Technology Digests / Non-Contact Ultrasonic NDE for Joint Bars Defect Detection

TD22-025

September 1, 2022
Authors
  • Anish Poudel
  • Glenn Washer
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Key Findings

  • Laboratory proof-of-concept testing done in an immersion water tank shows that non-contact ultrasonic NDE methods are able to reliably identify man-made defects in joint bars despite the complex geometry involved. Testing indicated that a 5 MHz ultrasonic transducer launching a 45-degree shear wave (S-wave) provided the best sensitivity for detecting man-made defects.
  • Test results with a naturally occurring crack in a joint bar produced a much lower signal-to-noise ratio compared to the man-made defects (on the order of -20 dB for 2.25 MHz probe) meaning that cracks would be more difficult to find.
  • Performance differences between water-coupled and air-coupled non-contact UT testing will need to be quantified in future work.

Non-Contact Ultrasonic NDE for Joint Bars Defect Detection

MxV Rail (formerly TTCI), in collaboration with the University of Missouri, investigated the use of non-contact ultrasonic nondestructive evaluation (NDE) methods for inspecting railroad joint bars for internal defects in a laboratory test environment. Existing automated inspection methodologies for joint bars include a machine vision system (MVS) that uses multiple high-resolution cameras to acquire and analyze images to identify and report cracks exposed to the surface. While this approach has proven effective for finding broken joint bars, it cannot find internal defects and it cannot detect cracks exposed to the surface but visually obscured. Ultrasonic testing (UT) is an effective and well-proven technology for detecting cracks. Ultrasonic waves are reflected from cracks, and the reflected waves are analyzed to identify the cracking and determine their locations. A variety of techniques exist for implementing the UT NDE method. However, joint bars present a challenging geometry with surfaces that are not parallel—a…