Spatial Resolution and Strain Scanning

Abstract

Neutron strain scanning is being increasingly used to determine internal and through surface strains in a widening range of engineering components. The locations within components that are of most concern to engineers are those at which failures are most likely to occur or to initiate. They include, in particular, regions of high stress and steep stress gradients. Extended regions of high stress often arise inside thick components where neutron beam attenuation may be a principal measuring constraint. High stresses and the steepest gradients usually occur in combination at surfaces, interfaces and sharp discontinuities where precise positioning and edge effects pose problems. In this paper the importance and practicalities of defining the size, shape and location of the “gauge volume” are discussed. Examples are presented of the methods and equipment employed to optimise measurements made at surfaces and internally in a range of components of different shapes, sizes and residual stress distributions.