1、在求有载结构的固有频率时要打开“预应力效应—PSTRES,ON”其步骤如下:
(1)建模及加载;
(2)打开“预应力效应”做静力分析;
(3)打开“预应力效应”做模态分析;
2、源程序修改如下:
(1)未打开“预应力效应”
finish
/clear
/prep7
et,1,beam3
mp,ex,1,2.1e11
mp,prxy,1,0.3
mp,dens,1,7800
r,1,0.06,0.00045,0.3
k,1
k,2,6
l,1,2
lesize,all,,,20
lmesh,all
dk,1,ux,,,,uy
dk,2,uy
fk,1,fx,1e10
fk,2,fx,-1e10
finish
!/solu
!pstres,on
!solve
!finish
/solu
antype,2
!pstres,on
modopt,lanb,3
mxpand,3
solve
finish
/post1
set,list
(2)打开“预应力效应”
finish
/clear
/prep7
et,1,beam3
mp,ex,1,2.1e11
mp,prxy,1,0.3
mp,dens,1,7800
r,1,0.06,0.00045,0.3
k,1
k,2,6
l,1,2
lesize,all,,,20
lmesh,all
dk,1,ux,,,,uy
dk,2,uy
fk,1,fx,1e4
fk,2,fx,-1e4
finish
/solu
pstres,on
solve
finish
/solu
antype,2
pstres,on
modopt,lanb,3
mxpand,3
solve
finish
/post1
set,list
3、结果如下:
打开“预应力效应”时的结果:
1 6.2132
2 24.850
3 55.893
未打开“预应力效应”时的结果:
1 6.2144
2 24.851
3 55.894
结论:轴向压力使结构固有频率降低,轴向拉力使结构固有频率升高。
但是我想问一下:当轴向力很大时,比如1e10N,计算得出的频率很大,这是为什么呢?
[ 本帖最后由 twg2009 于 2010-5-18 22:51 编辑 ] |