Surface Residual Stresses Evolution in API 5L X80 Steel with Different Surface Finish under Tensile Monotonic Loads

Residual stresses exist intrinsically in any manufactured or processed material, significantly influencing its mechanical properties. Shot peening enhances fatigue life by introducing compressive residual stresses at the surface, however, the beneficial effects may be reduced under external loads. This study investigates the behavior of surface residual stresses induced by shot peening in API 5L X80 steel. Specimens underwent tensile monotonic loading cycles below the yield strength, incrementally increasing the load until reaching the yield limit. Residual stresses were measured using the X-ray diffraction by sin2 psi method, revealing a progressive stress relief of compressive residual stresses field induced by shot peening. The development of tensile residual stresses was observed following the monotonic tests. Loads below yield stress were able to completely reverse compressive stresses to tensile stresses. A correlation was observed between residual stresses and magnetic Barkhausen noise, suggesting it as a potential method for analyzing residual stress behavior qualitatively in shoot peened steel samples.