The plastic deformation showing instability has been a subject receiving considerable attention for centuries due to its importance in many industrial processes.For Al alloys,the major instability is the Portevin-Le C...The plastic deformation showing instability has been a subject receiving considerable attention for centuries due to its importance in many industrial processes.For Al alloys,the major instability is the Portevin-Le Chatelier(PLC)effect that appears within a certain region of strain,strain rate and temperature.It manifests itself on the stress−strain curve as serrations associating with the rapid accumulation of plastic deformation within inclined slip bands.The PLC effect has severe practical consequences,which damages the surface quality after the sheet metal forming process and threatens the tensile ductility.Therefore,it is crucial to investigate the fundamental mechanisms underlying the PLC effect and in particular to investigate how it can be tempered by tailoring the material microstructure.In this paper,we review the common interpretations of the PLC effect and summarize the experimental results of the effects of the precipitation and the grain refinement,two conventional strengthening methodologies in Al alloys,on the serrated plastic flow.The effectiveness of solute atom clusters in suppressing the PLC effect is emphasized.展开更多
Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain...Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain coordination results of 34 reinforced concrete beams(four groups)strengthened with different methods were presented including external-bonded or near-surface mounted glass or carbon FRP or helical rib bar in order to study the strain coordination of the strengthening materials and steel rebar of RC beam.Because there is relative slipping between concrete and strengthening materials(SM),the strain of SM and steel rebar of RC beam satisfies the double linear strain distribution assumption,that is,the strain of longitudinal fiber parallel to the neutral axis of plated beam within the scope of effective height(h0)of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of SM and steel rebar satisfies the equation εGCH=βεsteel,where the value of β is equal to 1.1-1.3 according to the test results.展开更多
The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In ord...The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.展开更多
基金Projects(52001249,51761135031,51790482,51722104)supported by the National Natural Science Foundation of ChinaProject(2017YFB0702301)supported by the National Key Research and Development Program of ChinaProject(2019M653595)supported by the China Postdoctoral Science Foundation。
文摘The plastic deformation showing instability has been a subject receiving considerable attention for centuries due to its importance in many industrial processes.For Al alloys,the major instability is the Portevin-Le Chatelier(PLC)effect that appears within a certain region of strain,strain rate and temperature.It manifests itself on the stress−strain curve as serrations associating with the rapid accumulation of plastic deformation within inclined slip bands.The PLC effect has severe practical consequences,which damages the surface quality after the sheet metal forming process and threatens the tensile ductility.Therefore,it is crucial to investigate the fundamental mechanisms underlying the PLC effect and in particular to investigate how it can be tempered by tailoring the material microstructure.In this paper,we review the common interpretations of the PLC effect and summarize the experimental results of the effects of the precipitation and the grain refinement,two conventional strengthening methodologies in Al alloys,on the serrated plastic flow.The effectiveness of solute atom clusters in suppressing the PLC effect is emphasized.
基金Project(11B033)supported by the Foundation for Excellent Young Scholars of Hunan Scientific Committee,ChinaProject(116001)supported by the Consultative Program of the Chinese Academy of Engineering+1 种基金Project(11JJ6040)supported by the National Natural Science Foundation of Hunan Province,ChinaProject(2010GK3198)supported by the Science and Research Program of Hunan Province,China
文摘Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain coordination results of 34 reinforced concrete beams(four groups)strengthened with different methods were presented including external-bonded or near-surface mounted glass or carbon FRP or helical rib bar in order to study the strain coordination of the strengthening materials and steel rebar of RC beam.Because there is relative slipping between concrete and strengthening materials(SM),the strain of SM and steel rebar of RC beam satisfies the double linear strain distribution assumption,that is,the strain of longitudinal fiber parallel to the neutral axis of plated beam within the scope of effective height(h0)of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of SM and steel rebar satisfies the equation εGCH=βεsteel,where the value of β is equal to 1.1-1.3 according to the test results.
基金Project(2006BAJ03A03)supported by the National Key Technology R&D Program during the 11th Five-Year Plan Period of China
文摘The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.
