Experimental application of the crack compliance method in beams with hardened surfaces

In general the mechanical design is developed by considering the lineal behavior of the components, which means that the stress reached by the requested work that takes place is under the yield stress. The stresses left in the component are known as residual stresses. This kind of stress has the characteristic of been either beneficial or damaging depending on their direction. They exist without the application of external agents and are able to extend or reduce the components lifetime, hence the importance of their study and evaluation. This paper presents the obtained results on the residual stress field evaluation induced in a beam. Three cases involving superficial hardening are analyzed, namely; hardened surface by laser shot, hardened surface by shot-penning, and superficial hardened by four points bending and pre-pulling. In this research the Crack Compliance Method was applied to evaluate the residual stress field induced in each case. This method consists in the introduction of a slot of incremental depth. The cut relaxed the residual stress field, and then the relaxed strain can be measured by strain gauges to quantify the original stress state.