Study of the plastic deformation of metals by indentation method

Abstract

All-Russian Scientific Research Institute of Aviation Materials, 17, ul. Radio, Moscow, 105005 Russia; e-mail: 89639619741@mail.ruPlastic deformation is a type of material damage which can disrupt the normal operation of the structure. In this regard, the method for assessing the degree of damage to a metal sample has been developed. A corset sample for tensile tests was made from an aluminum alloy of the Al – Zn – Mg – Cu system. The ANSYS finite element complex was used to simulate an inhomogeneous stress state occurred in the sample working zone due to the variable cross-section upon tension. First, the hardness of the corset sample was measured, then it was tested for tension until the onset of necking and the load drop on the deformation diagram. After unloading along the sample working area, the Brinell hardness and surface roughness were measured. The results of the hardness measurements showed that in the areas where the tensile stresses are below the conditional yield stress of the material, the hardness value corresponds to the hardness of the starting material. In the areas where the tensile stresses are higher than the conventional yield stress, the hardness increases and reaches the maximum value in the center of the specimen, i.e., in the zone of the minimum cross-section. Thus, the damageability of the material can be assessed through the change in the hardness and roughness of the surface along the sample length. Proceeding from the results of instrumental spherical indentation, a technique for assessing the mechanical characteristics of the material was developed. The method consists in testing one sample for hardness and tensile strength with subsequent construction of the correlation dependences of tensile and indentation loads using the experimental results to obtain calculated tensile diagrams from the indentation diagrams of the material under study.