Contact’s New Keyoption 6
by Rod Scholl
In ANSYS 10.0, a new keyoption was added for the 17X contact elements. As you recall from a previous article, setting Keyopt 10=1 or 2 improved convergence by as much as 10 times over the default setting of 0.
In evaluating the new keyoption, our brief and pretty much unscientific tests of Keyopt6=1 or 2 determine that this new keyoption should give you another factor of 2 reduction in required iterations over the advantage gained from Keyopt 10 = 1 or 2. Keyoption 7 = 1 or more should help further, but it was hard to test, because convergence was so fast for our test cases! But as luck would have it, our actual analyses will need everything we can throw at them.
We also tested out the new real constant FKOP option of damping. By entering a negative value (positive values are ignored), a damping term on any contact motion/separation reduces chattering and likelihood of rigid body motion and subsequent pass-through of surfaces. With our tests, the FKOP damping wasn’t able to completely eliminate the need for displacement-controlled contact methodology for surfaces separated beyond the pinball region. However, for regions within the pinball region, force-controlled problems were very stable in our tests!
Below is a table of the runs of some of our test cases. The three cases in red are the default settings and exemplify the impact of turning on Keyoption 10 and Keyopt 6.
But there’s more to learn here. Notice that macro tcont3d saw no improvement with any setting, so you might encounter the same. Further, cases with the macro Tcontblock with Keyopt 6 and 7 turned on doubled the required iterations! Thus, in some cases, especially those that are already stable, don’t turn the Keyopts 6 and 7 on — only use it if needed. We’ve almost never seen a slow down with Keyopt 10=1, and I use it for nearly every contact problem I encounter.
Maybe toy with the macros yourself with setups most similar to your own industry.
• tcont2d.mac • tcont3d.mac • tcontblock.mac •
Macro Name |
D or F Controlled |
Convergence Norm |
keyopt 10 |
keyopt 6 |
keyopt 7 |
Iterations |
| Tcont2d | D | F | 0 | 0 | 0 | 48 |
| Tcont2d | D | F | 1 | 0 | 0 | 31 |
| Tcont2d | D | F | 1 | 1 | 0 | 25 |
| Tcont2d | D | U | 0 | 0 | 0 | 64 |
| Tcont2d | D | U | 1 | 0 | 0 | 33 |
| Tcont2d | D | F | 1 | 2 | 0 | 25 |
| Tcont2d | F | U | 0 | 0 | 0 | 201 |
| Tcont2d | F | U | 1 | 0 | 0 | 200 |
| Tcont2d | F | F | 0 | 0 | 0 | 66 |
| Tcont2d | F | F | 1 | 0 | 0 | 58 |
| Tcont2d | F | F | 1 | 1 | 0 | 24 |
| Tcont2d | F | F | 1 | 2 | 0 | 24 |
| Tcont2d | D | F | 1 | 1 | 0 | 25 |
| Tcont2d | D | F | 1 | 2 | 0 | 25 |
| Tcont2d | F | F | 1 | 1 | 0 | 23 |
| Tcont3d | D | F | 1 | 0 | 0 | 57 |
| Tcont3d | D | F | 1 | 1 | 0 | 57 |
| Tcont3d | D | F | 1 | 2 | 0 | 57 |
| Tcont3d | D | F | 1 | 0 | 1 | 57 |
| Tcont3d | D | F | 1 | 0 | 2 | 57 |
| Tcont3d | D | F | 1 | 0 | 3 | 57 |
| Tcont3d | D | F | 1 | 1 | 3 | 57 |
| Tcont3d | D | F | 1 | 2 | 3 | 57 |
| Tcontblock | D | F | 1 | 0 | 0 | 11 |
| Tcontblock | D | F | 1 | 1 | 0 | 24 |
| Tcontblock | D | F | 1 | 2 | 0 | 24 |
| Tcontblock | D | F | 1 | 0 | 1 | 26 |
| Tcontblock | D | F | 1 | 0 | 2 | 26 |
| Tcontblock | D | F | 1 | 0 | 3 | 26 |