Diffraction measurements of elastic strains in stainless steel subjected to in situ biaxial loading

The lattice strains in AL6XN stainless steel specimens subjected to in situ biaxial stress states have been measured by neutron diffraction. The biaxial stress states were generated in tubular specimens using a specially designed loading apparatus that is capable of applying axial loads to specimens under internal pressure. Lattice strains in the axial and hoop directions were measured for different levels of stress biaxiality in numerous loaded and partially unloaded states. The results revealed the role of the biaxial stress state in the differences in average lattice strains between various crystallographic fibers. These trends are examined in light of the orientational dependencies of the lattice strains on the stress biaxiality under an assumption of uniform stress. Possible additional factors contributing to the observed trends are discussed.