Neutron Transmission Strain Tomography for Non-Constant Stress-Free Lattice Spacing
This work addresses a limitation in strain tomography for materials science, enabling study of stresses from processes that alter lattice spacing, though it is incremental as it extends existing methods.
The paper tackles the problem of jointly reconstructing strain and stress-free lattice spacing fields from neutron transmission measurements, which was previously limited by assuming constant spacing, and demonstrates successful reconstruction on simulated data with realistic noise.
Recently, several algorithms for strain tomography from energy-resolved neutron transmission measurements have been proposed. These methods assume that the stress-free lattice spacing $d_0$ is a known constant limiting their application to the study of stresses generated by manufacturing and loading methods that do not alter this parameter. In this paper, we consider the more general problem of jointly reconstructing the strain and $d_0$ fields. A method for solving this inherently non-linear problem is presented that ensures the estimated strain field satisfies equilibrium and can include knowledge of boundary conditions. This method is tested on a simulated data set with realistic noise levels, demonstrating that it is possible to jointly reconstruct $d_0$ and the strain field.