Fatigue resistance of metal construction materials and its relationship with changes in the state of thin surface layers

Abstract

The paper considers the proven clear relationship between the fatigue resistance of a number of structural materials and the processes occurring in their thin surface layers. The fatigue studies of the samples were carried out over a wide range of temperatures and amplitudes of cyclic stresses under uniaxial tension-compression with simultaneous microhardness measurement of the thickness of the hardened surface layer. On the basis of experimental studies of the fatigue of metallic structural materials, using the microhardness method, the regularities of hardening (softening) of their surface layer are established depending on the level of the amplitude of high-cycle loading and temperature. A method for the accelerated determination of the fatigue limit of structural materials based on the determination of microhardness during cyclic loading has been developed and tested. The dependence of the formed hardened film of the surface layer on the level of plasticity of the material has been established - the greater its plasticity, the thicker the resulting hardened film. With an increase in the amplitude of cyclic loading, the thickness of the hardened surface layer decreases.