The effect of residual thermal stresses on the fatigue crack growth of laser-annealed 304 stainless steels
The effect of residual thermal stresses on the fatigue crack growth of laser-annealed 304 stainless steels
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残余热应力对激光退火304不锈钢疲劳裂纹扩展的影响
DOI：
10.1016/j.matchemphys.2004.07.020
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
R. Shiue
中科院分区：
文献类型：
--
作者：
L. Tsay;M. Young;F. Y. Chou;R. Shiue
本研究研究了 CO2 激光退火后的 AISI 304 不锈钢的疲劳裂纹扩展行为。对于引入缺口之前的激光退火样品，在激光退火区（LAZ）中心周围获得残余拉应力，并且随着距LAZ中心线距离的增加，残余应力场逐渐从拉应力变为压应力。根据实验结果，在低 ΔK 下测试的激光退火样品在引入垂直于 LAZ 的缺口后，在 LAZ 之前的区域具有更高的抗疲劳裂纹扩展能力。相比之下，对于在 850°C 消除应力一小时的激光退火样品，疲劳裂纹扩展的延迟消失了。裂纹尖端前方残余压应力场的存在导致疲劳裂纹扩展速率（FCGR）降低。此外，残余压应力增强了裂纹闭合效果，导致疲劳断裂表面形成摩擦痕迹。当疲劳裂纹进一步扩展至 LAZ 时，裂纹尖端前方的残余拉应力场并没有加速裂纹扩展。结果表明，裂纹尖端前的拉应力场对延性304不锈钢的FCGR影响不大。
The fatigue crack growth behavior of AISI 304 stainless steels annealed by a CO2laser was investigated in the study. For the laser-annealed specimen prior to introducing a notch, the residual tensile stress was obtained around the center of the laser-annealed zone (LAZ), and the residual stress field changed gradually from tensile into compressive stress with increasing the distance away from the centerline of LAZ. Based on the experimental result, the laser-annealed specimen tested under low ΔK had a higher resistance to fatigue crack growth in the region preceding the LAZ after introducing a notch perpendicular to the LAZ. In contrast, the retardation of fatigue crack growth disappeared for the laser-annealed specimen stress-relieved at 850°C for one hour. The presence of residual compressive stress field ahead of the crack tip resulted in the decreased fatigue crack growth rate (FCGR). Moreover, residual compressive stresses enhanced the effect of crack closure, and led to the formation of rubbed marks on the fatigue-fractured surface. As the fatigue crack propagated further into the LAZ, the residual tensile stress field ahead of crack tip did not accelerate the crack growth. The results indicated that tensile stress field ahead of the crack tip had little effect on the FCGR of the ductile 304 stainless steel.