CONTF

I/O Options and Subcase Information Entry The CONTF entry can be used to request contact results output for all s or individual linear static, nonlinear analysis, linear inertia relief and explicit dynamic analysis s.

Format

CONTF (format, type, nlout=nloutid) = option

Description

Type	Options	Description
`format`	<H3D, OPTI, OP2, blank>	H3D Results are output in Hyper3D format (.h3d file). OPTI The total contact force, normal contact force, tangential contact force, and contact area results are output to the .cntf file (in case of Implicit Analysis) and _expl.cntf file (in case of Explicit Dynamic Analysis). 5 OP2 Results are output in Nastran output2 format (.op2 file) blank (Default) Results are output in all active formats for which the result is available.
`type`	<ALL,FORCE, PCONT,FRICT>	ALL (Default) All available contact results types are output. FORCE Contact force results are output. PCONT Pressure-type contact results are output: pressure, open-closed status, contact gap opening and penetration. 2 FRICT Friction-related results are output: frictional traction, sliding distance, and stick-slip status. 2
`nlout`	<nloutid> No default	ID of an NLOUT Bulk Data Entry. If present, the incremental output control parameters are taken from the referenced NLOUT Bulk Data Entry, instead of the one selected by Subcase Entry NLOUT, when results are written into the *_impl.h3d file. 7
`option`	<YES, ALL, NO, NONE, SID> Default = ALL	YES, ALL, blank Contact results are output for all grid points. NO, NONE Contact results are not output. SID If a set ID is given, contact results are output only for grid points listed in that set.

Comments

The CONTF entry is applicable in linear static, linear inertia relief, nonlinear analysis s (identified by the presence of an NLPARM Subcase Entry) and explicit dynamic analysis.
Most of the contact results are real numbers and are self-explanatory. Some results that may require clarification are:
- Contact Status (s) is output as Open/Closed/Frozen status is represented by 0.0 for Open, 1.0 for Closed, and 2.0 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 is represented by 0.0 for Open, 1.0 for Slip and 2.0 for Stick. 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
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.)
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.
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.
Multiple instances of this card are allowed; if instances are conflicting, the last instance dominates.
nlout=<nloutid> applies only to implicit nonlinear subcases.
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 slave surface during nonlinear solution of the finite element model and the raw data is post-processed for pressure output on both the slave and master surfaces.

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