[Getdp] Linear Elasticity Question

François Henrotte francois.henrotte at uclouvain.be
Sun Mar 15 10:46:54 CET 2020


Le 3 mars 2020 à 11:43, Alberto Sánchez Ramírez <albertosanchezramirez94 at gmail.com<mailto:albertosanchezramirez94 at gmail.com>> a écrit :

Good morning,

I would like to start by thanking you for creating such a great software and distributing it for free.

I intend to use to it perform calculations on linear elasticity.

To illustrate my question, I will use a simple example:

Let's say I want to compute the stress that arises inside a tube when it is subjected to an internal pressure.

I have created the mesh on gmsh by creating two cylinders and substracting them, giving rise to a tube. Then I have defined the inner wall of the tube as a physical surface.

I am following one of the tutorials provided with GetDp, in particular the file wrench2D.pro

When it comes to defining the pressure acting on the surface, the file says:


Integral { [ pressure_x[] , {ux} ];
        In Sur_Force_Mec ; Jacobian Sur ; Integration Gauss_v ; }


Hello Alberto,

You do not give the files of your model, but in principle
you have the function

Normal[] : Computes the normal to the element

which you can use as follows (2D case):


Integral { [ pressure[] * CompX[ Normal[] ]  , {ux} ];
        In Sur_Force_Mec ; Jacobian Sur ; Integration Gauss_v ; }
Integral { [ pressure[] * CompY[ Normal[] ]  , {uy} ];
        In Sur_Force_Mec ; Jacobian Sur ; Integration Gauss_v ; }


Regards,

Fr.


Because in that case the pressure was acting in the x direction. However, in my case, the pressure is not acting in a defined direction, but normally to a surface.

How can I translate this equation to take into account pressures acting normally against a surface with an arbitrary shape?

Do I have to change other parts of the code?

Thanks in advance.

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