Coupled structural-thermal modeling of Taylor impacts using Eulerian mechanics
magliarj
Member Posts: 5
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.
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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
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
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.