| A series of experiments to determine whether the eddy currents can be used to nondestructively measure the residual stress induced by shot peening in Ti6Al4V and Aluminum 7075 plates was performed. The SmartEddy module, a commercially available eddy current testing instrument, was chosen for this research. Because of the extremely small magnitude of the shot peening induced conductivity changes, strict noise control was vital and was finally achieved by modifying the instrument. Experimental results indicate that the eddy current testing system we have developed can measure the intensity of the residual stress induced by shot peening for both Ti6Al4V and Aluminum 7075, and can estimate the stress profile, as a function of depth, for Aluminum 7075. The non-destructive eddy current technique also has great potential to measure the residual stress in many other kinds of non-magnetic materials and, possibly, under certain conditions, for magnetic materials. Further, this eddy current testing system is simple, fast and economic, it should have a significant impact on many industries which use shot peening to increase the fatigue lifetime of manufactured parts. |
