Research on Advancement of Stress-Intensity Factor Measurement by Means of A-C Potential Drop Technique

1.作为ACPD技术中关于空气中磁通的基本原理，提出了通过比较理论A-C势降和实测值来分析反问题的方法。2.作为电流作用下导体行为的基本原理，分析了既考虑焦耳加热又考虑汤姆逊效应的裂纹尖端的电流密度分布和温度分布。3.接着2.分析了仅考虑焦耳加热的电流作用下裂纹尖端附近的电流密度分布和温度分布。4.在文献2和3的基础上，分析了电流作用下裂纹尖端的电流密度分布和温度分布。在考虑焦耳加热和汤姆逊效应的情况下，分析了电流作用下拐角附近的温度分布。5.提出了电势降随负载变化的理论模型。在空气中磁通量较大的测量系统情况下，从理论上阐明了由于空气中磁通的增加，电势降随载荷的增加而增大。6.为了验证上述模型，提出了实验方法。7.在空气中磁通较大的测量系统情况下，从实验结果中可以看出，电势降的变化幅度很大。电势降的变化与应力强度因子的变化呈线性关系，与裂纹长度无关。8.证实了提出的模型能够解释实验结果。9.为了将该技术应用于实际结构，阐明了测量系统应满足的必要条件。

1.As the fundamentals concerning the magnetic flux in the air in the ACPD technique, the analysis of inverse problem by means of the comparison of the theoretical A-C potential drops to the neasured one was proposed.2.As the fundamentals of the behavior of the conductor subjected to current flow, the current density distribution and the temperature distribution near the crack tip were analyzed considering not only the Joule heating but also the Thomson effect.3.Following 2., the current density distribution and the temperature distribution near the corner subjected to current flow were analyzed considering only the Joule heating.4.Based on the results obtained from 2. and 3., the temperature distribution near the corner subjected to current flow was analyzed considering not only the Joule heating but also the Thomson effect.5.A theoretical model of the change in potential drop due to load was proposed. In the case of the measuring system with a large amount of magnetic flux in the air, it was theoretically clarified that the potential drop increased with increasing the load due to the increase of the magnetic flux in the air.6.In order to verify the above model, experimental methods were developed.7.In the case of the measuring system with a large amount of magnetic flux in the air, it was clarified from the results obtained experimentally that the chenge in potential drop was large. The relationship between the change in potential drop and that in the stress-intensity factor was linear and independent of the crack length.8.It was confirmed that the proposed model was able to explain the results obtained experimentally.9.For the application of this technique to the actual structures, the necessary conditions which the measuring system should satisfy were clarified.