Investigation on fatigue life prediction and reliability design of 304 stainless steel manufactured by laser metal deposition

Abstract

Laser metal deposition (LMD) is an advanced technology to manufacture the specimen by layer-by-layer method. In this paper, the fatigue tests of 304 stainless steel (SS304) smooth specimens manufactured by LMD are conducted with the stress ratio of −1 and the frequency of 10 Hz. Considering that the fatigue crack is caused by the material defect on the subsurface, the fatigue life of smooth specimen under the different cyclic stress amplitudes are predicted based on the dislocation model, equivalent initial crack size and empirical formula. Lognormal, two-parameter Weibull and extreme maximum value distributions are applied to describe the fatigue life of the smooth specimens at the different cyclic stress amplitudes. The result shows that two-parameter Weibull distribution has the best ability to describe the fatigue life distribution. Based on two-parameter Weibull distribution, the probabilistic-stress-number ( P- S-N) curves at the four different reliability levels are plotted. Combined with the material strength degradation rule, the design checkpoint method is adopted to analyze the fatigue life reliability of smooth specimens under the different cyclic stress amplitudes. The reliability results are close to those of two-parameter Weibull distribution.