Finite simulation of weld inspection using time-of-flight diffraction method based on laser ultrasonic

Pipelines are now using Fitness-For-Service (FFS) for accept/reject of weld defects. FFS requires accurate measurement of defect height for Fracture Mechanics assessments. The standard pipeline weld inspection technique of radiography is incapable of such measurements. However, the newer technique of ultrasonics can measure defect height, in principle. Initially ultrasonic amplitude methods were used for height measurement, but these proved unreliable. Now diffraction methods, especially Time-Of-Flight-Diffraction (TOFD), are being used in conjunction. This paper reviews previous work — mainly large nuclear studies like PISC II — and published pipeline sizing studies. The best nuclear sizing was within a few millimetres, using diffraction. In contrast to nuclear, pipeline AUT uses zone discrimination, focused transducers, much thinner material and simpler analysis techniques. Current accuracies are typically ± 1 mm (terminology undefined), which correlates with the beam spot size and typical weld pass. Requests for accuracies of ± 0.3 mm are probably unachievable, though future R&D should significantly improve pipeline sizing.

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Time-of-flight diffraction method for joint with linear misalignment

Insight - Non-Destructive Testing and Condition Monitoring ◽

10.1784/insi.2021.63.11.654 ◽

2021 ◽

Vol 63 (11) ◽

pp. 654-658

Author(s):

Y Kurokawa ◽

T Kawaguchi ◽

H Inoue

Keyword(s):

Exact Solution ◽

Approximate Solution ◽

Geometric Model ◽

Time Of Flight ◽

Diffraction Method ◽

Approximate Solutions ◽

Weld Joints ◽

Time Of Flight Diffraction ◽

Flaw Sizing ◽

Probe Spacing

The time-of-flight diffraction (TOFD) method is known as one of the most accurate flaw sizing methods among the various ultrasonic testing techniques. However, the standard TOFD method cannot be applied to weld joints with linear misalignment because of its basic assumptions. In this study, a geometric model of the TOFD method for weld joints with linear misalignment is introduced and an exact solution for calculating the flaw tip depth is derived. Since the exact solution is extremely complex, a simple approximate solution is also derived assuming that the misalignment is sufficiently small relative to the probe spacing and the flaw tip depth. The error in the approximate solution is confirmed to be negligible if the assumptions are satisfied. Numerical simulations are conducted to assess the flaw sizing accuracy of both the exact and approximate solutions considering the constraint of the probe spacing and the influence of the excess metal shape. Finally, experiments are conducted to prove the applicability of the proposed method. As a result, the proposed method is proven to enable accurate flaw sizing of weld joints with linear misalignment.

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A metrological approach to the time of flight diffraction method (ToFD)

Measurement ◽

10.1016/j.measurement.2020.108298 ◽

2021 ◽

Vol 167 ◽

pp. 108298

Author(s):

R.C. Mayworm ◽

A.V. Alvarenga ◽

R.P.B. Costa-Felix

Keyword(s):

Time Of Flight ◽

Diffraction Method ◽

Time Of Flight Diffraction ◽

Metrological Approach

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In-situ quantitative monitoring of fatigue crack using fastest time of flight diffraction method

Transactions of Nonferrous Metals Society of China ◽

10.1016/s1003-6326(11)61517-3 ◽

2012 ◽

Vol 22 (11) ◽

pp. 2679-2684 ◽

Cited By ~ 3

Author(s):

Chao-liang DU ◽

Yi-shou WANG ◽

Dong-yue GAO ◽

Ke-hai LIU ◽

Xin-lin QING

Keyword(s):

Fatigue Crack ◽

Time Of Flight ◽

Diffraction Method ◽

Time Of Flight Diffraction ◽

Quantitative Monitoring

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Time of Flight Diffraction Method Using Laser Ultrasound for Noncontact Flaw Height Measurement

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.261-263.987 ◽

2004 ◽

Vol 261-263 ◽

pp. 987-992 ◽

Cited By ~ 1

Author(s):

T. Mihara ◽

Y. Otsuka ◽

H. Cho ◽

Kazushi Yamanaka

Keyword(s):

Aluminum Alloy ◽

Shear Wave ◽

Time Of Flight ◽

Diffraction Method ◽

Laser Ultrasound ◽

Height Measurement ◽

Alloy Plate ◽

Time Of Flight Diffraction ◽

Probe Distance ◽

Aluminum Alloy Plate

We developed a laser TOFD (Time of flight diffraction) algorithm which utilizes not only longitudinal wave but also shear wave. This algorithm made it possible to obtain accurate flaw depth without knowing the specimen velocity and probe distance previously. We constructed the laser TOFD system and applied it to estimate the slit depth of aluminum alloy plate. Time of flight of lateral wave, flaw tip diffraction waves and mode converted shear wave at flaw tip were used to estimate the slit depth using new algorithm.

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