Elementary studies on the inducement and relaxation of residual stress

In order to qualify residual stress relaxation as an indicator of mechanical overloading of machined parts, an individually designed residual stress profile has to be allocated. Even though numerous investigations have been carried out in the past, residual stress profiles cannot be predicted to a satisfactory degree. For this reason, essential studies on the reproducibility of residual stress profiles for several external cylindrical turning parameters are conducted and it is demonstrated that identical residual stress profiles can be induced successfully. Subsequently, specimens with defined residual stress profiles are loaded in bending tests with various numbers of test cycles. The amount of residual stress relaxation in the specimen’s surface layer is measured to determine the influence of the applied load on the stress relaxation. By applying single tensile and compressive loads below and above the material’s yield and ultimate strength, the stress relaxation can be evaluated in detail.