workshop 4b contact with friction

ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

April 30, 2009Inventory #002660WS4B-1

Workshop 4B

Contact with Friction

Workbench-MechanicalStructural Nonlinearities

Workbench Mechanical – Structural Nonlinearities

WS4B-2ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

April 30, 2009Inventory #002660

Workshop Supplement

Goal– Create contact pairs between three parts (piston,

cylinder and seal).– Run 2 load step analysis to simulate assembly of

the three parts together.– Post Process force along axis to assembly parts.

Model Description– 2D Axisymmetric– Piston is constrained from movement.– Cylinder is displaced to simulate assembly– Materials:

• Steel for Piston and Cylinder• Elastomer for O-Ring

– 1st load reconciles interference between piston and inside diameter of O-ring

– 2nd load step slides cylinder onto piston-O-ring subassembly.

Workshop 4B: Contact with Friction

Piston

Cylinder

O-ring




Workshop Supplement

Steps to Follow:• If you already have Workbench open from a previous run, start a new

analysis with Utility Menu>File>New…

• Browse for and open “W4b-Oring.wbpj” project file.

… Workshop 4B: Contact with Friction




Workshop Supplement

The project Schematic should look like the

picture to the right. – Highlight the Engineering Data Cell and open by

clicking on the Right Mouse Button (RMB)=>Edit to verify the predefined material properties

• elastomer and Structural Steel

– Verify that the units are in Metric(Tonne,mm,…) system. If not, fix this by clicking on…

• Utility Menu=>Units=>Metric(Tonne, mm,…)





Workshop Supplement

• Return to the project schematic page

• Double click (or RMB=>Edit…) on the Model Cell to open a Mechanical Session





Workshop Supplement

• Once inside the Mechanical application, verify the working unit system– “Unit > Metric (mm,kg,N,s,mV,mA)”

• The piston-cylinder assembly is already set up as a 2D axisymmetric model with the necessary boundary conditions and loads. It remains to define the contact pairs between the parts, set up the solution control analysis settings, run the solution and post process the results.

• Expand each folder in the project tree to become familiar with the model and to confirm material assignments for each part, boundary conditions, loads and Analysis Settings.





Workshop Supplement

Note: Auto contact detection did not create adequate contact relationships for this model. There is only one bonded contact pair created by default and it is insufficient for representing the assembly.





Workshop Supplement

– Revise Target definition to include the three surfaces of the O-ring groove as shown.

– Change Type to Frictional Contact

• Friction Coefficient = 0.05

– Switch to Asymmetric behavior

– Formulation = Augmented Lagrange

– Pinball Radius = 2mm

• Redefine the O-ring To Piston contact region as follows:

target





Workshop Supplement

• Insert an additional manual contact region between O-ring and Cylinder wall by highlighting Connections branch and RMB>Insert>Manual Contact. Defined this new region with specifications below.

Target

Contact





Workshop Supplement

• Confirm the Analysis Settings

• Note:

Large deflection is turned on:

There are two load steps with different autotime stepping specifications





Workshop Supplement

• Confirm the displacement load of 10mm is applied to the cylinder at load step 2.





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• Execute the solve. After many iterations and a few bisections, the solution converges.





Workshop Supplement

• Review the Total Deformation results.

Change the contour bar to clarify the deformation of the O-ring geometry

Animate the result





Workshop Supplement

• Highlight Solution Branch and RMB>Insert>Contact ToolInsert and post process contact status, pressure, frictional stress and

penetration


workshop 4b contact with friction

Documents