'In the field' NDT mapping of plastic damage in metal and alloy components using positron annihilation techniques and comparison with residual stresses

Positron annihilation methods for determining the spatial distribution of plastic damage in metal and alloy components are described. The relationship between the damage distribution and the associated residual stress variation, as measured by diffraction, is considered with reference to typical cases using ideal samples. The results can be correlated with the known thermomechanical histories and suggest such nondestructive measurements may have application in optimising the design and extending the service life of engineering components. A recently developed transportable positron annihilation system, which could be used in the field in conjunction with X-ray diffraction stress measurements, is briefly outlined. (author)