The strain in the crystal lattice is measured by x-ray diffraction from which the residual stress is then calculated. Electrolytic material removal is required for subsurface measurement. The high spatial and depth resolution possible are ideally suited for the study of residual stresses from machining, shot peening, grinding, and similar surface treatments, or for high spatial resolution adjacent to fractures, welds, and similar features. Field electropolishing support is available for subsurface measurement. Measurements can be made in a wide variety of alloys, including carbon steels, ferritic and austenitic stainless steels, nickel base alloys, aluminums, and titanium base alloys.
Measurements are possible in many ceramic and composite manufacturing materials.
Quantification of residual stresses due to processes, such as turning, grinding, and milling, welding, shot peening, carburizing, and induction hardening. The hole is drilled in the center of the strain gage grids. The average residual stress occurring over the depth of the drilled hole can be calculated from the strain relaxations. Center-hole drilling yields the principal residual stresses and is ideally suited to stresses from welding, heat treatment, forming, and similar processes where high spatial resolution may not be required. Measurements are made per ASTM specification E837.