Abstract
To clarify the generating mechanism of the wrinkles on the surface of the test piece in a rotary draw bending forming, the processing experiment and the simulation analysis using finite element method (FEM) were done. The result of obtaining is as follows: the wrinkle is generated by not only curved part but also the straight run of the original pipe as the processing progresses; the frictional force between the pipe and bending die generates the wrinkle, and promotes the wrinkle generated in addition; the occurrence condition of the wrinkle depends on parameters other than frictional properties, because the wrinkle is generated even when the frictional force between the pipe and the die is disregarded.
