Mechanism of Environmental Assisted Cracking by the AE Source Inversion and Moment Tensor Analyzes

为了弄清活性路径腐蚀型应力腐蚀开裂（APC-SCC）的机理，进行了8通道声发射（AE）监测。声发射源反演、矩张量和纵波辐射模式分析表明，在室温下，聚硫氨酸溶液对aisi304奥氏体不锈钢的SCC过程中存在连续或多个晶间裂纹。然而，对声发射波的矩张量分析显示，由于所有传感器都无法监测到第一次裂缝发出的纵波，结果出现了异常。两步微裂纹产生的面外位移计算结果与监测结果吻合良好。首次证实了AISI304钢在140C时的氯化物- scc与穿晶脆性断裂有关。我们还提出了一种确定紧绷试样实验传递函数的新方法。利用实验传递函数计算的试件面外位移与实测位移吻合较好，表明穿晶氯化物-SCC也发生了极快的开裂，开裂速度几乎是SCC平均扩展速度的10^7倍。采用研制的耐热电容式声发射传感器，对aisi304钢在600℃时的熔盐和熔锌侵蚀机理进行了研究。在这些高温冲击中，也首先出现了多重解理型裂纹。

Aming to clarify the mechanism of the so-called active path corrosion type stress corrosion cracking (APC-SCC), eight channel acoustic emission (AE) monitoring was attempted. The AE source inversion, moment tensor and radiation pattern analysis of the longitudinal waves revealed that the successive or multiple intergranular crackings were involved in the SCC of austenitic stainless steel AISI 304 by the polythionine acid solution at ambient temperature. Moment tensor analysis of the AE waves, however, showed an abnormal result because all sensors could not monitor the longitudinal wave emitted by the first fracture The out-of-plane displacement computed for two-step generation of microcracks was found to agree well with the monitored one.It was first demonstrated that the chloride-SCC of the AISI304 steel at 140C was associated with the transgranular brittle fracutre. We also proposed a new method to determine the experimental trasnfer function of the compact tension specimen. The out-of-plane displacement computed using the experimental transfer function of the specimen sharply agreed with the monitored one, and indieated that the extremely fast cracking, almost 10^7 times that of average SCC propagation rate, occured even in the transgranular chloride-SCC.The mechanism of the molten chloride salt and fused zinc attack of AISI 304 steel at 600C was also examined using the developed heat resistant capacitive AE sensor. Multiple cleavage type crackings were firstly revealed to occur even in these high temperature attacks.