[求助]悬臂梁的瞬态动力学分析

本人最近在做一个悬臂梁的瞬态动力学分析，就是让一个悬臂梁收到一个横向的作用力之后自由摆动，但是现在做出来的振幅图谱都是一条直线，不是衰减曲线，求各位大神帮忙，下面是我的命令流。
/PREP7
ET,1,beam188
MP,EX,1,200E9
MP,NUXY,1,0.3
MP,DENS,1,7.85e3
sectyp,1,beam,ctube
secdata,0.025,0.0285
k,1
k,2,,,1.643
l,1,2
TYPE,1
esize,0.001
lmesh,1
finish
/solu
antype,trans
trnopt,full
node1=node(0,0,0)
D,node1,all
TIMINT,off
TIME,0.001
node2=node(0,0,1.643)
d,node2,ux,0.003
NSUBST,10
kbc,1
allsel,all
lswr,1 !
TIMINT,ON
time,1
ddele,node2,all
NSUBST,500
allsel,all
lswr,2
LSSOLVE,1,2
FINISH