Determination of Residual Stresses in Plate Material by Layer Removal with Machine-integrated Measurement

Structural aircraft components are usually manufactured from rolled plate material. Despite a stress relief treatment residual stress remains in the plates. This can result in distortions of the workpiece after the final manufacturing step, which leads to time-consuming repair processes or even a scrap part. Using an FEM simulation, it is possible to predict distortions caused by residual stress and to avoid them by adjusting the manufacturing process. However, the known methods to determine the residual stress state in plate material are expensive in terms of time and material and require specially trained staff. This paper describes a novel method to measure residual stress in plates with little effort. The method is derived from the well-known Layer-Removal-Method and utilizes a machine tool with a standard probing device. The measuring task is fully automated and can be performed by untrained staff. No special preparation of the specimen is necessary. The paper describes the procedure and the results of residual stress measurement on samples of the material EN AW-7075 T651. The results are in line with values published by other authors.