Tomographic Reconstruction of Two-Dimensional Residual Strain Fields from Bragg-Edge Neutron Imaging

TL;DR

This paper introduces a general least squares-based method constrained by equilibrium for reconstructing two-dimensional residual strain fields from Bragg-edge neutron imaging, validated experimentally and compared with traditional measurements.

Contribution

It presents a novel, general approach for 2D residual strain reconstruction from neutron imaging data, extending beyond previous limited solutions.

Findings

Successful experimental reconstruction of 2D strain fields

Validation against conventional strain measurements

Discussion on extending to 3D reconstructions

Abstract

Bragg-edge strain imaging from energy-resolved neutron transmission measurements poses an interesting tomography problem. The solution to this problem will allow the reconstruction of detailed triaxial stress and strain distributions within polycrystalline solids from sets of Bragg-edge strain images. Work over the last decade has provided some solutions for a limited number of special cases. In this paper, we provide a general approach to reconstruction of an arbitrary system based on a least squares process constrained by equilibrium. This approach is developed in two- dimensions before being demonstrated experimentally on two samples using the RADEN instrument at the J-PARC spallation neutron source in Japan. Validation of the resulting reconstructions is provided through a comparison to conventional constant wavelength strain measurements carried out on the KOWARI engineering diffractometer within ANSTO in Australia. The paper concludes with a discussion on the range of problems to be addressed in a three-dimensional implementation.