ElectroMechanical Transducer Permittivity in ANSYS Mechanical
EM Transducer is a boundary condition commonly used in the simulations of MEMS devices. Workbench users can download the Piezo & MEMS ACT module from the ANSYS Customer portal to gain access to EM transduce capabilities. EM Transducer automatically generates TRANS126 elements in Workbench based on the EMTGEN APDL command.
The EM Transducer object uses permittivity of Air as a default and does not allow users to define their own permittivity. If a user wants to define a custom permittivity, they can create an APDL command object that updates the 7th real constant of the generated TRANS126 elements. See the sample code below:
!!! EXAMPLE APDL CODE !!!
epsr=ARG1 ! USED TO DEFINE THE RELATIVE PERMITTIVITY
! IN THE DETAILS OF THE COMMAND FILE
fini ! LEAVE THE SOLUTION PROCESSOR
fini ! LEAVE THE SOLUTION PROCESSOR
/prep7
esel,s,ename,,126
*get,nelems,elem,,count ! nelems = NUMBER OF THESE ELEMENTS
elm=0 ! INITIALIZE ELEMENT NUMBER
*do,i,1,nelems elm=elnext(elm) ! elm = NEXT HIGHEST ELEMENT NUMBER
*get,rnum,elem,elm,attr,real ! rnum = REAL CONSTANT ID # ASSIGNED TO ELEMENT elm
*get,r7,rcon,rnum,const,7 ! r7 = VALUE OF 7th REAL CONSTANT IN REAL CONSTANT SET #rnum
r7_new=epsr*r7 ! MODIFIED VALUE TO SUBSTITUTE FOR ORIGINAL VALUE
rmod,rnum,7,r7_new ! MODIFY THE 7th REAL OF REAL CONSTANT SET ID #rnum
*enddo
fini ! LEAVE PREP7
/solu ! REENTER THE SOLUTION PROCESSOR
/solu ! REENTER THE SOLUTION PROCESSOR
alls
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