NX CAE Tips & Tricks – Contact

By SiemensPLM

Contact is an everyday occurrence for a wide range of mechanical systems.  The human body is no exception.  Consider for example the contact between your hip bone and its socket as you saunter about your living room, contemplating the meaning of life.  In fact if you think about it, any joint in our musculo-skeletal system is subject to contact behavior – cool!

Contact can occur between inter-meshing gears – say in an automotive transmission, or between a rotating shaft and bearings – say in a hydraulic pump.  Contact stresses can occur between parts that are already partially or completely in contact (like the examples above), or between parts that come into contact as a result of a kinematic event.  The latter could be a systematically programmed event such an industrial press stamping out a part, or a completely random occurrence – like you dropping your beloved smartphone on the bathroom tile (hope you got the hardware replacement plan!)

Contact Stresses on a Plastic Latch

Like trying to loosen the death grip of a black Friday shopper on deeply discounted merchandise, modeling contact can be tricky.  Why? Well, for one contact can occur between parts that have rough edges or other awkward geometric characteristics which can hamper convergence.  Also, depending on the materials and forces involved, heavy deformations may result that require the deployment of non-linear approaches.  Finally, there’s this pesky thing called friction which can change the game if not properly accounted for.

The goal of today’s post is to introduce you to basic, linear surface-to-surface contact in NX Advanced Simulation.  Think of this as the basis from which more complex contact phenomena can be pursued.  Our example below illustrates contact between caliper and wheel rim in a bicycle brake assembly.  You squeeze the brakes, that force gets transmitted via cable to the calipers, which then force the brake pads against the surface of the rim – bringing your two-wheeled personal mobility solution to a gradual halt.

Things to keep in mind – you can manually select source and target contact regions, tweak global contact parameters to influence convergence as necessary, and customize output requests so you get the results you want.

Contact Analysis

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This article first appeared on the Siemens Digital Industries Software blog at