A critical review of residual stress technology

The current technology for evaluating residual in materials has been critically reviewed from the perspective of LLNL needs. The primary technique available continues to be x-ray diffraction (XRD). Substantial analytical and experimental refinements have been made in the past decade. An especially promising development in XRD is the use of energy dispersive spectroscopy for evaluating triaxial stress. This would provide an alternative to neutron diffraction, a technique limited to a relatively small number of outside laboratories. Recent research in residual stress measurement using ultrasonics have concentrated on shear wave techniques. Substantial progress has been made in the use of electromagnetic acoustic transducers (EMAT's), surface waves, corrections for texture, and, of special interest to LLNL, the ability to characterize interfacial stress. Strain gages and related technologies continue to be actively used in field measurements of residual stress, although there is generally some destructive nature to those techniques. An increased use of multiple technique approaches to residual stress evaluation is occurring for the purposes of both verification and complementary measurements. Among a number of miscellaneous techniques found in the recent literature are several involving the use of stress-sensitive magnetic properties and an especially promising use of the thermoelastic effect for noncontact stressmore » mapping. Recommendations for LLNL activity include energy dispersive XRD, ultrasonics characterization of anisotropy and interfacial stress, and investigation of the thermoelastic effect. 57 refs.« less