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Solid5 coupling problem for piezo stack

Solid5 coupling problem for piezo stack

Solid5 coupling problem for piezo stack

(OP)
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?


Quote:


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
 

RE: Solid5 coupling problem for piezo stack

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.

RE: Solid5 coupling problem for piezo stack

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

RE: Solid5 coupling problem for piezo stack

(OP)
Hi,

Thanks for you reply!... It is always better then no reply winky smile
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.

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