Coupled structural-thermal modeling of Taylor impacts using Eulerian mechanics

I am simulating a Taylor impact for AA6061-T6 plugs using Eulerian, Lagrangian and ALE models. I have noticed inconsistent findings for the thermal contours between the Eulerian (ELFORM=12) predictions and the Lagrangian (ELFORM=1) and Eulerian (ELFORM=5) predictions. The former exhibits peak temperatures at the periphery of the mushroom while the latter predict peak temperatures of similar magnitude towards the center of the specimen at the impact surface. Additionally, we noted that the von Mises stresses are moderately comparable between modeling approaches and the plastic strains/deformed profiles are near-identical. 

 

I have attempted to change the thermal solver from nonlinear to linear and implemented various thermal solvers other than the default but none of these combinations had a significant impact on the findings. Modifying the thermal timestep and inputs in the *CONTROL_ALE command also had no impact on the results. A brief presentation is attached to this post, which illustrates the above points, along with the current input deck for our Eulerian simulation. The analyses are performed using a double precision, SMP version of R10.1. Based on our current attempts I am unsure of there is an issue/shortcoming with our modeling approach or if this is potentially associated with the solver. Any suggestions or insights would be greatly appreciated.


Answers

  • AniketAniket Forum Coordinator

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  • Hello Aniket,


    Thank you for your reply, The images from the presentation are included in this reply along with the text from my input deck.

    LS-DYNA input deck:


    $# HSC Study 6061-T6 plug Taylor bar impact test

    $# Created on Oct-13-2020 (21:50:47)

    $ Input deck with base units: kg, m, s

    *KEYWORD MEMORY=150M NCPU=4

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    $                             (1) CONTROL CARDS

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    *CONTROL_ALE

    $#    dct     nadv     meth     afac     bfac     cfac     dfac     efac

           -1        5        2 -1.000000    0.000    0.000    0.000    0.000

    $#  start      end    aafac    vfact     prit      ebc     pref  nsidebc

        0.0001.0000E+20 1.000000      0.0        0        0    0.000        0

    $#   ncpl     nbkt   imascl   checkr     

            1       50        0    0.000

    *CONTROL_ENERGY

    $#   hgen     rwen   slnten    rylen    

            2        2        2        1

    *CONTROL_HOURGLASS

    $#    ihq       qh 

            5 0.100000

    *CONTROL_SOLUTION

    $#   soln      nlq    isnan    lcint    

            2        0        0      100

    *CONTROL_TERMINATION

    $# endtim   endcyc    dtmin   endeng   endmas     

     2.5000E-5        0    0.000    0.000 1.0000E+8

    *CONTROL_THERMAL_NONLINEAR

    $# refmax      tol      dcp   lumpbc   thlstl   nlthpr   phchpn     

           10    0.000 1.000000        0    0.000        0    0.000

    *CONTROL_THERMAL_SOLVER

    $#  atype    ptype   solver    cgtol      gpt   eqheat    fwork      sbc

            1        1        3 1.0000E-4        8 1.000000 0.800000    0.000

    $# msglvl   maxitr   abstol   reltol    omega   unused   unused      tsf

            0      5001.0000E-10 1.0000E-4 1.000000                     1.000000

    *CONTROL_THERMAL_TIMESTEP

    $#     ts      tip      its     tmin     tmax    dtemp     tscp     lcts

            0 0.500000 2.4000E-7 3.5000E-8    0.000 1.000000 0.500000        0

    *CONTROL_TIMESTEP

    $# dtinit   tssfac     isdo   tslimt    dt2ms     lctm    erode    ms1st

        0.000 0.900000        0    0.000    0.000        0        0        0

    $# dt2msf  dt2mslc    imscl   unused   unused    rmscl    

        0.000        0        0                        0.000

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    $                             (2) DBASE CARDS

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    *DATABASE_GLSTAT

    $#     dt   binary     lcur    ioopt    

       4.0e-9        0        0        1

    *DATABASE_MATSUM

    $#     dt   binary     lcur    ioopt    

       4.0e-9        0        0        1

    *DATABASE_SLEOUT

    $#     dt   binary     lcur    ioopt    

       4.0e-9        0        0        1

    *DATABASE_BINARY_D3PLOT

    $#     dt     lcdt     beam    npltc   psetid     

          1.0        0        0       50        0

    $#  ioopt    

            0

    *DATABASE_EXTENT_BINARY

    $#  neiph    neips   maxint   strflg   sigflg   epsflg   rltflg   engflg

            0        0        3        1        1        1        1        1

    $# cmpflg   ieverp   beamip    dcomp     shge    stssz   n3thdt  ialemat

            0        0        0        1        1        1        2        0

    $# nintsld  pkp_sen     sclp    hydro    msscl    therm   intout   nodout

            1        0      0.0        0        0        0STRESS   STRESS

    $#   dtdt   resplt    neipb    quadr    cubic    

            0        0        0        0        0

    $*DATABASE_FSI

    $   4.0e-9

    $#dbsfi_id      sid    stype     swid   convid  ndsetid      cid  

    $        3        3        1        0        0        0        0

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    $                             (3) PART DEFINITIONS.

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    *SET_PART_LIST

    $#    sid      da1      da2      da3      da4   solver     

            1      0.0      0.0      0.0      0.0MECH

    $#   pid1     pid2     pid3     pid4     pid5     pid6     pid7     pid8

            1        2        0        0        0        0        0        0

    *INITIAL_VOID_PART

    $#    pid  

            2

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    $                             (4) SECTION DEFINITIONS.

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    *SECTION_SOLID_TITLE

    ALE_airmesh

    $#  secid   elform      aet  

            1       12        0

    *SECTION_SOLID_TITLE

    CSE

    $#  secid   elform      aet  

            2        1        0

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    $                             (5) MATERIAL CARDS

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    *MAT_JOHNSON_COOK_TITLE

    6061-T6 JC

    $#    mid       ro        g        e       pr      dtf       vp   rateop

            6   2730.02.65000E106.89000E10      0.3      0.0      0.0      0.0

    $#      a        b        n        c        m       tm       tr     epso

    3.240000E81.140000E8     0.43    0.002     1.34    925.0    294.0      1.0

    $#     cp       pc    spall       it       d1       d2       d3       d4

        896.0      0.0      2.0      0.0      0.0      0.0      0.0      0.0

    $#     d5     c2/p     erod    efmin    

          0.0      0.0        01.00000E-6

    *EOS_LINEAR_POLYNOMIAL_TITLE

    6061-T6

    $#  eosid       c0       c1       c2       c3       c4       c5       c6

            3      0.06.75000E10      0.0      0.0      0.0      0.0      0.0

    $#     e0       v0 

          0.0      1.0

    *MAT_THERMAL_ISOTROPIC_TITLE

    6061-T6

    $#   tmid      tro    tgrlc   tgmult     tlat     hlat   

            1   2760.0      0.0      0.0      0.0      0.0

    $#     hc       tc 

        896.0    167.0

    *MAT_THERMAL_ISOTROPIC_TITLE

    6061-T6

    $#   tmid      tro    tgrlc   tgmult     tlat     hlat   

            2   2760.0      0.0      0.0      0.0      0.0

    $#     hc       tc 

        896.0    167.0

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    $                             (6) BOUNDARY CONDITIONS

    $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8

    *CONSTRAINED_GLOBAL

    $#     tc       rc      dir        x        y        z

            1        5        1      0.0      0.0      0.0

            2        6        2      0.0      0.0      0.0

    *RIGIDWALL_GEOMETRIC_FLAT_ID

    $#     id                                                                title

            1                                                                     

    $#   nsid   nsidex    boxid    birth    death    

            0        0        0    0.0001.0000E+20

    $#     xt       yt       zt       xh       yh       zh     fric   

        0.000    0.000 -1.000E-4    0.000    0.000 0.100000    0.000

    $#   xhev     yhev     zhev     lenl     lenm   

        0.000    0.000    0.000    0.000    0.000

    *INITIAL_VELOCITY

    $#   nsid   nsidex    boxid   irigid     icid   

            0        0        0        0        0

    $#     vx       vy       vz      vxr      vyr      vzr  

        0.000    0.000 -339.000    0.000    0.000    0.000

    *INITIAL_TEMPERATURE_SET

    $#   nsid     temp      loc  

            0    294.0        0

    *INCLUDE

    plug1.txt

    *END

  • idoido Member

    Hello magliarj,

    If you zoom in closely you will see that LAG and ALE5 (ALE with ELFORM=5) has sharper gradients then Eulerian (ALE12 or ALE11). This may be due to 2 factors: (a) the mesh is finer for the first 2 cases ==> more elms to resolve/capture sharper gradients. ALE12 has less elms to resolve the same region so the gradient may be diffused; (b) ALE12 resolve the mat interface within half the ALE elm width due to volume fraction representation of the ALE mat. The LAG and ALE5 cases has precise mat interface. To compare better, you will need much finer meshes for all 3 cases until they converge.

    Hope this helps,

    Ian Do, PhD

  • magliarjmagliarj Member
    edited October 28

    Hello Dr Do,


    Thank you for your reply, in response to your suggestions:


    (a) An identical mesh was implemented for the plug in all 3 cases. For the Eulerian case a comparable airmesh was added as an extension. I created an additional 'fine' mesh for the Eulerian case where the number of elements was increased by a factor of 10. The results are shown in this reply.

    (b) The temperature-time history for the center of the plug was plotted for the coarse (original) and fine (revised) Eulerian simulations and compared to the Lagrangian results. The Eulerian results generally converge with each other but do not match the Lagrangian results. Additionally, note that peak temperature at the end of the impact, shown in the attached image, was in a consistent location for the Eulerian simulations but with a peak value of 760 K for the fine mesh (in comparison to 550 K in the original, coarse mesh).


    Thank you again for your reply, any further suggestions would be greatly appreciated. If you need further information please let me know.





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