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Tractor
Trailer Wheel Failure
A metallurgical failure analysis of the right rear inside tandem wheels on a tractor
trailer was requested after a trailer wheel failure. The
rear tandem wheels exited the trailer and
struck an oncoming vehicle. The fifth axle
hub, onto which the wheels had been mounted was
lost (spoliated), leaving only the failed wheel
available for metallurgical failure analysis.
A metallurgical failure analysis was requested
including both visual and stereomicroscopic
examinations. Visual examination revealed the
existence of a weld nugget on the wheel rim. This
weld nugget resulted from an attempted weld repair
of a previous crack and/or localized damage or
defect in the wheel rim. The failed trailer
wheel exhibited a circumferential fracture, as a
result of metal fatigue, of the
wheel rim through each of the ten wheel stud holes.
The fatigue crack, once initiated in the trailer
wheel, propagated circumferentially as a result of
normal (or possibly abnormal) operating stress until
final separation
of the dual wheels from the subject vehicles fifth
axle hub. Weld repair is denoted by white arrow in
photograph of wheel rim shown below.
Photograph A: Failed truck wheel rim. Repair weld was
placed on the truck wheel rim. This improper weld
repair lead to truck wheel rim failure as a result
of metal fatigue. White arrow denotes location of
weld nugget.
A close-up
examination revealed the presence/remnants of a weld
nugget between lug bolt holes denoted "C" and "D". A
close-up view of the area containing the weld nugget
is shown below
Photograph B: Close-up view of remnants of weld nugget between the lug holes denoted C and D.
White arrow denotes repair weld nugget.
Microscopic view of the weld
nugget area shown above confirms the presence of the
repair
weld nugget. Weld repair (which is strictly forbidden by
the U.S. DOT codes and standards) was evidently attempted. The result
of this rim weld repair was initiation of a fatigue
crack which propagated to the C and D lug holes and
then circumferential propagated around the rim and
through the adjacent lug stud holes, as the truck was
used.
Photograph C: Microscopic view of repair weld nugget used to repair
a crack/defect in the subject truck rim.
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Dr.
R. Craig Jerner, Ph.D., PE specializes in accident
investigation and metallurgical failure analysis,
with over 30 years experience as a metallurgical
consultant and accident investigator. He has
testified as a metallurgical expert in over 250
depositions and more than 70 court appearances. If you or someone you know should need the services of Dr. Jerner and J.E.I. Metallurgical, please visit our web site at the buttons below, or e-mail Dr. Jerner --- 