Strain and hardness distributions of folded sheet products

Abstract

The measurements of hardness and strain distributions on the bend points of metals suggest the forming mechanism for the bending operation.This paper reports their distributions of the sheet products for folding operation.The materials used for the experiments were aluminum and mild steel. At first, uni-axial strains were given to a cylindrical test piece, and then, the correspondence between the specified strains and hardness were examined.The specified strains given for test pieces were tension, compression, and compression after tension.Secondly, plane test pieces were cut out of the same materials to perform folding tests. After the tests, the strain and hardness distributions on the bend point of specimens were measured.The results obtained were as follows:1) The propagation of strain and hardness distributions was made more clear with the proceeding of operation.2) The relations between strain and hardness on the bend point were obtained.3) In the early stage of folding operation, the neutral plane of the specimen moved from the central position in thickness to tension side.4) The position of moved neutral plane could be estimated from the minimum value of hardness distribution.5) The error of the above estimation was analyzed and the mechanism due to material properties was explained.