Calculation of Residual Stresses and Axial Fatigue in Nickel-Plated 4340H Steel

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. Sixteen 4340H steel samples were nickel plated according to standard plating operations. The samples were divided into four groups representing different processing methods: shot peening, hard shot peening, milling and abusive milling. X-ray diffraction residual stress analysis indicated that processes produced low surface compressive stresses. In general, compressive surface stresses enhance fatigue properties. Fatigue testing of the samples confirmed that the compressive stresses induced by the shot peening operations improved fatigue life when compared to the milling processes. X-ray diffraction stress analysis can be effectively utilized for process control and determination of remaining life in plated parts.

Keywords:

Residual Stress , Fatigue , Shot peening , Milling