Experimental and Computing Method for Constructing True Deformation Diagrams at Large Strains on the Basis of Tests for Hardness

摘要

Tests for hardness by forcing an elastic indenter into a structural component under study is one of the well-known and inexpensive sample-free approaches to investigating deformation properties of elastoplas-tic materials (see [1-3] and references therein). Presently, the most popular are methods in which impressing a ball into a sample occurs along the normal to its surface. A ball is used insofar as, in contrast to a cone or a pyramid, it is a universal indenter having a variable contact angle that increases with penetration into the material. In order to have the most exhausting data on deformation properties of a material, it is necessary to continuously record the diagram of indenter loading as a function of the indenter penetration depth. In constructing deformation diagrams, the dependence (called the hardness curve) of the mean stress in an imprint on the degree of deformation is usually determined. The ratio of the loading force to either the imprint area (Brinell hardness, HB) or the imprint projection area (Maier harness, HM) is chosen as the mean stress. The ratio of the diameters of the imprint and of the ball and other parameters are used as characteristics of the deformation degree. The majority of well-known methods for investigating material properties by testing for hardness are based on constructing correlation dependences of a deformation diagram for the uniaxial tension of a sample and a hardness curve or an indentation diagram. The basic disadvantage of these methods is the fact that they are not universal.