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ASNT Rewind
2401 ME January.indd 25 12/20/23 8:01 AM

RAILCAR AXLE
INSPECTION
Current State, Future Needs,
and Opportunities
BY ANISH POUDEL, PHD
This tutorial article briefly overviews the current state-of-the-art railcar axle
inspection methods to detect and characterize axle discontinuities or indications.
This paper also presents and discusses some of the initiatives conducted by MxV
Rail (formerly TTCI) and other researchers on the use of emerging and advanced
nondestructive evaluation (NDE) technologies that are at different phases of
development and not commercially available. Finally, a brief discussion is provided
on the need for novel in-motion axle inspection NDE methods for moving trains.
Such technology would enhance the safety of railcar axles. The need depends
on the regulations in a given jurisdiction and on the class of service (passenger,
freight, certain regulated hazardous materials).
Introduction
Railcar axles connect the wheels and bearings.
An essential component of railway systems,
axles play a crucial role in supporting the
weight of railcars and ensuring the safe and
efficient transportation of passengers and
freight. Railcar axles are usually made of high-
strength heat-treated carbon steel. They are
designed to last indefinitely while enduring
extreme dynamic and static loads, along with
torsional and bending stresses, during oper-
ation (Hannemann et al. 2019 Lonsdale and
Stone 2004 Zerbst et al. 2013). Railway axles
undergo a rigorous manufacturing process to
meet the necessary specifications for strength
and durability set by governing bodies and
authorities. The axles must be able to handle
the train’s weight, resist bending, and remain
straight under the stresses of heavy loads.
Additionally, they must withstand wear and
tear from prolonged use and maintain their
integrity even in extreme weather conditions.
Figure 1 (on page 28) shows the schematic of a
solid axle commonly used in North American
freight and passenger services. Railway
systems in Europe primarily use hollow, or
tubular, railcar axles for weight reduction and
energy efficiency.
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M A T E R I A L S E V A L U A T I O N • J A N U A R Y 2 0 2 4
2401 ME January.indd 26 12/20/23 8:01 AM