Reversed straining in axisymmetric compression test

A large group of the cold forging processes is carried out in a thick-walled container with the deformation force transmitted through a punch moving axially in the container. The work-piece, being entrapped between punch and container will expand and exert a radial pressure resulting in an expansion of the bore. After unloading, the container will try to reduce this expansion and thus in many cases cause a reversed plastic deformation of the work-piece. This will have an effect on the resulting diameter of the work-piece and-above all-on the resulting mechanical properties. In order to simulate these conditions a reversed axisymmetrical material tester is designed and constructed. Three different materials were tested, aluminum alloy AA6082, technically pure copper (99.5%) and cold forging steel Ma8, at different temperatures found during cold forging.