Effects of Multiple Scattering and Wavelength-Dependent Attenuation on Strain Measurements by Neutron Scattering

Abstract

Spatial maps of lattice strain inside bulk structures can be obtained by neutron diffraction. In this paper, we describe a systematic investigation of multiple scattering and wavelength-dependent attenuation effects on such measurements deep inside steel plates. The experimental results suggest that wavelength-dependent attenuation can generate peak shifts that correspond to apparent tensile strains of order 1 part in 10⁴ at depths of order 10 mm in ferritic steel. Moreover, near the wavelength corresponding to the (211) Bragg cut-off, even larger apparent compressive strains of the order 1 part in 10³ were observed. The experimental results are consistent in sign with a theoretical calculation but there is a discrepancy in magnitude. Multiple scattering was found to have no observable influence on measurements of strain at depth.