X-RAY STUDY OF THE INHOMOGENEITY OF SURFACE RESIDUAL STRESSES AFTER SHOT-PEENING TREATMENT

It is well known that shot-peer&g treatment increases the fatigue resistance of metals. It is considered that this effect is caused by compressive residual stresses arising in the treated surface. Usually the mean value of residual stress is taken into consideration to explain this phenomenon but the real residual stress state must be inhomogeneous due to the inhomogeneous character of deformation around the shot-peening indentation and due to the rough character of the shot-peened surface. In the present paper the following investigations were undertaken to analyse the inhomogeneity of the residual stress state after shot-peening: 1. Residual stress measurements at the bottom and top of a Brine11 indentation, simulating a shot-peer&g indentation, were made with local X-ray diffraction. 2. The measurements of residual stresses in the peaks of roughness of a shot-peened surface were carried out. The experimental results permit the explanation of the specific character of the residual stress distribution in the surface layer after shot-peening. 3. Analysis of the specific behaviour of residual stress depending on a removed surface layer at the initial stage of the stress distribution curve.