Learning Forum

[Md_Salem]

Hi Everyone,

My structure is a cantilever plate (shell element) equipped with 12 piezo patches (solid 226 element with a thickness of 1mm) that are attached to the midplane of the plate shell element.

I try to assign a load of 100 volts to the top surface of all piezo patches and 0 volts to the bottom surface ( which is contacted to the plate ) of them. and carry out harmonic analysis 

I used the next APDL command to do the selection process in Workbench 22R1

NSEL,S,LOC,Z,0.001

CM,top_elec,NODE
CP,1,VOLT,ALL
*GET,N1,NODE,,NUM,MIN
ALLSEL
D,top_elec,VOLT,100

to assign the 100 volt load to the top surface of all piezo patches 

NSEL,S,D,VOLT
NSEL,R,LOC,Z,0

CM,bottom_elec,NODE
CP,2,VOLT,ALL
*GET,N2,NODE,,NUM,MIN
ALLSEL

D,bottom_elec,VOLT,0

to assign the 0 volt load to the top surface of all piezo patches 

Then I did the harmonic analysis and compared the results with those obtained by using the GUI to do the selection process. .... the results were identical for the case of usage of the APDL node selection command for the upper surface only, when trying to use the APDL node selection command for the bottom surface, the results went wrong.

What do you think are the results of this error ?

OR is it possible to select nodes by the selection of the element type ? and how ?

Regards

[Chandra Sekaran]

Not sure why you are first selecting the nodes with VOLT value? You have not applied it yet. I think the "nsel,s,d,volt" is returning zero nodes and so when you do "nsel,r,loc,z,0" you are getting nothing. I would remove the "nsel,s,d,volt" command and just do "nsel,s,loc,z,0"

Also you can do a DLIST to make sure the voltage bc is applied.

NSEL,S,D,VOLT
NSEL,R,LOC,Z,0

CM,bottom_elec,NODE
CP,2,VOLT,ALL
*GET,N2,NODE,,NUM,MIN
ALLSEL

D,bottom_elec,VOLT,0

[Md_Salem]

Hi Chandra,

Thanks for your help,

I tired the next code but unfortunately the results are not the same as in case of using to select those nodes with GUI 

ESEL,S,TYPE,SOLID226
NSEL,R,ELEM

NSEL,R,LOC,Z,0

do you think there is any way to do such selection using APDL command in such case ?

Regards

[Chandra Sekaran]

I may not be understanding the way you have modeled. Why do you need to select nodes belonging to solid226 and then reselect nodes at z=0? Why not just do 'nsel,r,loc,z,0'? Also what is the response in solve.out file? Did you do a DLIST to see what nodes are being constrained?

 

[Md_Salem]

My structure is a plate modelled with the shell element, while the attached piezo patches are simulated with Solid226. So, if I just select the nodes at location z=0 it will take both the lower surface of the piezo patches in addition to all shell elements (plate) nodes

Actually I used the next code to assign 100 volt load to the top surface and do harmonic analysis

ESEL,S,ENAME,226
NSEL,R,LOC,Z,0
D,ALL,VOLT,0

ALLSEL

NSEL,S,LOC,Z,0.001

CM,top_elec,NODE
CP,1,VOLT,ALL

ALLSEL

D,top_elec,VOLT,100

*DIM,Fd
*VREAD,Fd,MODE_F,TXT,C:\Users\MD\Desktop
(F18.10)
*SET,x1,Fd(1,1,1)-0.02
*SET,x2,Fd(1,1,1)+0.02
HROPT,FULL
HROUT,ON
LUMPM,0
EQSLV, ,0,
PSTRES,0
HARFRQ,x1,x2
NSUBST,55
KBC,1

it worked properly compared with GUI results

Regards