Modulus of Rupture

Modulus of Rupture, frequently abbreviated as MOR, (sometimes referred to as bending strength), is a measure of a specimen’s strength before rupture. It can be used to determine a wood species’ overall strength; unlike the modulus of elasticity, which measures the wood’s deflection, but not its ultimate strength. (That is to say, some species of wood will bow under stress, but not easily break.)

Modulus of rupture (MOR) testing
Modulus of rupture (MOR) testing

MOR is expressed in pounds-force per square inch (lbf/in2) or megapascals (MPa). This number is given for wood that has been dried to a 12% moisture content, unless otherwise noted.

mor

In practical terms, the number itself isn’t all that meaningful, but it becomes useful to use in comparison with other woods. For instance, Hickory is known to have excellent strength properties among domestic species in the US, and has a MOR of 20,200 lbf/in2 (139.3 MPa). In comparison, Red Oak is another well-known wood used in cabinetry and furniture, and has a MOR of 14,300 lbf/in2 (98.6 MPa).

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Álvaro González Calvo

Hi Eric! I have a doubt about how you can use the MOR. I am working on my final degree project, and I am analyzing the neck of a wooden guitar in Ansys Workbench. I want to determine if it breaks under the loads applied by the strings. My question is, can I use the MOR as the stress I cannot surpass in the wood? It would be like using the yield stress of steel in a metal piece. I am modelling the guitar as an element in longitudinal bending, with the grains parallel to the longitudinal direction, so I… Read more »

Álvaro González Calvo

Hello! Thanks for your quick response. When you tighten the strings of the guitar, the guitar neck bends and a concentracion of stresses appears in the smallest section of it. I am doing my analysis there. You can see here an example of this tipe of analysis: https://www.slideshare.net/MattHayes5/fea-of-guitar-neck. My problem comes when I have to check if in that section a crack appears. That´s why I asked whether a crack should appear there if the stresses are higher than the MOR. And if the MOR is not convenient for that checking, my question was if I could use any other… Read more »

Christian Ademius-Kjellén

Eric, it still doesn’t make sense to me how MOE can be multiple times higher than a force that breaks the wood, MOR. According to the illustration of them both in your book, they look like they´re benchmarked exactly the same way. A wood blank supported on both sides and a force put perpendicular to the wood blank´s center. MOE bends it so you only measure the force to the point of where the wood bends, right? But how can then a force so strong bend the blank where a lower force which MOR tends to be break it? It… Read more »

chanikjo

which wood has highest moduls of rupture

Lex

Eric – What is the difference between the modulus of rupture vs. the Fb bending force. I have a book that lists them both.

Mark

The MOR is the stress in the wood when it physically breaks. Fb, which is the allowable bending stress, is the nominal bending stress that is used in the design equations in accordance with the NDS. There is a very large factor of safety for wood due to the variable nature of wood

Ryan

What are the factors of safety? More specifically for bending? How would I be able to determine the allowable bending if I was only given the MOR?

Collins

What is the size of the sample and specifics of the fulcrum points (Distance, length, shape) Also, I’m guessing that the MOR number is the highest force reached and not the force being applied at the time of rupture, is this correct?

Ernie Smith

Eric-
First and foremost, thank you for compiling, formatting and sharing this data publicly. The data is incredibly useful.

Second, can you point me to some additional resources that explain how the MOR tests are done for wood? I am curious how specimens are selected, what grain direction is used, size of test pieces, sample size, etc.

Again, thank you for this wonderful resource.

Regards,
Ernie

Christina Foley

What is the specimen size used to determine MOR presented here. I’m assuming 20 x 20 x360 mm, can you verify?

Thank you!

student that needs help

for a school project i need to develop my own furniture but i have trouble with the MOR.
width length & depth should have impact on the amount of pascal it can withstand, but when i go to Wikipedia it says Pa = n/m^2 wich means that only depth and length have influence on the MOR
what should i do when i need to know how thick i need to make my table for more than 4 students to sit on

Para Koirala

does 0.075 makes sense for the MOR of LVL?

naimatullah

what is the modulus of rupture of orange tree?

p.savarimuthu raja p.raja

Eric pls reply

p.savarimuthu raja p.raja

I need one question Madagascar pine and newzealand pine MOR and MOE standard

Sakura Chan

so thats means the higher the MOR value, higher the wood strength. Is it sir? because I’m still confuse. Thanks for the reply.

sea

sir, which wood has the highest modulus of rapture count and that too in Mpa?