Problem Description
A complex transient analysis is performed for a rectangular top plate fixed at two ends with a hole in the center. A voltage is applied to the bottom surface of the top plate for a specified time and the voltage is then set to a release value. The top plate does not make contact with the bottom plate. SOLID185 elements model the top plate. TRANS126 transducer elements are created between the plates. FLUID136 elements model the thin film surface and a FLUID138 element models the hole region. The applied voltage is shown in Figure 3.8: Applied Voltage. Displacement and pressure results at the bottom of the top plate on the circumference of the hole are shown in Figure 3.9: Displacement Time History and Figure 3.10: Pressure Time History.
Results
Command Listing
The input file for this example is shown below.
/batch,list /title, Complex Transient Analysis !/nerr,,,-1 /PREP7 /title, Complex Transient Analysis /com uMKS units ET, 1,136,1 ! 4-node option, High Knudsen Number keyop,1,3,2 !implicit keyop,1,4,0 !compressible keyop,1,5,2 !fluid gap option keyop,1,6,1 !mech gap option et,2,185 ET,3,185 ! Structural element s_l=100 ! Half Plate length (um) s_w=20 ! Plate width s_t=1 ! Plate thickness d_el=2 ! Gap pamb=.1 ! ambient pressure (MPa) visc=18.3e-12 ! viscosity kg/(um)(s) pref=.1 ! Reference pressure (MPa) mfp=64e-3 ! mean free path (um) Knud=mfp/d_el ! Knudsen number mingapf=1e-2 ! Minimum gap for real constanst on element 136 mech_mingapf=1e-2 ! Mechanical minumum gap for real constant on element 136 app_volt=23.281 ! Applied voltage app_pres=0 ! Applied pressure at boundaries mp,visc,1,visc ! Dynamic viscosity gap mp,ex,3,79e+3 ! Gold mp,dens,3,19300e-18 mp,nuxy,3,.1 r,1,d_el,,,pamb ! Real constants - gap rmore,pref,mfp,0,0,1,mech_mingapf rmore,mingapf,1.e+18,0.e-2,-4.e+0,-0.e-2,1.e-0 ! mingapf,penpar,deadpres,deadspr,deaddam,deadeps !top plate block,-s_l,s_l,-s_w,s_w,0,s_t !INSTALL TOP PLATE lsel,s,line,,4,5,1 !Set element depth lsel,a,line,,2,7,5 lesize,all,,,19,-.1 lsel,s,line,,1,8,7 lsel,a,line,,3,6,3 lesize,all,,,11,-.1 lsel,s,line,,9,12,1 lesize,all,,,2 type,3 !Mesh top plate with Gold material mat,3 real,3 !mshape,1,3d mshape,1,3d cyl4,0,0,s_w/50,,,,s_t+1 !Create a hole in top plate vsbv,1,2 numcmp,volu vmesh,1 !hole n,10000,0,0,0 !Specify nodes for hole element (138) n,10001,0,0,s_t et,6,138,1,,0 !Define hole shape r,10,s_w/200,,,pamb, !Define hole diameter and pressures rmore,pref,mfp type,6 real,10 mat,1 e,10000,10001 lsel,s,line,,13,16 nsll,s,1 !Tie top plate hole edge to hole element. nsel,a,node,,10000 cp,next,pres,all d,10001,pres,0 allsel !else emtgen computes INCORRECT areas nsel,s,loc,z,0 cm,trun,node allsel emtgen,'TRUN',,,'uz',-d_el,mingapf*d_el,1.e-18 !Create transducer elements 126 using emtgen !apply gap information !fluid nsel,s,loc,z,0 !Define Fluid region esln,s TYPE, 1 MAT, 1 real,1 esurf !Surface the solid top plate with 136 squeeze film elements nsel,s,loc,x,-s_l nsel,a,loc,x,s_l nsel,a,loc,y,-s_w nsel,a,loc,y,s_w nsel,r,loc,z,-1e-9,1e-9 d,all,pres !Fix pressure at outer plate boundary nsel,all nsel,s,loc,x,-s_l nsel,a,loc,x,s_l d,all,ux d,all,uy d,all,uz allsel nsel,s,loc,z,s_t !Apply pressure at boundary sf,all,pres,app_pres allsel !fix bottom node voltage/disp nsel,s,loc,z,-d_el !Set voltage/displacement at bottom plate d,all,ux !V(bottom)=0V d,all,uy !displacement(bottom)=(0,0,0) d,all,uz d,all,volt allsel !fix top node voltage cmsel,s,trun !Set voltage on top side to applied voltage value d,all,volt,app_volt !for pulldown allsel fini /solu antype,trans !Pulldown stage kbc,1 time,11.e-5 !autots,on !enforce regular timesteps deltim,1.e-5, nsubst,10,1000,2 outres,all,none outres,nsol,2 outres,rsol,2 outres,esol,2 cnvtol,pres,,5.e-6 cnvtol,u ,,5.e-6 nropt,full neqit,500 save solve time,20e-5 nropt,full !Reduce number of equilibrium iterations to save time. neqit,100 outres,all,none outres,nsol,2 outres,rsol,2 outres,esol,2 cnvtol,pres,,5.e-6 cnvtol,u ,,5.e-6 solve cmsel,s,trun !Setup release time d,all,volt,1.5 !Set release voltage across allsel time,20.4e-5 !only limited time here outres,all,none outres,nsol,20 !Long grinding period here, reduce result steps so we don't go outres,rsol,20 !over 1000 results. outres,esol,20 cnvtol,pres,,5.e-6 cnvtol,u ,,5.e-6 cnvtol,pres,,1.e-4 cnvtol,u ,,1.e-4 autots,on !Let Autotimestep run here deltim,.005e-5,0.001e-5,1e-5 !to better capture the overshoot movement on release solve time,30e-5 !After initial snapback, autots,on !increase timestep as overshoot decays. deltim,.5e-5,0.02e-5,1e-5 solve fini /POST1 allsel GG=node(0,-0.4,0) SET,LIST,999 SET,,, ,,, ,30 !* !* PLESOL, NMISC,13, 0,1.0 presol,nmisc,13 /out, fini !*list,closes,lis1 !*list,closes,lis2 /post26 NUMVAR,200 SOLU,191,NCMIT STORE,MERGE FILLDATA,191,,,,1,1 REALVAR,191,191 NSOL,2,GG,U,Z,UZ_2 NSOL,3,GG,PRES,,PRES_3 NSOL,4,GG,VOLT,,VOLT_4 plvar,2 plvar,3 plvar,4 fini