数学统计方法在应力腐蚀噪声中的应用

APPLICATION OF MATHEMATICAL STATISTICAL METHODS TO ELECTROCHEMICAL NOISE OF STRESS CORROSIONCRACKING

研究了不锈钢和黄铜应力腐蚀的电化学噪声,得到了应力腐蚀的特征电位噪声谱。根据特征噪声的出现,可以监测应力腐蚀的发生。标准方差和功率谱等数学方法可以使得监测更加实用和有效,但应将直流背底扣除,否则会带来假象和错误的结论。

Electrochemical noises generated during stress corrosion cracking (SCC) of 304 stainless steel and α-brass were studied. SCC noise pattern showed common characteristics, i.e., the quick drop and slow recovery of the potential. The quick drop corresponded to a crack initiation and/or discontinuous propagation where fresh metal surface was exposed. The slow recovery corresponded to repassivation process of the exposed bare metal. For random noises, the rates of potential rise and drop were similar. The frequency of the noise generated during SCC increased with the increase in the applied stress. SCC initiation could be monitored and determined according to the noise characteristic and distribution. Mathematical treatments of standard deviation and power spectrum density (PSD) made the determination easier and realistic. But the background shift of the potential must be eliminated before the process. Standard deviation was more convenient and effective than PSD in the practice application.