IMPACT INDENTATION OF METALS AT THE SMALL ELASTOPLASTIC STRAIN

The aim of this paper is to study and describe the behavior features of metals under impact loading in the area of elastic-plastic transition, with strains not exceeding 3–4 %, which are typical for measuring the hardness of materials during dynamic indentation. It has been established that until the state of full plasticity is reached, the excess of the dynamic hardness over the static one cannot be explained only by an increase of the strain rate and requires taking into account the elastic properties of the material. It is shown that a grow of the yield stress and the part of elastic deformation leads to a significant increase in the dynamic hardness of the material. This is due to the feature of measurements, which consists in fixing the value of the initial impact energy, which is distributed between elastic and plastic part of strain, depending on the characteristics of the material: yield stress, elastic modulus, strain-hardening coefficient.