【求助】LS-DYNA如何对刚体施加重力加速度？

关键字*load body，具体参数设置看手册 需要注意的是 重力加速度的方向不要搞错了。

以下是我写的一个简单例子，为一个弹簧系统在简支梁上运动，因为不会加重力加速度，所以用重力等效的力来代替，不知道可否？但是，有点问题，那个力貌似没加上去，还望大神帮忙看看哪里出问题了，谢谢！
FINISH
/CLEAR
/CONFIG,NRES,2000 !max子步骤
/PREP7
LB=25 !梁长
NE=50 !单元
NN=NE+1
NN1=NN+1
NE1=NE+1
P=56350 !荷载
V=27.78 !速度
DELTL=LB/NE
DELTT=DELTL/V
EM=2.87E9
AREA=1
IM=2.9
DENG=2303
GRA=9.8
F1=ACOS(-1)/2/LB/LB*SQRT(EM*IM/(AREA*DENG)) !自振频率
ET,1,BEAM161
KEYOPT,1,4,0
KEYOPT,1,1,2
ET,2,SOLID164
ET,3,COMBI165
KEYOPT,3,1,0
TB,DISC,3,,,0, !线性弹簧
TBDAT,1,1595E3 !弹簧刚度
R,3
MP,EX,1,EM
MP,NUXY,1,0.2
MP,DENS,1,DENG
*SET,_RC_SET,1,
R,1
RMODIF,1,8,AREA,IM,IM,IM,1
EDMP,RIGI,2,4,5
MP,DENS,2,P/GRA/(0.1*0.1*3.1415926*0.2)
MP,EX,2,210e9
MP,NUXY,2,0.2
EDMP,RIGI,4,4,5
MP,DENS,4,1
MP,EX,4,210e9
MP,NUXY,4,0.2
!********************梁
TYPE,1
MAT,1
REAL,1
*DO,I,1,2
K,I,(I-1)*DELTL
*ENDDO
L,1,2
K,3,LB/NE/2,2
LATT,1,1,1,,3
LESIZE,1,,,1
LMESH,1
EGEN,NE,10000,all, , , , , , , ,DELTL
NUMMRG,ELEM, , , ,LOW
NUMMRG,NODE, , , ,LOW
NUMMRG,KP, , , ,LOW
NUMCMP,NODE
NUMCMP,ELEM
NUMCMP,KP
ALLSEL,ALL
nsel,s,loc,y,0
cm,mass,nodes
ALLSEL,ALL
!********************轮子
k,,0,0.1,0
kwpave,4
CSYS,4
CYLIND,0.1,0,-0.1,0.1,0,360,
TYPE,2
MAT,2
REAL,2
esize,0.05
mshkey,1 !映射划分网格
VSEL,s , , , 1
wprota,,90
vsbw,all !坐标系平面切割体
wprota,,-90,90
vsbw,all
VSWEEP,all
wpcsys,-1,0
!*********************上面质量块
block,-0.1,0.1,0.5,0.7,-0.1,0.1
type,2
real,4
mat,4
vsel,s,loc,y,0.5,0.7
wpoffs,,0.4
vsbw,all
lsel,s,loc,y,0.5,0.7
lesize,all,0.05
vmesh,all
allsel,all
wpcsys,-1,0
!***********弹簧
TYPE,3
MAT,3
REAL,3
E,NODE(0,0.1,0),NODE(0,0.5,0)
!D,1,UX
!D,1,UY
!D,2*NE,UY
D,1, , , , , ,UX,UY,UZ, , ,
D,2*NE, , , , , ,,UY,UZ, , ,
nsel,s,loc,x,LB/2
cm,nod1,node
!******************************************************** 定义接触
EDPART,CREATE
EDCGEN,ANTS,MASS,2, !定义接触参数，自动点面接触，轨道和轮接触
!EDCGEN,AG, , ,0,0,0,0,0, , , , ,0,10000000,0,0
EDCONTACT,0.1 ,1 , 2, 0, 1, 1, 1, 4, 0 !定义接触面控制
!**************
*DIM,vtime,ARRAY,400,1,1 !定义矩阵
*VFILL,vtime, RAMP,0,LB/V/400 !填充矩阵
*DIM,RBVX,ARRAY,400,1,1
*VFILL,RBVX, RAMP,V,0
*DIM,RBFY1,ARRAY,400,1,1
*VFILL,RBFY1, RAMP,P,0
*DIM,gy,ARRAY,400,1,1
*VFILL,gy, RAMP,GRA,0
!********* 定义速度和力
EDLOAD,ADD,RBFY,0,2,VTIME,RBFY1, 0, , -1, , ,
EDLOAD,ADD,RBVX,0,2,VTIME,RBVX, 0, , , , ,
EDLOAD,ADD,RBVX,0,3,VTIME,RBVX, 0, , , , ,
!edload,add,acly,0,mass,vtime,gy,0,,,,,
FINISH
/SOL
TIME,LB/V+5/F1
EDRST,100, !输出间隔步数
EDHTIME,1000, !输出到时程函数文件的间隔步数
EDENERGY,1,1,1,1 !定义能量耗散控制
EDHIST,nod1
EDOUT,SPCFORC
EDOUT,RCFORC
EDOUT,NCFORC
EDMP,HGLS,2,4,0.145,1.5,0.06, , , !定义材料动力属性
edcts,0,0.6
allsel
SOLVE
finish
!/solu
!edwrite,lsdyna,'111','k'
!FINISH
/POST26
NC=NODE(LB/2,0,0)
NSOL,2,NC,U,Y
PLVAR,2