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[lll202]

Hi all,

I am brushing off cobwebs after not using Mathcad since last spring and I can't figure out why what I've got isn't working.

I've attached my sheet; basically, I'm trying to use the finite element method to find a stiffness matrix over a length L, where the area is changing from 0 < x < L/4. I need to make a 3x3 matrix involving an area equation (which I've called A1 in my sheet), shape functions (psi), and the material stiffness E (which would just be a variable carried through until the end).

I've read through a couple of other forums and I haven't been able to apply any of this to my particular problem (whatever it is).

Is there something I'm overlooking?

[tselvan]

You can't index a function while defining it. you may consider something like below:

[Werner_E]

First of all it should be K(E,A,L) and not K(E,A0,L), because you have used A as argument when calling function A1 in your integral.

If you want to do it on worksheet level using range variables, you have to use an intermediate variable ("Result" in the attached sheet). Don't mind the error and the fact, that no result is shown when defining that variable. This is due to the numerics which moan about undefined variables. Its all OK when you later assign it a function with the correct variable names AND symbolically evaluate it when you define the function.

Personally I would prefer to get rid of the range variables and let for-loops in a program do the job: