Experimental Research Regarding the Evolution of Some Parameters of the Superficial Layer in Low Cycle Fatigue Process

Abstract

The development of some mechanic engineering systems in, feasible to pressure vessels, aeronautics, ship building technology, requires a full investigation of the material features that are to be examined under a low cycles fatigue to strains close to the limit of the material elasticity. In this paper we present a testing machine at variable stresses in oligocyclic range. An own testing stand was patented by Romanian Standard Office, some results concerning the evolution of inner second order tensions, microhardness in superficial layer during low cycles fatigue process and the microscopic images of cracks, some results concerning the evolution of the crystalline lattice parameter, level of the texture were realised in steps of each two thousand cycles until a limit of 10⁴ cycles. Two types of steel are tested.