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Recommendations for structural impact

The following is a general set of recommendations for modeling of structural impact. Some of these recommendations will result in additional CPU costs as compared to a run where default values are used. These recommendations will not overcome fundamental modeling deficiencies such as poor meshing, inappropriate constraints, etc. 

 

Basic remarks:

  • Shell Element Selection: Avoid or minimize use of triangular elements. (See *CONTROL_SHELL)
  • Solid Element Selection: Avoid or minimize use of tetrahedrons, pentahedrons. (See *CONTROL_SOLID)

 

*CONTACT

  • Use only "_AUTOMATIC" type contacts, e.g., *CONTACT_AUTOMATIC_SINGLE_SURFACE.
  • Set SOFT on optional card A to 1.
  • For contact treatment of angular (sharp-edged) surfaces, SOFT=2 is generally very effective.
  • For problematic shell-edge-to-shell-edge or beam-to-beam contact situations, use *CONTACT_AUTOMATIC_GENERAL.

 

*CONTROL_HOURGLASS, *HOURGLASS

  • For formulation 16 shells, set the hourglass type to 8.
  • For other element formulations, set the hourglass type to 4 and hourglass coefficient to 0.03. 

 

*CONTROL_SHELL

  • If triangles are intermixed with quads in any shell part, set ESORT to 1.
  • If using B-T shells, set BWC and PROJ to 1.

 

*CONTROL_SOLID

  • If tetrahedrons or pentahedrons are used (not recommended) and these shapes are intermixed with hexahedrons in any solid part, set ESORT to 1.

 

*CONTROL_ENERGY

  • Set all parameters to 2 so that all energies are computed.
  • Include *DATABASE_GLSTAT, _MATSUM, _SLEOUT commands so that energies are reported.

 

*CONTROL_CONTACT

  • As a starting point, set NSBCS to zero or leave blank so that the default bucket sorting interval is used. This default value is dependent on the contact type chosen.
  • If small penetrations are reported in the messag file, set IGNORE=1. IGNORE can also be set using *CONTACT.

 

*SECTION_SHELL

  • If triangles are used (not recommended), set ESORT to 1.
  • If inelastic/plastic response of the shell part is expected, set NIP to a minimum of 3.
  • Set SHRF to 5/6 (0.833).

 

*MAT

  • For plasticity models where strain rate effects are invokes, set the parameter VP=1 (invokes viscoplastic strain rate formulation).