多种压强叠加？

cyh3278

如图：1个6mX3m的板，先对其施加梯度载荷，然后施加5的均布载荷，如图，我用如下命令流会出现问题（红色部分），红色部分要对板施加5的均布载荷，但变成了剃度载荷.
/PREP7
L=6
H=3
YOUNG=210E9
THICKNESS=0.02
FORCE=10E3
DENSITY=7.85E3
/PREP7
MP,EX,1,YOUNG
MP,NUXY,1,0.3
MP,DENS,1,DENSITY
ET,1,SHELL63
R,1,THICKNESS,THICKNESS,THICKNESS,THICKNESS
K,1,0
K,2,L,0
K,3,L,H
K,4,0,H
A,1,2,3,4
LSEL,ALL
!LESIZE,ALL,,,0.05
!AMESH,ALL
LSEL,S,LINE,,1,1
LSEL,A,LINE,,3,3
LESIZE,ALL,,,8
LSEL,S,LINE,,2,2
LSEL,A,LINE,,4,4
LESIZE,ALL,,,4
AMESH,ALL
FINI
/SOLU
Lsel,S,LINE,,2,2
lsel,a,LINE,,4,4
DL,all,,all
*get, ELMAX,elem,,count    !获取单元个数
*DIM,ELEM_X,,ELMAX,1,1
*DO,i,1,ELMAX,1            !获取每个单元X坐标
   *GET,ELEM_X(i),ELEM,i,CENT,X
*ENDDO
ESEL,S,ELEM,,ELMAX, ELMAX
*DO,i,1, ELMAX
   *IF,ELEM_X(i),GE,0.5*L,THEN
      ESEL,A,ELEM,,i,i
   *ENDIF
*ENDDO
SFGRAD,PRES, ,X,0.5*L,10/(0.5*L)     !施加剃度载荷
SFE,all,1,PRES, ,0
allsel
!!!!!!!!!!!!!!!!!!!!    施加均布压强5到板上（此处发生错误，也是剃度载荷，怎么改？）                ！
*DO,i,1,ELMAX,1
   SFCUM,PRES,ADD   !压力叠加
   ESEL,S,ELEM,,i,i
   SFE,all,1,PRES, ,5
   allsel
*ENDDO
!!!!!!!!!!!!!!!!!!!!!!!!!!
allsel
solve

cyh3278

答案找到，将梯度置为0就可以了。
SFGRAD,PRES   !把斜率置零
*DO,i,1,ELMAX,1
   SFCUM,PRES,ADD   !压力叠加
   ESEL,S,ELEM,,i,i
   SFE,all,1,PRES, ,5
   allsel
*ENDDO