Modal response of membrane subjected to uniform pressure

- November 20, 2023 at 2:08 pm
  r.bombardieri
  Subscriber
  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:
  1. I am utilizing a fully integrated Belytschko-Tsay membrane (ELFORM=9) that is designed to be hourglass-free.
  2. I am using a linear elastic material (*MAT_ELASTIC).
  3. The pressure load is applied using the *LOAD_SHELL_SET_ID keyword.
  4. Currently, I have opted for the explicit solver, applying the pressure linearly.
  5. I am constraining the translational degrees of freedom (DOF) of the edges only.
  6. 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?
  
  Best regards,
  Rocco
- November 20, 2023 at 5:41 pm
  
  r.bombardieri
  Subscriber
  
  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
  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
  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
  5 2 0.0 0.0 0.0 0.0
- November 20, 2023 at 5:55 pm
  r.bombardieri
  Subscriber
  Interestingly enough, reducing the time step by keyword *CONTROL_TIMESTEP help achieve a good solution. Same soluction could be obtained using the implicit solver with the following settings.
```
*CONTROL_ACCURACY
$#     osu       inn    pidosu      iacc    
         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     
         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    
         5         2       0.0       0.0       0.0       0.0
```

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Modal response of membrane subjected to uniform pressure

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