Technology Digests / Fatigue Testing of Rails with Detected Defects Under Simulated Heavy Axle Loads

TD23-013

July 25, 2023
Authors
  • Ananyo Banerjee
  • Gavin Whetstone
  • David H. Allen
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Key Findings

  • In addition to fatigue stresses under heavy axle loads and thermal tension, residual stresses inside the rail play a major role in growth rates of rail head defects and cracks.
  • Variability in crack growth rates was found in the tests. The seemingly random increase and decrease of the crack growth rates could be related to the complex interplay of tensile and compressive residual stresses inside the rail.
  • An algorithm has been developed to process phased array ultrasonic test readings and better anticipate the crack area and defect geometry for better prediction of crack growth rates as a function of the number of loading cycles applied on the rail.

Fatigue Testing of Rails with Detected Defects Under Simulated Heavy Axle Loads

In 2016, MxV Rail tasked Texas A&M University (TAMU) with building a rail fatigue test fixture at the Center for Infrastructure Renewal (CIR) and provided partial funding for this project from the Association of American Railroads’ (AAR) Strategic Research Initiatives (SRI) program. Over the last six years, MxV Rail has been testing rails with detected defects using this fatigue testing fixture. The aim of this project is to test rail samples to fracture and compare the actual crack growth with simulated outputs from RailGrow, a fatigue crack growth model developed by MxV Rail.1 A rail with a pre-existing crack is loaded in the test fixture to simulate conditions of moving freight cars. Loading includes 1) vertical bending to simulate wheel load cycles and 2) axial tension to simulate thermal stresses. A series of tests simulating conditions used in RailGrow model led to an improved understanding of crack growth behavior, and…