Solving ANSYS Contact Problem for FEA of Rail Fastening Systems

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Discussion Overview

The discussion revolves around the challenges of defining contact areas in ANSYS for finite element analysis (FEA) of rail fastening systems under dynamic loads. Participants share insights and seek guidance on contact settings, mesh quality, and friction considerations in the context of their respective projects.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant expresses uncertainty about defining the contact area between the clip and angle guide plate due to deformation under load.
  • Another participant suggests improving mesh quality by using a "Method" object for a hex dominant mesh and increasing mesh density.
  • It is proposed to start with frictionless contact conditions and later introduce friction, emphasizing the importance of selecting an appropriate coefficient of friction.
  • Recommendations include using "augmented Lagrange" for contact formulation, ensuring contacts update every substep, and activating "automatic bisection."
  • A later post raises a different topic about contact settings for a surgical scissor design, indicating a need for guidance on friction between moving surfaces.

Areas of Agreement / Disagreement

Participants generally agree on the importance of mesh quality and contact settings in ANSYS, but there is no consensus on the specific approaches to take, particularly regarding friction settings and contact definitions.

Contextual Notes

Participants mention various assumptions about mesh density, contact conditions, and the variability of friction based on material properties, but these aspects remain unresolved.

Who May Find This Useful

This discussion may be useful for individuals working on finite element analysis in ANSYS, particularly those dealing with contact problems in mechanical systems or new users seeking guidance on best practices.

albertop
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I'm currently writing my thesis on a "Finite Element Analysis of rail fastening systems under dynamic load", and I'm using ANSYS Workbench 14.0 for that matter.

I don't know how to define the contact area for the clip and the angle guide plate, since it will be changing over time as the clip (and the plate) deform due to the loads applied.
http://imgur.com/xbLPbOl
http://imgur.com/eVhZB6G

This picture shows the existing gap between them, for you to see the future contact areas:
http://imgur.com/YdmPnxy

The CAD data for both objects were obtained with a 3D scanner, which means that the surfaces are neither smooth nor perfectly fitting to each other.

I'm too experienced with ANSYS; therefore a thorough answer will be greatly appreciated!

Thank you in advance!
 
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There is a lot to consider, you'll have to get into the gritty details of the contact conditions if you hope to defend the thesis. From a high level, the main considerations you should address from what I'm seeing:

  • You should clean up your mesh by inserting a "Method" object in the mesh portion of the problem tree, and select "hex dominant." This will give you a quad-primary mesh. You're also going to want a much denser mesh than what you have right now.
  • I would select frictionless contact conditions for a start, and then add friction as you have a reliably converging problem setup. Make sure you select your coefficient of friction carefully though, it can vary wildly with subtle changes in material and surface finish.
  • Select "augmented lagrange" for your contact condition formulation, make sure the contacts update every substep, and have "automatic bisection" active.
  • Make sure you have similarly sized elements on both sides of the contact condition using a "contact sizing" mesh element.
  • Substeps: you'll want a lot of them. Possibly hundreds.

That should give you a good start anyway.
 
Hello Mech_Engineer,

Yes, it's kind of a hard project considering I'm pretty new to ANSYS.

Thanks for the advice, I really appreciate it!
 
Ansys 14.5 contact setting help

Hello to all ,
I new to ansys workbench and I am need guidance as to how to do contact settings and how to find the friction between two moving surfaces. Im designing a surgical scissor. Kindly let me know what settings are preferable for contact setting of scissor and how to find friction between surfaces.

thanks for taking time and helping me.
 

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