Other Reports

Ultrasonice Railroad Wheel Inspection Using EMATs

  • 01
  • Dec
  • 1988
AUTHOR: Raymond E. Schramm, A. Van Clark Jr.
SUBJECT: Rail and Infrastructure Integrity
KEYWORDS: Nondestructive Evaluation, Residual Stress, Roll-By Inspection
ABSTRACT: This is report number 18 in a series covering the research performed by the National Institute of Standards and Technology (formerly National Bureau of Standards) for the Federal Railroad Administration. This issue collects seven reprints and preprints of papers written by the Fracture and Deformation Division over the last two years on the ultrasonic nondestructive evaluation of railroad wheels for the presence of residual stresses and cracks. All this work concentrated on the use of electromagnetic-acoustic transducers (EMATs). Tensile residual stresses and tread cracks are major factors in wheel failure. Catastrophic breakdowns may lead to injuries, repair costs, and lost time. Current inspection methods are largely visual, and thus inefficient. Two ultrasonic techniques are applicable to these wear defects: 1. Birefringence. A stress field effects the velocity of a shear horizontal wave depending on its polarization. Precise velocity measurements in a wheel rim may allow calculation of the amount and direction of stresses; 2. Pulse-echo. A Rayleigh (surface) wave transducer mounted inside the rail can introduce a signal to interrogate the circumference of a wheel as it rolls by. An echo indicates a flaw's presence and size. For both systems, we hope to produce instruments for testing at a field site.