TAGGED: -2d-materials-and-metals, lsdyna, membrane-elements
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November 20, 2023 at 2:08 pmRocco BombardieriSubscriber
I am attempting to evaluate the modal response of a pressurized membrane-like structure.
I have created a simple example consisting of a square membrane, simply supported along the edges, and subjected to uniform pressure. Here are some additional details:
I am utilizing a fully integrated Belytschko-Tsay membrane (ELFORM=9) that is designed to be hourglass-free.
I am using a linear elastic material (*MAT_ELASTIC).
The pressure load is applied using the *LOAD_SHELL_SET_ID keyword.
Currently, I have opted for the explicit solver, applying the pressure linearly.
I am constraining the translational degrees of freedom (DOF) of the edges only.
I am using version R13.1.1-13-g5480eca294 mpp_dp for Windows.
Upon running the simulation, I immediately observe what I thin kto be significant hourglassing in the membrane deformation and am unsure about the cause (please see the attached picture).
How can I suppress this behavior? What is causing it?
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Best regards,
Rocco
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November 20, 2023 at 5:41 pmRocco BombardieriSubscriber
Interestingly enough, reducing the time step using keyword *CONTROL_TIMESTEP delivered a very good result. Also the implicit solver was able to deliver the same robust results using the following settings:
*CONTROL_ACCURACY
$#   osu    inn   pidosu    iacc  Â
     1     4     0     0
*CONTROL_IMPLICIT_AUTO
$#  iauto   iteopt   itewin   dtmin   dtmax   dtexp   kfail   kcycle
     1     30     10    0.0   1.0E-4    0.0     0     0
*CONTROL_IMPLICIT_DYNAMICS
$#  imass   gamma    beta   tdybir   tdydth   tdybur   irate   alpha
     1    0.6    0.38    0.01.00000E281.00000E28     0    0.0
*CONTROL_IMPLICIT_GENERAL
$#  imflag    dt0   imform    nsbs    igs   cnstn    form   zero_v
     1   1.0E-4     2     1     1     0     0     0
*CONTROL_IMPLICIT_SOLUTION
$#  nsolvr   ilimit   maxref   dctol   ectol   rctol   lstol   abstol
    12     15     15   0.001    0.011.00000E10    0.91.0000E-20
$#  dnorm   diverg   istif  nlprint   nlnorm  d3itctl   cpchk   Â
     1     1     1     1     0     1     0
$#  arcctl   arcdir   arclen   arcmth   arcdmp   arcpsi   arcalf   arctim
     0     0    0.0     1     2     0     0     0
$#  lsmtd   lsdir    irad    srad    awgt    sred  Â
     5     2    0.0    0.0    0.0    0.0 -
November 20, 2023 at 5:55 pmRocco BombardieriSubscriber
Interestingly enough, reducing the time step by keyword *CONTROL_TIMESTEPÂ help achieve a good solution. Same soluction could be obtained using the implicit solver with the following settings.Â
*CONTROL_ACCURACY
$#   osu    inn   pidosu    iacc  Â
     1     4     0     0
*CONTROL_IMPLICIT_AUTO
$#  iauto   iteopt   itewin   dtmin   dtmax   dtexp   kfail   kcycle
     1     30     10    0.0   1.0E-4    0.0     0     0
*CONTROL_IMPLICIT_DYNAMICS
$#  imass   gamma    beta   tdybir   tdydth   tdybur   irate   alpha
     1    0.6    0.38    0.01.00000E281.00000E28     0    0.0
*CONTROL_IMPLICIT_GENERAL
$#  imflag    dt0   imform    nsbs    igs   cnstn    form   zero_v
     1   1.0E-4     2     1     1     0     0     0
*CONTROL_IMPLICIT_SOLUTION
$#  nsolvr   ilimit   maxref   dctol   ectol   rctol   lstol   abstol
    12     15     15   0.001    0.011.00000E10    0.91.0000E-20
$#  dnorm   diverg   istif  nlprint   nlnorm  d3itctl   cpchk   Â
     1     1     1     1     0     1     0
$#  arcctl   arcdir   arclen   arcmth   arcdmp   arcpsi   arcalf   arctim
     0     0    0.0     1     2     0     0     0
$#  lsmtd   lsdir    irad    srad    awgt    sred  Â
     5     2    0.0    0.0    0.0    0.0
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