Technology Digests / Optimizing Surface Waves for Joint Bars Defect Detection

TD24-016

February 11, 2025
Authors
  • Anish Poudel
  • Glenn Washer
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Key Findings

  • The maximum signal amplitude of the ultrasonic surface wave was observed at approximately 29.2 degrees incidence angle, 30 degrees yaw angle, and 1.5 inches offset from the joint bar head.
  • The surface wave signal amplitude values measured from the implanted cracks in joint bar specimens were found to be approximately 10 percent (20 dB) of the signal amplitude measured from the saw-cut notch in the joint bar calibration specimen.
  • The similarity between Phase II (joint bars not attached to rail sections) and Phase III (joint bars attached to rail sections) strongly suggests that the coupling of joint bars to the rail and the associated surface/contact stresses do not impede the ultrasonic surface waves' ability to detect cracks in the inaccessible areas of the joint bars.
  • After the completion of Phase III, challenges remain regarding the reliable detection of cracks with good signal-to-noise ratio (SNR) using an ultrasonic surface wave approach for varying profiles and complex geometry of joint bar surface.
  • Further work is needed to advance the technology readiness level of the explored ultrasonic approach.

Optimizing Surface Waves for Joint Bars Defect Detection

In late 2023, MxV Rail and the University of Missouri completed the Phase III of laboratory investigations of non-contact ultrasonic nondestructive evaluation (NDE) methods for detecting fatigue cracks in railroad joint bar heads. Earlier phases of work1,2 focused on exploring shear and surface waves specifically used to detect simulated fatigue cracks of varied sizes in areas of joint bar heads that are inaccessible to visual inspections during revenue service. The current phase focused on optimizing surface waves to detect simulated fatigue cracks in the inaccessible regions of the joint bar heads when joined to the parent rails. In addition, this phase focused on assessing the optimal test arrangements for launching surface waves from the accessible area of the joint bar into the inaccessible areas of the joint bar. BACKGROUND Some challenges associated with using ultrasonic testing (UT) NDE technology for joint bar inspection include surface conditions, complex geometry, and limited…