A new ultrasonic technique for detection and sizing of small cracks in studs and bolts
If small cracks in stud bolts are not detected early enough, they can grow rapidly and cause catastrophic disasters in industrial facilities such as nuclear power plants. Their detection, despite its importance, is known to be a very difficult problem due to the complicated structures of the stud bolts. This study shows a method of detecting the existence and determining the size of a small crack in a root between two crests in the bolt threads using ultrasound. The Rayleigh wave propagating from the tip of a crack to the opening of the same crack is utilized. A delayed pulse, due to the Rayleigh wave, is detected between regularly spaced pulses from the threads, with the delay time being proportional to the size of the crack. Theoretical explanation is presented and experimental results demonstrating detection of cracks as small as 0.5 mm are shown.
key wordsUltrasonics threads bolts Rayleigh waves tip diffraction
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- 1.NRC Bulletin SSINS NO.: 6820, OMB NO.: 3150-0086, Degradation of Threaded Fasteners in the Reactor Coolant Pressure Boundary of PWR Plants, June 2, 1982.Google Scholar
- 2.G. M. Light, Ultrasonic detection of stress-corrosion cracks in reactor pressure vessel and primary coolant system anchor studs(bolts),Mater. Eval. 1413–1418 (1987).Google Scholar
- 3.NUREG-1339, Resolution of Generic Safety Issue 29: Bolting Degradation or Failure in Nuclear Power Plants, U.S. Nuclear Regulatory Commission, June 1990.Google Scholar
- 4.NUREG-1445, Regulatory Analysis for the Resolution of Generic Safety Issue-29: Bolting Degradation or Failure in Nuclear Power Plants, U.S. Nuclear Regulatory Commission, September 1991.Google Scholar