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Ansys hyperelastic + viscoelastic material trouble

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  • Ansys hyperelastic + viscoelastic material trouble

    Hi everyone,
    I'm having trouble when using the combined hyperelastic material (neo-hookean) with viscoelastic (one term prony) in Ansys. The problem is a cone being pulled by uniform pressure at the top and fixed at the
    bottom. Plane183 (8 node plane element with uniform reduced integration) is used with axisymmetric option. This element empolyed mixed u-p formation. The hyperelastic material is assumed to be incompressible (u=0.5) or nearly incompressible (u=0.4995). (actually if use u=0.4995, Ansys will not run at all, the element will not form at the first substep)

    The model runs fine if only the neo-hookean hyperelastic
    material (u=0.5) is used but will crash at about 30% of completion when viscoelastic material is combined. By looking at the hydrostatic pressure distribution in post-processing, there is obvious checkerboard pattern along the loading edge, so it seems that volumetric locking causes the analysis to stop.

    My question is why this happens when viscoelastic material is combined but not happens when only hyperelastic material is used.

    My guess is our version of Ansys is too limited (university intermediate version)?

    So if anyone in this forum has higher version Ansys in his/her hand, can he/she kindly run this analysis for me and see if it's due to the version problem?


    The attached input file ?scripts_e02r1pull? combines hyperelastic and viscoelastic material. The run will take only a couple of minutes. Thanks a lot.

    rz


    /BATCH
    /FILNAME,e02r1_pull,0
    /TITLE,e02r1

    /PREP7

    /com >> define element type and material
    ET,1,PLANE183

    KEYOPT,1,3,1
    KEYOPT,1,6,1
    KEYOPT,1,10,0

    TB,HYPE,1,1,2,NEO
    TBTEMP,0
    TBDATA,,1,0,,,,

    TB,PRONY,1,1,1,SHEAR
    TBTEMP,0
    TBDATA,1,0.4,14,,,,

    /com TB,PRONY,1,1,1,bulk
    /com TBTEMP,0
    /com TBDATA,,0.4,2,,,,

    /com >> define keypoint
    K,1,0,0,,
    K,2,0,1,,
    K,3,1,0,,
    K,4,0.1,1.012916581,,
    K,5,0.117647058,0.993055471,,
    K,6,0.12,0.992916581,,
    K,7,0.6,0.992916581,,
    K,8,0.1,1.6,,


    /com >> generate quater circle
    FLST,2,2,8
    FITEM,2,0,0,0
    FITEM,2,1,0,0
    CIRCLE,P51X, , , ,90, ,

    /com >> generate straight lines
    LSTR, 9, 1
    LSTR, 1, 10
    LSTR, 8, 4
    LSTR, 6, 7

    /com >> generate small circle
    LARC, 4, 6, 5

    /com >> divide lines
    LDIV, 1, 0.70

    /com >> copy contact zone lines
    LGEN,2,7, , ,0,-0.04, , ,0

    /com >> shorten copied lines
    LDIV, 8, 0.4539919309218844E-01
    LDELE, 8

    LSTR, 11, 14
    LSTR, 10, 13


    /com >> create area
    AL,10,7,9,8

    LSBL, 3, 9
    AL,9,11,8,1,2

    /com >> manual meshing the contact zone
    /com >> transverse lines
    LESIZE,8, , ,5, , , , ,1
    LESIZE,7, , ,80, , , , ,1

    /com >> mesh the area
    MSHAPE,0,2D
    MSHKEY,1
    AMESH,1,1

    SMRT,4
    MSHKEY,0
    AMESH,2,2

    SAVE

    /com >> apply surface load
    DL,10, ,UX,0
    DL,11, ,UX,0
    FLST,2,68,1,ORDE,3
    FITEM,2,1
    FITEM,2,290
    FITEM,2,-340
    SF,P51X,PRES,-2.5

    NSEL,S,node,,1418,1452
    NSEL,a,node,,1372,1372
    NSEL,a,node,,1373,1373

    D,all,UY,0, ! APPLY DISPL
    NSEL,ALL

    /COM, CONTACT PAIR CREATION - START

    /COM, CONTACT PAIR PROPERTIES - END

    /sol
    /com >>analysis parameters
    ANTYPE,0
    NLGEOM,1
    NSUBST,100,10000,30
    OUTRES,ALL,3
    AUTOTS,1
    NEQIT,80
    RESCONTRL,DEFINE,ALL,3,10
    TIME,1

    /com >>message display control
    /UIS,MSGPOP,3
    /NERR,0,10000,


    /com >>nonlinear diagnose
    NLDIAG,MAXF,16
    NLDIAG,NRRE,1
    NLDIAG,EFLG,1
    NLDIAG,CONT,1

    /com >>run the job
    SOLVE

    /com 2nd step
    /com nsubst,50
    /com time, 2000
    /com solve
    FINISH
    ! /EXIT,ALL

  • #2
    I would be happy to run your simulation is you provide an input file for ABAQUS

    Perhaps someone else can run it through ANSYS...

    -Jorgen
    Jorgen Bergstrom, Ph.D. PolymerFEM Administrator

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