CONTF

Format

CONTF (format, type, utilisation, SUBSYS, NLOUT) = option

Description

Comments

1. The CONTF entry is applicable in linear static (only if the contact type is SLIDE), linear inertia relief, nonlinear analysis subcases (identified by the presence of an NLPARM Subcase Entry) and explicit dynamic analysis.
2. Most of the contact results are real numbers and are self-explanatory. Some results that may require clarification are:
   • Contact Status is output. The Open/ClosedSlip/ClosedStick/Frozen status is represented by 0.0 for Open, 1.0 for ClosedSlip (closed Coulomb friction contact at slipping status or closed SLIDE contact), 2.0 for ClosedStick (closed Coulomb friction contact at sticking status or closed STICK contact), and 3.0 for Frozen. On graphical display, intermediate values may appear due to transition from open to closed, across individual elements.
   • Contact Coulomb Friction Status (s) is output. The Slipping/Sticking Status of Coulomb friction is represented by 1.0 for Slipping, 2.0 for Sticking, and 0.0, otherwise. On graphical display, intermediate values may appear due to transition of status across individual elements.
   • Contact Deformation (s) in both the Normal and Tangential directions are output. This represents both the Gap Opening and Penetration.
   • Sliding Distance represents total sliding distance accumulated while the surfaces are in contact. This may be different than just the difference in displacements between the starting and final position.
   • Contact force represents the resultant sum of the normal and tangential contact forces.
   • Frictional traction is output in vector form and scalar form respectively for H3D format. Contact Traction/Tangent Vector (v) contains the components of the friction in the basic coordinate system, while Contact Traction/Tangent(s) contains the components of the friction in the local coordinate system of the contact surface. Friction results are always tangential to the surface and Contact Traction Normal (s), which is the Normal pressure, is always perpendicular to the surface.
     The T1/T2 local coordinate system for Frictional Shear Contact Traction/Tangent (s) results is determined as:

     • T1 is the axis parallel to the X axis of the Basic coordinate system, projected onto the contact surface
     • T2 is the axis parallel to the surface and perpendicular to T1
     • If X-axis of the basic system cannot be projected, then the Y-axis is projected, and it becomes T2. Subsequently, T1 is reconstructed as parallel to the surface and normal to T2
3. The calculation of contact results on both sides of contact interface involves projections and mappings. Therefore, a perfect match of results between two sides cannot be expected, especially on mismatched meshes. Also, the resolution of different types of results (pressure versus gap opening) differs according to their respective FEA interpolation order. Therefore, such results may appear locally inconsistent, especially on second order meshes and mismatched mesh densities. (Usually pressure and traction will appear smoother than gap opening or penetration.)
4. Multiple formats are allowed on the same entry; these should be comma separated. If a format is not specified, this output control applies to all formats defined by the OUTPUT command, for which the result is available.
5. Only total contact results for each contact interface are output to the .cntf file (for Implicit Analysis) or _expl.cntf file (for Explicit Dynamic Analysis). For individual grid-based results, use the H3D format.
6. Multiple instances of this card are allowed. If instances are conflicting, the last instance dominates.
7. nlout=<nloutid> applies only to implicit nonlinear subcases.
8. Depending on the formulation, OptiStruct solves for the following, during the calculation of contact pressure:
   • Contact force (normal and tangential)
   • Contact traction (normal and tangential)

   Tangential contact force is the frictional force, normal contact traction is the normal contact pressure and tangential contact traction is the frictional contact pressure.

   The above quantities are obtained for the grids on secondary surface during nonlinear solution of the finite element model and the raw data is post-processed for pressure output on both the secondary and main surfaces.

   When contact force is solved, the contact area of each grid is also calculated to obtain the pressure.

9. The following results are printed to the H3D file with the CONTF output request:
   • Contact force
   • Contact force/normal
   • Contact force/tangent
   • Contact traction/tangent vector
   • Contact Coulomb friction status
   • Contact deformation/normal
   • Contact deformation/tangent
   • Contact status
   • Contact traction/normal
   • Contact traction/tangent
   • Contact wear
   • Contact wear loss volume
   For non-freeze contact with shell surfaces as its main and/or secondary entities, the contact results on respective sides of the shell elements will be printed to the H3D file. SPOS/SNEG denotes the positive/negative side of the shell elements, and the positive/negative side is decided by the shell element orientation (Zelem in the element coordinate system):

   • Contact Force SPOS
   • Contact Force SNEG
   • Contact Force SPOS / Normal
   • Contact Force SNEG / Normal
   • Contact Force SPOS / Tangent
   • Contact Force SNEG / Tangent
   • Contact Traction SPOS / Tangent Vector
   • Contact Traction SNEG / Tangent Vector
   • Contact Coulomb Friction Status SPOS
   • Contact Coulomb Friction Status SNEG
   • Contact Deformation SPOS / Normal
   • Contact Deformation SNEG / Normal
   • Contact Deformation SPOS / Tangent
   • Contact Deformation SNEG / Tangent
   • Contact Status SPOS
   • Contact Status SNEG
   • Contact Traction SPOS / Normal
   • Contact Traction SNEG / Normal
   • Contact Traction SPOS / Tangent
   • Contact Traction SNEG / Tangent