Basic Research on Electro-Magnetic Failure and Quench of High Tc oxide Superconductor by Means of SQUID

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In order to establish a reliable use of high Tc uxide superconductor such as YBCO, mechanistic understanding of brittle failure of these ceramics superconductors have to be achieved to apply these materials for engineering parts and / or component which can be subjected a large current causing large electromagnetic force. In micro crack initiation and propagation can be failure processes as well as other ceramics materials. In this research, SQUID (Superconducting Quantum Interference Device) has been successfully applied to detect micro crack for formation and growth of YBCO under leading condition. Magnetic field analysis was also performed for determination of location of micro cracking and result in identify the cracking site of specimens. Results can be summarized as follows,1) Micro crack initiation and stable crack growth were observed in YBCO under mechanical loading and confirmed by use of Kaiser effect.2) These stable micro crack formation was detected nondestructively by means of SQUID.3) Quench phenomenon can be detected at a very early stage by SQUID.