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Simulation study on 2x4 lumber just for practice using simulation module.....(to see how much can be applied before it breaks)

Question asked by Dave Krum on Dec 29, 2017
Latest reply on Dec 29, 2017 by J. Mather

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Good morning all,

I thought I'd do a little practice exercise using the simulation module on some wood just for kicks. I am not a structural engineer so do not know the math formulas for the handwritten workup, but thought it would be cool to see how much weight I could apply to the center of a standard 2x4 oriented the strong way before it breaks. I took an 8' length and have each end fixed 2" inch from end on center. I used the split line command to apply the force points as someone suggested on here years ago from an older post (see snips below). I'm not sure though what the modulus of elasticity is for standard wood from hardware store. Is it oak? Nothing is in the material database for SW apparently. I pulled up the matweb database (MatWeb - The Online Materials Information Resource) and am not sure what should be chosen for this value in order to update the SW materials database as far as the modulus. Any help would be appreciated for this value, as well as my approach. I think I have it all set up properly, just when going to run the simulation there is no elastic modulus value on file within the software. Thanks in advance.

J. Mather Dec 29, 2017 3:06 PM

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Dave Krum wrote:
... (but maybe not that simple since the wood isn't isotropic as you guys mentioned).

Doesn't matter if it was isotropic.

SolidWorks linear static analysis does not calculate fracture. So even if it was steel, you are not going to calculate (with that analysis) when it breaks.

See the reply in context

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wood 2x4 beam test.SLDPRT.zip72.2 KB

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John Stoltzfus Dec 29, 2017 11:08 AM

Dave Krum - what version are you running?

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Dave Krum @ John Stoltzfus on Dec 29, 2017 11:38 AM

Hi John,

Still on SW2015. Solid for me.

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John Stoltzfus @ Dave Krum on Dec 29, 2017 11:42 AM

I don't have an answer for you, the reason I asked is - it's always best to list the version you're using when it comes to something like this, maybe the information you get back is from guy's using 2018 and it don't help you at all. or there maybe a special fix for your version... etc.

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Matt Peneguy Dec 29, 2017 11:40 AM

Generally 2x4s are made of pine. I think it is Ponderosa Pine, but don't quote me on that. Also remember the fiber direction makes a huge difference in the property (wood is anisotropic, steel is isotropic). So, make sure you choose the correct modulus.

A quick web search turned up this resource:

http://www.conradlumberco.com/pdfs/ch4-Mechanical-Properties-of-Wood.pdf

I haven't looked through it completely and verified that resource. But, it looks pretty legit to me.

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Dave Krum @ Matt Peneguy on Dec 29, 2017 11:43 AM

Hello Matt,

Thanks for the heads up. I'll take a look

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Matt Peneguy @ Dave Krum on Dec 29, 2017 11:56 AM

Dave,

Here's the math for comparison:

Let us know how it works out.

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Dave Krum @ Matt Peneguy on Dec 29, 2017 12:02 PM

Thanks! I sure will. Happy New Year to you.

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Dave Krum Dec 29, 2017 11:42 AM

forgot to add that these are the values I have for oak in SW2015 out of the box:

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J. Mather Jan 2, 2018 9:10 AM

...the math formulas for the handwritten workup
... thought it would be cool to see how much weight I could apply to the center of a standard 2x4 oriented the strong way before it breaks.

What are the limitations of a linear static stress analysis?

1. The math is appropriate within the linear portion of the stress/strain curve. (Break (fracture) might occur well past the linear portion of the curve.)

2. Istropic material properties. (Wood is not isotropic.)

3. Relatively small displacements. (Relative is, well, relative.)

4. More reliable if the aspect ratio between width, depth and height is not too great (another relative term). (Take a veneer strip of that material and you can bend into a loop. Now you do not have an aspect ratio that extreme, but you have a pretty long, skinny part.)

Use caution with your analysis.

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Dave Krum @ J. Mather on Dec 29, 2017 2:24 PM

Hi. Not building anything really. More of a curiosity thing just to get a flavor for simple simulation practice (but maybe not that simple since the wood isn't isotropic as you guys mentioned). Sorry if sounding ignorant.

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J. Mather @ Dave Krum on Dec 29, 2017 3:06 PM

Dave Krum wrote:
... (but maybe not that simple since the wood isn't isotropic as you guys mentioned).

Doesn't matter if it was isotropic.

SolidWorks linear static analysis does not calculate fracture. So even if it was steel, you are not going to calculate (with that analysis) when it breaks.

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11 Replies

John Stoltzfus Dec 29, 2017 11:08 AM
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Dave Krum - what version are you running?
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- Dave Krum @ John Stoltzfus on Dec 29, 2017 11:38 AM
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  Hi John,
  Still on SW2015. Solid for me.
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  - John Stoltzfus @ Dave Krum on Dec 29, 2017 11:42 AM
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    I don't have an answer for you, the reason I asked is - it's always best to list the version you're using when it comes to something like this, maybe the information you get back is from guy's using 2018 and it don't help you at all. or there maybe a special fix for your version... etc.
    Like • Show 2 Likes2
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Matt Peneguy Dec 29, 2017 11:40 AM
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Correct Answer
Generally 2x4s are made of pine. I think it is Ponderosa Pine, but don't quote me on that. Also remember the fiber direction makes a huge difference in the property (wood is anisotropic, steel is isotropic). So, make sure you choose the correct modulus.
A quick web search turned up this resource:
http://www.conradlumberco.com/pdfs/ch4-Mechanical-Properties-of-Wood.pdf
I haven't looked through it completely and verified that resource. But, it looks pretty legit to me.
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- Dave Krum @ Matt Peneguy on Dec 29, 2017 11:43 AM
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  Hello Matt,
  Thanks for the heads up. I'll take a look
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  - Matt Peneguy @ Dave Krum on Dec 29, 2017 11:56 AM
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    Dave,
    Here's the math for comparison:
    Let us know how it works out.
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    - Dave Krum @ Matt Peneguy on Dec 29, 2017 12:02 PM
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      Thanks! I sure will. Happy New Year to you.
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Dave Krum Dec 29, 2017 11:42 AM
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forgot to add that these are the values I have for oak in SW2015 out of the box:
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J. Mather Jan 2, 2018 9:10 AM
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...the math formulas for the handwritten workup
... thought it would be cool to see how much weight I could apply to the center of a standard 2x4 oriented the strong way before it breaks.
What are the limitations of a linear static stress analysis?

1. The math is appropriate within the linear portion of the stress/strain curve. (Break (fracture) might occur well past the linear portion of the curve.)
2. Istropic material properties. (Wood is not isotropic.)
3. Relatively small displacements. (Relative is, well, relative.)
4. More reliable if the aspect ratio between width, depth and height is not too great (another relative term). (Take a veneer strip of that material and you can bend into a loop. Now you do not have an aspect ratio that extreme, but you have a pretty long, skinny part.)

Use caution with your analysis.
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- Dave Krum @ J. Mather on Dec 29, 2017 2:24 PM
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  Hi. Not building anything really. More of a curiosity thing just to get a flavor for simple simulation practice (but maybe not that simple since the wood isn't isotropic as you guys mentioned). Sorry if sounding ignorant.
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  - J. Mather @ Dave Krum on Dec 29, 2017 3:06 PM
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    Dave Krum wrote:
    ... (but maybe not that simple since the wood isn't isotropic as you guys mentioned).
    Doesn't matter if it was isotropic.
    SolidWorks linear static analysis does not calculate fracture. So even if it was steel, you are not going to calculate (with that analysis) when it breaks.
    Like • Show 3 Likes3
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Simulation study on 2x4 lumber just for practice using simulation module.....(to see how much can be applied before it breaks)

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