Effects of an innovative deep rolling process on the subsurface properties of thin-walled components

In aerospace industry, the need for components with high fatigue life is increasing steadily. In particular, aircraft engines have to withstand high aerodynamic, mechanical and thermal loads during operation. The most common defect of compressor blades is caused by impact damage of small foreign objects. Out of such damage, vibration cracks during operation arise and cause safety-critical blade loss. Consequently, the fatigue life of such components is reduced [1]. By mechanical work hardening of the subsurface area compressive residual stresses can be induced, which has a positive impact on the fatigue life of these components [2-5]. Currently the residual stress state of compressor blades is optimized by shot peening. This procedure allows the processing of complex geometries and undercuts. A major drawback of this process is the high surface roughness which has a lasting influence on the flow characteristics. Furthermore, an additional process step in order to increase surface quality is required. An alternative process to induce residual stresses is deep rolling whereby these disadvantages are avoided. At present, it is not possible to influence the subsurface properties of thin-walled components by deep rolling due to shape deviations of the component after machining. Moreover, currently no deep rolling tool exists which allows the machining of complex geometries and undercuts. A further disadvantage is the application of fluid medium in order to build up the rolling pressure which leads to a high leakage flow affecting the environment.