mechanical properties,application reliability,and processing.In this study,the creep rupture life(CRL)of components with different wall thicknesses and positions in a combustion chamber casing simulator made of K439B superalloy was investigated.The intrinsic mechanisms of the SSE were explored from the dendrite structure,volume fraction and size of theγ'phase,and element segregation,etc.It is shown that this casting exhibits a strong SSE of creep rupture life,characterized by a significant difference in the CRL values up to 60%with the variation of wall thickness and position in the casing.In terms of casting technology,the influence of SSE on CRL is actually determined by the cooling rate.The SSE on the creep rupture life originates from the dendrite structure(such as the secondary dendrite arm spacing),volume fraction size of theγ'phase in the dendrite trunk,and elements segregation rate.This work may have implications for the design and application of engineering components with large sizes and complex structures.
文摘BACKGROUND Orthopaedic surgical education has traditionally depended on the apprenticeship model of“see one,do one,teach one”.However,reduced operative exposure,stricter work-hour regulations,medicolegal constraints,and patient safety concerns have constrained its practicality.Simulation-based training has become a reliable,safe,and cost-efficient alternative.Dry lab techniques,especially virtual and augmented reality,make up 78%of current dry lab research,whereas wet labs still set the standard for anatomical realism.AIM To evaluate the effectiveness,limitations,and future directions of wet and dry lab simulation in orthopaedic training.METHODS A scoping review was carried out across four databases-PubMed,Cochrane Library,Web of Science,and EBSCOhost-up to 2025.Medical Subject Headings included:"Orthopaedic Education","Wet Lab","Dry Lab","Simulation Training","Virtual Reality",and"Surgical Procedure".Eligible studies focused on orthopaedic or spinal surgical education,employed wet or dry lab techniques,and assessed training effectiveness.Exclusion criteria consisted of non-English publications,abstracts only,non-orthopaedic research,and studies unrelated to simulation.Two reviewers independently screened titles,abstracts,and full texts,resolving discrepancies with a third reviewer.RESULTS From 1851 records,101 studies met inclusion:78 on dry labs,7 on wet labs,4 on both.Virtual reality(VR)simulations were most common,with AI increasingly used for feedback and assessment.Cadaveric training remains the gold standard for accuracy and tactile feedback,while dry labs-especially VR-offer scalability,lower cost(40%-60%savings in five studies),and accessibility for novices.Senior residents prefer wet labs for complex tasks;juniors favour dry labs for basics.Challenges include limited transferability data,lack of standard outcome metrics,and ethical concerns about cadaver use and AI assessment.CONCLUSION Wet and dry labs each have unique strengths in orthopaedic training.A hybrid approach combining both,supported by standardised assessments and outcome studies,is most effective.Future efforts should aim for uniform reporting,integrating new technologies,and policy support for hybrid curricula to enhance skills and patient care.
