表面粗糙度对国产316LN钢低周疲劳性能的影响

表面粗糙度对材料服役过程中表面缺陷的形成有着重要影响,由于实验室一般采用光滑试样测试疲劳性能,而真实主管道经过多道工序,其表面粗糙度远大于实验室测试试样,这会给主管道的设计、使用带来风险。本文通过测试不同粗糙度316LN不锈钢的疲劳性能,分析粗糙度(分别为0.08、0.4、1.0μm)对疲劳寿命的影响。结果表明,随着粗糙度的增加,疲劳寿命会相应减少,两者在双对数坐标下呈线性关系。通过断口观察对比和裂纹萌生机理分析可知,粗糙度增加会引起应力集中,增加微裂纹的萌生速度,从而导致疲劳寿命下降。

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.