Plastic deformation of workpiece during unloading in plate compression

Abstract Deformation behaviour during loading and unloading is studied in compression of an aluminium plate with a high ratio between the diameter and the thickness by a DLC coated die. A compressed plate becomes thinner during unloading after the plate is compressed to a larger reduction in thickness in loading. The plastic deformation of a compressed plate during unloading is confirmed by measuring the increase of the plate diameter during unloading. The optimum profile of a die crown approaches to the reverse shape of the elastic deflection of a flat die at the loading stroke end with increasing reduction in thickness.