help on simply supported cylinder analysis

Hello everyone

I am finding problems in doing static and modal analysis on a simply supported cylinder.
Static case: i apply pressure on the center of the cylinder simply supported at its ends.
modal case: i perform modal calculation on the same cylinder which is simply supported.

If anyone could tell me the boundary conditions i have taken is good or not and why am i getting errors like in matrix is singular etc.. could you please have a look at my two .comm files.I also attach my .med file.

Thanking you in advance

ashraf

Hello kees.

I model the cylinder in salome. First i make a circle and then extrude it to both sides. Later i make a compound with the circle and extrusion. Then i make groups on the compound. I select the two ends and make the group-edges.Also i select the circle i created first and made the group - load.

Is there another possible way to apply the load on a surface especially point load. Because the group will be created in the geometry module but in the mesh module the group on nodes goes missing. Could you please give me some advice to apply this kind of loads.Thank you for your time and help you share with beginners like me.

Cdlt

Ashraf

Also i want to highlight whether my boundary conditions of simply supported shell are correctly specified. Because i have some doubts about them too and am not sure.

Cdlt

Ashraf

Hello Kees.

I have attached the .hdf file for your reference. Yes i had tried the same Bcs for a rectangular plate simply supported on all sides and the results match with the analytical solution. But i dont understand why i dont get the same on a cylinder. Even though i tried applying pressure on the entire surface and tried to solve the problem but i founded the same error.
I encounter problems in finding the natural frequencies too of a simply supported cylinder.

Is it because in plates we use rectilinear cordinate system to apply Bcs where as in cylinders we need to use Cylindrical cordinate system theorotically.

Also i found a reference in the forums too to apply Bcs in cylindrical Cordinate system. here is the link
www.code-aster.org/forum2/viewtopic.php?pid=18957#p18957

I am trying to solve it using that too. Not sure how it would work though. hope you could understand it better.

Regards

Ashraf