Effect of wavelength-dependent attenuation on strain measurement using pulsed neutron diffraction

The measurement of stresses in engineering components and structures by neu tron diffraction has traditionally been limited to depths of a few centimet res. However, recent developments in instrumentation open up the possibilit y of deeper measurements. It has been suggested that a systematic error may occur when measuring stresses deep in materials due to wavelength-dependen t attenuation of the incident and/or diffracted beam. A series of experimen ts to evaluate the magnitude of this effect on ENGIN, a pulsed neutron stra in scanner will be presented in this paper. It was found that the pseudo-st rains induced by the attenuation of the diffracted beam were negligible, wh ereas there was a small but still noticeable effect produced by the attenua tion in the incident beam. The possible causes of this shift and the conseq uences for deep measurements are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.