Optimization of TOFD Detection for Generator Retaining Ring with Inner Wall Defect

doi:10.11930/j.issn.1004-9649.2014.3.65.3

Abstract

Abstract: Probes for ultrasonic time of flight diffraction (TOFD) are considered to be conventional, such as 45°, 60° and 70°. Austenitic steel is widely used in generator retaining ring. Coarse grain size and large thickness play an aggravating role in acoustic wave attenuation. Inner wall defect can not be detected accurately even 45° probe is used. In order to optimize the detection process, the 20° probe is proposed based on analysing of the characteristic of acoustic wave. Through TOFD detection of inner wall with natural crack, the optimal frequency (2.25MHz) is determined. And artificial defect detection is in good agreement with actual fact by the optimal frequency. So the optimum detection process is 20° probe, 2.25MHz, transducer diameter of 12mm. And beam is focused on inner wall of generator retaining ring. By optimization detection process, inner wall artificial defect with height of 2mm can be effectively distinguished in generator retaining ring with thickness of 50mm.

Key words: Generator retaining ring, defect detection, acoustic wave, TOFD, 20°, probe

CLC Number:

DAI Zhen, LI Wei, HAO Xiao-jun, LIU Hong-quan, JING Shang-qian. Optimization of TOFD Detection for Generator Retaining Ring with Inner Wall Defect[J]. Electric Power, 2014, 47(3): 65-68.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.2014.3.65.3

https://www.electricpower.com.cn/EN/Y2014/V47/I3/65

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