Solid5 coupling problem for piezo stack

[trigger01]

Hi Guys,

For my research i want to simulate the total deformation of a piezo stack. For this I use SOLID5 elements.
I manage to successfully simulate the deformation of one piezo element.
If i want to model a stack of piezo element i get into troubles when i apply the VOLT DOF to the elements. Because the elements are stacked they share the same nodes for the Positive VOLT DOF and Ground VOLT DOF (The nodes between Piezo 1 and 2).

(Stack of two piezoelectric elements)

+ -+ -
---------
| 1 | 2 |
| | |
| | |
| | |
---------


Do i have to mesh the two volumes separate and then define the VOLT DOF?

Is there another way to couple the two SOLID5 elements?

FINISH
/CLEAR
!/plopts,info,3 ! Use multi window legend

/com ** ==========================================
/com ** DEFORMATION OF A PIEZOELECTRIC STACK
/com ** BY ...
/com ** ==========================================

!Dimentions one piezo 20*20*2 mm
h_PZt = 20E-3 ! Height of PZt (along y axis)
w_PZt = 20E-3 ! Width of PZt layer (along x axis)
t_PZt = 2E-3 ! Thickness of PZt (along z axis)
n_PZt = 2 ! Number of PZt in Stack


/prep7 ! Enter preprocessor

/title, Total Deformation of a Piezo Stack

/com ** ==========================================
/com ** DEFINE ELEMENT TABLES
/com ** ==========================================

ET,1,solid5,3 ! Element 1: 8-node coupled field solid with all DOFs used for PZt

/com ** ==========================================
/com ** PZ26 PIEZO ELEMENT Z-POLARIZED MAT PROP
/com ** ==========================================
/com
/com ** ==========================================
/com ** STIFFNESS
/com ** ==========================================
TB, ANEL, 1 , 1 , 0
TBDATA, 1, 1.6800E+11 , 1.1035E+11 , 9.9905E+10
TBDATA, 7, 1.6800E+11 , 9.9905E+10
TBDATA, 12, 1.2264E+11
TBDATA, 16, 2.8825E+10
TBDATA, 19, 3.0126E+10
TBDATA, 21, 3.0126E+10

/com ** ==========================================
/com ** PIEZO MATRIX
/com ** ==========================================
TB, PIEZ, 1
TBDATA, 3, -2.8012
TBDATA, 6, -2.8012
TBDATA, 9, 14.6913
TBDATA, 14, 9.8568
TBDATA, 16, 9.8568

/com ** ==========================================
/com ** PERMITTIVITY
/com ** ==========================================
EMUNIT, EPZRO, 8.85E-12
MP, PERX, 1 , 829
MP, PERY, 1 , 829
MP, PERZ, 1 , 701

/com ** ==========================================
/com ** DENSITY
/com ** ==========================================
MP, DENS, 1 , 7.70E+003

/com ** ==========================================
/com ** DEFINE GEOMETRY
/com ** ==========================================

z = 0
*DO,I,1,n_PZt ! Repeat for each actuator
BLOCK,x,x+w_PZt,y,y+h_PZt,z,z+t_PZt
z = z+t_PZt
*ENDDO

/PNUM,Volu,1 ! turn on numbering and colours for material types

VSEL,S,VOLU,,1 ! Select volume 1
TYPE,1 ! Use element table type 1 for meshing
MAT,1 ! Use material 1 attributes for meshing
VMESH,ALL ! Mesh

VSEL,S,VOLU,,2 ! Select volume 2
TYPE,1 ! Use element table type 1 for meshing
MAT,1 ! Use material 1 attributes for meshing
VMESH,ALL ! Mesh

VSEL,ALL

NSEL,S,LOC,Z,0
CM,t_elec,NODE ! Top electrode node component
CP,1,VOLT,ALL ! Couples volt DOF on top electrode

Thanks!

Christian

 

[saikin84]

Hi.
Probably the "7.13 Sample Piezoelectric Analysis" from "Coupled-Field Analysis Guide" would help. Especially the part where they set up the local coordinate systems.

 

[saikin84]

Oh, I am so inattentive. Please excuse me for the previous post.

 

[trigger01]

Hi,

Thanks for you reply!... It is always better then no reply ;-)
I solved the problem by making the model more accurate... I added a top and bottom nickel electrode and a Epoxy layer to add the components together...

Cheers.