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1-Newbie

## ODEsolve with units - is it possible to solve?

Hello,

I have a problem with odesolve function in my algorithm in mathcad 15. The puprose is to receive deflection (and deflection curve) of statically determinated beam. The only load is prestressed which generates bending moment. According to Clebsch method I'd like to solve this equation in my case:

So I was trying with and without units (You can see it in my file) and I didn't get even one working solution. I'd like to ask You for an advice, because I'm trying to use this function for the first time and I've got no more ideas what should be changed here.

Greetings
Piotr

1 ACCEPTED SOLUTION

Accepted Solutions
24-Ruby V
(To:Werner_E)

I see that Fred was a bit faster than I.

The problem he encountered is due the aforementioned functions missing an otherwise statement (h4, h5, Mp and especially Ics).

Obviously the solver goes beyond the limit of  9 m and then your function(s) will fail.

@Fred: is there a reason you write UnitsOf(m) instead of simply m? is it so it also works in sheets where the default length unit is not meter?

5 REPLIES 5
24-Ruby IV
(To:ps-7)

It is possible in Mathcad Prime.

23-Emerald I
(To:ps-7)

Mathcad 15 cannot deal with units in the ode solvers.  I fixed that with "UnitsOf()" function.

Then I get:

When I trace that error, Mathcad points to the function for Mp.  I don't know why it plots, but Mathcad apparently can't evaluate that function in the solve block.

If I change the range of the solve block:

24-Ruby V
(To:ps-7)

Mathcad 15 and below can't deal with units in a solve block with odesolve. So you would have to chose a unitless approach (just concerning the solve block),

Fred had shown a way how to do it here -> Re: Problem with the solver Odesolve

Furthermore you have defined a couple of functions using various if statements. You should add an "otherwise" statement every time to cope with the cases not covered by your if-statements.

24-Ruby V
(To:Werner_E)

I see that Fred was a bit faster than I.

The problem he encountered is due the aforementioned functions missing an otherwise statement (h4, h5, Mp and especially Ics).

Obviously the solver goes beyond the limit of  9 m and then your function(s) will fail.

@Fred: is there a reason you write UnitsOf(m) instead of simply m? is it so it also works in sheets where the default length unit is not meter?

24-Ruby IV
(To:ps-7)

I do so

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