Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study i...Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study is a generalization of the prior an alytical-experimental examination of strain-gradient light deflections produced in stressed plates, which had concentrated on the simplest case where in- formation of interest is collected along a line of symmetry of the stress field. Main purpose of the present investigation is to document the efficacy of the strain-gradient method in analysis of the general case of stress state. The most interesting stress state is that in a beam subjected to the Saint-Venant bending, where the transversal and the longitudinal axes of the beam are in pure shear. The obtained results are compared with the predictions of the developed analytical models and with the pre- dictions of Filon's stress function. The procedures of evaluating the photoelastic and material coefficients using strain-gradient techniques were tested positively.展开更多
GH4169 superalloy stress relaxation test was investigated to study its characteristics of stress relaxation curves at various temperatures( 550,650,and 750 ℃). These curves presented jointly two distinct stages,the s...GH4169 superalloy stress relaxation test was investigated to study its characteristics of stress relaxation curves at various temperatures( 550,650,and 750 ℃). These curves presented jointly two distinct stages,the stage of inner stress relaxing quickly,and the stage of inner stress relaxing slowly and closing to the stress relaxation limit. And these curves obtained could be fitted by second order exponential decay function well. Based on the experimental stress relaxation curves,the relationship between stress relaxation rate and time were derived, which showed that the higher relaxation temperature and the greater initial rate of stress relaxation. The whole process presented two different stages,the stage of stress relaxation rate falling rapidly and the stage of stress relaxation rate slowing down and tending to be constant. The relation curve between creep strain rate and stress of GH4169 superalloy can be divided into three stages,low stress stage,transition stage,and high stress stage.Both the high stage and the low stage present linear correlation.展开更多
A numerical model was established to calculate the cycle feed rate through studying the case of a cold pilger mill with the 304 stainless steel pipe. Firstly, the precise constitutive equation of 304 stainless steel w...A numerical model was established to calculate the cycle feed rate through studying the case of a cold pilger mill with the 304 stainless steel pipe. Firstly, the precise constitutive equation of 304 stainless steel was obtained through nonlinearly fitting the true stress-strain data from unidirectional tensile test. Then, the numerical method to calculate the equivalent deformation was determined according to the plastic deformation feature of the steel tube during cold rolling and the incremental theory. Finally, the cycle feed rate of cold roiled 304 stainless steel pipe was extracted when formulating springback through utilizing above results comprehensively and unloading law. Stress state, metal flow, finished pipe size and distribution of residual stress were obtained by finite element method to calculate the whole rolling process when the cycle feed rate was 10 mm, and the optimized model was verified through finished pipe size.展开更多
The residual stress generated in the manufacturing process of inertial platform causes the drift of inertial platform parameters in long-term storage condition.However,the existing temperature cycling experiment could...The residual stress generated in the manufacturing process of inertial platform causes the drift of inertial platform parameters in long-term storage condition.However,the existing temperature cycling experiment could not meet the increased repeatability technical requirements of inertial platform parameters.In order to solve this problem,in this paper,firstly the Unigraphics(UG) software and the interface compatibility of ANSYS software are used to establish the inertial platform finite element model.Secondly,the residual stress is loaded into finite element model by ANSYS function editor in the form of surface loads to analyze the efficiency.And then,the generation based on ANSYS simulation inertial platform to accelerate the stability of experiment profile is achieved by the application of the analysis method of orthogonal experimental design and ANSYS thermal-structural coupling.The optimum accelerated stability experiment profile is determined finally,which realizes the rapid,effective release of inertial platform residual stress.The research methodology and conclusion of this paper have great theoretical and practical significance to the production technology of inertial platform.展开更多
基金the Natural SciencesEngineering Research Council of Canadathe NATO Scientific Affairs Division
文摘Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study is a generalization of the prior an alytical-experimental examination of strain-gradient light deflections produced in stressed plates, which had concentrated on the simplest case where in- formation of interest is collected along a line of symmetry of the stress field. Main purpose of the present investigation is to document the efficacy of the strain-gradient method in analysis of the general case of stress state. The most interesting stress state is that in a beam subjected to the Saint-Venant bending, where the transversal and the longitudinal axes of the beam are in pure shear. The obtained results are compared with the predictions of the developed analytical models and with the pre- dictions of Filon's stress function. The procedures of evaluating the photoelastic and material coefficients using strain-gradient techniques were tested positively.
文摘GH4169 superalloy stress relaxation test was investigated to study its characteristics of stress relaxation curves at various temperatures( 550,650,and 750 ℃). These curves presented jointly two distinct stages,the stage of inner stress relaxing quickly,and the stage of inner stress relaxing slowly and closing to the stress relaxation limit. And these curves obtained could be fitted by second order exponential decay function well. Based on the experimental stress relaxation curves,the relationship between stress relaxation rate and time were derived, which showed that the higher relaxation temperature and the greater initial rate of stress relaxation. The whole process presented two different stages,the stage of stress relaxation rate falling rapidly and the stage of stress relaxation rate slowing down and tending to be constant. The relation curve between creep strain rate and stress of GH4169 superalloy can be divided into three stages,low stress stage,transition stage,and high stress stage.Both the high stage and the low stage present linear correlation.
基金The authors are grateful for the financial assis- tance from the National Science Foundation of China (U1710113), the China Postdoctoral Science Foundation (2017M622903), the Fund for Shanxi Key Subjects Construction, Excellent innovation projects of graduate students in Shanxi (2017SY077), Heavy Machinery Engineering Research Center of Ministry of Education (20172004).
文摘A numerical model was established to calculate the cycle feed rate through studying the case of a cold pilger mill with the 304 stainless steel pipe. Firstly, the precise constitutive equation of 304 stainless steel was obtained through nonlinearly fitting the true stress-strain data from unidirectional tensile test. Then, the numerical method to calculate the equivalent deformation was determined according to the plastic deformation feature of the steel tube during cold rolling and the incremental theory. Finally, the cycle feed rate of cold roiled 304 stainless steel pipe was extracted when formulating springback through utilizing above results comprehensively and unloading law. Stress state, metal flow, finished pipe size and distribution of residual stress were obtained by finite element method to calculate the whole rolling process when the cycle feed rate was 10 mm, and the optimized model was verified through finished pipe size.
文摘The residual stress generated in the manufacturing process of inertial platform causes the drift of inertial platform parameters in long-term storage condition.However,the existing temperature cycling experiment could not meet the increased repeatability technical requirements of inertial platform parameters.In order to solve this problem,in this paper,firstly the Unigraphics(UG) software and the interface compatibility of ANSYS software are used to establish the inertial platform finite element model.Secondly,the residual stress is loaded into finite element model by ANSYS function editor in the form of surface loads to analyze the efficiency.And then,the generation based on ANSYS simulation inertial platform to accelerate the stability of experiment profile is achieved by the application of the analysis method of orthogonal experimental design and ANSYS thermal-structural coupling.The optimum accelerated stability experiment profile is determined finally,which realizes the rapid,effective release of inertial platform residual stress.The research methodology and conclusion of this paper have great theoretical and practical significance to the production technology of inertial platform.