Axisymmetry is a type of symmetry about a line. It is best described in terms of a cylindrical coordinate system having its Z axis on the line of symmetry. The structure, loading, and displacements are each said to be axisymmetric about a line if they do not vary with angular position around the line, i.e., they are independent of the angular coordinate CA.
Enforce axisymmetry using the Local Constraint as follows:
Model any cylindrical sector of the structure using any axisymmetric mesh of joints and elements.
Assign each joint a local coordinate system such that local axes 1, 2, and 3 correspond to the coordinate directions +CR, +CA, and +CZ, respectively.
For each axisymmetric set of joints (i.e., having the same coordinates CR and CZ, but different CA), define a Local Constraint using all six degrees of freedom: U1, U2, U3, R1, R2, and R3.
Restrain joints that lie on the line of symmetry so that, at most, only axial translations (U3) and rotations (R3) are permitted.
See Also