Evaluating the Range of Applicability of Existing Models of Stress Distribution in the Neck Forming on Cylindrical Specimens during Tensile Testing

Abstract

This paper is devoted to the post-processing the results of testing the cylindrical specimens for tension. The tensile test are considered from the point of view of studying the rheological properties of metals and alloys. The main problem in identifying hardening curves from tensile test results is the formation of a neck, inside which the stress state of the material differs from uniaxial. The paper considers theoretical solutions to the problem of stress distribution in the neck region, namely, the models of Bridgman, Davidenkov-Spiridonova and Ostsemin. These models make it possible to calculate equivalent stress values even after specimen deformation localizes in the neck. Using the finite element method, the range of applicability of these models was evaluated. It was shown in the paper that the Ostsemin stress distribution model allows to achieve the best results of the material hardening curves identification regardless of its rheological properties. However, the range of applicability of this model is limited by the maximum strain value of 1.5-2.0. With further deformation of the specimen, an overestimation of the calculated values of equivalent stresses with respect to the proper values is observed.