  A pulsed neutron imaging technique is used to reconstruct the residual strain
within a polycrystalline material from Bragg edge strain images. This technique
offers the possibility of a nondestructive analysis of strain fields with a
high spatial resolution. A finite element approach is used to reconstruct the
strain using the least square method constrained by the conditions of
equilibrium. The procedure is developed and verified by validating for a
cantilevered beam problem. It is subsequently demonstrated by reconstructing
the strain from experimental data for a ring-and-plug sample, measured at the
spallation neutron source RADEN at J-PARC in Japan. The reconstruction is
validated by comparison with conventional constant wavelength strain
measurements on the KOWARI diffractometer at ANSTO in Australia. It is also
shown that the addition of a simple Tikhonov regularization can improve the
reconstruction.
