Abstract
The true stress is a value for which the change in the cross section of the material with load has been taken into consideration There are some calculation methods for the true stress, but the applicable range of the equation in those calculation methods is unclear. Therefore, the true stress should only be considered in the plastic region At present, since the measurement of the boundary between the elastic region and the plastic region is impossible except in a part of the material, the boundary between the elastic and the plastic regions is unclear. Howaver, the elastic-plastic transition point, which is the boundary between the elastic and plastic regions, has been found using a newly developed intelligent universal test machine. In this study, the plastic region in which the elastic-plastic transition point was within the applicable range of true stress including the starting point was determinea
