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16-Pearl
June 27, 2011
Question

3 unknowns but only 2 equations: Iterative approach?

  • June 27, 2011
  • 3 replies
  • 10796 views

The problem consists of 3 intervals (m) (they are called steps in the data below because the problem represents a physical glued joint with 3 steps (ie 3 different thicknesses) of length Lstep. The numerical problem I need to solve is finding constant A1 and A2 for each step (knowing a number of inputs). I was provided with the “raw” date for the solved problem and it seems that the constant A1 and A2 were found by an iterative process. For each step with length Lstep an initial (random?) value TR, at right hand end of a step together with the value at the left hand end (TL = T given at x=0) and does an Iterative process to calculate A1 and A2.

There are 3 unknowns but only 2 equations, Is there an easy (built-in!) iterative approach that can be used to find the value of TR, A1 and A2?

Thanks

Regards

JXB

3 replies

1-Visitor
June 27, 2011

The problem is, as you stated, you have 3 unknowns and only two equations. I'm positive that there must be another relationship between the inputs which you haven't included.

Looking at it briefly, I don't think it can be solved with the imformation provided.

Mike

24-Ruby IV
June 27, 2011

Mike Armstrong wrote:

The problem has 3 unknowns and only two equations.

See same task:

http://communities.ptc.com/message/158454

23-Emerald I
June 27, 2011
1-Visitor
June 27, 2011

Your solve block yields results, but they are not the same as the expected results.

Mike

16-Pearl
June 28, 2011

Thanks for that. Could the same be said for the 1st step (segment) as T1=Tinput at x=0.

How does one write this differential equation problem in MathCAD?

Regards

JXB

24-Ruby IV
June 29, 2011

I must use one unknown but 2 equations by solving this task

http://communities.ptc.com/videos/2045

Why!?

See here http://communities.ptc.com/message/164665 this two equations in the Given-Find block!