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Units in matrix for FEM analysis

mrotne
1-Newbie

Units in matrix for FEM analysis

Hi

I am wondering wether or not you can calculate FEM matrixes with units, does anyone have any experience with that?

The main issue I am stuck at is when you need to take the inverse of a matrix with mixed units, then you'll get into trouble...

Would be really sweet if you could calculate them with units though any ideas on how to?

I have attached a file example

Best regards

Martin

6 REPLIES 6
-MFra-
21-Topaz I
(To:mrotne)

Hi Martin,

the quantity A is not defined so mathcad consider it a unit of measurement (Amps)

A not defined.jpg

inagi
1-Newbie
(To:mrotne)

You can use matrices with mixed units & solve in Mathcad Prime 3.1 but not in Mathcad 15 & lower versions. Here in the below image you can see that there are two different sub matrices of 500x100 in a matrix "sumotho" one of which is unit less & other has a unit of kg*m^2

mixed units.jpg

LucMeekes
23-Emerald I
(To:mrotne)

There's no problem of having, even different, units in a matrix that you want to take the inverse of. You have to abide by the rules.

So either all elements must have the same units (and then it should work in Mathcad 15 and below as well) or the units should be the same in each row, or in each column.

Apparently in your setup you've introduced some units problem. Look at what F.M. posted, and correct the error it indicates, and possibly more until Mupdate is defined instead of having errors in there.

Success!
Luc

You are correct Luc, however Mathcad 15 & lower versions do not have this particular feature. For matrix calculations in these versions, you need to have all the elements with same units. This was the only reason we moved from version 14 to Prime 3.1.

LucMeekes
23-Emerald I
(To:inagi)

"need to have all the elements with same units":

That's what I said: "must have the same units (and then it should work in Mathcad 15 and below as well)"

Mathcad 11:

"This was the only reason we moved from version 14 to Prime 3.1.":

It is one of the few advantages of Prime over Mathcad.

Luc

Fred_Kohlhepp
23-Emerald I
(To:mrotne)

Mathcad Prime, unlike the older versions (15 and before) will allow matrices with mixed units.

So Prime will allow you to create a matrix with mixed units.  Whether it has the horsepower to do your calculation may be another matter . . .

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