Fatigue behaviour improvement on notched specimens of two different steels through deep rolling, a surface cold treatment

Abstract

Deep rolling is a type of surface treatment which allows increasing the lifetime under cyclic loads through compressive residual stress induced in the outer layers, improving this way the fatigue strength of the treated components. It is used in several sectors, such asaeronautic industry, wind turbines, as well as in vehicle components, among others. Deep rolling process enables to reduce the notch effect in those zones where fatigue damage could take place.Fatigue behaviour improvement is achieved through the enhancement of the surface finish, surface hardening and, mainly, due to the external layer of compressive residual stresses originated in the deep rolling process. In this way, fatigue crack initiation is retarded and the crack propagation rate is reduced.The increase of the endurance limit in two different D38MnV5S steels used in the manufacture of forged crankshafts was studied in this work. Notched specimens were employed in this study and the behaviour of those materials under cyclic loads before and after a deep rolling process was analysed and compared with the results obtained using smooth specimens. Furthermore, residual stress profiles were evaluated for different deep rolling process parameters by means of X-ray diffraction.