Tensile tests with bending: a mechanism for incremental forming

In incremental sheet forming (ISF) large uniform strains can be obtained well above the common forming limit. Bending-under-tension has been proposed as a possible mechanism. This paper describes tension tests with repetitive bending to simulate this effect. Indeed very large levels of uniform elongation have been obtained, up to 300 %. The maximum strain increases with decreasing bending radius, and is reached at a certain optimum pulling speed. The material hardening seems little affected by the cyclic bending operations, and a hardening curve for large strains could be constructed.