Effect of Surface Roughness on Low-cycle Fatigue of Domestic 316LN Austenitic Stainless Steel

The surface roughness has important effects on the surface defect production during material in service. Normally, the specimens used by laboratory for fatigue are smooth, but the real main pipes in reactor would manufacture multi-machining processes. So the surface roughness of main pipe is greater than that of the laboratory specimen. Therefore it will bring to big risks in main pipe design and application. The effects of surface roughness on the low-cycle fatigue life of 316LN stainless steel were investigated. The analysis results show that for the surface roughness of 0.08, 0.4 and 1.0 μm specimens, the fatigue life reduces with the increase of surface roughness. When both of them under the double logarithm, they show linear relationship. Through theoretical analysis and fracture surface observation, it is shown that the stress concentration will increase and the micro crack will initiate more easily with the surface roughness increase, and then the fatigue life will reduce.