Abstract
The multi-media finite element (MME) treating the discontinuity of the conductivity within the element was proposed by authors for fast simulation of the eddy current testing (ECT) signals of a conductive crack such as a stress corrosion crack. However, in the cases when eddy current consists of a large component perpendicular to the crack surface, the simulation accuracy is sometimes not very good because of the appearance of electric charge on the crack surface. In this paper, the influences of the surface electric charge on the implementation of the numerical method and on the simulation of the ECT signals were analyzed theoretically. A series of numerical analyses were designed to investigate the scope of feasibility of the MME. The simulation accuracy of the MME for different probe orientations and crack shapes was discussed based on the analysis of the distribution of the surface charge.
Highlights
Stress corrosion crack (SCC) occurs in key structural components of nuclear power plants (NPPs) such as fuel clad, steam generator tubes, heat exchangers, and coolant pipes.1–5 From the standpoint of ensuring the safety of NPPs, quantitative nondestructive evaluation (QNDE) is of great need for sizing the SCC and monitoring its propagation
Due to the contact and bridging between the crack surfaces, the SCC can be regarded as a narrow crack with a non-zero conductivity,8,9 and it has been found that the width of the crack has an evident influence on eddy current testing (ECT) signals
As for the electric charge accumulated on the crack surface, it can be accurately simulated by the media finite element (MME) because the crack surface is coincident with the element boundary and the discontinuity of the gradient of Φ can be modeled
Summary
Stress corrosion crack (SCC) occurs in key structural components of nuclear power plants (NPPs) such as fuel clad, steam generator tubes, heat exchangers, and coolant pipes. From the standpoint of ensuring the safety of NPPs, quantitative nondestructive evaluation (QNDE) is of great need for sizing the SCC and monitoring its propagation. To make an accurate prediction of the ECT signals, the width of the SCC has to be considered in the numerical model. To improve the simulation efficiency, a multi-media finite element (MME), i.e., an element containing both the base material and crack regions, was proposed, which allows modeling cracks of complicated shapes with a regular mesh.. With the help of the MME, the width of the element is possible to be larger than that of the crack, which can reduce the number of finite elements and improve the computational efficiency, especially for the inverse problem of ECT using an optimization approach.. Different coil orientations and crack sizes were considered to comprehensively simulate the ECT problem of SCC. The numerical accuracy of the MME was discussed, combining the simulation results and the electric charge analysis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
