求助：三维六面体试件热应力分析出错，如何解决

xukyle

一三维六面体试件，尺寸30mm×10mm×10mm，顶底面位移固定，底面温度200度，顶面温度20度，求在试件内部产生的热应力。下面是我的apdl流程文件，出现错误信息：Large negative pivot value(-0.458137512) in Eqn.system.
May be because of a bad temperature-dependent material property used in the model.   请教各位高手，该如何解决？我的Email地址：xukyle@163.com.

/BATCH  
finish
/clear
/PREP7  
!*  
ET,1,SOLID70
MP,KXX,1,5
BLOCK,0,30,0,10,0,10,   

/RGB,INDEX,100,100,100, 0   
/RGB,INDEX, 80, 80, 80,13   
/RGB,INDEX, 60, 60, 60,14   
/RGB,INDEX, 0, 0, 0,15   

Lsel,s,line,,1,3,2  
LESIZE,all, , ,10   
Lsel,s,line,,6,10,2
LESIZE,all, , ,10   
Lsel,s,line,,11,12,1
LESIZE,all, , ,10   
Lsel,s,line,,2,4,2  
LESIZE,all, , ,30   
Lsel,s,line,,5,7,2  
LESIZE,all, , ,30   
vmesh,1   
FINISH  

/solu
antype,static
asel,s,area,,5
nsla,s,0
d,all,temp,200
lsel,s,line,,1
nsll,s,1
d,all,temp,200
lsel,s,line,,12
nsll,s,1
d,all,temp,200
lsel,s,line,,8,9
nsll,s,1
d,all,temp,200

asel,s,area,,6
nsla,s,0
d,all,temp,20
lsel,s,line,,3,6,3
nsll,s,1
d,all,temp,20
lsel,s,line,,10,11,1
nsll,s,1
d,all,temp,20

allsel
Outpr,basic,all
solve
finish

/post1
set,last
plnsol,temp
finish

/PREP7  
ETCHG,TTS   

MP,EX,1,5e10
MP,PRXY,1,0.25   
MP,ALPX,1,5e-6

asel,s,area,,5
nsla,s,1
cp,8,ux,all
asel,s,area,,6
nsla,s,1
cp,9,ux,all
allsel
finish
  
/SOL
!*  
ANTYPE,0
asel,s,area,,5,6
nsla,s,1
d,all,ux,0
LDREAD,TEMP,,, ,,,rth
allsel
solve
finish

fishernet

怎么没有定义热容呢，定义一下再算吧