ansys受力分析

各位大侠，我在做分析时遇到了困惑，烦请各位协助，多谢了。
我要做一个弹性材料（一种类似橡胶的有机物）的受力变形分析。发现变形比实际小，而且当压力变大的时候分析就会出错。下面是我的命令流，请大家帮忙看看吧：
finish
/clear
/prep7
ch=500e-6 !width
mh=40e-6 !thickness
ml=8.7E-04 !length
!material characteristics
Et,1,visco107
Mp,EX,1,8e5
Mp,PRXY,1,0.499
K,1,0,0,0
K,2,ch,0,0
K,3,ch,ml,0
K,4,0,ml,0
K,5,0,0,-mh
K,6,ch,0,-mh
K,7,ch,ml,-mh
K,8,0,ml,-mh
v,1,2,3,4,5,6,7,8
!mesh control
/pnum,line,1
Lesize,8,,,20
Lesize,12,,,20
Lesize,6,,,10
Lesize,10,,,10
lsel,s,,,2,4,2
Lesize,all,,,20
lsel,s,,,1,3,2
Lesize,all,,,10
lsel,s,,,5,11,2
Lesize,all,,,5
vmesh,all
finish
/solu
antype,static
NLGEOM,ON
SSTIF,ON
!constrain
NSEL,S,LOC,x,0
D,ALL,all
NSEL,S,LOC,x,ch
D,ALL,all
NSEL,S,LOC,y,0
D,ALL,all
NSEL,S,LOC,y,ml
D,ALL,all
!pressure
NSEL,S,LOC,z,0
ESLN,S,0
SFE,ALL,,PRES,,150000
ALLSEL
solve