Research On Bend Forming Limit Forrectangular Tube Of 22MnB5

22Mn B5 is a kind of high-strength steel. 22 Mn B5 rectangular tube applied to bus body frames can guarantee the strength for safty and significantly reduce the weight of the vehicles, to achieve the purpose of energy saving and emission reduction. With the radius of rectangular tube bending decreasing, it generates multiple defects such as wrinkling instability at the intrados, wall thinning(cracking) at the extrados, cross section distortion. So master the rectangular tube bending forming rule, obtain the bend forming limit for rectangular tube of 22 Mn B5 has very important meaning in guiding the design of rectangular elbow tube and processing.Based on the theory of plastic mechanics, the distribution of the stress and strain for rectangular tube bending were analyzed. In considering the effect of tangential force at rectangular tube rotary draw bending, the stress and strain formula of the rectangular tube bending and the position of strain neutral layer were deduced. The influence of the tensile force on bending strain neutral layer and the strain when tube bending were studied. The evaluation criterion and prediction methods of bending forming limit for 22 Mn B5 rectangular tube were raised. By tensile test the materials constitutive relation of 22 Mn B5, the plane strain points of the forming limit at different heat treatment states and thickness for 22 Mn B5 material were obtained, and the influence factors of rectangular tube bending forming limit was studied.Through the Explicit algorithm of ABAQUS, the finite element simulation software, the simulation model of the rectangular tube rotary draw bending process was established. The finite element simulation of different bending parameters for the rectangular tube rotary draw bending process was carried on. The forming rule for the rectangular tube rotary draw bending of 22 Mn B5 was analyzed. The relationship between the tangential strain, strain neutral layer of rectangular tube and bending parameters was obtained. Combined with the theory of analytic, the prediction method of tube bending forming limit was established, and the bending forming limit of 22 Mn B5 rectangular tube under different material heat treatment, height, thickness and friction, and the influence rule of different parameters on tube forming limit were obtained.Through the comparison with the experimental data, the numerical simulation and the theoretical analysis result, the correctness of the numerical simulation model, the tube bending rules obtained by the theoretical analysis and numerical simulation, and the bending forming limit of the simulation results were verified.