ESPI Hole Drilling Equipment

Hole drilling is the most commonly used stress relaxation technique for measuring residual stresses. Stressed material is removed by drilling a small blind hole in the area of interest and the material around the hole spontaneously finds a new stress equilibrium. This leads to a displacement of the surface near the hole which is traditionally measured using strain gauges. Prism measures these displacements using optical interferometry. The measured displacements are then used to calculate stresses which existed in the volume prior to drilling