Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to pr...Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to predict the stiffness and shear distribution of glulam beams in elastic-plastic stage,and consequently,the failure of such glulam beams cannot be predicted effectively.To address these issues,an analytical method considering material nonlinearity was proposed for glulam beams,and the calculating equations of deflection and shear stress distribution for different failure modes were established.The proposed method was verified by experiments and numerical models under the corresponding conditions.Results showed that the theoretical calculations were in good agreement with experimental and numerical results,indicating that the equations proposed in this paper were reliable and accurate for such glulam beams with wood material in the elastic-plastic stage ignoring the influence of mechanic properties in radial and tangential directions of wood.Furthermore,the experimental results reported by the previous studies indicated that the method was applicable and could be used as a theoretical reference for predicting the failure of glulam beams.展开更多
Crack line field analysis method has become an independent method for crack elastic-plastic analysis, which greatly simplifies the complexity of crack elastic-plastic problems and overcomes the corresponding mathemati...Crack line field analysis method has become an independent method for crack elastic-plastic analysis, which greatly simplifies the complexity of crack elastic-plastic problems and overcomes the corresponding mathematical difficulty. With this method, the precise elastic-plastic solutions near crack lines for variety of crack problems can be obtained. But up to now all solutions obtained by this method were for different concrete problems, no general steps and no general form of matching equations near crack line are given out. With crack line analysis method, this paper proposes the general steps of elastic plastic analysis near crack line for mode I crack in elastic-perfectly plastic solids under plane stress condition, and in turn given out the solving process and result for a specific problem.展开更多
The characterization mad testing methods of the dynamic fracture initiation toughness of elas-tic-plastic materials under tensile impact are studied.By using the self-designed bar-bar tensile impact appa-ratus,a novel...The characterization mad testing methods of the dynamic fracture initiation toughness of elas-tic-plastic materials under tensile impact are studied.By using the self-designed bar-bar tensile impact appa-ratus,a novel test method for studying dynamic fracture-initiation has been proposed based on the one-di-mensional test principle.The curve of average load v.s.displacement（-δ）is smooth until unstablecrack propagation,and the kinetic energy which does not contribute to the crack growth can be removed fromtotal work done by external-force to the specimen.The fracture-initiation point is determined by compliance-changing rate method.The results show that these methods are feasible and effective.Through the analysis ofthe conversion between work and energy of a fracture specimen,the dynamic J-integral is adopted as a char-acteristic parameter for elastic-plastic materials under impact loading.The J-integral is calculated from-△and P-δ curves by using the formula proposed by Rice.The J-integral at fracture initiation is employedto describe the dynamic fracture-initiation toughness of elastie-plastic materials and the experimental resultsindicate that J<sub>10</sub>can be regarded as a material constant.展开更多
The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzedusing finite element calculations.The crack initiation and steady propagation behaviours havealso been investigated by mean...The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzedusing finite element calculations.The crack initiation and steady propagation behaviours havealso been investigated by means of slip line pattern etching technique and mechanical tests.The results show that there are HRR near field and distant field in the crack tip region,andthe later depends on the specimen configuration.The crack initiation behaviour is controlledby a single parameter J.In contrast,the steady crack propagation is affected by the distantstrain field and can not be described by single parameter only.展开更多
A Harten-Lax-van Leer-contact(HLLC) approximate Riemann solver is built with elastic waves(HLLCE) for one-dimensional elastic-plastic flows with a hypoelastic constitutive model and the von Mises' yielding criteri...A Harten-Lax-van Leer-contact(HLLC) approximate Riemann solver is built with elastic waves(HLLCE) for one-dimensional elastic-plastic flows with a hypoelastic constitutive model and the von Mises' yielding criterion. Based on the HLLCE,a third-order cell-centered Lagrangian scheme is built for one-dimensional elastic-plastic problems. A number of numerical experiments are carried out. The numerical results show that the proposed third-order scheme achieves the desired order of accuracy. The third-order scheme is used to the numerical solution of the problems with elastic shock waves and elastic rarefaction waves. The numerical results are compared with a reference solution and the results obtained by other authors. The comparison shows that the presented high-order scheme is convergent, stable, and essentially non-oscillatory. Moreover,the HLLCE is more efficient than the two-rarefaction Riemann solver with elastic waves(TRRSE).展开更多
Impact processes between flexible bodies often lead to local stress concentration and wave propagation of high frequency. Therefore, the modeling of flexible multibody systems involving impact should consider the loca...Impact processes between flexible bodies often lead to local stress concentration and wave propagation of high frequency. Therefore, the modeling of flexible multibody systems involving impact should consider the local plastic deformation and the strict requirements of the spatial discretization. Owing to the nonlinearity of the stiffness matrix, the reduction of the element number is extremely important. For the contact-impact problem, since different regions have different requirements regarding the element size, a new subregion mesh method is proposed to reduce the number of the unnecessary elements. A dynamic model for flexible multibody systems with elastic-plastic contact impact is established based on a floating frame of reference formulation and complete Lagrange incremental nonlinear finite-element method to investigate the effect of the elastic-plastic deformation as well as spatial discretization.Experiments on the impact between two bodies are carried out to validate the correctness of the elastic-plastic model.The proposed formulation is applied to a slider-crank system with elastic-plastic impact.展开更多
The paper proposes a new approach of predicting the bifurcation points of elastic-plasticbuckling of plates and shells,which is obtained from the natural combination of the Lyaponov’s dy-namic criterion on stability ...The paper proposes a new approach of predicting the bifurcation points of elastic-plasticbuckling of plates and shells,which is obtained from the natural combination of the Lyaponov’s dy-namic criterion on stability and the modified adaptive Dynamic Relaxation(maDR)method developedrecently by the authors.This new method can overcome the difficulties in the applications of the dy-namic criterion.Numerical results show that the theoretically predicted bifurcation points are in verygood agreement with the corresponding experimental ones.The paper also provides a new means forfurther research on the plastic buckling paradox of plates and shells.展开更多
In this paper, a systematic approach is proposed to obtain the macro-scopic elastic-plastic constitutive relation of particle reinforced composites (PRC).The strain energy density of PRC is analyzed based on the cell ...In this paper, a systematic approach is proposed to obtain the macro-scopic elastic-plastic constitutive relation of particle reinforced composites (PRC).The strain energy density of PRC is analyzed based on the cell model, and the ana-lytical formula for the macro-constitutive relation of PRC is obtained. The strengtheffects of volume fraction of the particle and the strain hardening exponent of ma-trix material on the macro-constitutive relation are investigated, the relation curve ofstrain versus stress of PRC is calculated in detail. The present results are consistentwith the results given in the existing references.展开更多
In this paper, based on energy variational principles of elastic-plastic solids, the path-independent J-integral and its dualform in elastic-plastic solids with finite displacements are presented. Whose testification ...In this paper, based on energy variational principles of elastic-plastic solids, the path-independent J-integral and its dualform in elastic-plastic solids with finite displacements are presented. Whose testification is given there afler.展开更多
A new algorithm for the solution of quadratic programming problems is put forward in terms ofthe mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures.Themethod propo...A new algorithm for the solution of quadratic programming problems is put forward in terms ofthe mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures.Themethod proposed is different from the traditional one,for which the unknown variables are selected just inone class such as displacements or stresses.The present method selects the variables in the mixed form withboth displacement and stress.As the method is established in the hybrid space,the information found in theprevious incremental step can be used for the solution of the present step,making the algorithm highly effi-cient in the numerical solution process of quadratic programming problems.The results obained in the exam-ples of the elastie-plastic solution of the truss structures verify what has been predicted in the theoretical anal-ysis.展开更多
Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seis...Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seismic loads,besides conventional analysis,elastic-plastic time history analysis under rare seismic intensity is carried out.An ideal finite element(FEM) elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes.Furthermore,according to elastic-plastic time history analysis theory,deformation,stress and damage pattern of the structure under rare seismic intensity are investigated.Based on the above analysis,the established reliability model according to the reliability theory,together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis.The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity,and the structure needs to be reinforced.展开更多
A elastic-plastic fatigue crack growth(FCG)finite element model was developed for predicting crack growth rate under cyclic load.The propagation criterion for this model was established based on plastically dissipated...A elastic-plastic fatigue crack growth(FCG)finite element model was developed for predicting crack growth rate under cyclic load.The propagation criterion for this model was established based on plastically dissipated energy.The crack growth simulation under cyclic computation was implemented through the ABAQUS scripting interface.The predictions of this model are in good agreement with the results of crack propagation experiment of compact tension specimen made of 304 stainless steel.Based on the proposed model,the single peak overload retardation effect of elastic-plastic fatigue crack was analyzed.The results shows that the single peak overload will reduce the accumulation rate of plastic energy dissipation of elements at crack tip plastic zone,so that crack growth will be arrested.The crack growth rate will not recover until the crack tip exceed the affected region.Meanwhile,the crack growth rate is mainly determined by the amplitude rather than the mean load under the condition of small scale yielding.The proposed model would be helpful for predicting the growth rate of mode I elastic-plastic fatigue crack.展开更多
The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying...The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.展开更多
The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elast...The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elastic perfectly plastic. Analysis is carried out to study the effect of varying modulus of elasticity and sphere radius in wide range of dimensionless interference until the inception of plasticity as well as in plastic range. Results are compared with previous elastic-plastic models. It is found that materials with Young’s modulus to yield strength (E/Y) ratio less than and greater than 300 show strikingly different contact phenomena. The dependency of E on dimensionless interference at which the plastic region fully covers the surface is observed. However with different radius, finite element study exhibits similar elastic-plastic phenomena.展开更多
Based on the Plastica theory(see ref.[12]),the large deflection of an elastic-perfectlyplastic cantilever subjected to an inclined concentrated force at its tip,before the unloadingin the plastic region occurs,is anal...Based on the Plastica theory(see ref.[12]),the large deflection of an elastic-perfectlyplastic cantilever subjected to an inclined concentrated force at its tip,before the unloadingin the plastic region occurs,is analyzed in this paper.The emphasis of the analysis is put onthe effects of the angle of inclination of the concentrated force upon the deformed shape,theload-deflection relationship and the length of the plastic region.Both analytical andcomputed results are given.展开更多
Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness...Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness,layer number and elastic modulus ratio of layer to the substrate. A model of multi-layered surface contact with rough slider was studied. The effect of the surface structure parameters on the elastic-plastic deformation was analyzed.展开更多
A novel variable stiffness model was proposed for analyzing elastic-plastic bending problems with arbitrary variable stiffness in detail.First,it was assumed that the material of a rectangular beam is an ideal isotrop...A novel variable stiffness model was proposed for analyzing elastic-plastic bending problems with arbitrary variable stiffness in detail.First,it was assumed that the material of a rectangular beam is an ideal isotropic elastic-plastic material,whose elastic modulus,yield strength,and section height are functions of the axial coordinates of the beam respectively.Considering the effect of shear on the deformation of the beam,the elastic and elastic-plastic bending problems of the axially variable stiffness beam were studied.Then,the analytical solutions of the elastic and elastic-plastic deformation of the beam were derived when the cross-section height and the elastic modulus of the material were varied by special function along the length of the beam respectively.The elastic and elastic-plastic analysis of the variable stiffness beam was carried out using Differential Quadrature Method(DQM)when the bending stiffness varied arbitrarily.The influence of the axial variation of the bending stiffness on the elastic and elastic-plastic deformation of the beam was analyzed by numerical simulation,DQM,and finite element method(FEM).Simulation results verified the practicability of the proposed mechanical model,and the comparison between the results of the solutions of DQM and FEM showed that DQM is accurate and effective in elastic and elastic-plastic analysis of variable stiffness beams.展开更多
A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various ...A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various levels of GMs.The robustness of a design is measured by an incremental dynamic analysis(IDA)curve and an ideal drift response curve(IDRC).The IDRC is a plot of the optimized maximum deformation under a constraint on the total damper quantity vs.the design level of the GMs.The total damper quantity corresponds to the total cost of the added dampers.First,a problem of generation of IDRCs is stated.Then,its solution algorithm,which consists of the sensitivity-based algorithm(SBA)and a local search method,is proposed.In the application of the SBA,the passive added dampers are removed sequentially under the specified-level GMs.On the other hand,the proposed local search method can search the optimal solutions for a constant total damper quantity under GMs’increased levels.In this way,combining these two algorithms enables the comprehensive search of the optimal solutions for various conditions of the status of the GMs and the total damper quantity.The influence of selecting the type of added dampers(oil,hysteretic,and so on)and the selection of the input GMs on the IDRCs are investigated.Finally,a robust optimal design problem is formulated,and a simple local search-based algorithm is proposed.A simple index using the IDRC and the IDA curve of the model is used as the objective function.It is demonstrated that the proposed algorithm works well in spite of its simplicity.展开更多
Based on the minimum principle of acceleration in the elastic-plastic continua under fi-nite deformation,the dynamic response of an elastic-perfectly plastic pin-ended beam subjected to rect-angular impulse loading is...Based on the minimum principle of acceleration in the elastic-plastic continua under fi-nite deformation,the dynamic response of an elastic-perfectly plastic pin-ended beam subjected to rect-angular impulse loading is studied with the help of a numerical approach.The calculated results once a-gain show the anomalous behavior of the beam during its response process,which was previously foundin[1].By carefully analyzing the instantaneous distribution of the bending moment,the membraneforce,the curvature and displacement during the response process,it is concluded that the interactiveeffect between the geometry and materials nonlinearities of the structure is the key reason for leading tothe anomalous behavior.This will be helpful for clarifying some misunderstandings in explaining theproblem before.展开更多
基金support from High-Level Natural ScienceFoundation of Hainan Province of China (Grant No. 2019RC055)National Natural Science Foundation ofChina (Grant No. 51808176) and the Project Funded by the National First-Class Disciplines (PNFD).
文摘Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to predict the stiffness and shear distribution of glulam beams in elastic-plastic stage,and consequently,the failure of such glulam beams cannot be predicted effectively.To address these issues,an analytical method considering material nonlinearity was proposed for glulam beams,and the calculating equations of deflection and shear stress distribution for different failure modes were established.The proposed method was verified by experiments and numerical models under the corresponding conditions.Results showed that the theoretical calculations were in good agreement with experimental and numerical results,indicating that the equations proposed in this paper were reliable and accurate for such glulam beams with wood material in the elastic-plastic stage ignoring the influence of mechanic properties in radial and tangential directions of wood.Furthermore,the experimental results reported by the previous studies indicated that the method was applicable and could be used as a theoretical reference for predicting the failure of glulam beams.
文摘Crack line field analysis method has become an independent method for crack elastic-plastic analysis, which greatly simplifies the complexity of crack elastic-plastic problems and overcomes the corresponding mathematical difficulty. With this method, the precise elastic-plastic solutions near crack lines for variety of crack problems can be obtained. But up to now all solutions obtained by this method were for different concrete problems, no general steps and no general form of matching equations near crack line are given out. With crack line analysis method, this paper proposes the general steps of elastic plastic analysis near crack line for mode I crack in elastic-perfectly plastic solids under plane stress condition, and in turn given out the solving process and result for a specific problem.
文摘The characterization mad testing methods of the dynamic fracture initiation toughness of elas-tic-plastic materials under tensile impact are studied.By using the self-designed bar-bar tensile impact appa-ratus,a novel test method for studying dynamic fracture-initiation has been proposed based on the one-di-mensional test principle.The curve of average load v.s.displacement（-δ）is smooth until unstablecrack propagation,and the kinetic energy which does not contribute to the crack growth can be removed fromtotal work done by external-force to the specimen.The fracture-initiation point is determined by compliance-changing rate method.The results show that these methods are feasible and effective.Through the analysis ofthe conversion between work and energy of a fracture specimen,the dynamic J-integral is adopted as a char-acteristic parameter for elastic-plastic materials under impact loading.The J-integral is calculated from-△and P-δ curves by using the formula proposed by Rice.The J-integral at fracture initiation is employedto describe the dynamic fracture-initiation toughness of elastie-plastic materials and the experimental resultsindicate that J<sub>10</sub>can be regarded as a material constant.
文摘The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzedusing finite element calculations.The crack initiation and steady propagation behaviours havealso been investigated by means of slip line pattern etching technique and mechanical tests.The results show that there are HRR near field and distant field in the crack tip region,andthe later depends on the specimen configuration.The crack initiation behaviour is controlledby a single parameter J.In contrast,the steady crack propagation is affected by the distantstrain field and can not be described by single parameter only.
基金Project supported by the National Natural Science Foundation of China(Nos.11172050 and11672047)the Science and Technology Foundation of China Academy of Engineering Physics(No.2013A0202011)
文摘A Harten-Lax-van Leer-contact(HLLC) approximate Riemann solver is built with elastic waves(HLLCE) for one-dimensional elastic-plastic flows with a hypoelastic constitutive model and the von Mises' yielding criterion. Based on the HLLCE,a third-order cell-centered Lagrangian scheme is built for one-dimensional elastic-plastic problems. A number of numerical experiments are carried out. The numerical results show that the proposed third-order scheme achieves the desired order of accuracy. The third-order scheme is used to the numerical solution of the problems with elastic shock waves and elastic rarefaction waves. The numerical results are compared with a reference solution and the results obtained by other authors. The comparison shows that the presented high-order scheme is convergent, stable, and essentially non-oscillatory. Moreover,the HLLCE is more efficient than the two-rarefaction Riemann solver with elastic waves(TRRSE).
基金supported by the National Natural Science Foundation of China (Grants 11132007, 11272203)
文摘Impact processes between flexible bodies often lead to local stress concentration and wave propagation of high frequency. Therefore, the modeling of flexible multibody systems involving impact should consider the local plastic deformation and the strict requirements of the spatial discretization. Owing to the nonlinearity of the stiffness matrix, the reduction of the element number is extremely important. For the contact-impact problem, since different regions have different requirements regarding the element size, a new subregion mesh method is proposed to reduce the number of the unnecessary elements. A dynamic model for flexible multibody systems with elastic-plastic contact impact is established based on a floating frame of reference formulation and complete Lagrange incremental nonlinear finite-element method to investigate the effect of the elastic-plastic deformation as well as spatial discretization.Experiments on the impact between two bodies are carried out to validate the correctness of the elastic-plastic model.The proposed formulation is applied to a slider-crank system with elastic-plastic impact.
文摘The paper proposes a new approach of predicting the bifurcation points of elastic-plasticbuckling of plates and shells,which is obtained from the natural combination of the Lyaponov’s dy-namic criterion on stability and the modified adaptive Dynamic Relaxation(maDR)method developedrecently by the authors.This new method can overcome the difficulties in the applications of the dy-namic criterion.Numerical results show that the theoretically predicted bifurcation points are in verygood agreement with the corresponding experimental ones.The paper also provides a new means forfurther research on the plastic buckling paradox of plates and shells.
基金The project supported by the National Natural Science Foundation of China (No. 19704100) National Science Foundation of Chinese Academy of Sciences (Project KJ951-1-20)
文摘In this paper, a systematic approach is proposed to obtain the macro-scopic elastic-plastic constitutive relation of particle reinforced composites (PRC).The strain energy density of PRC is analyzed based on the cell model, and the ana-lytical formula for the macro-constitutive relation of PRC is obtained. The strengtheffects of volume fraction of the particle and the strain hardening exponent of ma-trix material on the macro-constitutive relation are investigated, the relation curve ofstrain versus stress of PRC is calculated in detail. The present results are consistentwith the results given in the existing references.
文摘In this paper, based on energy variational principles of elastic-plastic solids, the path-independent J-integral and its dualform in elastic-plastic solids with finite displacements are presented. Whose testification is given there afler.
基金the National Natural Science Foundation of China(No.50178916,No.19732020 and No.19872016)the National Key Basic lteseareh Special Foundation(No.G1999032805)+1 种基金the Special Funds for Major State Basic Researeh Projectsthe Foundation for University Key Teachers by the Ministry of Education of China
文摘A new algorithm for the solution of quadratic programming problems is put forward in terms ofthe mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures.Themethod proposed is different from the traditional one,for which the unknown variables are selected just inone class such as displacements or stresses.The present method selects the variables in the mixed form withboth displacement and stress.As the method is established in the hybrid space,the information found in theprevious incremental step can be used for the solution of the present step,making the algorithm highly effi-cient in the numerical solution process of quadratic programming problems.The results obained in the exam-ples of the elastie-plastic solution of the truss structures verify what has been predicted in the theoretical anal-ysis.
基金supported by National High Technology Research and Development Program 863 Plan (No. 2009AA043000)
文摘Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seismic loads,besides conventional analysis,elastic-plastic time history analysis under rare seismic intensity is carried out.An ideal finite element(FEM) elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes.Furthermore,according to elastic-plastic time history analysis theory,deformation,stress and damage pattern of the structure under rare seismic intensity are investigated.Based on the above analysis,the established reliability model according to the reliability theory,together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis.The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity,and the structure needs to be reinforced.
基金Project No.51575076 supported by the National Natural Science Foundation of China.
文摘A elastic-plastic fatigue crack growth(FCG)finite element model was developed for predicting crack growth rate under cyclic load.The propagation criterion for this model was established based on plastically dissipated energy.The crack growth simulation under cyclic computation was implemented through the ABAQUS scripting interface.The predictions of this model are in good agreement with the results of crack propagation experiment of compact tension specimen made of 304 stainless steel.Based on the proposed model,the single peak overload retardation effect of elastic-plastic fatigue crack was analyzed.The results shows that the single peak overload will reduce the accumulation rate of plastic energy dissipation of elements at crack tip plastic zone,so that crack growth will be arrested.The crack growth rate will not recover until the crack tip exceed the affected region.Meanwhile,the crack growth rate is mainly determined by the amplitude rather than the mean load under the condition of small scale yielding.The proposed model would be helpful for predicting the growth rate of mode I elastic-plastic fatigue crack.
基金Science Research Foundation of Shanghai Municipal Education Commission (No.06VZ004)
文摘The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.
文摘The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elastic perfectly plastic. Analysis is carried out to study the effect of varying modulus of elasticity and sphere radius in wide range of dimensionless interference until the inception of plasticity as well as in plastic range. Results are compared with previous elastic-plastic models. It is found that materials with Young’s modulus to yield strength (E/Y) ratio less than and greater than 300 show strikingly different contact phenomena. The dependency of E on dimensionless interference at which the plastic region fully covers the surface is observed. However with different radius, finite element study exhibits similar elastic-plastic phenomena.
文摘Based on the Plastica theory(see ref.[12]),the large deflection of an elastic-perfectlyplastic cantilever subjected to an inclined concentrated force at its tip,before the unloadingin the plastic region occurs,is analyzed in this paper.The emphasis of the analysis is put onthe effects of the angle of inclination of the concentrated force upon the deformed shape,theload-deflection relationship and the length of the plastic region.Both analytical andcomputed results are given.
基金Project(50071014) supported by the National Natural Science Foundation of China
文摘Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness,layer number and elastic modulus ratio of layer to the substrate. A model of multi-layered surface contact with rough slider was studied. The effect of the surface structure parameters on the elastic-plastic deformation was analyzed.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51175058).
文摘A novel variable stiffness model was proposed for analyzing elastic-plastic bending problems with arbitrary variable stiffness in detail.First,it was assumed that the material of a rectangular beam is an ideal isotropic elastic-plastic material,whose elastic modulus,yield strength,and section height are functions of the axial coordinates of the beam respectively.Considering the effect of shear on the deformation of the beam,the elastic and elastic-plastic bending problems of the axially variable stiffness beam were studied.Then,the analytical solutions of the elastic and elastic-plastic deformation of the beam were derived when the cross-section height and the elastic modulus of the material were varied by special function along the length of the beam respectively.The elastic and elastic-plastic analysis of the variable stiffness beam was carried out using Differential Quadrature Method(DQM)when the bending stiffness varied arbitrarily.The influence of the axial variation of the bending stiffness on the elastic and elastic-plastic deformation of the beam was analyzed by numerical simulation,DQM,and finite element method(FEM).Simulation results verified the practicability of the proposed mechanical model,and the comparison between the results of the solutions of DQM and FEM showed that DQM is accurate and effective in elastic and elastic-plastic analysis of variable stiffness beams.
基金Part of the present work is supported by the Grant-in-Aid for Scientific Research(KAKENHI)of the Japan Society for the Promotion of Science(Nos.18H01584,JP20J20811)This support is greatly appreciated.
文摘A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various levels of GMs.The robustness of a design is measured by an incremental dynamic analysis(IDA)curve and an ideal drift response curve(IDRC).The IDRC is a plot of the optimized maximum deformation under a constraint on the total damper quantity vs.the design level of the GMs.The total damper quantity corresponds to the total cost of the added dampers.First,a problem of generation of IDRCs is stated.Then,its solution algorithm,which consists of the sensitivity-based algorithm(SBA)and a local search method,is proposed.In the application of the SBA,the passive added dampers are removed sequentially under the specified-level GMs.On the other hand,the proposed local search method can search the optimal solutions for a constant total damper quantity under GMs’increased levels.In this way,combining these two algorithms enables the comprehensive search of the optimal solutions for various conditions of the status of the GMs and the total damper quantity.The influence of selecting the type of added dampers(oil,hysteretic,and so on)and the selection of the input GMs on the IDRCs are investigated.Finally,a robust optimal design problem is formulated,and a simple local search-based algorithm is proposed.A simple index using the IDRC and the IDA curve of the model is used as the objective function.It is demonstrated that the proposed algorithm works well in spite of its simplicity.
基金the National Natural Science Foundation of China.
文摘Based on the minimum principle of acceleration in the elastic-plastic continua under fi-nite deformation,the dynamic response of an elastic-perfectly plastic pin-ended beam subjected to rect-angular impulse loading is studied with the help of a numerical approach.The calculated results once a-gain show the anomalous behavior of the beam during its response process,which was previously foundin[1].By carefully analyzing the instantaneous distribution of the bending moment,the membraneforce,the curvature and displacement during the response process,it is concluded that the interactiveeffect between the geometry and materials nonlinearities of the structure is the key reason for leading tothe anomalous behavior.This will be helpful for clarifying some misunderstandings in explaining theproblem before.
