单个冲击对不锈钢管道焊接头低周疲劳寿命的影响.docVIP

单个冲击对不锈钢管道焊接头低周疲劳寿命的影响 摘　要　完成了单个冲击对1Cr18Ni9Ti不锈钢管道焊接头试样低周疲劳寿命影响的试验研究。单个试验最大瞬时峰值应变率达480s-1。试样未经消除焊接残余应力。采用成组法试验(每组7个试样)，对称加载模式，总应变幅为0.00228。结果表明，冲击影响受到焊接残余应力和冲击塑性导入机制的耦合作用。焊接残余应力与冲击应力叠加将增加材料损伤，而冲击塑性导入将减缓疲劳损伤和降低疲劳寿命分散性。前者扼制后者。考虑疲劳寿命的分散性，建议基于概率的冲击影响评价方法。试验结果的分析验证了方法的有效性。关键词　不锈钢；焊接头；低周疲劳；冲击；疲劳寿命；概率评价中图分类号　TG142.71；TG405　文献标识码　A文章编号　1001-4381(1999)11-0014-05 Single Impact Effects on the Low Cycle Fatigue Life ofa Stainless Steel Pipe-Welded Joint Abstract：An experimental investigation of the single impact effects with high strain rate on the low cycle fatigue life of 1Cr18Ni9Ti stainless steel pipe-welded joint was performed.A group test ( 7 specimens for each group) was used. The joint was made without eliminating the welding residual stress. Transient peak strain rate of the test was up to 480 s－1. All fatigue tests were made at total strain amplitude of 0.00228 under fully reversal loading mode. The results reveal that the effects are related to a coupling action of the welding residual stress and the impact plastic-induced mechanism. The welding residual stress, plus impact stress, tends to increase fatigue damage, and in contrast, the impact plasticity-induced tends to slow fatigue damage and to decrease the scatter of fatigue life. The former checks the later. In addition, taking into account the scatter of fatigue lifes a probabilistic assessment approach of the single impact effects is presented and its availability is verified by the statistical analysis of test results.Key words：stainless steel; welded joint; low cycle fatigue; impact; fatigue life; probabilistic assessment 　　结构材料在受爆炸或冲击载荷下的力学行为，是重要设备(如反应堆)安全技术和结构延寿的一个重要研究领域。疲劳是反应堆结构的潜在失效模式［1］。研究单个冲击对结构疲劳性能的影响是其中一个重要课题。　　对结构承受非常规疲劳加载的试验研究，在过载或周期性过载［1～3］和冲击疲劳［4～8］方面做了有益探索。但在偶然爆炸或冲击载荷对疲劳性能的影响方面，研究尚少。过载或周期过载对疲劳性能影响的研究［2～4］，一般是在常规疲劳恒幅加载史中插入高于材料屈服应力的高应力幅，材料应变率较低（一般小于10 s－1）；冲击疲劳试验一般采用旋转四点弯曲加载形式［5］或在修正Hopkinson杆应力波加载装置上进行［6～7］，材料应变率可达400 s－1, 但其中没有常规疲劳载荷。本工作研究低周疲劳中出现高应变率单个冲击加载情况，以用于制造反应堆冷却管道的1Cr18Ni9Ti不锈钢管焊接头为对