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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2023, Vol. 44 ›› Issue (4): 426674.doi: 10.7527/S1000-6893.2021.26674

• Material Engineering and Mechanical Manufacturing • Previous Articles     Next Articles

TOFD detection of bottom defects in aluminum alloy plate by half-skip mode wave

Shijie JIN, Zhicheng WANG, Xin TIAN, Xu SUN, Li LIN()   

  1. NDT & E Laboratory,Dalian University of Technology,Dalian  116085,China
  • Received:2021-11-17 Revised:2021-12-10 Accepted:2021-12-24 Online:2022-01-05 Published:2022-01-04
  • Contact: Li LIN E-mail:linli@dlut.edu.cn
  • Supported by:
    National Key Research and Development Program of China(2019YFA0709003);National Natural Science Foundation of China(51905079);Liaoning “Revitalization Talents Program”(XLYC1902082)

Abstract:

When Time-of-Flight Diffraction (TOFD) technique is used to detect the bottom defects in the aluminum alloy plate, there is a near-surface dead zone under the effect of the pulse duration of lateral wave. In this paper, a TOFD half-skip mode wave method is proposed to reduce the dead zone. The characteristics of the diffracted wave of the first back-wall reflected wave at the defect tip and its symmetry in B-scan image are employed to derive the depth determination formula of bottom defect. Simulation and experiment results show that with the proposed method, the range of the near-surface dead zone is reduced by more than 64%, and the positioning errors of the defects with depth of no less than 2.0 mm are within 6.32% for the aluminum alloy plate with a thickness of 7.0 mm by using the probes with 10 MHz center frequency and 40 mm probe center spacing. Compared to the mode-converted wave and the TOFD-W wave, the half-skip mode wave is decoupled with the back-wall wave and is close to the lateral wave, presenting stronger applicability in detecting the bottom defect in aluminum alloy plate.

Key words: Time-of-Flight Diffraction (TOFD), dead zone, half-skip mode wave, aluminum alloy, quantitative detection

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