The precise microscopic feature of carbon-carbon（C/C） composites is essential {or an accurate predic tion of their mechanical behavior. After fabrication, actual microscopic feature differs from simple ideal spatial...The precise microscopic feature of carbon-carbon（C/C） composites is essential {or an accurate predic tion of their mechanical behavior. After fabrication, actual microscopic feature differs from simple ideal spatial model. Micro computed lomography（CT） scan can well describe internal microstruetures of composites. Therefore, a reconstructed model is developed based on mireo-CT, by a series of prodcedures including extrac tlng components, generating new binary images and establishing a finite element （FE） model. Compared with the model designed by reconstructed commercial software MIMICS. the presented reconstructed FE model is superior in terms of high mesh quality and eontrollable mesh cluantity. The precision of the model is verified by experiment.展开更多
An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell ...An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell and the blade heater contactor structure by three-dimensional finite element modeling are compared with each other during RESET operation. The simulation results show that the programming region of the phase change layer in the BTL cell is much smaller, and thermal electrical distributions of the BTL cell are more concentrated on the TiN/GST interface. The results indicate that the BTL cell has the superiorities of increasing the heating efficiency, decreasing the power consumption and reducing the RESET current from 0.67mA to 0.32mA. Therefore, the BTL cell will be appropriate for high performance PCRAM device with lower power consumption and lower RESET current.展开更多
At the first time,the finite element method was used to model and analyze the free vibration and transient response of non-uniform thickness bi-directional functionally graded sandwich porous(BFGSP)skew plates.The who...At the first time,the finite element method was used to model and analyze the free vibration and transient response of non-uniform thickness bi-directional functionally graded sandwich porous(BFGSP)skew plates.The whole BFGSP skew-plates is placed on a variable visco-elastic foundation(VEF)in the hygro-thermal environment and subjected to the blast load.The BFGSP skew-plate thickness is permitted to vary non-linearly over both the length and width of the skew-plate,thereby faithfully representing the real behavior of the structure itself.The analysis is based on a four-node planar quadrilateral element with eight degrees of freedom per node,which is approximated using Lagrange Q_(4)shape function and C^(1)level non-conforming Hermite shape function based on refined higher-order shear deformation plate theory.The forced vibration parameters of the non-uniform thickness BFGSP skew-plate are fully determined using Hamilton's principle and the Newmark-βdirect integration technique.Accuracy of the calculation program is validated by comparing its numerical results with those from reputable sources.Furthermore,a thorough assessment is conducted to determine the impact of various parameters on the free and forced vibration responses of the non-uniform thickness BFGSP skew-plate.The findings of the paper may be used in the development of civil and military structures in situations that are prone to exceptional forces,such as explosions and impacts load.展开更多
The aim of this study is to develop coupled matrix formulations to characterize the dynamic interaction between the vehicle,track,and tunnel.The vehicle–track coupled system is established in light of vehicle–track ...The aim of this study is to develop coupled matrix formulations to characterize the dynamic interaction between the vehicle,track,and tunnel.The vehicle–track coupled system is established in light of vehicle–track coupled dynamics theory.The physical characteristics and mechanical behavior of tunnel segments and rings are modeled by the finite element method,while the soil layers of the vehicle–track–tunnel(VTT)system are modeled as an assemblage of 3-D mapping infinite elements by satisfying the boundary conditions at the infinite area.With novelty,the tunnel components,such as rings and segments,have been coupled to the vehicle–track systems using a matrix coupling method for finite elements.The responses of sub-systems included in the VTT interaction are obtained simultaneously to guarantee the solution accuracy.To relieve the computer storage and save the CPU time for the large-scale VTT dynamics system with high degrees of freedoms,a cyclic calculation method is introduced.Apart from model validations,the necessity of considering the tunnel substructures such as rings and segments is demonstrated.In addition,the maximum number of elements in the tunnel segment is confirmed by numerical simulations.展开更多
To control the vibration level of ships under construction,MSC Software’s Patran&Nastran modeling solutions can be used to establish a detailed finite element model of a new manned submersible support mother ship...To control the vibration level of ships under construction,MSC Software’s Patran&Nastran modeling solutions can be used to establish a detailed finite element model of a new manned submersible support mother ship based on a line drawing,including the deck layout,bulkhead section,and stiffener distribution.After a comprehensive analysis of the ship simulation conditions,boundaries,and excitation forces of the main operating equipment,modal analysis and calculation of the ship vibration can be conducted.In this study,we calculated and analyzed the vibration response of key points in the stern area of the ship’s main deck and the submersible warehouse area under design loading working conditions.We then analyzed the vibration response of typical decks(including the compass deck,steering deck,captain’s deck,forecastle deck,and main deck)under the main excitation forces and moments(such as the full swing pod and generator sets).The analysis results showed that under DESIDEP working conditions,the vibration of each deck and key areas of the support mother ship could meet the vibration code requirements of the ship’s preliminary design(using the pod excitation and generator sets).Similarly,the vibration response of a scientific research ship under other loading conditions also met the requirements of the code and provided data support for a comprehensive understanding of the ship’s vibration and noise levels.Using actual vibration measurements,the accuracy of the vibration level simulations using finite element modeling was verified,the vibration of each area of the ship comfortably meeting the requirements of the China Classification Society.展开更多
Quantitative analysis of mine-wide subsidence at the kilometer scale and details of stress distribution about an advancing longwall face are estimated using an adaptation of the finite element method. The method is we...Quantitative analysis of mine-wide subsidence at the kilometer scale and details of stress distribution about an advancing longwall face are estimated using an adaptation of the finite element method. The method is well suited to the tasks at hand. For greater realism, variability of strata properties is taken into account as are the effects of joints and cleats on elastic moduli and strengths. Evolution of pillar stress and entry closure remote from the face is readily quantified in a series of analyses that simulate face advance. Computed results compare favorably with the evolution of closure measurements about an instrumented pillar in a two-entry headgate. The appropriateness of the finite element method is confirmed. This method is based on first principles that avoid empirical schemes of uncertain applicability and numerical models ‘‘calibrated" by fitting computer output to mine measurements.展开更多
Theoretical studies on the multi-bubble interaction are crucial for the in-depth understanding of the mechanism behind the applications of ultrasound contrast agents （UCAs） in clinics. A two-dimensional （2D） axisy...Theoretical studies on the multi-bubble interaction are crucial for the in-depth understanding of the mechanism behind the applications of ultrasound contrast agents （UCAs） in clinics. A two-dimensional （2D） axisymmetric finite element model （FEM） is developed here to investigate the bubble-bubble interactions for UCAs in a fluidic environment. The effect of the driving frequency and the bubble size on the bubble interaction tendency （viz., bubbles＇ attraction and repulsion）, as well as the influences of bubble shell mechanical parameters （viz., surface tension coefficient and viscosity coefficient） are discussed. Based on FEM simulations, the temporal evolution of the bubbles＇ radii, the bubble-bubble distance, and the distribution of the velocity field in the surrounding fluid are investigated in detail. The results suggest that for the interacting bubble-bubble couple, the overall translational tendency should be determined by the relationship between the driving frequency and their resonance frequencies. When the driving frequency falls between the resonance frequencies of two bubbles with different sizes, they will repel each other, otherwise they will attract each other. For constant acoustic driving parameters used in this paper, the changing rate of the bubble radius decreases as the viscosity coefficient increases, and increases first then decreases as the bubble shell surface tension coefficient increases, which means that the strength of bubble-bubble interaction could be adjusted by changing the bubble shell visco-elasticity coefficients. The current work should provide a powerful explanation for the accumulation observations in an experiment, and provide a fundamental theoretical support for the applications of UCAs in clinics.展开更多
This article proposes a finite element model （FEM） for predicting the acoustic scattering from an encapsulated microbubble near rigid boundary. The validity of the model is first examined by comparing the acoustic n...This article proposes a finite element model （FEM） for predicting the acoustic scattering from an encapsulated microbubble near rigid boundary. The validity of the model is first examined by comparing the acoustic nonlinear response of a free microbubble with that obtained by the Church model. Then this model is used to investigate the effect of the rigid boundary on acoustic scattering signals from microbubble. The results indicate that the resonance frequency decreases while the oscillation amplitude increases as the microbubble approaches the rigid boundary. In addition, the fundamental component of the acoustic scattering signal is enhanced compared with that of the free microbubble.展开更多
In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix...In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix are stressed. The FEM equations of mechanics characteristics, natural frequency and main mode are set up based on the first order matrix perturbation theory. Applicantion of the proposed model to analyze a real arch bridge proved the improvement in the simulation precision of dynamical characteristics of the arch bridge by considering the effects of suspender length variation.展开更多
Rail vehicles generate huge longitudinal impact loads in collisions.If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body,the risk of ...Rail vehicles generate huge longitudinal impact loads in collisions.If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body,the risk of car body structure damage and train derailment will increase.Herein,a four-stage rigid-flexible coupling finite element model of the coupler is established considering the coupler buckling load.The influence of the coupler buckling load on the train longitudinal-vertical-hori-zontal buckling behavior was studied,and the mechanism of the train horizontal buckling instability in train collisions was revealed.Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically.The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision.If the strength of the two sides of the car body structure in the lateral direction is asymmetrical,the deformation on the weaker side will be larger,and the end of the car body will begin to deflect under the action of the coupler force,which in turn causes the train to undergo sawtooth buckling.展开更多
In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditio...In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditional FEM of slab non-ballast track structures was improved.The multiscale FEM of CRTSII type slab nonballast track structures was established based on the general finite element program ABAQUs.Then the comparative calculation was made between various FEMs,showing that the high solution precision,fast modelling speed and high solution efficiency could be obtained.Therefore,the multiscale FEM was suitable for the parametric study on mechanical behaviour of CRTSII type slab non-ballast track structures,and then the key influence factor and constructions could be optimized.展开更多
The finite-element modeling and simulations of the intra-body communication （IBC） were investigated to provide a theoretical basis for biomedical monitoring. A finite-element model for the whole human body was devel...The finite-element modeling and simulations of the intra-body communication （IBC） were investigated to provide a theoretical basis for biomedical monitoring. A finite-element model for the whole human body was developed to simulate the IBC. The simulation of galvanic coupling IBC and electrostatic coupling IBC were implemented along with different signal transmission paths, and their attenuations were calculated. Our study showed that the position near the signal electrode had higher potential than other positions in the two types of IBC, while the potential generally decreased along the axis of the body parts. Both signal attenuations of the two types IBC increased with increasing signal transmission distance, and the electrostatic coupling IBC had comparatively higher receiving potential than the galvanic coupling IBC. The results indicated that the proposed modeling method could be used for the research of biomedical monitoring based on IBC technology.展开更多
This paper is concerned about the automatic finite element modeling of a wing structure. The row and column method is used to identify the structure parts(ribs, spars, skins and pillars). A customization module of...This paper is concerned about the automatic finite element modeling of a wing structure. The row and column method is used to identify the structure parts(ribs, spars, skins and pillars). A customization module of PCL(PATRAN Command Language under PATRAN 6.0) code from constructing airfoil curves to creating the entire wing FEM model is designed and developed. The geome tric, mesh density, material, load and boundary parameters can be easily and correctly input with the friendly interactive interface. A VFW614 wing is analyzed from creating airfoil curves to the show of stresses calculated by using NASTRAN 68 as an example. The results show that this customization module is very effective and efficient.展开更多
High energy gas fracturing is a simple approach of applying high pressure gas to stimulate wells by gen- erating several radial cracks without creating any other damages to the wells. In this paper, a numerical algori...High energy gas fracturing is a simple approach of applying high pressure gas to stimulate wells by gen- erating several radial cracks without creating any other damages to the wells. In this paper, a numerical algorithm is proposed to quantitatively simulate propagation of these fractures around a pressurized hole as a quasi-static phenomenon. The gas flow through the cracks is assumed as a one-dimensional transient flow, governed by equations of conservation of mass and momentum. The fractured medium is modeled with the extended finite element method, and the stress intensity factor is calculated by the simple, though sufficiently accurate, displacement ex- trapolation method. To evaluate the proposed algorithm, two field tests are simulated and the unknown parameters are determined through calibration. Sensitivity analyses are performed on the main effective parameters. Considering that the level of uncertainty is very high in these types of engineering problems, the results show a good agreement with the experimental data. They are also consistent with the theory that the final crack length is mainly determined by the gas pressure rather than the initial crack length produced by the stress waves.展开更多
A new type of soft actuator material-ionic liquid gel （ILG）, which consists of HEMA, BMIMBF4, and TiO2, can be transformed into gel state under the irradiation of ultraviolet （UV） light. In this paper, Mooney-Rivl...A new type of soft actuator material-ionic liquid gel （ILG）, which consists of HEMA, BMIMBF4, and TiO2, can be transformed into gel state under the irradiation of ultraviolet （UV） light. In this paper, Mooney-Rivlin hyperelastic model of finite element method is proposed for the first time to study the properties of the ILG. It has been proved that the content of TiO2 has a great influence on the properties of the gel, and Young＇s modulus of the gel increases with the increase of its content, despite of reduced tensile deformation. The results in this work show that when the TiO2 content is 1.0 wt%, a large tensile deformation and a strong Young＇s modulus can be obtained to be 325% and 7.8 kPa, respectively. The material parameters of ILG with TiO2 content values of 0.2 wt%, 0.5 wt%, 1.0 wt%, and 1.5 wt% are obtained, respectively, through uniaxial tensile tests, including C10, C01, C20, C11, C02, C30, C21, C12, and C03 elements. In this paper, the large-scaled general finite element software ANSYS is used to simulate and analyze the ILG, which is based on SOLID186 element and nonlinear hyperelastic Mooney-Rivlin model. The finite element simulation analysis based stress-strain curves are almost consistent with the experimental stress-strain curves, and hence the finite element analysis of ILG is feasible and credible. This work presents a new direction for studying the performance of soft actuator for the ILG, and also contributes to the design of soft robot actuator.展开更多
This is the second paper of a series where we introduce a control volume based finite element method （CVFEM） to simulate multiphase flow in porous media. This is a fully conservative method able to deal with unstruc...This is the second paper of a series where we introduce a control volume based finite element method （CVFEM） to simulate multiphase flow in porous media. This is a fully conservative method able to deal with unstructured grids which can be used for representing any complexity of reservoir geometry and its geological objects in an accurate and efficient manner. In order to deal with the inherent heterogeneity of the reservoirs, all operations related to discretization are performed at the element level in a manner similar to classical finite element method （FEM）. Moreover, the proposed method can effectively reduce the so-called grid orientation effects. In the first paper of this series, we presented this method and its application for incompressible and immiscible two-phase flow simulation in homogeneous and heterogeneous porous media. In this paper, we evaluate the capability of the method in the solution of highly nonlinear and coupled partial differential equations by simulating hydrocarbon reservoirs using the black-oil model. Furthermore, the effect of grid orientation is investigated by simulating a benchmark waterflooding problem. The numerical results show that the formulation presented here is efficient and accurate for solving the bubble point and three-phase coning problems.展开更多
Laser powder bed fusion(LPBF),like many other additive manufacturing techniques,offers flexibility in design expected to become a disruption to the manufacturing industry.The current cost of LPBF process does not favo...Laser powder bed fusion(LPBF),like many other additive manufacturing techniques,offers flexibility in design expected to become a disruption to the manufacturing industry.The current cost of LPBF process does not favor a try-anderror way of research,which makes modelling and simulation a field of superior importance in that area of engineering.In this work,various methods used to overcome challenges in modeling at different levels of approximation of LPBF process are reviewed.Recent efforts made towards a reliable and computationally effective model to simulate LPBF process using finite element(FE)codes are presented.A combination of ray-tracing technique,the solution of the radiation transfer equation and absorption measurements has been used to establish an analytical equation,which gives a more accurate approximation of laser energy deposition in powder-substrate configuration.When this new analytical energy deposition model is used in in FE simulation,with other physics carefully set,it enables us to get reliable cooling curves and melt track morphology that agree well with experimental observations.The use of more computationally effective approximation,without explicit topological changes,allows to simulate wider geometries and longer scanning time leading to many applications in real engineering world.Different applications are herein presented including:prediction of printing quality through the simulated overlapping of consecutive melt tracks,simulation of LPBF of a mixture of materials and estimation of martensite inclusion in printed steel.展开更多
A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching a...A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching and forming process of cartridge cases are established,and the corresponding simulation result model of each intermediate procedure is obtained by continuously performing the forming process simulation. The simulation model cannot annotate size and process information due to poor interface between DEFORM software and CAD software. Thus,a 3D annotation module is developed with secondary development technology of UG NX software. Consequently,the final process model with dimension and process information is obtained. Then,with the current 3D process management system,the 3D punching and forming process design of cartridge cases can be completed further. An example is also provided to illustrate that the relative error between the simulation process model and the physical model is less than 2%,which proves the validity and reliability of the proposed method in this study.展开更多
Objective To investigate the changes of hipbone biomechanics after the resection of ischiopubic tumors and their relationships with the complications in the convalescent stage, and directing the postoperative pelvic r...Objective To investigate the changes of hipbone biomechanics after the resection of ischiopubic tumors and their relationships with the complications in the convalescent stage, and directing the postoperative pelvic reconstruction. Methods DICOM data were used to create an intact hipbone finite element model and postoperative model. The biomechanical indices on the same region in the two models under the same boundary condition were compared. The differences of displacement, stress, and strain of the two models were analyzed with statistical methods. Results The distribution areas of the hipbone nodes' displacement, stress, and strain were similar before and after the simulated operation. The sacroiliac joint nodes' displacement (P=0.040) and strain (P=0.000), and the acetabular roof nodes' stress (P=0.000) and strain (P=0.005) of two models had significant differences, respectively. But the sacroiliac joint nodes' stress (P=0.076) and the greater sciatic notch nodes' stress (P=0.825) and strain (P=0.506) did not have significant differences. Conclusions The resection of ischiopubic tumors mainly affect the biomechanical states of the homolateral sacroiliac joint and acetabular roof. The complications in the convalescent stage are due to the biomechanical changes of the sacroiliac joint and the acetabular roof and disappearances of the stabilization and connection functions of the pubic symphysis and superior ramus of pubis.展开更多
The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The b...The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The boundary value method(BVM),based on the finite difference method(FDM),can be used to reconstruct the source wavefield in the reverse time propagation in the same way as the receiver wavefield,which can reduce the storage burden of the RTM data.Considering that the FDM cannot well handle models with discontinuous material properties and rough interfaces,we develop a source wavefield reconstruction strategy based on the finite element method(FEM),using proper orthogonal decomposition(POD)to enhance computational efficiency.In this method,we divide the whole time period into several segments,and construct the POD basis functions to get a reduced order model(ROM)for the source wavefield reconstruction in each segment.We show the corresponding quantitative analysis of the storage requirement of the POD-FEM.Numerical tests on the homogeneous model show the effectiveness of the proposed method,while the layered model and part of the Marmousi model tests indicate that the POD-FEM can keep an excellent balance between computational efficiency and memory usage compared with the full-stored method(FSM)and the BVM,and can be effectively applied in imaging.展开更多
基金supported by the National Natural Science Foundation of China (Nos.11272147,10772078)the Aviation Science Foundation (No.2013ZF52074)+1 种基金the State Key Laboratory of Mechanical Structural Mechanics and Control (No.0214G02)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The precise microscopic feature of carbon-carbon（C/C） composites is essential {or an accurate predic tion of their mechanical behavior. After fabrication, actual microscopic feature differs from simple ideal spatial model. Micro computed lomography（CT） scan can well describe internal microstruetures of composites. Therefore, a reconstructed model is developed based on mireo-CT, by a series of prodcedures including extrac tlng components, generating new binary images and establishing a finite element （FE） model. Compared with the model designed by reconstructed commercial software MIMICS. the presented reconstructed FE model is superior in terms of high mesh quality and eontrollable mesh cluantity. The precision of the model is verified by experiment.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDA09020402the National Integrate Circuit Research Program of China under Grant No 2009ZX02023-003+1 种基金the National Natural Science Foundation of China under Grant Nos 61261160500,61376006,61401444 and 61504157the Science and Technology Council of Shanghai under Grant Nos 14DZ2294900,15DZ2270900 and 14ZR1447500
文摘An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell and the blade heater contactor structure by three-dimensional finite element modeling are compared with each other during RESET operation. The simulation results show that the programming region of the phase change layer in the BTL cell is much smaller, and thermal electrical distributions of the BTL cell are more concentrated on the TiN/GST interface. The results indicate that the BTL cell has the superiorities of increasing the heating efficiency, decreasing the power consumption and reducing the RESET current from 0.67mA to 0.32mA. Therefore, the BTL cell will be appropriate for high performance PCRAM device with lower power consumption and lower RESET current.
文摘At the first time,the finite element method was used to model and analyze the free vibration and transient response of non-uniform thickness bi-directional functionally graded sandwich porous(BFGSP)skew plates.The whole BFGSP skew-plates is placed on a variable visco-elastic foundation(VEF)in the hygro-thermal environment and subjected to the blast load.The BFGSP skew-plate thickness is permitted to vary non-linearly over both the length and width of the skew-plate,thereby faithfully representing the real behavior of the structure itself.The analysis is based on a four-node planar quadrilateral element with eight degrees of freedom per node,which is approximated using Lagrange Q_(4)shape function and C^(1)level non-conforming Hermite shape function based on refined higher-order shear deformation plate theory.The forced vibration parameters of the non-uniform thickness BFGSP skew-plate are fully determined using Hamilton's principle and the Newmark-βdirect integration technique.Accuracy of the calculation program is validated by comparing its numerical results with those from reputable sources.Furthermore,a thorough assessment is conducted to determine the impact of various parameters on the free and forced vibration responses of the non-uniform thickness BFGSP skew-plate.The findings of the paper may be used in the development of civil and military structures in situations that are prone to exceptional forces,such as explosions and impacts load.
基金supported by the National Natural Science Foundation of China(Grant Nos.52008404,11790283,and 51735012).
文摘The aim of this study is to develop coupled matrix formulations to characterize the dynamic interaction between the vehicle,track,and tunnel.The vehicle–track coupled system is established in light of vehicle–track coupled dynamics theory.The physical characteristics and mechanical behavior of tunnel segments and rings are modeled by the finite element method,while the soil layers of the vehicle–track–tunnel(VTT)system are modeled as an assemblage of 3-D mapping infinite elements by satisfying the boundary conditions at the infinite area.With novelty,the tunnel components,such as rings and segments,have been coupled to the vehicle–track systems using a matrix coupling method for finite elements.The responses of sub-systems included in the VTT interaction are obtained simultaneously to guarantee the solution accuracy.To relieve the computer storage and save the CPU time for the large-scale VTT dynamics system with high degrees of freedoms,a cyclic calculation method is introduced.Apart from model validations,the necessity of considering the tunnel substructures such as rings and segments is demonstrated.In addition,the maximum number of elements in the tunnel segment is confirmed by numerical simulations.
基金Supported by the Research and Implementation of Sea Trial Technology(Grant No.2016YFC03000704).
文摘To control the vibration level of ships under construction,MSC Software’s Patran&Nastran modeling solutions can be used to establish a detailed finite element model of a new manned submersible support mother ship based on a line drawing,including the deck layout,bulkhead section,and stiffener distribution.After a comprehensive analysis of the ship simulation conditions,boundaries,and excitation forces of the main operating equipment,modal analysis and calculation of the ship vibration can be conducted.In this study,we calculated and analyzed the vibration response of key points in the stern area of the ship’s main deck and the submersible warehouse area under design loading working conditions.We then analyzed the vibration response of typical decks(including the compass deck,steering deck,captain’s deck,forecastle deck,and main deck)under the main excitation forces and moments(such as the full swing pod and generator sets).The analysis results showed that under DESIDEP working conditions,the vibration of each deck and key areas of the support mother ship could meet the vibration code requirements of the ship’s preliminary design(using the pod excitation and generator sets).Similarly,the vibration response of a scientific research ship under other loading conditions also met the requirements of the code and provided data support for a comprehensive understanding of the ship’s vibration and noise levels.Using actual vibration measurements,the accuracy of the vibration level simulations using finite element modeling was verified,the vibration of each area of the ship comfortably meeting the requirements of the China Classification Society.
基金Financial support by the National Institute of Safety and Health under Contract 200-2016-90240, MIS Analysis and DINSAR Measurements-Tools for Improving Mine Ground Control Safety is gratefully acknowledged
文摘Quantitative analysis of mine-wide subsidence at the kilometer scale and details of stress distribution about an advancing longwall face are estimated using an adaptation of the finite element method. The method is well suited to the tasks at hand. For greater realism, variability of strata properties is taken into account as are the effects of joints and cleats on elastic moduli and strengths. Evolution of pillar stress and entry closure remote from the face is readily quantified in a series of analyses that simulate face advance. Computed results compare favorably with the evolution of closure measurements about an instrumented pillar in a two-entry headgate. The appropriateness of the finite element method is confirmed. This method is based on first principles that avoid empirical schemes of uncertain applicability and numerical models ‘‘calibrated" by fitting computer output to mine measurements.
基金Projects supported by the National Natural Science Foundation of China(Grant Nos.11474161,11474001,116741731,1774166,11774168,81527803,81627802,and 81420108018)the Fundamental Research Funds for the Central Universities,China(Grant No.020414380109)the Qing Lan Project,China
文摘Theoretical studies on the multi-bubble interaction are crucial for the in-depth understanding of the mechanism behind the applications of ultrasound contrast agents （UCAs） in clinics. A two-dimensional （2D） axisymmetric finite element model （FEM） is developed here to investigate the bubble-bubble interactions for UCAs in a fluidic environment. The effect of the driving frequency and the bubble size on the bubble interaction tendency （viz., bubbles＇ attraction and repulsion）, as well as the influences of bubble shell mechanical parameters （viz., surface tension coefficient and viscosity coefficient） are discussed. Based on FEM simulations, the temporal evolution of the bubbles＇ radii, the bubble-bubble distance, and the distribution of the velocity field in the surrounding fluid are investigated in detail. The results suggest that for the interacting bubble-bubble couple, the overall translational tendency should be determined by the relationship between the driving frequency and their resonance frequencies. When the driving frequency falls between the resonance frequencies of two bubbles with different sizes, they will repel each other, otherwise they will attract each other. For constant acoustic driving parameters used in this paper, the changing rate of the bubble radius decreases as the viscosity coefficient increases, and increases first then decreases as the bubble shell surface tension coefficient increases, which means that the strength of bubble-bubble interaction could be adjusted by changing the bubble shell visco-elasticity coefficients. The current work should provide a powerful explanation for the accumulation observations in an experiment, and provide a fundamental theoretical support for the applications of UCAs in clinics.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10774071)the National Basic Research Prgram 973 (Grant No. 2010CB732600)from Ministry of Science and Technology,China+1 种基金the Natural Science Foundation of Jiangsu Province,China (Grant No. BK2007518)the State Key Laboratory of Acoustics (Grant No. 200902)
文摘This article proposes a finite element model （FEM） for predicting the acoustic scattering from an encapsulated microbubble near rigid boundary. The validity of the model is first examined by comparing the acoustic nonlinear response of a free microbubble with that obtained by the Church model. Then this model is used to investigate the effect of the rigid boundary on acoustic scattering signals from microbubble. The results indicate that the resonance frequency decreases while the oscillation amplitude increases as the microbubble approaches the rigid boundary. In addition, the fundamental component of the acoustic scattering signal is enhanced compared with that of the free microbubble.
基金Supported by the Key Teacher Foundation of Chongqing University (No. 717411067)
文摘In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix are stressed. The FEM equations of mechanics characteristics, natural frequency and main mode are set up based on the first order matrix perturbation theory. Applicantion of the proposed model to analyze a real arch bridge proved the improvement in the simulation precision of dynamical characteristics of the arch bridge by considering the effects of suspender length variation.
基金This work was supported by the National Natural Science Foundation of China(No.52172409)Sichuan Outstanding Youth Fund(No.2022JDJQ0025).
文摘Rail vehicles generate huge longitudinal impact loads in collisions.If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body,the risk of car body structure damage and train derailment will increase.Herein,a four-stage rigid-flexible coupling finite element model of the coupler is established considering the coupler buckling load.The influence of the coupler buckling load on the train longitudinal-vertical-hori-zontal buckling behavior was studied,and the mechanism of the train horizontal buckling instability in train collisions was revealed.Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically.The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision.If the strength of the two sides of the car body structure in the lateral direction is asymmetrical,the deformation on the weaker side will be larger,and the end of the car body will begin to deflect under the action of the coupler force,which in turn causes the train to undergo sawtooth buckling.
基金supported by“111”Project(B18062)Fundamental Research Funds for the Central Universities(2019CDQYTM028).
文摘In order to make further study on the mechanical property of CRTSIII type slab non-ballast track structures,which was self-designed in China,based on the method of the multiscale finite element model(FEM),the traditional FEM of slab non-ballast track structures was improved.The multiscale FEM of CRTSII type slab nonballast track structures was established based on the general finite element program ABAQUs.Then the comparative calculation was made between various FEMs,showing that the high solution precision,fast modelling speed and high solution efficiency could be obtained.Therefore,the multiscale FEM was suitable for the parametric study on mechanical behaviour of CRTSII type slab non-ballast track structures,and then the key influence factor and constructions could be optimized.
基金Supported by the National Natural Science Foundation of China(60801050)the Excellent Talent Fund of Beijing(2011)Excellent Young Scholars Research Fund of Beijing Institute ofTechnology(2012)
文摘The finite-element modeling and simulations of the intra-body communication （IBC） were investigated to provide a theoretical basis for biomedical monitoring. A finite-element model for the whole human body was developed to simulate the IBC. The simulation of galvanic coupling IBC and electrostatic coupling IBC were implemented along with different signal transmission paths, and their attenuations were calculated. Our study showed that the position near the signal electrode had higher potential than other positions in the two types of IBC, while the potential generally decreased along the axis of the body parts. Both signal attenuations of the two types IBC increased with increasing signal transmission distance, and the electrostatic coupling IBC had comparatively higher receiving potential than the galvanic coupling IBC. The results indicated that the proposed modeling method could be used for the research of biomedical monitoring based on IBC technology.
文摘This paper is concerned about the automatic finite element modeling of a wing structure. The row and column method is used to identify the structure parts(ribs, spars, skins and pillars). A customization module of PCL(PATRAN Command Language under PATRAN 6.0) code from constructing airfoil curves to creating the entire wing FEM model is designed and developed. The geome tric, mesh density, material, load and boundary parameters can be easily and correctly input with the friendly interactive interface. A VFW614 wing is analyzed from creating airfoil curves to the show of stresses calculated by using NASTRAN 68 as an example. The results show that this customization module is very effective and efficient.
基金support of Iran National Science Foundation is also gratefully appreciated
文摘High energy gas fracturing is a simple approach of applying high pressure gas to stimulate wells by gen- erating several radial cracks without creating any other damages to the wells. In this paper, a numerical algorithm is proposed to quantitatively simulate propagation of these fractures around a pressurized hole as a quasi-static phenomenon. The gas flow through the cracks is assumed as a one-dimensional transient flow, governed by equations of conservation of mass and momentum. The fractured medium is modeled with the extended finite element method, and the stress intensity factor is calculated by the simple, though sufficiently accurate, displacement ex- trapolation method. To evaluate the proposed algorithm, two field tests are simulated and the unknown parameters are determined through calibration. Sensitivity analyses are performed on the main effective parameters. Considering that the level of uncertainty is very high in these types of engineering problems, the results show a good agreement with the experimental data. They are also consistent with the theory that the final crack length is mainly determined by the gas pressure rather than the initial crack length produced by the stress waves.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51538009 and 51605334)the Natural Science Foundation of Shanghai Municipality,China(Grant No.08002360285)
文摘A new type of soft actuator material-ionic liquid gel （ILG）, which consists of HEMA, BMIMBF4, and TiO2, can be transformed into gel state under the irradiation of ultraviolet （UV） light. In this paper, Mooney-Rivlin hyperelastic model of finite element method is proposed for the first time to study the properties of the ILG. It has been proved that the content of TiO2 has a great influence on the properties of the gel, and Young＇s modulus of the gel increases with the increase of its content, despite of reduced tensile deformation. The results in this work show that when the TiO2 content is 1.0 wt%, a large tensile deformation and a strong Young＇s modulus can be obtained to be 325% and 7.8 kPa, respectively. The material parameters of ILG with TiO2 content values of 0.2 wt%, 0.5 wt%, 1.0 wt%, and 1.5 wt% are obtained, respectively, through uniaxial tensile tests, including C10, C01, C20, C11, C02, C30, C21, C12, and C03 elements. In this paper, the large-scaled general finite element software ANSYS is used to simulate and analyze the ILG, which is based on SOLID186 element and nonlinear hyperelastic Mooney-Rivlin model. The finite element simulation analysis based stress-strain curves are almost consistent with the experimental stress-strain curves, and hence the finite element analysis of ILG is feasible and credible. This work presents a new direction for studying the performance of soft actuator for the ILG, and also contributes to the design of soft robot actuator.
基金Iranian Offshore OilCompany (IOOC) for financial support of this work
文摘This is the second paper of a series where we introduce a control volume based finite element method （CVFEM） to simulate multiphase flow in porous media. This is a fully conservative method able to deal with unstructured grids which can be used for representing any complexity of reservoir geometry and its geological objects in an accurate and efficient manner. In order to deal with the inherent heterogeneity of the reservoirs, all operations related to discretization are performed at the element level in a manner similar to classical finite element method （FEM）. Moreover, the proposed method can effectively reduce the so-called grid orientation effects. In the first paper of this series, we presented this method and its application for incompressible and immiscible two-phase flow simulation in homogeneous and heterogeneous porous media. In this paper, we evaluate the capability of the method in the solution of highly nonlinear and coupled partial differential equations by simulating hydrocarbon reservoirs using the black-oil model. Furthermore, the effect of grid orientation is investigated by simulating a benchmark waterflooding problem. The numerical results show that the formulation presented here is efficient and accurate for solving the bubble point and three-phase coning problems.
基金Project supported by Singapore Maritime Institute and the Advanced Material&Manufacturing R&D Program(Grant Nos.SMI-2016-OF-04 and R261502032592)。
文摘Laser powder bed fusion(LPBF),like many other additive manufacturing techniques,offers flexibility in design expected to become a disruption to the manufacturing industry.The current cost of LPBF process does not favor a try-anderror way of research,which makes modelling and simulation a field of superior importance in that area of engineering.In this work,various methods used to overcome challenges in modeling at different levels of approximation of LPBF process are reviewed.Recent efforts made towards a reliable and computationally effective model to simulate LPBF process using finite element(FE)codes are presented.A combination of ray-tracing technique,the solution of the radiation transfer equation and absorption measurements has been used to establish an analytical equation,which gives a more accurate approximation of laser energy deposition in powder-substrate configuration.When this new analytical energy deposition model is used in in FE simulation,with other physics carefully set,it enables us to get reliable cooling curves and melt track morphology that agree well with experimental observations.The use of more computationally effective approximation,without explicit topological changes,allows to simulate wider geometries and longer scanning time leading to many applications in real engineering world.Different applications are herein presented including:prediction of printing quality through the simulated overlapping of consecutive melt tracks,simulation of LPBF of a mixture of materials and estimation of martensite inclusion in printed steel.
基金Supported by the National Defense Basic Scientific Research Project(A1020131011)
文摘A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching and forming process of cartridge cases are established,and the corresponding simulation result model of each intermediate procedure is obtained by continuously performing the forming process simulation. The simulation model cannot annotate size and process information due to poor interface between DEFORM software and CAD software. Thus,a 3D annotation module is developed with secondary development technology of UG NX software. Consequently,the final process model with dimension and process information is obtained. Then,with the current 3D process management system,the 3D punching and forming process design of cartridge cases can be completed further. An example is also provided to illustrate that the relative error between the simulation process model and the physical model is less than 2%,which proves the validity and reliability of the proposed method in this study.
基金Supported by Medical Scientific Research Foundation Item of Guangdong Province(A2008800)Science and Technology ProgramItem of Zhongshan City(20082A071and20113A049)
文摘Objective To investigate the changes of hipbone biomechanics after the resection of ischiopubic tumors and their relationships with the complications in the convalescent stage, and directing the postoperative pelvic reconstruction. Methods DICOM data were used to create an intact hipbone finite element model and postoperative model. The biomechanical indices on the same region in the two models under the same boundary condition were compared. The differences of displacement, stress, and strain of the two models were analyzed with statistical methods. Results The distribution areas of the hipbone nodes' displacement, stress, and strain were similar before and after the simulated operation. The sacroiliac joint nodes' displacement (P=0.040) and strain (P=0.000), and the acetabular roof nodes' stress (P=0.000) and strain (P=0.005) of two models had significant differences, respectively. But the sacroiliac joint nodes' stress (P=0.076) and the greater sciatic notch nodes' stress (P=0.825) and strain (P=0.506) did not have significant differences. Conclusions The resection of ischiopubic tumors mainly affect the biomechanical states of the homolateral sacroiliac joint and acetabular roof. The complications in the convalescent stage are due to the biomechanical changes of the sacroiliac joint and the acetabular roof and disappearances of the stabilization and connection functions of the pubic symphysis and superior ramus of pubis.
基金This work was supported by Natural Science Basic Research Program of Shaanxi(Program No.2023-JC-YB-269)the National Natural Science Foundation of China(Grant No.41974122).
文摘The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The boundary value method(BVM),based on the finite difference method(FDM),can be used to reconstruct the source wavefield in the reverse time propagation in the same way as the receiver wavefield,which can reduce the storage burden of the RTM data.Considering that the FDM cannot well handle models with discontinuous material properties and rough interfaces,we develop a source wavefield reconstruction strategy based on the finite element method(FEM),using proper orthogonal decomposition(POD)to enhance computational efficiency.In this method,we divide the whole time period into several segments,and construct the POD basis functions to get a reduced order model(ROM)for the source wavefield reconstruction in each segment.We show the corresponding quantitative analysis of the storage requirement of the POD-FEM.Numerical tests on the homogeneous model show the effectiveness of the proposed method,while the layered model and part of the Marmousi model tests indicate that the POD-FEM can keep an excellent balance between computational efficiency and memory usage compared with the full-stored method(FSM)and the BVM,and can be effectively applied in imaging.
