Study On The Subsequent Yield Behavior Of Q235 Steel

Large structural parts(such as hydraulic beam)are usually subjected to complex stresses and cyclic loads in the process of work,and their mechanical response characteristics are very different from those under uniaxial loading.At present,scholars have formed systematic theoretical results on the yield behavior of structural materials under single load and uniaxial cyclic load,but the research on the initial yield behavior and cyclic subsequent yield behavior under complex loading path is not enough.Therefore,a comprehensive and in-depth study of the mechanical properties of large bulk structural materials under complex stress states and cyclic loads can better provide theoretical support for the accurate evaluation of the bearing capacity and life of structures.In this paper,Q235 steel,a commonly used material for beam of welded structure hydraulic press,is selected as the research object.SCS compression shear and STS tension shear samples of non-national standard are designed,and the sample size is optimized through numerical simulation.At room temperature,uniaxial tensile,uniaxial compression,pure shear,SCS compression shear,SCBS compression shear and STS tension-shear tests were carried out to obtain the stress-strain curves of Q235 under various loading conditions,and the mechanical response characteristics of Q235 under different stress states at the elastic stage,the yield stage and the plastic strengthening stage were analyzed.The method to obtain the yield strength of the material under different loading modes was determined,and the initial yield surface of Q235 steel was obtained.By comparing the theoretical yield surfaces with Von-Mises yield criterion,Ellipse yield criterion,Drucker-Prager yield criterion and Cazacu-Barlat yield criterion,the yield criterion which can accurately describe the yield behavior of Q235 steel was determined.The mechanical behavior of Q235 steel after yielding was discussed,and the plastic subsequent yield surface of the material was obtained.Based on the selected yield criterion and hardening law,a prediction model of the plastic subsequent yield surface of Q235 was established,and the model was compared with the subsequent yield surface obtained from the test,and the validity of the model was verified.On Q235 steel after compression-unloading cycle loading uniaxial tension,uniaxial compression and pure shear and different angles of SCBS compression-shear composite load test,the characteristics of mechanical response of Q235 steel in the circulation process and after compression-unloading cyclic loading history yield behavior under different stress state,the subsequent yield surface of Q235 cycle evolution,discusses the peak stress and cyclic time on the material cycle the influence law of subsequent yield surface shape and position.