Learning Forum

[Shian Li]

I need to set the maximum displacement between the two surfaces of the two disc springs to 0.1mm. How should I set this? Thank you so much.

[peteroznewman]

Frictional contact is used to prevent two surfaces from penetrating each other. If you have that and the inner edges of the two disc springs are initially touching, forces or displacements can squeeze the two discs together and the contact will develop out to a larger radius until the outside edge of the two disc springs are touching.

[Shian Li]

I would like to know how to set the two outermost circles of the disc spring. In the direction along the axis, the maximum change in distance is 0.1mm. Is this possible to set? If so, which parameter should be set?

[peteroznewman]

A simple way to model what you want is to select the outer circle of the right side disc and insert a Remote Displacement. Set all six degrees of freedom to be 0.  Assuming the X axis goes left to right, select the outer circle of the left side disc. Set five degrees of freedom to be 0 except for the X displacement which will be 0.1 mm.  Both remote displacements should have the Behavior set to Deformable.

Under Analysis Settings, turn on Auto Time Stepping. Set the Initial Substeps to 10, the Minimum Substeps to 10 and the Maximum Substeps to 100.  Turn Large Deflection to be On.

The simple boundary conditions are not ideal because the loads are going through edges, which have no area, so the stress may be higher than reality. This may also cause excessive element distortion errors.

A realistic model would have two additional bodies, one touching the left side disc and one touching the right side disc. Two additional frictional contacts would be defined between the faces of these new bodies and the opposite faces of the spring discs. In this way, a contact area will develop as the force increases so that the stress may be reduced. The face of the right body would have a Fixed Support, the Face of the left body would have a Remote Displacement with the same settings as the left disc. Edit the Remote Displacement of the left disc and change the X axis to be Free.

The realistic model will take some time to solve and the contact conditions may slow down convergence.

Both the loads and geometry in this model are axisymmetric about the X axis.  Ansys can solve this problem much faster using an axisymmetric analysis. To do that, the axis of symmetry must be along the Y axis. Take a slice in the X-Y plane and keep the cut faces on the +X side of the Y axis. There are only 2 degrees of freedom on each node instead of 3 and many fewer nodes so the solution runs much faster. The contact is now between the edges of the bodies.