Re: [DML] Torsion Bars

["tmpintnl" <tobyp@xxxx>]

Sean - What you are describing is classic crack propagation due to 
fatigue. That's what my broken trailing arm bolt looked like. A 
crack starts in an imperfection of some sort (corrosion pit, scratch, 
manufacturing surface defect, etc.) and grows slowly through the 
thickness of the part every time it is stressed. At some point, the 
cross-sectional area becomes too small to handle the stresses, and the 
crack shifts into fast crack growth, until you reach a kind of 
"critical mass" , and then the part fails due to ductile rupture. 
With a scanning electron microscope, you can actually count the 
striations, and estimate how many stress cycles the part went through 
for each of the crack growth phases. Isn't the mechanics of materials 
a fascinating subject?

Toby Peterson VIN 2248
Winged1

--- In dmcnews@xxxx, "spaceboy_2912" <seanm@xxxx> wrote:

> I noted that the break had appeared to have started some time before 
> the the torsion bar gave out, due to a dirty part then a clean part 
> of the break.
> Later,
> Sean
>