polar coordinate system

drudland

I'm new to Mecway and trying to analyze a pipe with corrosion. I would like to define displacements, constraints (no circumferential displacement allowed) and output stresses in polar coordinates (radial, circumferential stress). Is that possible?

disla

Hi Drudland,

Welcome.
Yes , you can do it .
There are many references on the forum about it.

Imposing the radial and circumferential displacement boundary condition is the only tricky part.

You need to impose the displacement to each node on the stiffener in the radial direction as (x,y,0) and (-y,x,0) for circumferential direction.

To get the stresses in cylindrical go to stress in element coordinates or use cylindrical directly

Find a file you can run and test in Mecway. Its is made with shell elements .

Regards.

drudland

Thanks, so if I understand correctly, for solid elements, the formulas are needed for stresses in the radial and circumferential directions? Is that what you mean by "use cylindrical directly"?

disla

Formulas for BC in shells and solids are essentially the same.
By "cylindrical directly" I mean that there is formulation already developed to see the results in cylindrical coordinates without having to transform anything. Just put the pipe centered and aligned with the Y axis load the formulas. The GUI will display Hoop Stress, Longituinal and radial stresses.


10.7.2 Cylindrical coordinate system

The files DisplacementCylindrical.liml and StressCylindrical.liml in the samples folder contain formulas which transform the displacement and stress fields of a solution into cylindrical coordinates.

Manual page 79.

DRQ

Hi,
I might be too late to help with this but I stumbled across this post because I'd been having some issues with cylindrical coordinates.
I realised that I'd aligned things differently to how the DisplacementCylindrical.liml and StressCylindrical.liml are set up, and it looks like others might be in danger of making the same error.

10.7.2 Cylindrical coordinate system
The files DisplacementCylindrical.liml and StressCylindrical.liml in the samples folder contain formulas which transform the displacement and stress fields of a solution into cylindrical coordinates with Z as the axis of symmetry. You can use File → Import... to add these formulas to an existing model.

(emphasis has been changed here, see page 84 of manual for 14.0 or page 79 of manual for 13.1).
Y is the axis of symmetry when doing a 2D axisymmetric model but the formulae for 3D models in DisplacementCylindrical.liml and StressCylindrical.liml are, as I understand it, based on using Z as the central axis of the cylindrical coordinate system.
I realise that the earlier posts may have been referring to different formulae but I thought I'd add this in case it helps anyone else.