Mechanism and process influence of inner diameter expansion during forward hot spinning of 5A06 aluminum alloy tube

During hot spinning process of aluminum alloy tube parts, it is easy to have the phenomenon of inner diameter expansion, which makes it difficult to guarantee the dimensional accuracy of tube. For better understanding of the mechanism and find the way to solve this problem, finite element numerical simulation method was applied to systematically study the relation of stress, strain evolution with the inner diameter expansion, and the quantitively influence of spinning process parameters including feed speed, rotation speed, thinning rate, spinning temperature on the inner diameter expansion data. The results show that during the spinning process, there is a line with the same three-dimension principal stress in the radial direction of the tube in the contact area between the roller and the tube, which is the plastic flow boundary of the material. The contact area is divided into two regions by the dividing line. The stress state of these two regions is three-dimensional compressive stress, but the different flow directions of the two regions lead to the inner diameter expansion. The change of spinning process parameters affects the size of inner diameter expansion by affecting the position of plastic flow boundary. Within a reasonable range, the smaller the feed speed, thinning rate and the spinning temperature, the higher the rotation speed, the closer the boundary position to the unformed area of the tube, and the smaller the inner diameter expansion of the tube. The achievement of this study has certain theoretical guiding significance for selecting appropriate process parameters to control the inner diameter expansion amount to improve the dimensional accuracy of spinning forming tube.