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2401 ME January.indd 41 12/20/23 8:01 AM

IN-MOTION RAILCAR WHEEL INSPECTION
USING MAGNETOSTRICTIVE EMATS
ANISH POUDEL*, BORJA LOPEZ†, SYED ALI†, AND JOSH BENSUR†
ABSTR ACT
Due to cyclic mechanical loading, railcar wheels are
subject to the development of internal fatigue cracks
in the rim underneath the tread surface. Off-line
inspections are extremely laborious and require
extended out-of-service time, and most existing
in-line inspection systems that use conventional
ultrasonics or electromagnetic acoustic transducer
(EMAT) techniques have several drawbacks that
limit their full-scale deployment in service. This
paper discusses the work performed on the initial
research and development of a proof-of-concept novel
magnetostrictive EMAT sensor for in-motion railcar
wheel inspection. Wheelsets with known internal
discontinuities and a 3.7 m long panelized track were
used to demonstrate the feasibility of the developed
approach and methods. The results obtained from
these tests have shown that the magnetostrictive
EMAT sensor that generates 5 mm wavelength
shear horizontal waves detects both surface defects
and internal fatigue cracks with an excellent signal-
to-noise ratio. Different wavelengths can also be
added to the sensors to enhance or complement
the detection of fatigue cracks at different depths.
A total of four or five sensors located at standard
concrete crosstie spacing along each rail would be
able to provide complete coverage on wheels ranging
from 711 to 965 mm in diameter with ±90° wheel
coverage per sensor, and a theoretical inspection
speed of 56 kph can be achieved using this approach.
KEYWORDS: nondestructive evaluation (NDE), electromagnetic
acoustic transducer (EMAT), wheels, fatigue, cracks, defects
Introduction
Railcar wheels are subject to heavy loads and stresses that
cause both wear and material fatigue during routine service.
Cyclic mechanical loading can cause surface defects and
shallow internal fatigue cracks to form in the rim underneath
the tread surface. In North American railroads, railcar wheels
are inspected regularly and removed from service when they
exceed the Association of American Railroads’ (AAR) specifi-
cations for condemnable defect criteria as defined in Rule 41 of
the AAR Field Manual of the AAR Interchange Rules (AAR 2023).
Railcar wheel condition is traditionally assessed using wayside
inspection systems that include wheel impact load detectors
(WILD) and a wheel profile measurement system or detectors
(WPMS/WPDs) (Asplund et al. 2016 Gage et al. 2001 Kalay 1993
Lonsdale et al. 2004 Robeda et al. 2002, 2004 Stratman et al.
2007 Tournay and Cummings 2005). Often installed on tangent
tracks, WILD systems measure the vertical and lateral forces of
passing wheels using a series of strain gages installed on the rail
web and grouped in cribs between the ties. The crib placements
are strategically chosen to maximize the portion of the wheel cir-
cumference measured, and each instrumented crib is optimized
to measure vertical and lateral loads. The WILD systems can
effectively find out-of-round wheels or wheels with surface irreg-
ularities, but these systems cannot effectively identify cracked
and broken wheels. Researchers have reported that many
cracked wheels fail in service before exhibiting high impacts
(90 kips or higher, AAR condemnable limit) as measured by the
traditional WILD systems (Poudel et al. 2019b).
The WPMs/WPDs use high-speed digital cameras and
lasers mounted below the top of rail to (a) view the wheel
tread, (b) collect images of the individual wheels as trains pass,
and (c) automatically analyze these images to extract wheel
profile measurements. Critical wheel dimensions, such as
rim thickness, tread hollow, and flange height, thickness, and
angle, are measured and compared with the reference profile
of the new wheel. Any irregularities are identified based on the
measurements taken by the system, and if needed, severely
worn wheels that exceed the AAR condemnable limits are
removed from the railcars (Lee et al. 2023 FRA 2019).
Recent advancements in technology have facilitated the
emergence of other wayside inspection systems based on
lasers, fiber optics, and machine vision systems (Galvan-Nunez
et al. 2022 Nayebi 2017 Poudel et al. 2019b, 2022). These visual
wayside inspection systems can only find wheel defects that
(a) have already reached the surface, (b) are visible, (c) are
in direct line of sight, or (d) could already compromise the
wheel’s integrity. Although effective in finding internal cracks,
manual nondestructive evaluation (NDE) processes, such as
*MxV Rail, 350 Keeler Parkway, Pueblo, CO 81001 anish_poudel@aar.com
† Innerspec Technologies Inc., Forest, VA 24551
Materials Evaluation 82 (1): 42–50
https://doi.org/10.32548/2024.me-04376
©2024 American Society for Nondestructive Testing
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