Re: 1921 ARA Tank Car Committee Report Note

Kurt Laughlin <fleeta@...>


Fatigue is a less than maximum load applied over many cycles that causes failure. Combined stress can cause a failure in one cycle because the combination of two types of loading can be much higher than the failure load for a single type of loading. Even though it may take a number of cycles to actually fail, it's not considered "fatigue" but an overload. At this point in time, without seeing a failed part, you really can't tell what the exact cause was, just that "they broke".


----- Original Message -----
From: Tony Thompson
To: STMFC@...
Sent: Monday, October 16, 2006 7:44 PM
Subject: Re: [STMFC] 1921 ARA Tank Car Committee Report Note

Not sure what you mean, Kurt. Stress causes fatigue if not a
steady stress; little in a rail car is a steady stress on the road.
Bending, especially when not allowed for, is a notorious "hidden" cause
of fatigue in machinery.

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