Evaluation of change in material properties due to plastic deformation

In sheet metal forming, quantitative evaluation of the spring-back phenomenon is one of the most important issues. In this study, in order to clarify the influence of plastic deformation on the changes of material properties such as the elastic modulus, both macroscopic and microscopic experiments were performed. The change in the elastic modulus was measured before and after plastic deformation using a precision tensile test. The microscopic variation in the elastic modulus was investigated by nano-indentation testing, by means of which micro regional material properties can be obtained. Both macroscopic and microscopic measurements show that the elastic moludi decreases according to increasing plastic strain and that the decrease of the elastic modulus affects the spring-back significantly.