Define analytical field in terms of R = f(Th)

[apal21]

Hello,

I know that by default, the analytical fields are of the form Z = f(X,Y), where we only get to input f(X,Y). However, I have a problem in cylindrical coordinates, where I need to input an expression of the form R = f(Th). How do I do this?

 

[FEA way]

Analytical expression fields are by default defined in global coordinate system (XYZ) but you can create local cylindrical CSYS and select it when defining expression field. Then you will be able to build expressions using R,Th,Z coordinates.

 

[apal21]

Sorry, I should have been clearer. I know that I can choose a cylindrical CSYS. But how do I create an expression of the form R = f(Th), or Th= f(R), instead of the default Z = f(R,Th).

 

[FEA way]

If there's an expression that can't be formulated in a way required by Abaqus then you may have to utilize a subroutine instead. What do you want to use this expression for ?

 

[apal21]

I want to impose a sinusoidal BC at the edge of a cylinder. Hence, I need to impose the positions R = A Sin(5 Th), let's say.

 

[FEA way]

The thing is, the formula used in expression field must give magnitude as a result (so that when Abaqus substitutes coordinates of a given node for R,Th and Z parameters used in the formula, it obtains the magnitude of prescribed condition). There is a DISP subroutine that allows you to specify advanced distribution of boundary condition but if you use it, you will have to assign BC magnitude to each node anyway.