Cracked weld on my tongue.

[whoofit]

[p]Sean, whether or not it was related to the thermal expansion coefficients is unclear. I have some experience interpreting environmental chamber test results on sintered metal oxide ceramics used in temperature sensing and have seen a slew of catastrophic failures because of both large and rapid and large and slow thermal cycling.

One thing I feel certain of is this crack formed overnight with the trailer at rest. It wasn't like we were doing jumping jacks in there either.[/p][p]
[/p][p]It could also be vibration related but like you said...the weld was thin and almost foil like. Just plain crummy all around.[/p]

[djsamuel]

The crack probably started a while before you noticed it and took a while to propagate to the surface. Generally they start at a point of high stress concentration and then due to fatigue or an application of a high force, the crack begins. While at rest, the normal forces the weld would see from movement in the trailer and/or thermal was enough to bring the crack to the surface.