Strain History Curves and Simulative Materials Testing

Abstract

A way of describing the deformation history in a process where large plastic deformation occurs is presented. For a point in the volume, the total strain tensor history is described as a curve in the 6-dimensional shear strain/normal strain space henceforth called a strain history curve (SHC). This paper focuses on the SHC concept and the uniqueness of the SHC representation and on different associated simulative material testing methods, in particular the continuous shear process. The SHC may be used to give a useful representation of the total course of the deformation with respect to directions and magnitudes of the strain, and hence the development of the plastic properties, but may also be used for developing variables describing plasticity. A direct use of the SHC is to measure the yield surface at different points at a SHC, thus establishing data describing the importance of strain rotations or even strain reversals within a process. The reason for suggesting the SHC in this paper is to establish a method of classifying processes according to strain path and hence to demonstrate the need for using advanced plasticity models. Use of the SHC is presented in process and materials testing examples as well as splitting the process into sub-processes for materials testing purposes.