Hello,
I am experiencing an issue with the following APDL code. The crack does not propagate as expected.
Could someone help me identify what might be causing this behavior?
I have tried several approaches, including modifying the time stepping, DAMX, and convergence tolerances, but unfortunately without success.
Thank you
/FILENAME,CRACK_108
/TITLE,CRACK-FATIGUE
/COLOR,U,MAGE
/PREP7
/VIEW,1,-1
/ANG,1
/ANG,1,90,ZS,1
/ANG,1,-30,YS,1
/ANG,1,15,XS,1
/REP,FAST
/REPLOT
*SET,W,20E-3 !! SPECIMEN HEIGHT SEMB (m: meters)
*SET,B,7.7E-3 !! SPECIMEN THICKNESS SEMB (m: meters)
*SET,a2,1e-3 !! LENGTH USED FOR THE WIDTH OF THE REFINED MESH ZONE
*SET,GRAVEDAD,9.81 !! GRAVITATIONAL ACCELERATION
*set,CargaMax,550 !! Load in kg
*Set,CargaMin,250 !! Load in kg
SET,S,5W !! DISTANCE BETWEEN SUPPORTS THREE POINT BENDING
SET,L,6W !! SPECIMEN LENGTH SEMB - PARALLEL TO X-AXIS
*SET,ao1, 2.07e-3 !! Initial crack size for specimen. As-received condition
SET,P1,CargaMaxGRAVEDAD !!MAXIMUM LOAD (N: NEWTONS)
SET,P2,CargaMinGRAVEDAD !!MINIMUM LOAD (N: NEWTONS)
*SET,aa,W-ao1 !!LENGTH WITHOUT CRACK (+Y)
*SET,DIVC1,6 !!DIVISIONS CRACK ZONE, VERTICAL
*SET,DIVC2,DIVC1 !!DIVISIONS CRACK ZONE, HORIZONTAL
*SET,ASPECT1,8 !!Element aspect ratio in plane (Y-axis uncracked zone relative to pre-crack)
*SET,ASPECT2,6 !!Element aspect ratio in plane (X-axis uncracked zone relative to pre-crack)
*SET,ASPECT3,6 !!Element aspect ratio in plane (Y-axis crack notch zone relative to pre-crack)
*SET,ASPECT4,6 !!Element aspect ratio out-of-plane
SET,DIVW,NINT((aaDIVC1)/(ASPECT1a2)) !!DIVISIONS UNCRACKED ZONE Y
*SET,DIVS,NINT((WDIVC2)/(ASPECT2a2)) !!DIVISIONS UNCRACKED ZONE X AND CRACK ZONE X
*SET,DIVB1,NINT((BDIVC1)/(ASPECT4*a2)) !!THICKNESS DIVISIONS
!! Check if odd
*IF, MOD(DIVW,2), EQ, 0, THEN
DIVW = DIVW + 1
*ENDIF
*IF, MOD(DIVS,2), EQ, 0, THEN
DIVS = DIVS + 1
*ENDIF
*IF, MOD(DIVB1,2), EQ, 0, THEN
DIVB1 = DIVB1 + 1
*ENDIF
SET,DIVS2,NINT(((L-S)DIVC2/4)/(ASPECT2*a2)) !!DIVISIONS AFTER SUPPORTS
MP,EX,1,200E9 !!MECHANICAL PROPERTIES
MP,PRXY,1,0.28 !!MECHANICAL PROPERTIES
!STEP 1: FATIGUE CRACK GROWTH LAW: Paris Law Constants (3.8.2.2)
!====================
!As-received specimen
!C=2.79E-8 !Experimental (m/cycle)/(MPa*m^0.5)^m
C=7.3e-23 !Unit conversion since E is in Pa
M = 2.43 !Experimental
!====================
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
TB,CGCR,2,,,PARIS !CGCR: CRACK GROWTH, 1: Material, Paris: law used
TBDATA,1,C,m !Experimental Paris Law constants
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
SET,NN,1.
!! GEOMETRY
K,1, NNa2, 0 ! WIDTH OF THE CRACK MESH ZONE
k,2,S/2,0
k,3,L/2, 0
k,4,L/2,W
K,5,S/2,W
K,6,NN*a2,W ! WIDTH OF THE CRACK MESH ZONE
K,7,-NN*a2,W ! WIDTH OF THE CRACK MESH ZONE
K,8,-S/2,W
K,9,-L/2,W
K,10,-L/2,0
K,11,-S/2,0
K,12,-NN*a2,0 ! WIDTH OF THE CRACK MESH ZONE
L,1,2,DIVC1*4 !!!!
L,2,3,DIVC1
L,3,4,DIVC1*2 !!!!------
L,4,5,DIVC1
L,5,6,DIVC1*4 !!!!
L,6,7,DIVW
L,7,8,DIVC1*4 !!!!
L,8,9,DIVC1
L,9,10,DIVC1*2 !!!!-----
L,10,11,DIVC1
L,11,12,DIVC1*4 !!!!
L,12,1,DIVW
L,2,5,DIVC12 !!!!------
L,1,6,DIVW10
L,12,7,DIVW10
L,11,8,DIVC12 !!!!-----
AL,12,14,6,15
AL,1,13,5,14
AL,2,3,4,13
AL,15,7,16,11
AL,10,16,8,9
ET,1,PLANE182 !! 2D SECOND-ORDER ELEMENT
TYPE,1
mat, 1
MSHKEY,1
AMESH,1
MSHKEY,2
AMESH,2,
AMESH,4,
AMESH,3,
AMESH,5,
ALLSEL
ET,2,SOLID185 !! 3D SECOND-ORDER ELEMENT COMPATIBLE WITH 2D ELEMENT
!! Volumes
TYPE, 2
EXTOPT,ESIZE,DIVB1,0,
EXTOPT,ACLEAR,1
EXTOPT,ATTR,0,0,0
MAT,1
ESYS,0
VEXT,ALL, , ,0,0,B,,,, !!Extrude volumes
EPLOT
!POINTS TO DEFINE THE CRACK SURFACE
!AREA CANNOT COINCIDE WITH FACES. NOT POSSIBLE IN 3D
!THEREFORE A SMALL OFFSET (zo) IS CREATED TO AVOID ERROR
zo=0.05e-3
K,200,0,0,zo,
K,201,0,ao1,zo,
K,202,0,ao1,B-zo,
K,203,0,0,B-zo,
A,200,201,202,203 !DEFINE CRACK AREA
ET,3,200,4 ! keyopt(1) = 4 for mesh200 3D TRIANGLE WITH 3 NODES
TYPE,3
MAT,1 !MUST BE 1 because material constants defined with ID 1
!Do not confuse with Ansys demo which uses 2
AMESH,27
ALLSEL
! define Mesh200 element component defining the crack surface
ESEL,S,TYPE,,3
CM,m200el,ELEM
ALLSEL
! mesh200 node component for crack front
LSEL,S,LINE,,46 !SELECT CRACK FRONT LINE
NSLL,,1 !SELECT ALL NODES ASSOCIATED WITH LINE
CM, m200nd, node
ALLSEL
!! DEFINING XFEM MODEL: MESH ENRICHMENT
!! STEP 1: DEFINE CRACK ENRICHMENT PARAMETERS
ESEL,S,CENT,Y,0,W !SELECT ELEMENTS WHERE CRACK WILL PROPAGATE
ESEL,R,CENT,X,-a2,a2 !SELECT CRACK REGION ELEMENTS
CM,ELE_CRACK,ELEM !NAME OF SELECTED ELEMENT GROUP
ALLSEL
XFENRICH,ENRICH1,ELE_CRACK,,SING,3E-3,1E-5
ALLSELL
! define LSM values
XFCRKMESH,ENRICH1, m200el, m200nd
ALLSEL
!=========BOUNDARY CONDITIONS========
NSEL,S,LOC,X,S/2
NSEL,R,LOC,Y,0
CM,Support01,NODE
D,SUPPORT01,UX,0, , , ,UY,UZ, , , ,
ALLSEL
NSEL,S,LOC,X,-S/2
NSEL,R,LOC,Y,0
CM,Support02,NODE
D,SUPPORT02,UY,0, , , ,
ALLSEL
!======= LOAD CONDITIONS ========
NSEL,S,LOC,X,-a2/(2DIVC1)5.15,a2/(2DIVC1)5.15
NSEL,R,LOC,Y,W
CM,APPLYLOAD,NODE
*GET,NODS,NODES,0,COUNT
*IF,NODS,EQ,0,THEN
/COM, ERROR: No nodes selected for load application
*ABORT
*ENDIF
F,APPLYLOAD,FY,-P1/NODS
ALLSEL
!=========SOLUTION MODULE========
/SOLU
ANTYPE, STATIC
NLGEOM,ON !Large displacement nonlinear analysis
AUTOTS,ON !Automatic time stepping
NROPT,FULL !Full Newton-Raphson
NEQIT,250 !Maximum iterations
TIME,10
DELTIM, 0.01, 0.005,0.02
RESCONTROL,DEFINE,ALL,ALL !Save restart at each substep
OUTRES,all, all !Save all results
! Fracture parameter calculations
CINT, NEW, 1
CINT, CXFE, _XFCRKFREL1
CINT, TYPE, SIFS, 2
CINT, NCON, 6
! Crack growth parameters
CGROW, NEW, 1
CGROW, CID, 1
CGROW, METHOD, XFEM
CGROW, FCOPTION, MTAB, 2
CGROW, STOP, CEMX, 0.8*W
! Fatigue crack growth
CGROW, FCG, <?WORD FLAGGED?>, LC
CGROW,FCG, DAMX, 0.2E-4
CGROW,FCG,NINC,50
CGROW, FCG, SRAT, P2/P1
KBC, 1
CNVTOL,F,,0.01
CNVTOL,U,,0.0005
SOLVE
FINISH
SAVE
/POST1
FILE,,RST
FINISH
SAVE
RESWRITE
SET,LAST
/ESHAPE,1
PLDISP,2
