Discussion Forum

Hi, I´m trying to model a concact mechanic proble with COMSOL 4.1.

The initial geometry consists on a circle that lies on a rectangle (therefore the concact between the two surfaces is a point) . The circle is much softer that the substratum and tends to bind it (with a certain force). I would like to define an area that sorrounds the boundary of the sphere and the substratum in such a way that all the points that belong to this area become in contact with the force mentioned above.

I attached three files:

1) in the first one you have the geometry that I want to start with.
2) in the second one you have a snapshot that wants just to point out that the initial concact beetween the surfaces is just a point.
3) the third one is approximately what I expect as a solution.


The problem should be dynamic (time dependent) and to do this I would like to define a function that depends on the distance between a point on the sphere and a corrispective point on the rectangle and that has as output a force. This force, applied on each point on the boundaries of the sphere, should approach the sphere to the rectangle.

The volume of the sphere has to reamin constant.


the function has to be a decreasing function of the distance between the surfaces in such a way that points to far away from the rectangle don´t go in concact.

To have feeling on what I´m trying to model I will say that:

the sphere is a cell
the rectangle is a substrate
The substrate has these linear mechanical properties:

Young modulus 14 KPa
Poisson´s ratio 0.49
density 1000 K/m^3

the cell has an hyperelastic behavior, you can use neo Hookean equation (incompressible behavior) to model it with a shear moduls of 1.67 KPa and a bulk modulus 100 times bigger

How should I start to model this, cheers

Giulio