Laser-shock peening generates a compressive surface layer in components in order to extend their useful life by preventing the formation of cracks in the surface. The technique requires sufficient energy to be introduced but excess energy results in reverse plastic flow and a reduction in the beneficial stresses. EDX on ID15 is a practical tool to measure strain in such samples as it provides high spatial resolution (<100μm) in at least one direction and also high-penetration so that samples can be of a meaningful size. Combining strain measurements with an iterative FE model allows the determination of the eigenstrain (a measure of the plastic misfit) for a variety of samples subjected to fatigue and fretting. This provides a quantitative measure of the extent of plastic relaxation in such samples.
King A., Steuwer A., Woodward C., Withers P.J. - Effects of fatigue and fretting on residual stresses introduced by laser shock peening - Mater. sci. eng. A Struct. mater. prop. microstruct. proces. 435-436, 12-18 (2006).