Experimental Determination of the Surface Energy of a Metal Composite Based on Crack Development Parameters

Abstract

The paper proposes and tests a method for measuring the surface energy of an alloyed steel with a fibrous ferrite-martensite composite structure. The method is based on the cleavage test and the measurement of the material's mechanical characteristics based on the development of a crack. The relationship between the material parameters, surface energy, and crack length was described in accordance with the Griffiths and Irwin fracture criteria, expressed through the invariant integral. The crack developed under flat deformation conditions with low values of the average radius of the plastic zone at the crack tip. In this case, the fracture mechanism is quasi-elastic or elastoplastic. Using analytical expressions for fracture criteria and experimental data on crack formation, the values of the surface energy of the steel composite were obtained. The results are in good agreement with known experimental data for single crystals of polymorphic iron modifications, which demonstrates the correctness and applicability of the proposed methodology. In the future, it will be possible to account for the delamination of ferrite during crack growth and, by determining the thicknesses of the ferrite and martensite layers, to determine their surface energies.