The measurement of prior plastic deformation in metallic alloys using the neutron diffraction technique

Abstract

The neutron diffraction technique has been used to determine the extent of prior plastic deformation in an aluminium alloy weld and preloaded cracked steel beams. The change in peak width has been shown to be a function of the prior plastic deformation, and is found to be insensitive to the direction of prior straining, material and the orientation of the diffraction vector. Prior plastic deformation has also been shown to influence the reference peak angle. The distributions of prior plastic strain in the steel cracked beam subjected to an overload were found to be in good agreement with results from finite element analyses.

Diffraction measurements for evaluating plastic strain in A533B ferritic steel—a feasibility study

“…It can be seen that removal of the elastic component brings the loaded and unloaded measurements considerably closer together. Following the work of [28], an exponential fit was used to estimate the variation of ∆σ with plastic strain. The best fit equations are included in figures 10 and 11.…”

“…Increasing diffraction peak width was suggested as a method for plastic strain measurement on a welded aluminium bar by Smith [27], although in such cases it is difficult to separate the broadening effects of plastic deformation from those due to local material variations due to the welding process. The peak broadening approach was later used [28] to qualitatively estimate equivalent plastic strain levels in the aluminium sample of [27] as well as in a cracked ferritic steel beam. It was suggested, based on a fit to experimental data, that the relationship between the change in diffraction peak width at half height, δθ w , and the prior plastic strain p was given by…”