中文摘要：

裂纹长度是影响裂纹尖端力学特性及裂纹扩展速率的重要因素,但现有环境致裂研究中的裂纹类型主要为长裂纹而忽略了小裂纹。本工作采用有限元数值计算的方法,研究高温水环境下具有单边裂纹的镍基合金试样环境致裂过程中小裂纹裂尖力学特征。结果表明小裂纹裂尖具有比长裂纹更高的应力和应变,并使小裂纹具有更高的裂纹扩展趋势。研究中给出了计算小裂纹裂尖塑性区尺寸的修正方法,J积分计算的Irwin修正方法适用于长裂纹,但计算小裂纹条件下的J积分时会产生误差。提出在缺乏成熟理论指导下应采用弹塑性有限元数值计算的方法获取准确的小裂纹裂尖J积分。基于小裂纹与长裂纹裂尖力学特征的明显不同,建议在分析核电结构材料环境致裂时,将裂纹扩展分为小裂纹扩展及长裂纹扩展阶段分别研究。

英文摘要：

The crack tip mechanical characteristic and crack propagation rates are influenced by crack length, but the current research of environmentally assisted cracking（EAC） focuses on long crack, and small crack is usually ignored. The mechanical characteristics of small crack tips for single-edge crack panel specimens during the EAC in high temperature water were studied. The specimens were made of nickel-base alloy and the finite element method（FEM） was adopted. The results show that the stress and the strain are much higher for small crack compared to long crack, and this leads to a higher crack propagation tendency of small crack. A corrected method has been introduced to calculate the plastic zone size of small crack. The Irwin correction method can improve the accuracy of J integral of long crack, but errors still exist for small crack. So the numerical method with elastic plastic fracture method has been recommended to calculated J integral for small crack under larger load condition considering the lack of mature theoretical guidance about the small crack. The crack propagation process of the EAC of structure materials serviced in nuclear power plants is suggested to divide into small crack propagation and long crack propagation owing to their anomalous mechanical behaviors.