Computational-experimental method for stress-strain curve constructing under conditions of inhomogeneous stress fields

In order to ensure reliability of structures, it is necessary to study equilibrium damage accumulation which initiates softening zones in solids. It is considered appropriate to use postcritical deformation models when conducting strength analysis of structures. However, obtaining complete stress-strain curves in standard tests is difficult due to the strain localization in the form of a neck. At the same time, the use of true stresses taking into account changes in a specimen cross section is incorrect due to the implementation of a complex stress state. In this regard, it is necessary to develop computational and experimental methods for constructing material stress-strain curves under conditions of inhomogeneous stress fields. In this case it seems reasonable to use data on strain fields on the body’s surface, which can be obtained, for example, using non-contact optical video systems. The paper presents the computational-experimental method for constructing a stress-strain curve under conditions of inhomogeneous stress fields. An elastoplastic model of an isotropic material is considered. The initial data of the method are two elastic constants, the yield stress value, the load diagram of a body with a stress concentrator, and the maximum values of strain intensity corresponding to various states. The developed method was tested by a numerical simulation of deforming an hourglass specimen and a plate with a stress concentrator. Stress-strain curves with and without a yield plateau are considered. The results demonstrate a high agreement between the initially specified and reconstructed stress-strain curves. A conclusion is made about the rationality of using the developed method when constructing stress-strain diagrams and necessity for its modernization to describe the postcritical deformation stage.