Piezoresistive effect and change in resistance due to loading
Piezoresistive effect and change in resistance due to loading
(OP)
Dear all,
For a small project I am trying to simulate the change of resistance due to loading of a material. However, I am facing some issues. Following different test cases from the ANSYS help, I successfully obtained the change of resistance due to the piezoresistive effect. When I try to isolate (comment out the piezoresistive properties) the change of resistance due to the simple change of geometry caused by loading, I do not see any differences in resistance.
I think that the problem is coming from the fact that a first analysis should be performed to obtain the strain/stresses and a second to identify the electrical resistance.
dR/R = epsilon*[1+2*nu] + droh/roh
where epsilon is the strain, nu is Poisson's ratio, droh/roh the piezo resistive effect.
Thank you for your interest,
Cédric
For a small project I am trying to simulate the change of resistance due to loading of a material. However, I am facing some issues. Following different test cases from the ANSYS help, I successfully obtained the change of resistance due to the piezoresistive effect. When I try to isolate (comment out the piezoresistive properties) the change of resistance due to the simple change of geometry caused by loading, I do not see any differences in resistance.
I think that the problem is coming from the fact that a first analysis should be performed to obtain the strain/stresses and a second to identify the electrical resistance.
dR/R = epsilon*[1+2*nu] + droh/roh
where epsilon is the strain, nu is Poisson's ratio, droh/roh the piezo resistive effect.
Thank you for your interest,
Cédric
CODE --> APDL
FINISH /CLEAR /FILNAME,resistance,1 /RGB,INDEX,100,100,100,0 /RGB,INDEX,80,80,80,13 /RGB,INDEX,60,60,60,14 /RGB,INDEX,0,0,0,15 /PREP7 A=0.5 L=100 W=10 elsize=5 P=1000 E=165e3 nu=0.25 !Resistivity (p-type Si), TOhm*um rho=7.8e-8 !Piezoresistive coefficients (p-type Si), (MPa)^1 p11=6.5e-5 p12=-1.1e-5 p44=138.1e-5 ET,1,PLANE223,101 ! piezoresistive element type MAT,1 MP,EX,1,%E% MP,PRXY,1,%nu% MP,RSVX,1,%rho% ! piezoresistive stress matrix !TB,PZRS,1 !TBDATA,1,p11,p12,p12 !TBDATA,7,p12,p11,p12 !TBDATA,13,p12,p12,p11 !TBDATA,22,p44 RECTNG,0,%L%,0,%W% TYPE,1 ESIZE,%elsize% MSHAPE,1,2-D AMESH,1 ! Left voltage NSEL,S,LOC,X,0 CP,1,VOLT,all F,ALL,AMPS,%A% SF,ALL,PRES,%P% *get,nl,node,0,num,min ! get master node *get,nb,node,0,COUNT ! get node count ! Right voltage NSEL,S,LOC,X,%L% CP,2,VOLT,all D,ALL,UX,0, , , ,UY D,ALL,VOLT,0 ! ground right electrode *get,nr,node,0,num,min ! get master node ALLSEL,ALL /PBC,u,,1 /PBC,volt,,1 /PBC,cp,,1 /PNUM,TYPE,1 /NUMBER,1 EPLOT FINI /SOLU ! Solution antype,static cnvtol,amps,1,1.e-3 ! Optional to prevent a warning message solve fini /POST1 /com, /com, Results: /com, Res = %abs(volt(nl)-volt(nr))/(A*nb)% Ohm /com, ResOri = %rho*L/W% Ohm fini




