为什么virtual topology 不能用了

sherryrui

照着书做的一个实例，是模拟一辆小车向前行驶。
最后求解失败，自己解决不了。
因为轮子的外表面是由两个半圆面组成，所以想把它们合成一个面，但是virtual topology 却变灰不能用了。请问是什么原因？


下面附上错误信息：（求解失败的原因）
Error: The solver engine was unable to converge on a solution for the nonlinear problem as constrained.  Please see the Troubleshooting section of the Help System for more information.
Warning: The solution failed to solve completely at all time points. Restart points are available to continue the analysis.
Warning: The unconverged solution (identified as Substep 999999) is output for analysis debug purposes. Results at this time should not be used for any other purpose.
Warning: One or more MPC contact regions or remote boundary conditions may have conflicts with other applied boundary conditions or other contact regions. Tip: You can graphically display FE Connections from the Solution Information Object. Refer to Troubleshooting in the Help System for more details.
Warning: Although the solution failed to solve completely at all time points, partial results at some points have been able to be solved.  Refer to Troubleshooting in the Help System for more details.