topic Re: How much stress is too much? in Inventor Forum

How much stress is too much?

Anonymous — Sun, 29 Jul 2018 14:48:12 GMT

I did a stress analysis on the attached pictures. It is a low-carbon steel steel tube, .75" OD, .083" wall thickness with a 70 pound force as the pictures indicate. It is fixed at the other end of that bend. How do I interpret these results? Or to be more direct, will this part fail with this 70 pound load?

I've googled quite a bit to try and find hard answers of when to know if the simulated load will cause the part to fail but I can't come up with any definite answers. Any links would be appreciated as well.

Thanks!

Re: How much stress is too much?

TheCADWhisperer — Sun, 29 Jul 2018 16:11:09 GMT

@Anonymous wrote:
…. Or to be more direct, will this part fail with this 70 pound load?

Attach your file here.

Are you a student?

In your own words, what is your definition of "failure" for this part?

Re: How much stress is too much?

Anonymous — Sun, 29 Jul 2018 21:16:40 GMT

You need to know the material yield stress that the tube will be made of.

For instance a plate made of ASTM A36 has a yield stress of 36 ksi (1 ksi = 1,000 psi). Which means that if the max stress in the color bar is above 36 ksi, the part will fail. Also, you usually want a minimum safety factor of 1.5X the yield stress. Which means if you're using ASTM A36 steel you want your max stress to be 27 ksi (36 ksi * 0.75). This will give you minimum safety factor of 1.5.

However, I tend to aim for a safety factor of 2X. So, if I'm using ASTM A36 steel, I don't want to see a max stress higher than 18 ksi (36 ksi * 0.5).

To find out the max yield stress of the material you are using open the material editor, RMB click on the material assigned to your part and select edit. Click on the "Strength" tab and check what the yield strength is under the "Strength" section (see attached screenshot).

Hope this makes sense and helps you!

Re: How much stress is too much?

Anonymous — Sun, 29 Jul 2018 21:15:21 GMT

Perfect, exactly what I was looking for. Thank you!

Re: How much stress is too much?

SBix26 — Mon, 30 Jul 2018 01:01:31 GMT

Once you've verified that your material has the correct yield stress, you can use the Safety Factor display to avoid doing head or hand calculations, or so you don't have to remember the yield stress.

Sam B
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