MOR

[smntnz]

Hello everybody,
I am new in this forum, so quick infos for you:
Simone Tanzi, 26 years old, mechanical engineer.

Alright, I have a question: I am new in wood engineering, and I wanted to ask you about MOR. I know its definition, and the experimental procedure to obtain it, but I am still wondering how it can be useful to me. Regardless the study I am performing (FEA of a wooden cooking spatula), I wanted to know if MOR can be used as a stress limit or if it is just a reference for a quick comparison between materials.
Because, although many report that MOR is often similar to tensile strength, they are generally different, and they actually exist as two different definitions, so they must differ, conceptually; the case I am studying is basically a flexural problem, so I have been comparing the Von Mises equivalent stress with the tensile and compressive limits on the compressed and tense sides of the plies, that is with the compressive limit, since it is always lower.
So, how do I use MOR?

Thank you!

 

[smntnz]

P.S.: I know there are failure criteria for composite materials, and I was trying to see if I could validate these criteria's results using the VOn Mises stress and the material's stress limits.

 

[jayrod12]

Forgive my ignorance, but isn't the modulus of rupture just equal to the maximum tensile stress in bending?

 

[SlideRuleEra]

Wood is different than most other structural materials. Deflection is so large as stress approaches the Modulus of Rupture that MOR has little, if any, practical use. MOR varies with the wood species, and is really just a way to compare ultimate strength.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[smntnz]

Yeah, that's just what I was thinking: it is just a way to compare materials, with no practical use.
To jayrod12: I also read something like that, but it is not always the same, so I think one cannot just assume that all the time... I guess it just needs some carefulness.

Thanks everybody!