FEM model establishment and variation of cross section distortion in circle tube pressing and bending

In order to study the cross section distortion law of a continual process of circle tube pressing and bending, an FEM model for the process has been established using the FEM software ABAQUS. It has been validated by comparing the results u-sing the model and the experiment. The cross section distortion laws of circle tube pressing have been analyzed. The effects of frictions between dies and tube and round radius of lower die of bending on cross section distortion have been studied. The results show that: The outer layer of the tube which forms the straight part of the flat tube is compressed while the inner layer is tensiled. Collapse occurs in the area due to their resultant. The outer layer of the tube which forms the curved part of the flat tube is tensiled while the inner layer is compressed. Flattening appears in the area due to their resultant. The curved part flattens at the earlier stage of the pressing process either with or without mandrel, and the straight part collapses in the midst of pressing without mandrel. But flattening hasn't been found and the collapse can be improved at the last stage of the pressing with mandrel because of the support of the mandrel. The frictions between dies and tube and round radius of lower die of bending have no dramatic effect on cross section distortion because of the small contact of dies with tube during the whole forming process.