求助！！紧急！！加入几何非线性时出错（不收敛）

shalujin

小弟最近在做一个瞬态动力学分析，应用了大质量法，我把载荷都加在了大质量节点上（即命令流中的9404，这个大质量节点与结构基底刚性连接），求解时总是出现error提示如下：
One or more elements have become highly distorted.  Excessive           
distortion of elements is usually a symptom indicating the need for     
corrective action elsewhere.  Try incrementing the load more slowly     
(increase the number of substeps or decrease the time step size).  You  
may need to improve your mesh to obtain elements with better aspect     
ratios.  Also consider the behavior of materials, contact pairs,        
and/or constraint equations.  If this message appears in the first      
iteration of first substep, be sure to perform element shape checking
模型中我采用的是solid45单元，我一直尝试修改，加密了网格，也增加了载荷子步数，可是仍出现相同问题，希望大家指点一下，我的命令流如下
ANTYPE,TRANS
NSUBST,1, , ,1
OUTRES,ALL,1
dampratio=0.3
pi=3.142
freq1=10.996*2*pi
freq2=11.144*2*pi
ALPHAD,2*dampratio*freq1*freq2/(freq1+freq2)
BETAD,2*dampratio/(freq1+freq2)
NSEL,S,LOC,Y
D,ALL,ALL
DDELE,ALL,UY
D,9404,UY
DDELE,9404,ALL
NLGEOM,ON
TM_START=1E-20
TM_END=0.00236
TM_INCR=0.00004
F1=3059700000
freq=1000/4.72
*DO,TM,TM_START,TM_END,TM_INCR
TIME,TM
KBC,0
F,9404,FY,F1*sin(2*pi*freq*TM)
allsel,all
SOLVE
*ENDDO
TIME,0.0024
DELTIM,0.00004
KBC,0
F,9404,FY,0
allsel,all
SOLVE
TIME,0.0504         在这个载荷步中出错但不是第一个子步
DELTIM,0.00005
KBC,0
F,9404,FY,0
allsel,all
SOLVE

16443

提示已经很清楚了啊。
1.Try incrementing the load more slowly     
(increase the number of substeps or decrease the time step size).  
2.You may need to improve your mesh to obtain elements with better aspect     
ratios.
3.  Also consider the behavior of materials, contact pairs,  and/or constraint equations.  
4.If this message appears in the first  iteration of first substep, be sure to perform element shape checking
按照这4个思路去解决。

shalujin

我按照提示增加了载荷子步数，优化了网格都没有用，而且这个提示也不时出现在第一个载荷子步，我现在想问一下约束方程式不适用于大变形也就是说采用了约束方程能不能用几何非线性

shalujin

各位大侠帮帮忙啊