求解器为何自动调整为sparse solver？

a12330752

分析模型为一个小装配体，设置接触，实体单元为solid185和285,185单元选择为增强应变，提交分析出现如下错误：
*** WARNING ***                         CP =     116.906   TIME= 10:08:25
The sparse solver must be used if any current technology elements with  
u-P formulation or MPC184 elements using Lagrangian multiplier are      
included in the model.  The equation solver option has been switched   
to the sparse solver.
我模型里根本没有用u-p和mpc184，为何出现这个警告？请教高手，谢谢