• Г. Л. Петросян Национальный политехнический университет Армении
  • М. А. Маргарян Национальный политехнический университет Армении
  • А. К. Карапетян Национальный политехнический университет Армении
Keywords: plastic deformation, tension, neck, porosity, stress-state, deformation degree, von Mises stress.


The tensile test of a plastic deformed circular cross section sample is one of the most important method for determining the mechanical properties of a material. At small plasticdeformations, the stress state of the sample is uniaxial. With an increase of plastic deformations, a neck is formed in the sample, where there is quite complex concentration of stresses (three dimensional unhomogenious stress state), due to  which the initial microporosity in the material increases, additional pores are formed around nonmetallic inclusions of different origin, which, being connected with each other, make cracks, and the sample is
destroyed. Theoretical and experimental data known in literature have been used in the study, taking into account the porosity of the material and the change in the stress state in the neck (from uniaxial to triaxial), the values of the gradual change of the porosity of the material before and after the formation of the neck and at various points of its smallest cross section have been determined. While solving these problems, assumptions were admitted the accuracy of which can be estimated by using numerical methods. The tension test of a metal sample was modeled in the ABAQUS software environment. The problem was solved for different values of displacement from both ends of the sample. Data on the stress-strain state were obtained, and the analysis of these data was carried out. The finite element mesh of the sample in ABAQUS was obtained, using the tetrahedral CAX4R and trihedral CAX3 elements. The characteristics of elasticity (Young's modulus, Poisson's ratio, material density) and plasticity at different degrees of deformation (data of the deformation graph) of the material were chosen.