圆形钢管混凝土扭转 有限元曲线算不下去

采用三维实体单元进行建模，用solid65模拟混凝土，solid45模拟钢材，钢管与混凝土采用“硬”接触，边界条件为一端完全固结，另一端施加节点力。模拟了几个已有试验构件，都模拟的不错，但有一个构件，外径比较大，D=216.3mm 壁厚t=4.5mm, L=1620mm，fy=354.8MPa, fcu=39MPa,弹塑性段算一点点就停了，算不下去，，把力加大，时间历程出现负值，调小只算到弹性段，（钢材采用的四折线本构模型，混凝土采用的考虑套箍作用刘威修正后的核心混凝土本构模型；换成普通混凝土本构后结果也差不多），麻烦各位高手指导下，不胜感激，以下是命令流以及有限元与试验对比曲线

finish
/clear
/filname,C-T
/config,nres,2000
/prep7
es=2.01e11
fy=3.1932e8
fu=4.70e8
ec=5.928E+06/0.000200


L=1.620
t=0.0045
r1=0.10365
r2=r1+t
Wt=3.14*r2*r2*r2/2

MP,EX,1,es
MP,PRXY,1,0.263
TB,MISO,1,1,3, TBPT ,, 0 , 0 ,
TBPT ,, fy/es , fy,
TBPT ,, 10*fy/es, 1.1*fy,
tbplot,miso,1



MP,EX,2,ec
MP,PRXY,2,0.163
TB,MISO,2,1,19,
TBTEMP,0
TBPT,, 0.000000 , 0.000E+00
TBPT,, 0.000200 , 5.928E+06
TBPT,, 0.000400 , 1.123E+07
TBPT,, 0.000600 , 1.591E+07
TBPT,, 0.000800 , 1.997E+07
TBPT,, 0.001000 , 2.340E+07
TBPT,, 0.001200 , 2.621E+07
TBPT,, 0.001400 , 2.839E+07
TBPT,, 0.001600 , 2.995E+07
TBPT,, 0.001800 , 3.089E+07
TBPT,, 0.002000 , 3.120E+07
TBPT,, 0.002200 , 3.048E+07
TBPT,, 0.002400 , 2.976E+07
TBPT,, 0.002600 , 2.904E+07
TBPT,, 0.002800 , 2.832E+07
TBPT,, 0.003000 , 2.760E+07
TBPT,, 0.003200 , 2.688E+07
TBPT,, 0.003400 , 2.616E+07
TBPT,, 0.003600 , 2.544E+07
tbplot,miso,2


/view,1,1,1,1
wprot,0,90
k,1,-0.08,-0.08
k,2,.08,-0.08
k,3,0.08,0.08
k,4,-0.08,0.08
k,5,0,0

k,6,-0.02,-0.02
k,7,.02,-0.02
k,8,0.02,0.02
k,9,-0.02,0.02

wprot,0,-90
cswpla,11,0,1,1
csys,11
CYL4, , ,r1

l,6,1
l,7,2
l,8,3
l,9,4
l,6,7
l,7,8
l,8,9
l,9,6

FLST,3,8,4,ORDE,2
FITEM,3,5
FITEM,3,-12
ASBL, 1,P51X

!!核心混凝土!!!
VOFFST,3,L, ,
VOFFST,4,L, ,
VOFFST,5,L, ,
VOFFST,6,L, ,
VOFFST,2,L, ,

!!外钢管!!!
cyl4,,,r1,0,r2,90,L
cyl4,,,r1,90,r2,180,L
cyl4,,,r1,180,r2,270,L
cyl4,,,r1,270,r2,360,L
nummrg,all


!!面划分网数目!!
lesize,3,,,3
lesize,4,,,3
lesize,31,,,3
lesize,27,,,3
lesize,39,,,3
lesize,40,,,3
lesize,49,,,3
lesize,50,,,3

lesize,1,,,6
lesize,29,,,6
lesize,37,,,6
lesize,47,,,6

lesize,2,,,4
lesize,5,,,4
lesize,28,,,4
lesize,41,,,4

lesize,25,,,20
lesize,26,,,20
lesize,32,,,20
lesize,33,,,20
lesize,45,,,20
lesize,46,,,20
lesize,55,,,20
lesize,8,,,20

lesize,6,,,20
lesize,34,,,20
lesize,42,,,20
lesize,7,,,20

et,1,solid65
type,1
mat,2
vsweep,1
vsweep,2
vsweep,3
vsweep,4
vsweep,5

!!外钢管分网!!!
lesize,73,,,20
lesize,85,,,20
lesize,97,,,20
lesize,74,,,20

lesize,93,,,6
lesize,105,,,6
lesize,69,,,6
lesize,81,,,6

lesize,72,,,1
lesize,94,,,1
lesize,82,,,1
lesize,70,,,1

et,2,shell28
type,2
mat,1
vsweep,6
vsweep,7
vsweep,8
vsweep,9
NUMMRG,NODE, , , ,LOW


!!!!!!!
!!以上模型建立!!!
/view,1,1,1,1
cswpla,12,1,1,1
csys,12
nsel,s,loc,x,r2
nrotat,all
finish

/solu
nsel,s,loc,x,r2
!d,all,ux
nsel,r,loc,z,L !gai
f,all,fy,36500
allsel,all
da,3,all
da,4,all
da,5,all
da,6,all
da,35,all
da,41,all
da,47,all
da,53,all
da,2,all


!!弧长法
antype,static
arclen,on
!arctrm,u,0.2,4713,uy
outres,all,all
nsubst,300,1000,50
allsel,all
solve
finish


!!!!!!!!!!
!!!扭矩-端面转角!!!!
/post26
NSOL,2,3750,U,Y, !!!!3750为中截面边点!!!
prod,4,2,,,torsion angle,,,1/r2*2
prod,3,1,,,torsion moment,,,36500*r2*24/1000
/axlab,x,torsion angle(hudu)
/axlab,y,torsion moment(kN.m)
xvar,4
plvar,3
prvar,4,3
finish


!!!扭矩-中截面剪应变
/post26
NSOL,2,3750,U,Y,
prod,4,2,,,shear strain,,,1/r2*2*r2*1000000
prod,3,1,,,torsion moment,,,38000*r2*24/1000
/axlab,x,shear strain(yb)
/axlab,y,torsion moment(kN.m)
xvar,4
plvar,3
prvar,4,3
finish