bcho
Subscriber

Hi,

For the soil I model the quarter of a sphere with solid186 and add infin257 at the outer surface of the sphere. Additionally I apply a spring-mass-system with combin39 and mass21.

For the static analysis I add a load in z-direction. The transient analysis is done by a loop in time with a sinusodial load or an impulse.

So the model does not change between static and transient except for the analysis type and the load.

I tried the following:
linear + transient --> converges
non-linear + static --> converges
non-linear + transient --> does not converge

I added a picture of step 6 when the calculation does not converge and my APDL commands although I'm not sure if it'll be helpful for you since the comments are in german.

Kind regards,

Bettina Chocholaty

APDL commands:

finish
/clear

/PREP7
Gx=80000000        ! Schubmodul
NUxy=0.33        ! Poisson Zahl
freq=100        ! Frequenz in Hz
rho=2000        ! Dichte
cs=sqrt(Gx/rho)        ! Scherwellengeschwindigkeit
Exx=2*Gx*(1+NUxy)    ! E-Modul
lambda=cs/freq        ! Wellenlänge
le=lambda/8        ! maximale Elementlänge
lnele=(RM+RB)/le        ! Elementanzahl
lneleh=lnele/2
lnelemh=NINT(lneleh)
lnelem=lnelemh*2
!lnelem=48
dt=le/cs        ! Zeitschritt
t=(RM+RB)/cs        ! Ankunftszeitpunkt Welle an Rand von Modell
RGES=RM+RB

ET,1,SOLID186           ! 3D 20 NODE STRUCTURAL SOLID

MP,EX,1,Exx             ! Materialzuweisung
MP,PRXY,1,NUxy
MP,DENS,1,rho

!---Geometrie der Platte                                                         !*!
*SET,H,0.4                       ! Plattenhoehe [m]                                  !*!
*set,r,5/2            ! Halbe Breite/Länge Fundament
*set,ri,3.75/2            ! Halbe innere Breite/Länge Fundament

! MATERIAL
!---Materialdaten der Platte                                                     !*!
rho=0                          ! Dichte der Platte [kg/m^3]                        !*!
nue=0                         ! Querkontraktionszahl der Platte                   !*!
EModul=9710000000              ! E-Modul der Platte [N/m^2]
MP,EX,2,EModul                   ! E-Modul
MP,NUXY,2,nue                    ! Querkontraktionszahl
MP,DENS,2,rho,,,                 ! Dichte

! Angaben für Masseschwinger
m=10000                ! Masse
knl=597000000            ! Fließgrenze-Steifigkeit
Fnl=149000000            ! Fließgrenze-Kraft

K,1
K,2,,RM+T
PCIRC,0,RGES,0,90               ! Kreisfläche
!! für Plattengenerierung
!Pcirc,RM,RM+T/2,0,90
!PCIRC,0,RM,0,90
!Pcirc,RM/2,RM,0,90
VROTAT,all,,,,,,1,2,-90,,       ! Kugelvolumen

allsel
vplot

lsel,inve
lsel,s,length,,RGES
lesize,all,,,lnelem,,1         ! Linienunterteilung nach elementzahl
!lesize,all,le,,,,1        ! Linienunterteilung nach Elementgröße

! Unterteilung der Bogenlinien
Csys,2
lsel,s,loc,x,RGES
lesize,all,,,lnelem,,1        ! Linienunterteilung nach elementzahl
!lesize,all,le,,,,1        ! Linienunterteilung nach Elementgröße

allsel
csys,0

!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!! MASSE-SCHWINGER !!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!! Masse-Fdeder-System
ET,10,COMBIN39,,,,1,,1                ! ELEMENT WITH DISPLACEMENT ALONG NODAL z-AXIS
KEYOPT,10,4,1
ET,11,MASS21,,,0                      ! MASS WITHOUT ROTARY INERTIA
KEYOPT,11,3,2
R,10,-5,-Fnl,-0.5,-Fnl,0.0,0.0  ! SPRING DATA
RMORE,0.5,Fnl,5,Fnl
!R,11,0,0,m,0,0,0                  ! MASS DATA
R,11,m
csys,0
NSEL,All
!NSEL,S,LOC,X,-r+(r-ri)/2
!NSEL,R,LOC,Y,-r+(r-ri)/2
!NSEL,R,LOC,Z,-H
!*GET,n_center1,NODE,,NUM,MIN
!*GET,n_center1,NODE,1,NSEL,,
!NSEL,S,LOC,X,+r-(r-ri)/2
!NSEL,R,LOC,Y,-r+(r-ri)/2
!NSEL,R,LOC,Z,-H
!*GET,n_center2,NODE,,NUM,MIN
!*GET,n_center2,NODE,1,NSEL,,
*GET,knotenanzahl,NODE,,NUM,MAX
N,knotenanzahl+1,+r-(r-ri)/2,+r-(r-ri)/2,-H
NSEL,S,LOC,X,+r-(r-ri)/2
NSEL,R,LOC,Y,+r-(r-ri)/2
NSEL,R,LOC,Z,-H
!*GET,n_center3,NODE,,NUM,MIN
*GET,n_center3,NODE,,NUM,MIN
!*GET,n_center3,NODE,1,NSEL,,
!NSEL,S,LOC,X,-r+(r-ri)/2
!NSEL,R,LOC,Y,+r-(r-ri)/2
!NSEL,R,LOC,Z,-H
!*GET,n_center4,NODE,,NUM,MIN
!*GET,n_center4,NODE,1,NSEL,,

NSEL,all
*GET,n_max,NODE,,NUM,MAX
!N,n_max+1,-r+(r-ri)/2, -r+(r-ri)/2,-5*H
!N,n_max+2,+r-(r-ri)/2, -r+(r-ri)/2,-5*H
N,n_max+3,+r-(r-ri)/2 , +r-(r-ri)/2,-5*H
!N,n_max+4,-r+(r-ri)/2, +r-(r-ri)/2,-5*H
!TYPE,10
!REAL,10
!E,n_center1,n_max+1   !Non-linear spring
!TYPE,11
!REAL,11
!E,n_max+1 !Mass
!nummrg,all

!TYPE,10
!REAL,10
!E,n_center2,n_max+2   !Non-linear spring
!TYPE,11
!REAL,11
!E,n_max+2 !Mass
!nummrg,all

TYPE,10
REAL,10
E,n_center3,n_max+3   !Non-linear spring
TYPE,11
REAL,11
E,n_max+3 !Mass
nummrg,all

!TYPE,10
!REAL,10
!E,n_center4,n_max+4   !Non-linear spring
!TYPE,11
!REAL,11
!E,n_max+4 !Mass
!nummrg,all
NSEL,All
nummrg,nodes
nummrg,all

! Meshing
Mat,1
mshape,0,3D            ! Elementform
vmesh,1

! Infinite Elements oder Feste Auflager
*GET,NMAX,NODE,0,NUM,MAXD
NPOLE=NMAX+1
N,NPOLE

CSYS,2
ASEL,S,loc,x,RGES
NSLA,S,1
EINFIN,,NPOLE                   ! Infinite Elements
!d,all,all            ! Feste Auflager
ALLSEL

! Symmetriebedingungen
CSYS,0
!NSEL,S,LOC,Z,0
!DSYM,SYMM,Z                 ! SYMMETRIC CONSTRAINTS,UZ
ALLSEL,ALL,ALL
NSEL,S,LOC,Y,0
DSYM,SYMM,Y                    ! SYMMETRIC CONSTRAINTS,UY
ALLSEL,ALL,ALL
NSEL,S,LOC,X,0
DSYM,SYMM,X                    ! SYMMETRIC CONSTRAINTS,UX
ALLSEL,ALL,ALL

!shpp,on

!shpp,summ

! Knoten für Last auswählen
NSEL,All
nummrg,nodes

csys,2
!asel,s,loc,x,0,RM
nsel,s,loc,x,0,RM
csys,0
!asel,r,loc,z,0
nsel,r,loc,z,0

allsel

!*DIM,displ,Table,17                                ! Kraftvektor
!*VPLOt,displ(1,0),displ(1,1)

!!! LAST
NSEL,All
nummrg,nodes

*DIM,displ,Table,17                               ! Kraftvektor
*VPLOt,displ(1,0),displ(1,1)

/SOLU
ANTYPE,trans

tend=dt*300
!dt=0.9108e-5
ntime=NINT(tend/dt)+1

!timint,on
!nlgeom,on
EMATWRITE,YES

*do,itime,1,70 !* Beginn der Zeitschleife
zeit=itime*dt            ! Variable 'zeit' definieren
*MSG,WARN, itime, ntime, zeit,
*** Step %I von %I  Zeit %G
TIME,%zeit%            ! Zeit des nächsten Berechnungs-Schrittes
NSUB,10,30,1
SOLCONTROL,On
!NROPT,FULL
!LNSRCH,ON
!CNVTOL,F,,0.05 ! 5% Tolerance
!PRED,on,,on
!NEQIT,500
SOLVE                  ! selbstredend
save
*enddo

!*** ENDE DER ZEITSCHLEIFEN ***

FINISH                   ! Ende des Solution-Prozesses

/EOF