锆合金碘致应力腐蚀开裂应力强度因子阈值和开裂速率模型的研究

轻水堆的燃料包壳锆合金发生碘致应力腐蚀开裂(ISCC)是诸多因素共同作用的结果,确定应力强度因子阈值(KISCC),建立开裂速率模型是ISCC的主要工作。在ISCC众多的影响因素中,对KISCC影响最大的是织构、温度、快中子注量、碘浓度。本文根据实验数据拟合出KISCC的经验模型公式,并修正了开裂速率模型。结果表明,KISCC模型和修正后的开裂速率模型能够与试验结果符合较好。

锆合金包壳管氢致延迟开裂应力强度因子阈值研究

针对受对称双集中力作用的含双边缘裂纹的锆合金包壳管,采用数值模拟方法,获得裂纹尖端应力场,建立了应力强度因子与裂纹长度、对称双集中力大小之间的关系。结合氢致延迟开裂(DHC)应力强度因子阈值(KIH)的理论求解方法,获得受对称双集中力作用的包壳管的KIH和临界参数的解析表达式,据此考察实验研究了温度对其产生的影响。研究结果表明,受对称双集中力作用的含双边缘裂纹包壳管的KIH、临界载荷及临界裂纹长度均随温度的升高而增大,与实验所得到的变化趋势相吻合,这种随温度变化的趋势与预开裂区域的应力状态接近于平面应力状态这一事实密切相关。

Stress corrosion cracking and its anisotropy of a PZT ferroelectric ceramics

Stress corrosion cracking (SCC) of a PZT ferroelectric ceramics in various media, such as moist atmosphere, silicon oil, methanol, water and formamide, and its anisotropy have been investigated at constant load test using a single-edge notched tensile specimen. The results showed that SCC could occur in all media, and the threshold stress intensity factor of SCC in water and formamide, KISCC, revealed anisotropy. The KISCC for poling direction parallel to the crack plane, was greater than that perpendicular to the crack plane, similar to the anisotropy of fracture toughness KIC; however, the anisotropy factor of KISCC, which was =1.8 (in formamide) and 2.1 (in water), was larger than that of KIC, which is =1.4. The stress-induced 90° domain switching causes the anisotropy of KIC and KISCC, besides, the resistance of SCC also has anisotropy.