FEM Numerical Prediction And Compensation Research Of NC Tube Bending Springback

The thin-wall tubes are widely used in lots of fields because of their excellent properties, various functions and hige feature-price ratio, such as in aviation and astronavigation fields etc. The springback which happens consequentially after unloading is a flaw which acutely reduced the efficient production of the tubes, and at present, much research work have been done about finding the appropriate solution to the springback. This paper conducted the detailed research to obtain the rules existing in the bending springback phenomenon of the stainless steel tube and the Al-alloy tube, based on the elasto-plasticity FEM. The main research content and achievements are as follows:(1) Based on the research of the forming mechanism of tube bending, the elastic-plastic FEM simulation model which is very important to the research of the springback rules of bending tube has been established, the essential technical questions to carry out the simulation was treated as well. The deforming body was dispersed by eight-node solid element, and surface-to-surface contact element was used for creating the contact pair, besides, the Coulomb friction model was used to solve the friction questions between contact faces.(2) Based on the tube bending FEM simulation model, the tube bending springback rule under the different craft parameters and the material parameters was studied. The results indicated that the springback quantity of bent tube grows with the increasing of the elbow piece angle, the relative bending radius and the gap between the core craft and the tube wall, falls down with the increment of material hardening index value, and increases with the increment of the material hardening coefficient value.(3) Based on the obtained bent-tube's springback rules , the VB language, the SQL language and Microsoft Access database software, an over-bending compensate system of the NC tube bending springback was designed and developed. This system can provide a feasible method to compensate the springback angle of tube bending process.