Tomographic Reconstruction of Triaxial Strain Fields from Bragg-Edge Neutron Imaging.

This paper presents the first triaxial reconstruction of strain in three-dimensions from Bragg-edge neutron imaging. Bragg-edge neutron transmission can provide high-resolution tomographic images of strain within a polycrystalline material. This poses an associated rich tomography problem which seeks to reconstruct the full triaxial strain field from these images. Successful techniques to perform this reconstruction could be used to study the residual strain and stress within engineering components. This paper uses a Gaussian process based approach that ensures the reconstruction satisfies equilibrium and known boundary conditions. This approach is demonstrated experimentally on a non-trivial steel sample with use of the RADEN instrument at the Japan Proton Accelerator Research Complex. Validation of the reconstruction is provided by comparison with conventional strain scans from the KOWARI constant-wavelength strain diffractometer at the Australian Nuclear Science and Technology Organisation and simulations via finite element analysis.