Residual stress measurement via digital image processing and indentation technique

M. Kim, S. Yoo, N. Kim and C. Lee
Sogang University, Gyeonggi-do, South Korea

Keywords: Residual stress, no-contact measurement, non-destructive measurement, image processing analysis, micro-indentation test.

This research presents an innovative image acquiring system approach utilized for the estimation for the residual stresses after mechanical operations on metallic materials. The approach is based on the image acquisition before and after the manufacturing operation where the coordinates of specified control points are translated in to an estimation for the residual stresses in the components. Thanks to the contact-free typology of the proposed measurement system, this approach is applicable also to complex geometries and does cause any damage on the product surface. The developed image processing algorithm seeks the feature points on the components surface and defines them as control points for the analysis. After the manufacturing operation is carried out, the algorithms seeks once more the control points and defines the correlation between “before” and “after” images based on an image correlation algorithm. Finally, the Euclidian distance between the same points in the “before” and “after” images is utilized for the residual stresses estimation in the component. In comparison to other available method, the proposed one is non-destructive, easy to use, has a high reliability also for complex geometries and a nominal accuracy equal to ~15MPa in comparison to numerical simulations results.