VCCT delamination using plane182 with plane stress with thickness

Hello Team,

I faced an issue while validating the DCB test for delamination using Ansys plane 182 plane stress option using VCCT

-->The critical load as predicted by ansys doesn't seem to match with the expected values: It under-predicts the critical load for delamination. 

-->Also, the initial slope of the force-deflection before the failure initiates also appears to be not matching.

I tried refining the mesh and using higher order but the issue still persists. 

I have attached the input file: dcb.dat to reproduce this issue. Also attached is the image of the various simulated results.


The parameters of DCB are:

L=200           !* length

dh=40            !* total thickness

a0=100 ! pre-crack length

nel=200           !* no.elements along length

neh=40            !* no.elements along thick

emod=2.0e+05 ! E

thick=10 ! width

g1c=0.9628         !* critical energy-release rate

pratio=0.3 ! *Proisson ratio


Please let me know your comments on observed results and suggestions. also, may i know if there is any validation problem to verify using plane stress option.


Answers

  • Where do the expected results come from?

    Your plot legend says ref and in house code. What are those?

  • Hello,

    Ref is taken from the paper: Wei-Jian Li, Qi-Zhi Zhu, Tao Ni,

    A local strain-based implementation strategy for the extended peridynamic model with bond rotation, Computer Methods in Applied Mechanics and Engineering,

    Volume 358, 2020, 112625,ISSN 0045-7825, https://doi.org/10.1016/j.cma.2019.112625.(http://www.sciencedirect.com/science/article/pii/S0045782519305079)

    In house codes are ones we are trying to reproduce and match with Ansys results. i'm unable to attach the input file, so copied those contents here:


    finish

    /clear,nostart

    /prep7 

    dis1=0.35 ! >=0.397435 0.4 (1125.94)

    dis2=1.0

    n1=1000

    n2=1000

    n3=10

    dl=200           !* length

    dh=40            !* total thickness

    a0=100

    nel=200           !* no.elements along length

    neh=40            !* no.elements along thick

    toler=0.1e-5

    emod=2.0e+05

    thick=10

    g1c=0.9628         !* critical energy-release rate

    g2c=0.0

    g3c=0.0

    EI=emod*0.5*dh*0.5*dh*0.5*dh*thick/12

    deno=emod*0.5*dh*0.5*dh*0.5*dh

    Pc=sqrt(g1c*deno/3.0)*(thick/(2*a0))

    Uc=2*sqrt(g1c/(3*deno))*a0*a0

    pratio=0.4


    et,1,182          !* 2d 4-node structural solid element

    !keyopt,1,1,2        !* enhance strain formulation

    keyopt,1,3,3        !* plane strain

    et,2,182

    !keyopt,2,1,2

    keyopt,2,3,3


    et,3,202          !* 2d 4-node cohesive zone element

    !keyopt,3,2,2       !* element free option

    keyopt,3,3,3        !* plane strain


    R,1,thick

    mp,ex,1,emod

    mp,prxy,1,pratio

    tb,cgcr,1,,3,linear    !* linear fracture criterion

    tbdata,1,g1c,g2c,g3c


    ! fe model

    rectng,0,dl,0,dh/2      !* define areas

    rectng,0,dl,0,-dh/2

    lsel,s,line,,2,8,2     !* define line division

    lesize,all,dh/neh

    lsel,inve

    lesize,all, , ,nel

    allsel,all

    type,1           !* mesh area 2

    mat,1

    local,11,0,0,0,0

    esys,11

    amesh,2

    csys,0

    type,2           !* mesh area 1

    esys,11

    amesh,1

    seltol,1e-06

    csys,0

    nsel,s,loc,x,a0-toler,dl

    nummrg,nodes

    esln

    type,3

    mat,5

    czmesh,,,1,y,0,      !* generate interface elements

    allsel,all

    nsel,s,loc,x,dl      !* apply constraints

    d,all,all

    nsel,all


    !

    esel,s,ename,,202     !* select interface element to

    cm,cpath,elem       !* define crack-growth path


    nsle

    nsel,s,loc,x,a0

    nsel,r,loc,y,0

    esln

    cm,crack1,node      !* define crack-tip node component

    allsel

    finish


    /solu

    resc,,none

    esel,s,type,,2

    nsle,s

    nsel,r,loc,x

    nsel,r,loc,y,dh/2    !* apply displacement loading on top

    d,all,uy, dis1

    nsel,all

    esel,all

    esel,s,type,,1

    nsle,s

    nsel,r,loc,x

    nsel,r,loc,y,-dh/2     !* apply displacement loading on bottom

    d,all,uy,-dis1

    nsel,all

    esel,all

    autots,on

    nsubs,4,4,4

    time,1


    cint,new,1      !* crack id

    cint,type,vcct    !* vcct calculation

    cint,ctnc,crack1   !* crack-tip node component

    cint,norm,0,2


    ! crack-growth simulation set

    cgrow,new,1     !* crack-growth set

    cgrow,cid,1     !* cint id for vcct calculation

    cgrow,cpath,cpath  !* crack path

    cgrow,fcop,mtab,1  !* fracture criterion

    CGROW,DTIME,2.0e-3

    CGROW,DTMIN,2.0e-3

    CGROW,DTMAX,2.0e-3

    cgrow,fcra,1.02


    allsel,all

    outres,all,all

    solve

    esel,s,type,,2

    nsle,s

    nsel,r,loc,x

    nsel,r,loc,y,dh/2    !* apply displacement loading on top

    d,all,uy, dis2

    nsel,all

    esel,all

    esel,s,type,,1

    nsle,s

    nsel,r,loc,x

    nsel,r,loc,y,-dh/2     !* apply displacement loading on bottom

    d,all,uy,-dis2

    nsel,all

    esel,all

    time,2

    nsub,n1,n2,n3

    solve

    finish


    /post1

    set,list

    *GET,nmaxset, ACTIVE, 0, SET, NSET

    *dim,imp_vol,,nmaxset,4,1

    /com, *********************************

    /com, Reference results:

    /com, A local strain-based implementation strategy for the extended 

    /com, peridynamic model with bond rotation Comput. Methods Appl. Mech. Eng., 358 (2020), p. 112625

    /com, *********************************

    imp_vol(1,3,1)=0

    imp_vol(1,4,1)=0

    imp_vol(2,3,1)=0.056544503

    imp_vol(2,4,1)=144

    imp_vol(3,3,1)=0.136125654

    imp_vol(3,4,1)=350.7692308

    imp_vol(4,3,1)=0.184293194

    imp_vol(4,4,1)=474.4615385

    imp_vol(5,3,1)=0.262827225

    imp_vol(5,4,1)=679.3846154

    imp_vol(6,3,1)=0.339267016

    imp_vol(6,4,1)=876.9230769

    imp_vol(7,3,1)=0.396858639

    imp_vol(7,4,1)=1026.461538

    imp_vol(8,3,1)=0.436649215

    imp_vol(8,4,1)=1133.538462

    imp_vol(9,3,1)=0.49947644

    imp_vol(9,4,1)=1028.307692

    imp_vol(10,3,1)=0.62513089

    imp_vol(10,4,1)= 919.3846154

    imp_vol(11,3,1)=0.753926702

    imp_vol(11,4,1)= 838.1538462

    imp_vol(12,3,1)=0.823036649

    imp_vol(12,4,1)= 803.0769231

    imp_vol(13,3,1)=0.882722513

    imp_vol(13,4,1)=773.5384615

    imp_vol(14,3,1)=0.956020942

    imp_vol(14,4,1)= 744

    imp_vol(15,3,1)=1.02408377

    imp_vol(15,4,1)= 721.8461538

    *cfopen,dcb_disp_force-ref,dat

    *vwrite,imp_vol(1,3,1), imp_vol(1,4,1)

    (1x,2G20.8)

    *cfclose

    fini


    /post26

    nsel,s,loc,y,dh/2

    nsel,r,loc,x,0

    *get,ntop,node,0,num,max

    nsel,all

    nsol,2,ntop,u,y,uy

    rforce,3,ntop,f,y,fy

    prod,5,2, , ,dis_tip, , ,1.0

    prod,6,3, , ,rf   , , ,1.0

    xvar,5

    /title,, dcb: reaction at top node verses prescribed displacement

    /axlab,x,disp Uy (mm)

    /axlab,y,reaction force Fy (N)

    plvar,6

    /com, export data to array parameters

    vget,imp_vol(1,1,1),5

    vget,imp_vol(1,2,1),6

    *cfopen,dcb_disp_force,dat

    *vwrite,imp_vol(1,1,1), imp_vol(1,2,1)

    (1x,4G20.8)

    *cfclose

    finish

Sign In or Register to comment.