Modeling a piezo-brass bimorph

[sdravida123]

Hello,

I am working on FE modeling of a piezo-brass bimorph in ANSYS. The diameter of piezo (25 mm) is smaller than that of brass (35 mm). The electrode covers the entire area of the piezo. The thicknesses of piezo and brass are 0.23 and 0.3 mm repectively and the piezo is poled in thickness direction. The assumption is that piezo is rigidly bonded to brass.

Question 1: How do I apply this assumption in ANSYS.

I have to model the displacement response of the bimorph to a certain input voltage applied, across the thickness of the piezo, with clamped boundary conditions applied to the perimeter of the brass. I chose solid5 (with piezo option) as the element type and assigned it to both piezoelectric and brass. When I run the analysis, the piezo displaced but the brass was stationary.

Question 2: what do I have to do make the brass deform with the piezo?

However, When the diameters of piezo and brass were same and clamped BC was applied to the perimeter, both pizeo and brass did move with each other as expected. Why does it not work with different diameters? when I used VGLUE command before VMESH, I get this error message: "Volume 3 has invalid topology for mapped brick meshing".


Please help. Thank you.

The code is as follows:

/prep7
/title,Normal Deflection of Murata PiezoPlate 7-BB-35-3L0 under 1 Volt potential
/nopr
!
! Set up the model for the piezoelectric element
!
! Material properties for PZT-7
!
ET,1,solid5,3 !DEFINE ELEMENT TYPE WITH PIEZO OPTION
!
! MATERIAL PROPERTIES FOR BRASS
!
mp,DENS,2,8500 ! density of brass
mp,NUXY,2,0.3 !poisson ratio for brass
mp,EX,2,23.0E+10 ! Youngs Modulus of Brass
MP,PERX,2,-3 ! Permittivity of Brass
mp,DENS,3,7800 ! Density, kg/m**3
mp,PERX,3,9.637E-9 ! Permittivity at constant strain, F/m
mp,PERY,3,9.637E-9
mp,PERZ,3,8.305E-9
tb,ANEL,3 ! Anisotropic elastic stiffness, N/m^2
tbdata,1,12.996E10,8.254E10,8.345E10 ! c11,c13,c12
tbdata,7,11.9E10,8.254E10 ! c33,c13
tbdata,12,12.996E10 ! c11
tbdata,16,2.463E10 ! c44
tbdata,19,2.463E10 ! c44
tbdata,21,2.326E10 ! c66
tb,PIEZ,3 ! Piezoelectric stress coefficients, C/m^2
tbdata,2,-10.3372 ! e31
tbdata,5,14.6563 ! e33
tbdata,8,-10.3372 ! e31
tbdata,10,13.5468 ! e15
tbdata,15,13.5468 ! e15

! MODEL DIMENSIONS
RPIEZO=0.0125 ! RADIUS OF PIEZOELECTRIC ELEMENT
RBRASS=0.0175 ! RADIUS OF BRASS
!RELEC=0.0115 ! RADIUS OF ELECTRODE ON PIEZO ELEMENT
TBRASS=0.3E-3 ! THICKNESS OF PIEZO ELEMENT
T = 0.6E-3 !T = TBRASS + TPIEZO ! THICKNESS OF BRASS
RPDIV=25 ! NUM OF DIVISIONS ALONG RADIUS OF PIEZO
RBDIV=35 ! NUM OF DIVISIONS ALONG RADIUS OF BRASS
TPDIV=1 ! NUM OF DIVISIONS ALONG THICKNESS OF PIEZO
TBDIV=1 ! NUM OF DIVISIONS ALONG THICKNESS OF BRASS
ZRO=1E-5 ! DEFINE ZERO FOR KEYPOINT LOCATION
CSYS,1
K,1,ZRO,-5
K,2,RBRASS,-5
K,3,ZRO,-5,TBRASS
K,4,RPIEZO,-5,TBRASS
K,5,RBRASS,-5,TBRASS
K,6,ZRO,-5,T
K,7,RPIEZO,-5,T
KGEN,2,1,7,1,,10
L,1,2
LESIZE,1,,,RBDIV
L,3,4
LESIZE,2,,,RPDIV
L,1,3
LESIZE,3,,,TPDIV
L,4,7
LESIZE,4,,,TBDIV
V,1,2,5,3,8,9,12,10
VATT,2
V,3,4,7,6,10,11,14,13
VSEL,S,VOLU,,2
VATT,3
VSEL,ALL
MSHK,1
MSHA,0,3D
!ESIZE,,RBDIV
SHPP,OFF
!
VGLUE,ALL
VMESH,ALL
!
NSEL,S,LOC,Y,-5
DSYM,SYMM,Y,1
NSEL,S,LOC,Y,5
DSYM,SYMM,Y,1
NSEL,S,LOC,X,0,1E-5
DSYM,SYMM,X,1
!
! APPLY BOUNDARY CONDITIONS AND LOADS TO THE PIEZOELECTRIC TRANSDUCER
!
NSEL,S,LOC,Z,TBRASS
CP,1,VOLT,ALL
*GET,N_BOT,NODE,,NUM,MIN
D,N_BOT,VOLT,0
NSEL,S,LOC,Z,T
CP,2,VOLT,ALL
*GET,N_TOP,NODE,,NUM,MIN
D,N_TOP,VOLT,100
NSEL,S,LOC,X,RBRASS
D,ALL,UX,0,,,,UZ,ROTX
ASEL,S,AREA,9
NSLA,S,0
D,ALL,UX,0,,,,UZ
NSEL,ALL
FINI
!
/SOLU
ANTYPE,STATIC
SOLVE

 

[meshparts]

Hi,

I suppose the two deferent material properties that you assign with VATT are getting lost after VGLUE. You must use VATT after VGLUE. That's my guess. This could not be all, since I dit not run youre code in Ansys.

Good luck!

Alex

 

[nodalDOF]

Ans1. Best thing to do is to use some kind of contact between two volumes with option always bonded..

Ans2. I think you need to partition your volumes at the glued region. Otherwise Vmesh fails as there may an extra area at the glued region though you have one single voume. Now its a 7 area volume that ansys cant understand.

Mphys.