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07-01-2015
11:55 AM

07-01-2015
11:55 AM

Given/Find commands issue

Hi All,

I'm strugling with the following problem:

I'm calculating von Mises stresses where all the variables are known except TF and BM. These two parameters are defined only as the initial guess values. I'd like to find maximum value for TF and BM for which von Mises stress is equal to the allowable stress. Is this even possible to solve with given/find commands?

I appreciate your help in this matter.

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07-01-2015
01:33 PM

07-01-2015
01:33 PM

Re: Given/Find commands issue

TF and BM always appear as BM+TF, so combine them into one variable and solve for that. How you then split the answer into BM and TF is up to you.

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07-01-2015
01:41 PM

07-01-2015
01:41 PM

Re: Given/Find commands issue

1) You should always post a worksheet and not just a picture

2) Do you mean that VM should equal S.A=50? Then you might check your formula. VM is just dependable on the difference BM-TF, no matter what the actual values of those two variables might be. And the minimum value for VM as you had defined it is about 129.9 (for BM-TF=375). So no way to get to 50 and you can chose BM and TF as high as you like, as long as their difference is 375.

3) When you have corrected your formulas/values, you may want to look up maximize() in the help.

LT

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07-01-2015
05:04 PM

07-01-2015
05:04 PM

Re: Given/Find commands issue

VM is just dependable on the difference BM-TF

It depends on the sum, not the difference. Which doesn't fundamentally change what you (or I) said in that they can be treated as a single variable. It does mean that there is a limit to how high they can be though.

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07-01-2015
10:01 PM

07-01-2015
10:01 PM

Re: Given/Find commands issue

Richard Jackson wrote:

VM is just dependable on the difference BM-TF

It depends on the sum, not the difference.

Are you sure?

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07-01-2015
10:16 PM

07-01-2015
10:16 PM

Re: Given/Find commands issue

. You are right. I wonder if that is a mistake, and there are some missing parentheses. If it depends on the sum there is at least some reasonable domain for acceptable solutions. If it depends on the difference then TF and BM can take on any values, no matter how physically ridiculous, as long as the difference is not physically ridiculous. That cannot be correct.