Study On The Constitutive Model Of The Ratchet Effect Of Q235 Steel

When the hydraulic pressure machine with combined pre-tight structure is subjected to cyclic loading, the ratchet effect can’t be ignored. The accumulation of ratchet strain may lead to the component or the structure size exceeding the standard even destroyed. At present, many scholars have carried out a lot of research work on the deformation behavior of the materials under cyclic loading, but people have not studied on the deformation behavior of hydraulic machine body commonly used materials under cyclic loading, it is not clear whether the existing constitutive models are suitable for the common material of the hydraulic machine body. Therefore, it is necessary to carry out a certain amount of cyclic loading experiment on the commonly used materials of hydraulic machine, establish a constitutive model which can accurately describe the ratchet effect of the hydraulic machine commonly used material, and implement the model by finite element method. Then it can accurately predict the ratchet effect of the hydraulic machine body structur under cyclic loading, so that the safety, reliability and life assessment of the hydraulic machine structure can be more guaranteed.In this paper, the hydraulic machine commonly used materials Q235 steel is used as the research object. Under the room temperature, the tensile test, strain control and stress control of cyclic loading tests were carried out on Q235 steel. Through research and analysis of the experimental data, the basic characteristics of the uniaxial strain cyclic deformation behavior and the ratchet behavior of Q235 steel were obtained.On the basis of the existing model, a new constitutive model was established. This model gives a new kinematic hardening law. The finite element implementation of new model was based on the radial return algorithm and the fully implicit integration method, and the consistent tangent stiffness matrix expression was derived. Finally, the new model was embedded into ABAQUS by using user material subroutine.A simple and feasible method was used to determine the material parameters of model, then the test procedure were simulated. The results shows that the model in this paper was reasonable to describe the uniaxial strain cyclic deformation behavior and the ratchet behavior of Q235 steel, The finite element implementation of the constitutive model was successful.