Problem with Odesolve in good Old MC15

Forum|Forum|8 years ago
July 11, 2017
2 replies
3628 views

Hi,

I want to calculate a deflection of a beam with Odesolve in MC15.

The deflection consists of two parts: y1(x) and y2(x).

I could solve the y1(x), but when trying to solve y2(x), i got an error-message:

"this variable is not defined"

You can see it near the end of the sheet.

11-07-2017 19-03-41.jpg

The boundary-conditions are: deflection in the bearings are zero, the bending moments as well.

What am i doing wrong here?

Thank you for your help.

ps.: The MC15 File can be uploaded only as a zipped file.

2_Kragtraeger-mit-Streckenlast.rar

Other

Best answer by Werner_E

You can't use the prime symbol (Ableitungsstrich) for the derivative of y1.

I would suggest to define a function for the derivative.

But I don't think that the result is correct. When I look at what the value of the first derivative of y1 at lo (6) is, I sometimes get an error (which I would have suspected at the end of the interval)and sometimes it will (upon recalculation) evaluate to 0.

So I see two options, Either let the first odesolve block up to lo+0.1 (or something like lo*1.01) or you change the initial condition in your second solove block to y2*(lo)=y1_diff(lo-0.1) or something similar.

This gives a more plausible result:

W

Werner_E

Answer

25-Diamond I

You can't use the prime symbol (Ableitungsstrich) for the derivative of y1.

I would suggest to define a function for the derivative.

But I don't think that the result is correct. When I look at what the value of the first derivative of y1 at lo (6) is, I sometimes get an error (which I would have suspected at the end of the interval)and sometimes it will (upon recalculation) evaluate to 0.

So I see two options, Either let the first odesolve block up to lo+0.1 (or something like lo*1.01) or you change the initial condition in your second solove block to y2*(lo)=y1_diff(lo-0.1) or something similar.

This gives a more plausible result: