von Mises (psi) Means What?? 1

[jaywoo]

I have comleted a batch of cosmos analysis and I need to report the findings to the bosses. My question is, they ask Simply "when will it break?. I do not know how to report the Yield strengths into hard numbers. What exactly is the notation.

With a load force of 500 PSI on a target, cosmos delivers;

yeild strength of 2.017e+004

what is 6.253e+003 telling me? In "how many pounds". is that Von mises telling me is being stressed ad that point?

Please help and thanks if you can make sense of my question.

 

[corus]

Yield strength is a material property that you decide upon. If stresses in the structure are above that value then it doesn't necessarily mean that it will break, only that plasticity will occur at some places. A structure will break if stresses exceed the UTS of the material or will break over time due to fatigue (when stresses can be below yield).

Your load force of 500 psi doesn't make sense as that is expressed in pounds per square inch (psi) which is a unit of pressure and not load/force.

Von Mises is a measure of stress intensity for ductile materials such as steel. If the stress intensity calculated is 6.253e3 and the yield stress is 2e4 then stresses are within yield and the structure won't break. Fatigue damage should still be assessed though if your loads vary over time.

corus

 

[Tmoose]

Side note - for brittle materials, like cast iron, tensile strength is low, but strength under compression is high. Then it is sometimes useful to report principal stresses and pay attention to the sign to identify tension or compression.

 

[TheTick]

Terms you need to understand:
[ul][li]force[/li]
[li]stress[/li]
[li]strain[/li]
[li]elongation[/li]
[li]modulus of elasticity[/li]
[li]tensile stress[/li]
[li]shear stress[/li][/ul]

Until you understand these, you are dangerously underqualified and Von Mises stress is meaningless.

 

[Co]

Yes, I agree with the above. These are very basic strength of materials/applied elasticity fundamentals. If you do not know what the meaning of stress is then you should not be using a finite element program.
I suggest first extensively reviewing fundamentals and then attempt whatever problem you have by hand if possible (which in the far majority of cases is possible). Then the last step is verifying the results you obtain numerically.

cheers,