Prediction of forming limit based on cross-sectional distortion for rotary draw bending of H96 brass double-ridged rectangular tube

Cross-sectional distortion is one of the main defects severely restricting the improvement of the forming limit in the rotary draw bending of double-ridged rectangular tube. So, how to rapidly and efficiently predict the forming limit (minimum bending radius R (min) with allowed cross-sectional distortion) and improve it has become an urgent problem to be solved for the development of rotary draw bending of double-ridged rectangular tube. Based on ABAQUS/Explicit, finite element model of rotary draw bending for double-ridged rectangular H96 brass tube has been established and verified by experiment. Using the model combined with the virtual orthogonal experiment, the significance analysis of influence of processing parameters on cross-sectional distortion was carried out. And based on the technique of orthogonal regression analysis, a prediction model of the forming limit with allowed cross-sectional distortion was built. The results show that: (1) processing parameters significantly influencing cross-sectional distortion are tube-mandrel clearance Delta c (m), tube-bending die friction coefficient mu (b), bending radius R, and core number N. (2) Effect laws of significant parameters on R (min) were obtained: R (min) gradually decreases with increasing of mu (b); when the value of Delta c (m) is smaller than 0.37 mm, R (min) slightly decreases with increasing of Delta c (m); and when the value of Delta c (m) is larger than 0.37 mm, R (min) sharply increases with increasing of Delta c (m). (3) The 3D forming limit diagrams and the minimum bending radii in different processing conditions were obtained, which can provide a crucial guide for selecting of processing parameters in RDB of the double-ridged rectangular tube.