Residual stress analysis of shot-peened aluminum alloy by fine increment hole-drilling and X-ray diffraction methods

This paper proposes an analysis of the fine-increment hole-drilling and of the x-ray diffraction methods for residual stress measurement. This analysis was carried out on some shot-peened aluminum alloy samples, with particular attention to the surface. The shot-peening treatment introduces high compressive stress close to the surface of the sample, and for this reason it is widely used to extend the fatigue life of many mechanical components. The hole-drilling method is based on the measurement of the surface strain relaxed during the incremental drilling of a small hole in the material. According to the ASTM E837-08 standard, the residual stress distribution can be measured over a typical depth of 1 mm. X-ray residual stress analysis is based on the evaluation of interplanar distances in deformed samples along different orientations. This technique is suitable for the surface region, typically 10-40 |xm. In-depth stress evaluation can be obtained by progressively thinning the sample and collecting diffraction patterns after each step. The results obtained with the two methods are discussed, considering the different sources of uncertainty, to check the effectiveness of the two methods for the study of this class of materials.