Residual stresses under quasi-static and cyclic loading in shot peened Inconel 718

The residual stress state induced by shot peening should be taken into account in the dimensioning of turbine components. Understanding the changes in the residual stress state caused by the application of quasi-static and cyclic loads is a prerequisite. In order to describe the residual stress state after quasi-static loading, several different shot peened Inconel 718 specimens were loaded isothermally up to specific tensile loadings. To analyze the residual stress state after cyclic loading, isothermal low cycle fatigue tests were performed. These tests were stopped after a defined number of cycles. Finally, after the specimens had been subjected to different loads, the surface residual stresses and — for special loadings — the residual stress depth distributions were determined experimentally by using X-ray diffraction. The surface — core model was adapted so that the complete residual stress depth distribution after quasi-static and cyclic loading can now be described.