Residual Stress Measurement with Laser-Optical and Mechanical Methods

A new approach in hole-drilling residual stress analysis is described, applying a laser for quasi non-destructive material removal by laser ablation and measuring simultaneously the residual deformation around the hole by means of high-resolution, digital holographic interferometry. To evaluate this technology, an experimental bending device based on the European Standard for four-point bending tests was developed in order to prepare samples with a well-defined stress state by bending. This device was evaluated with the incremental-step hole-drilling/milling method. Residual stresses in thermal spray coatings were characterized by the hole-drilling/milling method, and residual strains were measured on the same coatings with the new, laser optical method. This paper describes preliminary results of work in progress.