Impact Failure Behavior Analysis Of SUS301L-MT Material And Vehicle End Structure

In order to comprehensively analyze the phenomena of material fracture,local buckling and instability deformation of the subway vehicle during collision,and improve the simulation accuracy of train collision,the dynamic failure characteristics of materials are used in the vehicle collision simulation.SUS301L-MT stainless steel and the end structure of the vehicle are objects.From the two levels of material and structure,its collision failure behavior is studied and analyzed through the combination of experiment and simulation.Firstly,the quasi-static fracture test of SUS301L-MT stainless steel was carried out.After obtaining the fracture strain under different stress states,the influence of the stress triaxiality on its fracture strain was analyzed.Through simulation analysis,the applicability of VM model and GISSMO model to this material was compared.The influence of the element size effect on parameters of the GISSMO model was analyzed.And through the thin-walled round tube crush test,the correctness of the failure parameters and the element size correction is verified.The research results show that: for SUS301L-MT stainless steel,the fracture strain is significantly affected by the stress triaxiality.The maximum difference of the fracture strain under different stress state is 51.10%.The fracture strain decreases with a negative exponential power change as the element size increases,while the stress weakening coefficient increases linearly.Then,according to the temperature rise and softening characteristics of SUS301L-MT stainless steel,the temperature term of the dynamic constitutive model was revised.The uniaxial tensile dynamic fracture test was carried out,and the fracture strain of the material at different strain rates was obtained.The GISSMO model was extended to a dynamic fracture model.The results show that there is strain rate strengthening effect and a yield lag phenomenon for SUS301L-MT stainless steel.The modified Johnson-Cook model of temperature effect can better describe the characteristic that it gradually softens with the increase of plastic strain.The fracture strain in dynamic is lower than that in quasi-static,but the fracture strain increases as the strain rate increases.Finally,a vertical offset impact simulation of the end of the vehicle at different speeds based on the material failure model was carried out.The structural optimization and improvement of the buckling failure of the end in a collision were carried out.The force flow distribution at the end in the collision and the characteristics of the longitudinal support beam are studied.The results show that the GISSMO model is more suitable for large deformation impact behavior than the VM model.The risk of climbing can be effectively reduced by increasing the vertical bending stiffness and setting the induction groove.The effect of the induction groove on reducing the initial peak force of the longitudinal support beam collision is more obvious with the higher the speed.During the collision,the main bearing object of the longitudinal force is transformed from the longitudinal support beam to the side beam.Through the above three aspects of research,the SUS301L-MT material dynamic constitutive model,dynamic fracture model,and the collision characteristics and failure behavior of the end structure are obtained.It can further improve the accuracy of train collision simulation and provide theoretical support for car body crashworthiness design.