Re: Need help with school work again.. This time with strength testing
 

I gotta say, what jago is saying is what my lab instructor taught us about this. It'll plastically deform between before yield, but only with uniform stretch and thin. Necking, or the narrowing of a specific point on the specimen, doesn't occur until after yield strength.

Re: Need help with school work again.. This time with strength testing
 

Yes that's what I was saying as well. Necking does occur after yeild when it starts to plastically deform but I didn't say if it was after or before UTS. I thought it was before but meh whatever. Must have been wrong.

Totally agree 100%

Re: Need help with school work again.. This time with strength testing
 

You can plactically deform without necking.

Re: Need help with school work again.. This time with strength testing
 

http://www.shodor.org/~jingersoll/we...rial/img21.png
http://www.shodor.org/~jingersoll/we...rial/img21.png

Faggots.

The question is simple. It will break at a lower stress than the ultimate because of necking. Just plug in the ultimate.

Ultimate Strength = Force/Area

Re: Need help with school work again.. This time with strength testing
 

^^ This graph shows it all.

Yield stress is given typically by the .2% rule, which means it is the stress that corresponds with the strain + .2% after that critical point. THAT is the yield stress. Volume is conserved in a specimen as until the you reach the materials Tensile Strength when necking occurs.

Re: Need help with school work again.. This time with strength testing
 

If I had a scanner I'd scan the pages of my Mechanics of Materials book. Seriously one of the best text books I've ever used. I'll probably never sell it.

These kind of questions are pretty easy. You either use Yield or Ultimate. You design for yield times a safety factor just about always. If you want to find if something fails, you set it to the ultimate. The actual length in this problem means nothing. You'd only need to know that if you were doing an elongation problem as this point in your semester.