The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cart...The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.展开更多
This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite elem...This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.展开更多
In this paper, a finite element method （FEM）-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as...In this paper, a finite element method （FEM）-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as SOFT, adopting unified field equations for thermo-hydro-mechanical-air （THMA） behavior of geomaterial and using finite element-finite difference （FE-FD） scheme for so/l-water-air three-phase coupling problem, is used in the numerical simulation. As an application of the newly proposed numerical method, two engineering problems, one for slope failure in unsaturated model ground and another for in situ heating test related to deep geological repository of high-level radioactive waste （HLRW）, are simulated. The model tests on slope failure in unsaturated Shirasu ground, carried out by Kitamura et al. （2007）, is simulated in the framework of soil-water-air three-phase coupling under the condition of constant temperature. While the in situ heating test reported by Munoz （2006） is simulated in the same framework under the conditions of variable temperature hut constant air pressure.展开更多
In recent years, inflatable structures have been a subject of interest for space applications such as communication antenna, solar thermal propulsion and entry/landing systems. The inflatable structures characterized ...In recent years, inflatable structures have been a subject of interest for space applications such as communication antenna, solar thermal propulsion and entry/landing systems. The inflatable structures characterized by high strength-to-mass ratios, minimal stowage volume, which makes them suitable for cost-effective large space structures. A typical example for the inflatable structure is the inflated torus which often used in order to provide structure support. In this study, our main focus is to understand the dynamic characteristics of an inflated torus in order to formulate an accurate mathematical model suitable for active vibration control applications. A commercial finite element package, ANSYS, is used to model the inflated torus. To verify the model the obtained frequencies and mode shapes are compared with the published results, which are derived using analytical approach, the verification shows a good agreement between the FEM and the analytical results. Based on the verified model, parametric study was investigated; the material thickness increase causes the natural frequencies decrease, while the increase of the inflation pressure simply results in stiffening the ring, which means that the natural frequency increased. The FEM analysis gives an easy and fast way for the vibration analysis of the structures compared with the complicated analytical solutions.展开更多
Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be m...Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be made from different materials with possibly different gradients of material properties.The present work proposes models to investigate the free vibration of FGM sectioned beams based on onedimensional(1D)finite element analysis.For this purpose,a sample beam is divided into discrete elements,and the total energy stored in each element during vibration is computed by considering either the Timoshenko or Euler-Bernoulli beam theory.Then,Hamilton’s principle is used to derive the equations of motion for the beam.The effects of material properties and dimensions of FGM sections on the beam’s natural frequencies and their corresponding mode shapes are then investigated based on a dynamic Timoshenko model(TM).The presented model is validated by comparison with three-dimensional(3D)finite element simulations of the first three mode shapes of the beam.展开更多
This study investigates the effectiveness of salicylate(SAL)as an electrolyte additive on the discharge behavior of high-purity(HP)Mg anode in an aqueous half-cell system,using an integrated approach of mathematical m...This study investigates the effectiveness of salicylate(SAL)as an electrolyte additive on the discharge behavior of high-purity(HP)Mg anode in an aqueous half-cell system,using an integrated approach of mathematical modeling and experimental analysis.A finite elementbased model is developed to elucidate the key mechanisms by which SAL influences the voltage profile and pH.Systematic electrochemical measurements,especially intermittent discharge tests combined with electrochemical impedance spectroscopy(EIS),demonstrate that SAL can enhance initial voltage stability of HP Mg anode.Moreover,the model incorporates the SAL-Mg complexation factor to describe the role of SAL in modifying the deposit film on HP Mg surface.The agreement between model predictions and experimental observations suggests that SAL facilitates the formation of compact Mg(OH)_(2) deposits and sustains a favorable pH environment within the half-cell compartment.This integrated approach provides new insights into understanding and optimizing additive effects for Mg-air batteries.展开更多
This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results.A database was created combining published experimental data with in-house tests.By me...This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results.A database was created combining published experimental data with in-house tests.By means of a comprehensive framework,a Coulomb-type failure criterion accounting for friction mobilization was defined.During the elastic phase,in which the interface joint is not yet created,the proposed model provides zero radial displacement,and once the interface joint is created,interface dilatancy is modeled using a non-associated plastic potential inspired from the behavior of rock joints.The results predicted by the proposed model are in good agreement with experimental results.The model has been implemented in a finite element method(FEM)code and numerical simulations have been performed at the elementary and the structural scales.The results obtained provide confidence in the ability of the new model to assist in the design and optimization of bolting patterns.展开更多
Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts, many bumpers, particularly in large vehicles, are too stiff for pedestrian protection. In designing...Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts, many bumpers, particularly in large vehicles, are too stiff for pedestrian protection. In designing a bumper for an automobile, pedestrian protection is as important as bumper energy absorption in low speed collisions. To prevent lower extremity injuries in car-pedestrian collisions, it is important to determine the loadings that car front structures impart on the lower extremities and the mechanisms by which injury is caused by these loadings. The present work was focused on gaining more insight into the injury mechanisms leading to both ligament damage and bone fracture during bumper-pedestrian collisions. The European Enhanced Vehicle-safety Committee （EEVC） legform impactor model was introduced and validated against EEVCAVG17 criteria. The collision mechanism between a bumper and this legform impactor was investigated numerically using LS-DYNA software. To identify the effect of the bumper beam material on leg injuries, four analyses were performed on bumpers that had the same assembly but were made from different materials.展开更多
Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes t...Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.展开更多
A study of the behaviour of constructional cold-formed stainless steel beams at elevated temperatures was conducted in this paper. An accurate finite element model (FEM) for stainless steel beams was developed using t...A study of the behaviour of constructional cold-formed stainless steel beams at elevated temperatures was conducted in this paper. An accurate finite element model (FEM) for stainless steel beams was developed using the finite element program ABAQUS. Stainless steel beams having different cross-sections were simulated in this study. The nonlinear FEM was verified against the experimental results. Generally, the developed FEM could accurately simulate the stainless steel beams. Based on the high temperature stainless steel material test results, a parametric study was carried out on stainless steel beams at elevated tem- peratures using the verified FEM. Both high strength stainless steel EN 1.4462 and normal strength stainless steel EN 1.4301 were considered. A total of 42 stainless steel beams were simulated in the parametric study. The effect of temperatures on the behaviour of stainless steel beams was investigated. In addition, a limiting temperature for stainless steel beams was also proposed.展开更多
The multi-wedge cross rolling process of forming balls is described. The process tool for rolling 8 balls with a diameter of 35 mm is presented. The course of the rolling process, distributions of forming forces as we...The multi-wedge cross rolling process of forming balls is described. The process tool for rolling 8 balls with a diameter of 35 mm is presented. The course of the rolling process, distributions of forming forces as well as maps of effective strain and temperature in the obtained balls are presented by finite element modeling （FEM）. Ex- perimental tests of simultaneous forming of 4 balls with a diameter of 22 mm conducted in laboratory conditions at Lublin University of Technology have proved that the balls obtained in multi-wedge cross rolling are of good quality and can therefore be used in both ball mills and rolling bearings.展开更多
The combined loading tests of 5754 O aluminum alloy sheet are used to verify the yield function. Three yield functions are implemented into the commercial finite element model(FEM) code ABAQUS as a user material subro...The combined loading tests of 5754 O aluminum alloy sheet are used to verify the yield function. Three yield functions are implemented into the commercial finite element model(FEM) code ABAQUS as a user material subroutine UMAT for the FEM simulation of the combined loading tests. The comparison of the simulating and experimental results shows that the modified Yld2000-2d yield function can describe the mechanical behavior of5754 O aluminum alloy sheet under combined loading paths reasonably while other three yield functions do not.The performance of the modified Yld2000-2d yield function on describing the mechanical behavior under combined loading paths is analyzed in detail. It is concluded that the modified Yld2000-2d yield function can be adopted to describe the deformation behavior of 5754 O aluminum alloy sheet for industrial applications.展开更多
The behavior of square-tubed reinforced concrete (STRC) short columns subjected to axial compression was studied in detail with an accurate nonlinear finite element model (FEM) . Different width to thickness ratios (D...The behavior of square-tubed reinforced concrete (STRC) short columns subjected to axial compression was studied in detail with an accurate nonlinear finite element model (FEM) . Different width to thickness ratios (D/t = 50 150) of the steel tube and the compressive strength of concrete (C80 and C50) were adopted in this research. The axial load strength,steel tube strain and load-shortening response were determined from FEM and the analysis results from FEM were compared with those from experiment. The analysis and test results indicate that the concrete strength little affectes the confinement of the steel tube on the concrete. The transverse stress of the tube at the axial load point increases with the increment in the width to thickness ratio. Based on the results from FEM and experiment,a formula for the prediction of the axial load strength was proposed in this paper.展开更多
In this paper, the 3D elastic-plastic simulation was carried out by using finite element （FE） code according to the phenomena of flange keeping straight, bending towards headstock and bending towards tailstock in th...In this paper, the 3D elastic-plastic simulation was carried out by using finite element （FE） code according to the phenomena of flange keeping straight, bending towards headstock and bending towards tailstock in the shear spinning experiments for TC4 alloy. The simulation results for the three kinds of deformations of the flange agree well with the experimental results. So it is possible to explain the reason of flange bending by analyzing the strain vectors in the flange for the three kinds of deformation, which shows that it is important to apply the FE simulation technology for predicting the defects and optimizing the spinning process of TC4 alloys.展开更多
In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due ...In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.展开更多
In automobiles, the CFRP （carbon fiber reinforced plastics） has a possibility of weight reduction in automotive structures which can contribute to improve mileage and then reduce carbon dioxide. On the other hand, t...In automobiles, the CFRP （carbon fiber reinforced plastics） has a possibility of weight reduction in automotive structures which can contribute to improve mileage and then reduce carbon dioxide. On the other hand, the safety of collision should be also made clear in the case of employing the CFRP to automotive structures. In this paper, the CFRP guarder belt equipped in the automotive door is developed and examined by an experiment and a numerical analysis for replacing the conventional steel door guarder beam. As the experimental relation of impact load to displacement for CFRP guarder belt agreed well with that of numerical result, the numerical method developed here is quite useful for estimating impact behaviors of CFRP guarder belt.展开更多
In this paper, a theoretical and numerical study on the impact of a rubber solid on the free surface of a granular plate is presented, showing a simulation of an aircraft wheel on impact with a flexible landing surfac...In this paper, a theoretical and numerical study on the impact of a rubber solid on the free surface of a granular plate is presented, showing a simulation of an aircraft wheel on impact with a flexible landing surface. This physical action, when we use a theological approach, becomes a fundamental parameter to investigate wear and tear, and consequently strength to micro and macro pavements failure. The study has developed initially from a microscopic point of view and subsequently on macroscale. The effects are strictly linked with material degradation associated with damage evolution. The problem is developed by energetic approach on an elastic-plastic element using the functional energy containing two contributions, bulk and surface. The model simulates the behaviour of flexible runway pavements during the landing phase.展开更多
Inverted pavements have proven performance across the world,and there is a need to opti-mize the layer thickness and material properties of the pavement addressing the critical failures in the mechanistic-empirical pa...Inverted pavements have proven performance across the world,and there is a need to opti-mize the layer thickness and material properties of the pavement addressing the critical failures in the mechanistic-empirical pavement design.The present study is made on bituminous concrete(BC)pavement with traffic up to 50 samples per second(MSA)and studying the critical factors affecting the pavement performance.The Minitab’s response surface methodology(RSM)box behnken method,was used for the design of experi-ments which includes critical factors and responses obtained from ANSYS finite element modeling of the inverted pavement.The critical factors and responses are normally dis-tributed and indicate a linear relationship with the least error.The composite desirability for minimum stress and strains in the pavement layers was found to be 0.89.The optimized pavement thickness and layer material properties were validated with two pavement field cross sections of different Indian national highways,and it is observed that the optimized cross-section is safe.Further,this research paper carried out life cycle cost analysis(LCCA)and life cycle assessment(LCA)of inverted pavement with optimized pavement cross-section obtained including the carbon footprint during the vehicle operation phase.The study demonstrated the benefits of inverted pavement with reduced costs and carbon emissions.Thus,this approach paves the way towards sustainable and long-lasting pavements.展开更多
Metal additive manufacturing,especially laser powder bed fusion(L-PBF),is increasingly being used to fabricate complex parts with fine features.Emerging L-PBF systems have large build volumes and several lasers that o...Metal additive manufacturing,especially laser powder bed fusion(L-PBF),is increasingly being used to fabricate complex parts with fine features.Emerging L-PBF systems have large build volumes and several lasers that op-erate simultaneously.Hence,they can produce large and complex parts at reduced costs and short build times.However,the thermal distortion remains a critical challenge.Hence,a thorough understanding of the impact of multiple lasers on part distortion in multi-laser PBF(ML-PBF)is imperative.Although experimental investigation is possible,a more conducive approach is to design and create suitable predictive models to understand the impact of multiple lasers consolidating a part into layers.To fulfill this goal,in this study,a commercially available and widely used thermo-mechanical model,Netfabb,was used to investigate the effects of multiple lasers for com-plex scan patterns such as raster,spiral,and Hilbert on the temperature distribution and thermal distortion.The results show that the thermal distortion is minimal for the spiral scan pattern.Additionally,multiple lasers were found to decrease the build time(as expected)while maintaining or reducing the thermal distortion compared with their single-laser counterparts for all scan patterns(except Hilbert).Therefore,the newly developed ML-PBF predictive model is capable of providing critical insights into the effects of using multiple lasers,thereby opening new possibilities for the faster production of complex parts.In the future,small-scale computational models will be expanded to include large-scale parts,and probabilistic models will be developed to establish correlations.展开更多
基金the National Natural Science Foundation of China (No. 81071235)the Medicine and Engineering Interdisciplinary Fund of Shanghai Jiaotong University (No. YG2010MS26)
文摘The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.
基金supported by the National Natural Science Foundation of China (No. 50575205)the Hi-Tech Research and Development (863) Program of China (Nos. 2006AA04Z233 and 2007AA04Z101)+1 种基金the Doctoral Foundation of Ministry of Education of China (No. 20070335204)the Zhejiang Provincial Natural Science Foundation of China (No. Z1080537)
文摘This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.
文摘In this paper, a finite element method （FEM）-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as SOFT, adopting unified field equations for thermo-hydro-mechanical-air （THMA） behavior of geomaterial and using finite element-finite difference （FE-FD） scheme for so/l-water-air three-phase coupling problem, is used in the numerical simulation. As an application of the newly proposed numerical method, two engineering problems, one for slope failure in unsaturated model ground and another for in situ heating test related to deep geological repository of high-level radioactive waste （HLRW）, are simulated. The model tests on slope failure in unsaturated Shirasu ground, carried out by Kitamura et al. （2007）, is simulated in the framework of soil-water-air three-phase coupling under the condition of constant temperature. While the in situ heating test reported by Munoz （2006） is simulated in the same framework under the conditions of variable temperature hut constant air pressure.
文摘In recent years, inflatable structures have been a subject of interest for space applications such as communication antenna, solar thermal propulsion and entry/landing systems. The inflatable structures characterized by high strength-to-mass ratios, minimal stowage volume, which makes them suitable for cost-effective large space structures. A typical example for the inflatable structure is the inflated torus which often used in order to provide structure support. In this study, our main focus is to understand the dynamic characteristics of an inflated torus in order to formulate an accurate mathematical model suitable for active vibration control applications. A commercial finite element package, ANSYS, is used to model the inflated torus. To verify the model the obtained frequencies and mode shapes are compared with the published results, which are derived using analytical approach, the verification shows a good agreement between the FEM and the analytical results. Based on the verified model, parametric study was investigated; the material thickness increase causes the natural frequencies decrease, while the increase of the inflation pressure simply results in stiffening the ring, which means that the natural frequency increased. The FEM analysis gives an easy and fast way for the vibration analysis of the structures compared with the complicated analytical solutions.
基金Project supported by Khalifa University of Science and Technology(No.CIRA 2019-024)。
文摘Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be made from different materials with possibly different gradients of material properties.The present work proposes models to investigate the free vibration of FGM sectioned beams based on onedimensional(1D)finite element analysis.For this purpose,a sample beam is divided into discrete elements,and the total energy stored in each element during vibration is computed by considering either the Timoshenko or Euler-Bernoulli beam theory.Then,Hamilton’s principle is used to derive the equations of motion for the beam.The effects of material properties and dimensions of FGM sections on the beam’s natural frequencies and their corresponding mode shapes are then investigated based on a dynamic Timoshenko model(TM).The presented model is validated by comparison with three-dimensional(3D)finite element simulations of the first three mode shapes of the beam.
基金the China Scholarship Council for the award of fellowship and funding No.201908510177 and No.202106050030supported by dtec.bw–Digitalization and Technology Research Center of the Bundeswehr which Dr.Deng gratefully acknowledges project DMF+1 种基金the AMABML project founded by the Zentrum für Hochleistungs-materialien(ZHM)DEZAIN project for financial support via grant from GIF,the German-Israeli Foundation for Scientific Research and Development.
文摘This study investigates the effectiveness of salicylate(SAL)as an electrolyte additive on the discharge behavior of high-purity(HP)Mg anode in an aqueous half-cell system,using an integrated approach of mathematical modeling and experimental analysis.A finite elementbased model is developed to elucidate the key mechanisms by which SAL influences the voltage profile and pH.Systematic electrochemical measurements,especially intermittent discharge tests combined with electrochemical impedance spectroscopy(EIS),demonstrate that SAL can enhance initial voltage stability of HP Mg anode.Moreover,the model incorporates the SAL-Mg complexation factor to describe the role of SAL in modifying the deposit film on HP Mg surface.The agreement between model predictions and experimental observations suggests that SAL facilitates the formation of compact Mg(OH)_(2) deposits and sustains a favorable pH environment within the half-cell compartment.This integrated approach provides new insights into understanding and optimizing additive effects for Mg-air batteries.
基金supported by the Research Fund for Coal and Steel(RFCS)in the context of the European project Advancing Mining Support Systems to Enhance the Control of Highly Stressed Ground(AMSSTED)。
文摘This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results.A database was created combining published experimental data with in-house tests.By means of a comprehensive framework,a Coulomb-type failure criterion accounting for friction mobilization was defined.During the elastic phase,in which the interface joint is not yet created,the proposed model provides zero radial displacement,and once the interface joint is created,interface dilatancy is modeled using a non-associated plastic potential inspired from the behavior of rock joints.The results predicted by the proposed model are in good agreement with experimental results.The model has been implemented in a finite element method(FEM)code and numerical simulations have been performed at the elementary and the structural scales.The results obtained provide confidence in the ability of the new model to assist in the design and optimization of bolting patterns.
文摘Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts, many bumpers, particularly in large vehicles, are too stiff for pedestrian protection. In designing a bumper for an automobile, pedestrian protection is as important as bumper energy absorption in low speed collisions. To prevent lower extremity injuries in car-pedestrian collisions, it is important to determine the loadings that car front structures impart on the lower extremities and the mechanisms by which injury is caused by these loadings. The present work was focused on gaining more insight into the injury mechanisms leading to both ligament damage and bone fracture during bumper-pedestrian collisions. The European Enhanced Vehicle-safety Committee （EEVC） legform impactor model was introduced and validated against EEVCAVG17 criteria. The collision mechanism between a bumper and this legform impactor was investigated numerically using LS-DYNA software. To identify the effect of the bumper beam material on leg injuries, four analyses were performed on bumpers that had the same assembly but were made from different materials.
文摘Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.
基金Project supported by the Hi-Tech Research and Development Program (863) of China (No. 2006AA04Z422)the Post-doctoral Fund of Zhejiang Province (No. 113000-X80703), China
文摘A study of the behaviour of constructional cold-formed stainless steel beams at elevated temperatures was conducted in this paper. An accurate finite element model (FEM) for stainless steel beams was developed using the finite element program ABAQUS. Stainless steel beams having different cross-sections were simulated in this study. The nonlinear FEM was verified against the experimental results. Generally, the developed FEM could accurately simulate the stainless steel beams. Based on the high temperature stainless steel material test results, a parametric study was carried out on stainless steel beams at elevated tem- peratures using the verified FEM. Both high strength stainless steel EN 1.4462 and normal strength stainless steel EN 1.4301 were considered. A total of 42 stainless steel beams were simulated in the parametric study. The effect of temperatures on the behaviour of stainless steel beams was investigated. In addition, a limiting temperature for stainless steel beams was also proposed.
基金Item Sponsored by Ministry of Science and Higher Education of Poland Over Years 2009-2012as a Project for Development(0457/R/T02/2009/06)
文摘The multi-wedge cross rolling process of forming balls is described. The process tool for rolling 8 balls with a diameter of 35 mm is presented. The course of the rolling process, distributions of forming forces as well as maps of effective strain and temperature in the obtained balls are presented by finite element modeling （FEM）. Ex- perimental tests of simultaneous forming of 4 balls with a diameter of 22 mm conducted in laboratory conditions at Lublin University of Technology have proved that the balls obtained in multi-wedge cross rolling are of good quality and can therefore be used in both ball mills and rolling bearings.
基金the National Natural Science Foundation of China(No.51475003)the Beijing Municipal Natural Science Foundation of China(No.3152010)the Beijing Municipal Education Committee Science and Technology Program(No.KM201510009004)
文摘The combined loading tests of 5754 O aluminum alloy sheet are used to verify the yield function. Three yield functions are implemented into the commercial finite element model(FEM) code ABAQUS as a user material subroutine UMAT for the FEM simulation of the combined loading tests. The comparison of the simulating and experimental results shows that the modified Yld2000-2d yield function can describe the mechanical behavior of5754 O aluminum alloy sheet under combined loading paths reasonably while other three yield functions do not.The performance of the modified Yld2000-2d yield function on describing the mechanical behavior under combined loading paths is analyzed in detail. It is concluded that the modified Yld2000-2d yield function can be adopted to describe the deformation behavior of 5754 O aluminum alloy sheet for industrial applications.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 50708027)the National Key Technology Research and Development Program of China (Grant No.2006BAJ01B02)
文摘The behavior of square-tubed reinforced concrete (STRC) short columns subjected to axial compression was studied in detail with an accurate nonlinear finite element model (FEM) . Different width to thickness ratios (D/t = 50 150) of the steel tube and the compressive strength of concrete (C80 and C50) were adopted in this research. The axial load strength,steel tube strain and load-shortening response were determined from FEM and the analysis results from FEM were compared with those from experiment. The analysis and test results indicate that the concrete strength little affectes the confinement of the steel tube on the concrete. The transverse stress of the tube at the axial load point increases with the increment in the width to thickness ratio. Based on the results from FEM and experiment,a formula for the prediction of the axial load strength was proposed in this paper.
文摘In this paper, the 3D elastic-plastic simulation was carried out by using finite element （FE） code according to the phenomena of flange keeping straight, bending towards headstock and bending towards tailstock in the shear spinning experiments for TC4 alloy. The simulation results for the three kinds of deformations of the flange agree well with the experimental results. So it is possible to explain the reason of flange bending by analyzing the strain vectors in the flange for the three kinds of deformation, which shows that it is important to apply the FE simulation technology for predicting the defects and optimizing the spinning process of TC4 alloys.
基金The authors would like to acknowledge the financial support provided by the National Natural Science Foundation of China(Grant No.41977240)the Fundamental Research Funds for the Central Universities(Grant No.B200202090).
文摘In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.
文摘In automobiles, the CFRP （carbon fiber reinforced plastics） has a possibility of weight reduction in automotive structures which can contribute to improve mileage and then reduce carbon dioxide. On the other hand, the safety of collision should be also made clear in the case of employing the CFRP to automotive structures. In this paper, the CFRP guarder belt equipped in the automotive door is developed and examined by an experiment and a numerical analysis for replacing the conventional steel door guarder beam. As the experimental relation of impact load to displacement for CFRP guarder belt agreed well with that of numerical result, the numerical method developed here is quite useful for estimating impact behaviors of CFRP guarder belt.
文摘In this paper, a theoretical and numerical study on the impact of a rubber solid on the free surface of a granular plate is presented, showing a simulation of an aircraft wheel on impact with a flexible landing surface. This physical action, when we use a theological approach, becomes a fundamental parameter to investigate wear and tear, and consequently strength to micro and macro pavements failure. The study has developed initially from a microscopic point of view and subsequently on macroscale. The effects are strictly linked with material degradation associated with damage evolution. The problem is developed by energetic approach on an elastic-plastic element using the functional energy containing two contributions, bulk and surface. The model simulates the behaviour of flexible runway pavements during the landing phase.
文摘Inverted pavements have proven performance across the world,and there is a need to opti-mize the layer thickness and material properties of the pavement addressing the critical failures in the mechanistic-empirical pavement design.The present study is made on bituminous concrete(BC)pavement with traffic up to 50 samples per second(MSA)and studying the critical factors affecting the pavement performance.The Minitab’s response surface methodology(RSM)box behnken method,was used for the design of experi-ments which includes critical factors and responses obtained from ANSYS finite element modeling of the inverted pavement.The critical factors and responses are normally dis-tributed and indicate a linear relationship with the least error.The composite desirability for minimum stress and strains in the pavement layers was found to be 0.89.The optimized pavement thickness and layer material properties were validated with two pavement field cross sections of different Indian national highways,and it is observed that the optimized cross-section is safe.Further,this research paper carried out life cycle cost analysis(LCCA)and life cycle assessment(LCA)of inverted pavement with optimized pavement cross-section obtained including the carbon footprint during the vehicle operation phase.The study demonstrated the benefits of inverted pavement with reduced costs and carbon emissions.Thus,this approach paves the way towards sustainable and long-lasting pavements.
基金supported by Defense Advanced Research Projects Agency of USA(Grant.No.D22AP00147-00).
文摘Metal additive manufacturing,especially laser powder bed fusion(L-PBF),is increasingly being used to fabricate complex parts with fine features.Emerging L-PBF systems have large build volumes and several lasers that op-erate simultaneously.Hence,they can produce large and complex parts at reduced costs and short build times.However,the thermal distortion remains a critical challenge.Hence,a thorough understanding of the impact of multiple lasers on part distortion in multi-laser PBF(ML-PBF)is imperative.Although experimental investigation is possible,a more conducive approach is to design and create suitable predictive models to understand the impact of multiple lasers consolidating a part into layers.To fulfill this goal,in this study,a commercially available and widely used thermo-mechanical model,Netfabb,was used to investigate the effects of multiple lasers for com-plex scan patterns such as raster,spiral,and Hilbert on the temperature distribution and thermal distortion.The results show that the thermal distortion is minimal for the spiral scan pattern.Additionally,multiple lasers were found to decrease the build time(as expected)while maintaining or reducing the thermal distortion compared with their single-laser counterparts for all scan patterns(except Hilbert).Therefore,the newly developed ML-PBF predictive model is capable of providing critical insights into the effects of using multiple lasers,thereby opening new possibilities for the faster production of complex parts.In the future,small-scale computational models will be expanded to include large-scale parts,and probabilistic models will be developed to establish correlations.
