Indirect residual stress measurement using the ESPI wellbore method

Residual stresses can be measured indirectly as well as directly, e.g. by radiographic methods. During the removal of residual stress containing material, the deformation of the remaining body is measured and herefrom the residual stresses are determined. The most familiar indirect method is the hole-drilling method, where deformation usually is measured by strain gauges. An alternative to strain gauges is Electron-Speckle-Interferometry (ESPI). The analysis of the speckle pattern enables a full-field strain measurement of the surface. Today, however, the method only delivers reliable results under certain conditions. The aim of the research project is to determine suitable measuring and drilling parameters that provide a reliable and reproducible result. Aluminium, steel in various quenched and tempered states, as well as TiAl6V4 are analysed. Residual stresses are induced into the workpieces in a specific and reproducible way using the deep rolling process.