General Mechanical

General Mechanical

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Solver pivot issues of elastic shell snadwiched between poroelastic solid

    • Fraser Shields



      I have a model of a biphasic/poroelastic solid reinforced with elastic shells. I have replaced solid 186 elements with CPT216 elements to model the fluid pressure and flux when the construct is under compression. However, I am getting solver pivot errors when running the model. The model has shared topolgy between the solid and shells, and runs completely fine when it has solid 186 elements consititing of a linear elastic material. However, upon changing elements, the error arises.

      Here is a link to the project: 

      It contains the following ADPL command snippet in the analysis section:


      !   Commands inserted into this file will be executed just prior to the ANSYS SOLVE command.
      !   These commands may supersede command settings set by Workbench.
      !   Active UNIT system in Workbench when this object was created:  Metric (um, kg, uN, s, V, mA)
      !   NOTE:  Any data that requires units (such as mass) is assumed to be in the consistent solver unit system.
      !                See Solving Units in the help system for more information.
      ! Define an element type with the desired real constant (CPT216)
      ET, 9991, CPT216
      KEYOPT, 9991, 12, 1
      ! Select the solid elements you want to modify (SOLID186)
      ESEL, S, TYPE,, 13, 57
      ! Modify the selected elements to use the specified element type (9991)
      EMODIF, ALL, TYPE, 9991
      ESEL, NONE
      ! Define proelastic material for solid elements
      MP,EX,99999,0.001 ! YOUNG'S MODULUS
      MP,NUXY,99999,0.3 ! POISSON'S RATIO
      FPX=2e-15 ! PERMEABILITY
      ESEL, NONE
      ! Define linear elastic material for shell elements 
      MP,EX,88888,0.1 ! YOUNG'S MODULUS
      MP,NUXY,88888,0.3 ! POISSON'S RATIO
      ! Select the solid elements you want to modify and assign material 1
      ESEL, S, TYPE,, 9991
      MPCHG, 99999, ALL
      ! Select the shell elements you want to modify and assign material 2
      ESEL, S, TYPE,, 1, 12
      MPCHG, 88888, ALL
      ! Select all elements
      ! Continue with the solution phase
      Any help would be much appreciated.
    • Ashish Kumar
      Forum Moderator


      Ansys employees cannot download the attachments. The command snippet is used to change the material. Can you share snapshots of the setup - with that, it might be easier for forum members to comment more on your post.



      Ashish Kumar

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