Nonlinear Analysis of a 2-D Rubber Seal

In this session we will simulate large deformation (stresses and deflections) of a rubber seal and its contact process with a trunk door when being pushed in. The complex shape of the seal also leads to rubber-rubber surface contact.

The purpose of the analysis is to examine the stresses and deflections created within the rubber
during the closing of a door. The seal is made of a rubber material and therefore is modeled using hyperelestic material properties.  Since the trunk door is much stiffer than rubber seal, the trunk door will be modeled as a rigid body. Additionally, the rubber seal will come in contact with itself.  This contact must be taken
into accout explicitly, otherwise the seal will pass through itself.

New features

• Hyper-elastic material using Mooney-Rivlin model
• Rigid-elastic body contact
• Elastic-elastic body contact
• Multiple domains (rubber seal vs trunk door)

The basic steps for performing a typical surface-to-surface contact analysis are listed below:

• Create the model geometry and mes.
• Identify the contact pairs.
• Designate contact and target surfaces.
• Define the target surface.
• Define the contact surface.
• Set the element key options and real constants.
• Define/control the motion of the target surface (rigid-to-flexible only).
• Apply necessary boundary conditions.
• Define solution options and load steps.
• Solve the contact problem.
• Review the results.

Contact emelents are constrained against penetrating the target surface. However, the target elements can penetrate through the contact surface.

For rigid-to-flexible contact, the designation is obvious: the target surface is always the rigid surface and the contact surface is always the deformable surface.

For felxible-to-flexible contact, the guidelines are:

• If a convex surface is expected come into contact with a flat or concave surface, the flat/concave surface should be the target surface.
• If one surface has a fine surface mesh and, in comparison, the other has a coarse mesh, the fine mesh should be the contact surface and the coarse mesh should be the target surface.
• If one surface is stiffer than the other, the softer surface should be the contact surface.

The ANSYS input file used in Spring 2002.

The model creation consists of six phases.  The ANSYS log files: Seal-MR.part1, Seal-MR.part2, Seal-MR.part3, Seal-MR.part4, are made to give you essentially
step-by-step instructions. The different phases are:

• PHASE I:   Creating the Geometry for the rubber seal and the trunk beam
• PHASE II: Define material and element properties for these finite elements
• PHASE III:  Creating the finite element mesh for the rubber seal and rigid body
• PHASE IV :  Modelling the Trunk to Seal Contact (rigid-elastic contact)
• PHASE V:  Modelling the Seal to Seal contact (elastic-elastic contact)
• PHASE VI:   Apply loads and boundary conditions to the model

 SOLUTION HISTORY INFORMATION FOR JOB: seal.mntr

 ANSYS RELEASE  5.6             .2      17:34:47    04/30/2001

 LOAD SUB-  NO.   NO.  TOTL   INCREMENT    TOTAL       VARIAB 1    VARIAB 2    VARIAB 3
 STEP STEP  ATTMP ITER ITER   TIME/LFACT   TIME/LFACT  MONITOR     MONITOR     MONITOR
                                                       CPU         MxDs        MxPl

   1     1    1     1     1   0.50000E-01 0.50000E-01  19.750     -.35000E-01 0.78886E-30
   1     2    1     1     2   0.50000E-01 0.10000      37.470     -.70000E-01 0.78886E-30
   1     3    1    11    13   0.75000E-01 0.17500      149.45     -.12250     0.78886E-30
   1     4    3     9    42   0.18750E-01 0.19375      430.70     -.13562     0.78886E-30
   1     5    1     3    45   0.18750E-01 0.21250      467.09     -.14875     0.78886E-30
   1     6    1     5    50   0.28125E-01 0.24062      522.28     -.16844     0.78886E-30
   1     7    1     7    57   0.28125E-01 0.26875      596.30     -.18813     0.78886E-30
   1     8    1     8    65   0.28125E-01 0.29688      679.88     -.20781     0.78886E-30
   1     9    1     5    70   0.42188E-01 0.33906      735.54     -.23734     0.78886E-30
   1    10    1     9    79   0.63281E-01 0.40234      832.39     -.28164     0.78886E-30
   1    11    1    11    90   0.63281E-01 0.46563      948.03     -.32594     0.78886E-30
   1    12    1    12   102   0.63281E-01 0.52891      1076.8     -.37023     0.78886E-30
   1    13    1    11   113   0.63281E-01 0.59219      1188.7     -.41453     0.78886E-30
   1    14    1     9   122   0.63281E-01 0.65547      1282.0     -.45883     0.78886E-30
   1    15    1     8   130   0.94922E-01 0.75039      1366.1     -.52527     0.78886E-30
   1    16    1    11   141   0.14238     0.89277      1478.1     -.62494     0.78886E-30
   1    17    2     8   160   0.53613E-01 0.94639      1704.6     -.66651     0.78886E-30
   1    18    1    11   171   0.53613E-01  1.0000      1822.1     -.70925     0.78886E-30