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

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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.