Other Reports

Report No. 30 - Dynamometer-Induced Residual Stress in Railroad Wheels: Ultrasonic and Saw Cut Measurements

  • 01
  • May
  • 1995
AUTHOR: Raymond E. Schramm, Jacek Szelazek, Alfred V. Clark Jr.
OFFICE: RPD
REPORT NUMBER: NIST/R 5043
SUBJECT: Rail and Infrastructure Integrity
KEYWORDS: EMAT, Nondestructive Testing, Piezoelectric, Railroad Wheel
ABSTRACT: This is Report Number 30 in a series covering research performed by the National Institute of Standards and Technology for the Federal Railroad Administration. This report covers a project by the Materials Reliability Division to develop and test an ultrasonic system for measuring residual stress in the rims of railroad wheels. The effect of stress on elastic parameters causes a small change in sound wave velocity. This acoustoelastic effect is the basis for a method of nondestructive evaluation (NDE). We used two types of ultrasonic transducers, piezoelectric and electromagnetic, to measure both thickness-averaged and near-surface stresses in the rims of twenty unused, cast-steel railroad wheels. The manufacturer mounted these wheels on a unique dynamometer and induced thermal damage by dragging tread brakes to simulate in-service conditions that might generate tensile hoop stress. After our ultrasonic nondestructive tests, they cut eighteen wheels with a saw along a radius to measure flange tip opening and verify the stress state. The displacement of the opening (after cutting completely through the rim) indicates the net rim force. We correlated the ultrasonic measurements and the saw cut opening, showing that this approach may be useful for field assessment of wheel safety. Wheels with negative net rim force are in compression and will likely arrest any cracks. Wheels with positive rim force may suffer failure by crack propagation.

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