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pfinger1-Visitor
1-Visitor
December 18, 2012
Question

Work arround SUC for Mecanical Engeniering

  • December 18, 2012
  • 4 replies
  • 1281 views

Hi,

i have to do a lot of calulations for differend tasks in the field of "Cutting and Erosion Manufacturing Engineering".

We have to deal with a lot of functions like you can see in the worksheet. I love MathCADs ability to deal with Units, but in this case it can not. Is there a way to work arround this error, or do i have to throw out the Units?

Peter

4 replies

P
ptc-16567211-Visitor
1-Visitor
December 18, 2012

Maybe this:

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
December 18, 2012

Are you sure of you equation? If this is brittle fracture, K1c should be psi x sqrt(inches) or N x sqrt(mm).

A
AndyWesterman12-Amethyst
12-Amethyst
December 18, 2012

Empirical equations of this form are always difficult.

I'm guessing but I doubt that you want results that include fractional exponents. so all of the mm^-0.2 factors must cancel out.

So , possibility 1 is that you write the equations cancelling the rejected portions out & adding corrction factors to account for the difference.

Difficult & prone to error & requires a lot of documentation to ensure that the reasoning does not get forgotten...

The 2nd possible solution is to use the symbolic processor to simplify the equations down & when there are required results convert them back to the numeric processor.

The symbolic engine has a distinct advantage in this case as it does not take account of the units it only sees variables. so no conflict with mm^-1.8.

However you will still need to exercise great care as there may be cases where the units don't cancel correctly.

I've only used this in a couple of circumstances where I know that it always works.

regards

Andy

R
RogerYeh1-Visitor
1-Visitor
December 18, 2012

This is slightly off-topic, but the constant in exponent constraint was lifted in Prime.

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