几何非线性分析后，怎么提取临界载荷

bluecmy

请问，用弧长法进行完非线性分析后，怎么提取临界载荷，以下是我找到的一个算例（摘自《锅炉结构有限元分析》）。
/com,structural
*set,mat_nonlinear,0
*set,max_defect,0.001
/prep7
et,1,solid95
mptemp,1,0
MPDATA,EX,1,,2e11   
MPDATA,PRXY,1,,.3


!mp,ex,1,2e11
!MP,PRXY,1,.3
cylind,0.4,0.416,0,2,0,360
esize,0.06,0
vsweep,1,,,



/solu
antype,0
da,1,ux,
da,1,uy,
da,2,ux,
da,2,uy,
dk,12,uz
sfa,3,1,pres,1
sfa,4,1,pres,1

allsel
pstres,on
solve
finish

/solu
antype,1
bucopt,subsp,5
subopt,0,0,0,0,0,all
mxpand,5,0,0,0,0.001,
solve
finish


*get,pressure1,mode,1,freq
nsort,u,sum
*get,max_disp_sum,sort,,max
*set,scale_factor,max_defect/max_disp_sum
finish



/prep7
upgeom,scale_factor,last,last,'stove','rst',''
*if,mat_nonlinear,eq,1,then
tb,miso,1,1,3,
tbtemp,0
tbpt,,0,0
tbpt,,0.00125,250e6
tbpt,,0.5,250e6
*endif
finish

/solu
antype,0
sfa,3,1,pres,pressure1
sfa,4,1,pres,pressure1
nlgeom,1
nsubst,10,0,0
arclen,1,4,0.001
outres,all,all
arctrm,l
solve
finish