Bill Bulat
Ansys Employee

I probably haven't used this command for over twenty years. It's hard to figure out how to use it effectively. As I recall, it is used in conjunction with the now undocumented PHYSICS command. Although undocumented, the PHYSICS command still works at 2022R1 (the most recent release I have tested). DAMORPH is probably not a good way to go if your objective is to simulate pull-in of a capacitively induced MEMS device (e.g., RF switch). For that, I would use coupled field PLANE223 with keyopt(1)=1001 and surface-to-surface contact elements with CNOF (contact normal offset) real constant to prevent complete closure of gaps (which would cause an element formulation error).

If you copy the following APDL into an input file and read that input file into MAPDL, you should have a working example of DAMORPH. Electrostatic and structural analyses are done sequentially (load vector coupling via LDREAD). The electrostatic mesh is then morphed via DAMORPH. A second sequence of electrostatic-then-structural calculations is made with the morphed mesh, and the electrostatic mesh is morphed again.

 

 

fini
/cle
/pnu,mat,1
/num,1
/sys,del *.ph
/sys,del *.png
 
 
C********************************************
C*** PARAMETERS (MKS)
C********************************************
l=0.00075 ! DOMAIN LENGTH
h=0.0002 ! DOMAIN HEIGHT
l_elctrd=0.0005 ! ELECTRODE (BEAM) LENGTH
t_elctrd=0.000005 ! ELECTRODE THICKNESS
gap0=0.00003 ! INITIAL GAP UNDER ELECTRODE
E_elctrd=2e10 ! ELECTRODE ELASTIC MODULUS
V_elctrd=150 ! ELECTRODE VOLTAGE
 
esz1=gap0/2 ! MESH SIZE

 

 
 
C********************************************
C*** GEOMETRY
C********************************************
/prep7
 
asel,none
rect,,l,,h
cm,scrap_a,area
 
asel,none
rect,,l_elctrd,gap0,gap0+t_elctrd
aatt,1,,1
cm,elctrd_a,area
 
alls
cmse,all
asba,scrap_a,elctrd_a,,dele,keep
cmse,u,elctrd_a
aatt,2,,2
cm,air_a,area
 
 
C********************************************
C*** ATTRIBUTES, MESH
C********************************************
et,1,183,1
mp,ex,1,E_elctrd
 
et,2,121
mp,perx,2,1
 
msha,1
alls
esiz,esz1
ames,all
 
 
 
C********************************************
C*** BCs
C********************************************
esel,s,mat,,1
nsle
esel,s,mat,,2
nsle,r
cm,V_elctrd_n,node
 
nsle
nsel,r,loc,x
cm,d_elctrd_n,node
 
nsel,s,loc,y
d,all,volt
alls
cmse,all
d,d_elctrd_n,ux
d,d_elctrd_n,uy
d,V_elctrd_n,volt,V_elctrd
 
esel,s,mat,,2
cmse,s,V_elctrd_n
sf,all,mxwf
 
 
C********************************************
C*** PHYSICS ENVIRONMENTS
C********************************************
alls
save,both,db
 
et,1,0
nlge,off
physics,write,es,es,ph
 
resu,both,db
 
alls
sfede,all,all,mxwf
et,2,0
nlge,on
physics,write,struct,struct,ph
 
fini
 
 
C********************************************
C*** SOLVE
C********************************************
/solu
 
physics,clear ! ELECTROSTATIC SOLVE
physics,read,es,es,ph
solv
fini
/post1
plns,volt 
/sho,png $plns,volt $/sho,close $/wait,2
fini
 
/solu
 
physics,clear ! STRUCTURAL SOLVE
physics,read,struct,struct,ph
asel,s,mat,,1
alls,belo,area
ldread,forc,,,,,file,rth
solv
fini
/post1
plns,u,y,2
/sho,png $plns,u,y,2 $/sho,close $/wait,2
fini
 
 
C********************************************
C*** MORPH ELECTROSTATIC MESH
C********************************************
/prep7
alls
!physics,clear
!physics,read,es,es,ph
ddel,all,all
sfed,all,all,mxwf
et,2,121
asel,s,mat,,2
damorph,air_a !,,1
/edg,1,0
eplo
/sho,png $eplo $/sho,close $/wait,2
fini
 
 
C********************************************
C*** SECOND SOLVE WITH MORPHED MESH
C********************************************
/solu
 
physics,clear ! ELECTROSTATIC SOLVE
physics,read,es,es,ph
solv
fini
/post1
plns,volt
/sho,png $plns,volt $/sho,close $/wait,2
fini
 
/solu
 
physics,clear ! STRUCTURAL SOLVE
physics,read,struct,struct,ph
asel,s,mat,,1
alls,belo,area
ldread,forc,,,,,file,rth
solv
fini
/post1
plns,u,y,2
/sho,png $plns,u,y,2 $/sho,close $/wait,2
fini
 
 
C********************************************
C*** SECOND MORPHING ELECTROSTATIC MESH
C********************************************
/prep7
alls
!physics,clear
!physics,read,es,es,ph
ddel,all,all
sfed,all,all,mxwf
et,2,121
asel,s,mat,,2
damorph,air_a !,,1
/edg,1,0
eplo
/sho,png $eplo $/sho,close $/wait,2
fini
 
 
/eof
 
 
Regards,
 
Bill