Determination of the Young’s modulus and hysteresis by the indentation method

Abstract

The development of nondestructive tests is based on continuously recording an indentation diagram (i.e., the load P applied to an indenter as a function of the dent depth h) [1–7]. In this case, the relation between the conventional (recovered) hardness H and nonrecovered hardness Hh becomes vitally important. These quantities are measured through the transverse size of an unloaded dent and the depth h of a loaded dent, respectively. Both further progress in nondestructive testing (based on the indentation method) of the stress–strain and the structural characteristics of materials and in forecasting the reliability and service life for constructions under various operating conditions depend on the possibility of accurately analytically evaluating the relationship between H and Hh. This relationship was first established in [3] and depends on the elastic and plastic properties of materials. The allowance for elastic strains in a dent is possible only by accurately measuring the contact elastic modulus Er . A technique for such a method of measuring according to the P–h diagram was first proposed in [2] and then developed in a series of papers [3–7]. It was shown in [2] (see Fig. 1) that the slope angle for an initial segment of the unloading branch for the P–h diagram is independent of the