Fatigue Properties of Reactor Pressure Vessel Steel and Damage Evaluation.
Fatigue Properties of Reactor Pressure Vessel Steel and Damage Evaluation.
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反应堆压力容器钢的疲劳性能及损伤评估。
DOI：
10.2472/jsms.41.1558
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
J. Fukakura
中科院分区：
文献类型：
--
作者：
T. Shoji;Yuji Kawamori;Yutaka Watanabe;J. Fukakura
在290°C下对反应堆压力容器钢进行了低周疲劳试验，以研究疲劳损伤和疲劳应变历史的评估方法。研究了表面微裂纹的萌生行为，得到了以下结果。(1)表面裂纹的萌生从疲劳寿命的早期阶段开始，并且裂纹密度（每单位表面积的裂纹数）在整个疲劳寿命期间持续增加。(2)裂纹密度的增加行为与Coffin-Manson型参数ΔeP·N 0·6相关，与施加的应变范围（Δet）无关。因此，用ΔeP·N 0·6表示的疲劳应变历程可以从表面裂纹密度的测量中估算出来。(3)晶界是裂纹萌生的优先位置之一，刚萌生的微裂纹有沿晶界沿着扩展的趋势。疲劳损伤试样的腐蚀性能也进行了研究，发现随着损伤的积累而变化。所得结果可归纳如下。(4)电化学腐蚀仅在疲劳损伤材料表面出现许多形状不规则的凹坑。这些随机形状的凹坑主要起源于晶界三相点，并优先沿晶界沿着生长。这些凹坑可以被认为是疲劳过程中晶界处或附近的微观结构变化引起的受损材料的耐腐蚀性降低的结果。(5)电化学腐蚀表面腐蚀区面积分数与ΔeP·N 0·6呈单一相关关系，电化学腐蚀可对疲劳损伤累积进行非破坏性定量评价。
Low-cycle fatigue tests were carried out on a reactor pressure vessel steel at 290°C in order to investigate an evaluation method for fatigue damage and fatigue straining histories. The initiation behavior of surface microcracks was examined, and the following results were obtained.(1) The initiation of surface cracks begins from the early stage of fatigue life and the crack density (number of cracks per unit surface area) continues to increase throughout the fatigue life.(2) The increasing behavior of the crack density can be correlated with the Coffin-Manson type parameter ΔeP·N0·6 irrespective of an applied strain range (Δet). Therefore, fatigue straining histories represented by ΔeP·N0·6 can be estimated from the measurement of surface crack density.(3) The grain boundary is one of the preferential sites of crack initiation, and micro-cracks which just initiated have a tendency to propagate along the grain boundary.The electrochemical etching was performed at a midplane of the fatigue damaged specimens where no geometrical damage could be expected. Etching properties of fatigue damaged specimens were also studied and were found to change with damage accumulation. The results obtained can be summarized as follows.(4) Many random-shape pits appeared only on the surface of the fatigue damaged material by the electrochemical etching. These random-shape pits initiated mainly at the triple point of grain boundaries and grew preferentially along the grain boundaries. These pits can be considered as a result from degradation of corrosion resistance of the demaged material caused by microstructural changes at or near grain boundaries during fatigue.(5) The area fraction of corroded region on the electrochemically etched surface shows a single correlation with ΔeP·N0·6, and quantitative evaluation of fatigue damage accumulation can be made nondestructively by the electrochemical etching.