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L
lferreira1-Visitor
1-Visitor
April 4, 2018
Solved

ODE Illegal context

  • April 4, 2018
  • 4 replies
  • 8911 views

Hello,

 

I am trying to solve a differential equation for a clamped Circular Kirchhoff-Love plate.

 

Why am I getting this error in my displacement function w(r)?

 

 

Best answer by Werner_E

So we can't use w(0)=0 as initial conditions as I did and you need to provide a new fourth condition.

How about w''(0)=0 ?

 

Bild.png

EDIT: I am not into mechanics myself so I am not sure but maybe Chapter 4 here

http://imechanica.org/files/4_Bending%20of%20plates.pdf

can help you to find two reasonable additional initial conditions.

 

4 replies

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
April 4, 2018

Attach please the Mathcad Prime sheet!

L
lferreira1-VisitorAuthor
1-Visitor
April 4, 2018

Sorry, the .prt with the embedded sheet is attached.

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
April 4, 2018

Probably because you're trying to solve a fourth order differential equation

Capture.PNG

L
lferreira1-VisitorAuthor
1-Visitor
April 4, 2018

Oh, so what are the restrictions when trying to solve differential equations?

W
Werner_E25-Diamond I
25-Diamond I
April 4, 2018

I would have expected 4 initial conditions for a fourth order DE, not just 2.

What are the values of q and D?

 

When Valery asked for the sheet he meant the mcdx file so we can open it in Prime. Chances are you will have to zip it first before you can upload it here because of a severe bug in the forum software.

L
LucMeekes23-Emerald IV
23-Emerald IV
April 4, 2018

I get this:

LM_20180404_Ode.png

Too few initial conditions...{also when the second is correctly written as w'(1000)=0}

You must add two (it's a fourth order).

 

I can't open you .prt file.... What are values for q and D ?

 

Luc

-
-MFra-21-Topaz II
21-Topaz II
April 4, 2018

Hi,

I have chosen Adams/BDF,

fourthorder.jpg

L
lferreira1-VisitorAuthor
1-Visitor
April 4, 2018
53 seconds ago

The thing is, when r=0 -> center of the plate in cylindrical coordinates , I don't know the value, in fact, that's the value I will be looking for, because it will be the maximum deflection of the circular plate.

 

What I know is that at the edge of the circular plate (r=1000) my deflection is 0, as well as my angle (clamped)

W
Werner_E25-Diamond IAnswer
25-Diamond I
April 4, 2018

So we can't use w(0)=0 as initial conditions as I did and you need to provide a new fourth condition.

How about w''(0)=0 ?

 

Bild.png

EDIT: I am not into mechanics myself so I am not sure but maybe Chapter 4 here

http://imechanica.org/files/4_Bending%20of%20plates.pdf

can help you to find two reasonable additional initial conditions.

 

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