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BS_98781591-Visitor
1-Visitor
April 6, 2021
Question

I can't get Mathcad to symbolically solve this equation

  • April 6, 2021
  • 3 replies
  • 3518 views

No matter how much I try, Mathcad can't add these expressions because it thinks they have different units (but they don't)... I need to simply and add the different stresses together but I can't. 

 

BS_9878159_0-1617706539974.png

As you can see in the picture, the stress at "A", is not simplified.  Because the stresses are not added together as the program thinks they have different unit.

3 replies

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-MFra-21-Topaz II
21-Topaz II
April 6, 2021

he is undefined!!!

B
BS_98781591-VisitorAuthor
1-Visitor
April 6, 2021

What are you talking about?  Only he is undefined, and even then, the program should be able to add the numerical values together and just leave he as it is.

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-MFra-21-Topaz II
21-Topaz II
April 6, 2021

A is a constant or a function of h.e? since h.e is unknown,  A must be necessarily a function of h.e, otherwise, the given definition isn't correct.

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
April 6, 2021

I keep preaching but few listen.

 

Mathcad (and especially, now, Prime 7) is a very poor symbolic engine!

 

It's still a good numeric solver.  Attached is your file adjusted to be numeric.  Are you looking for stress VS. h_e?  

 

You might try playing to its strength

    B
    BS_98781591-VisitorAuthor
    1-Visitor
    April 6, 2021

    I'm trying to find the stress as a function of he. So the stress has to be some numerical value divided by he. in this case it will be       419.1/he

     

    btw, I can't open it because I think the mathcad I have is the 2020 version. Can you just post a screenshot so I can see how you did it?

    L
    LucMeekes23-Emerald IV
    23-Emerald IV
    April 6, 2021

    Here is Fred's file for Prime 6

     

    Success!
    Luc

      L
      LucMeekes23-Emerald IV
      23-Emerald IV
      April 6, 2021

      LucMeekes_0-1617712559558.png

      NOTE that the symbolic processor doesn't 'know' units. It usually treats them as undefined variables. You can set an option such that can better deal with units: Look under Calculation -> Calculation options.

      Take heed of Fred's advice. And the following: If you want to work with symbolics, set up your equations and any solve(s) purely symbolic; best in the form of functions with parameters. That is: WITHOUT filling in any numbers.

      Once you have the desired symbolic outcome (in the form of a function), you can fill in the (numerical values of) the parameters to obtain a numeric answer.

      So instead of:

      LucMeekes_2-1617713460856.png

       

      you do:

      LucMeekes_1-1617713389580.png

       

      Success!
      Luc

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