X-Ray Diffraction Stress Analysis as an NDE Technique

Abstract

Plating processes are of the utmost importance to the Naval Air Rework Facilities as a means of prolonging the useful life of a part. Plating and associated processes, however, can reduce the effective fatigue life of a component. Since residual stresses are closely related to the fatigue response of a material, a series of experiments was performed to determine the optimum stress level produced by four different processing techniques. Twenty-eight 4340 steel samples were nickel plated according to standard plating operations. The samples were divided into four groups representing different processing methods--standard grinding, standard machining, abusive grinding, and abusive machining. X-ray diffraction stress analysis indicated that the standard and abusive grinding processes produced low surface stresses while the standard and abusive machining processes produced compressive stresses. In general, compressive surface stresses enhance fatigue properties. Fatigue testing of the samples confirmed that the compressive stresses induced by the machining operations improved fatigue life when compared to the grinding processes. X-ray diffraction stress analysis can be effectively utilized for process control and determination of remaining life in plated parts.