METHODS OF RESIDUAL STRESS ANALYSIS IN LAYER COMPOSITES AND THEIR APPLICATION

Residual stresses occur in most coating deposition and layer composite manufacturing processes. Main reasons are temperature gradients during the manufacturing and in the cooling period as well as different thermophysical properties of the component materials, but also solidification and phase transformation processes. In case of metal-ceramic or glass-ceramide composites, the mismatch in the thermophysical properties is of high importance. Residual stresses even can lead to crack formation and failure of the materials and components. Therefore, residual stress analysis is an important toot and essential for the optimization of layer composites and ceramic manufacturing processes in order to ensure stability and reliability of technical systems. This paper gives an overview and introduction to the most customary residual stress measurement techniques. The application ranges of the different methods are given with respect to the underlying measurement principle and the physical boundaries. Their advantages and disadvantages are compared with respect to the application on industrial machine parts. The incremental-step hole drilling and milling method is presented in more detail. Thereby, the measurement principle, analysis of the measured data and different possibilities for the determination of calibration curves are explained. Additionally, an application example for the hole drilling method is given from the field of process optimization in ceramic coating development with the atmospheric plasma spraying (APS) technique.