Discussion Groups

## Simulation Mechanical and Multiphysics

New Member
Posts: 2
Registered: ‎01-03-2012

# Buckling on connecting rod

789 Views, 3 Replies
01-03-2012 05:46 PM

I want to analysis buckling on Conrod, but I have several problems such as

1. how to apply bearing loads in both holes Conrod (small end & big end) with variation loads/cyclic loads from 720 degree (in a 4 stroke motor cycle) in certain rpm
2. how to determine the BLF (buckling load factor) or load multiplier

Employee
Posts: 398
Registered: ‎05-06-2010

# Re: Buckling on connecting rod

01-03-2012 07:42 PM in reply to: ansufw

In ASIM 2013 beta, there is an easy way to apply bearing loads.

Maybe you can have a try.

I guess this is doable (applying both bearing and centrifugal loads) in one buckling analysis.

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New Member
Posts: 2
Registered: ‎01-03-2012

# Re: Buckling on connecting rod

01-06-2012 02:08 AM in reply to: S.LI

how can I try to use ASIM 2013 Beta?
thanks you

Employee
Posts: 492
Registered: ‎03-25-2010

# Re: Buckling on connecting rod

01-06-2012 08:48 AM in reply to: ansufw

Hello,

You are welcome to join the beta testers and download the beta from https://beta.autodesk.com/home.html, but I would not use it to do important production work, especially something as "trivial" as bearing loads. There are other ways to approximate the bearing load. If you know the formula for the load distribution, you can apply it with the current software by using the "Setup > Loads > Variable Pressure" command. Or depending on how important the ovaling of the holes are, just use a "Mesh > CAD Additions > Joint" to fill each hole and apply the load to the center of the joint. Perhaps someone else on the group will have other ideas, too.

I think the first question to ask is how important is the dynamic motion of the rod to buckling. Does it buckle at a smaller or larger load when rotating at N rpm compared to when it is stationary?  If stationary is acceptable, then using "Linear > Critical Buckling Load" is the only analysis you need to perform.

If the dynamic motion is important, then I would suggest setting up an analysis such as the Piston Mechanical Event Simulation tutorial. That will show how to rotate the crank shaft. Then you can use the "results based loads" like described on the page "Help > Autodesk Simulation > Setting Up and Performing the Analysis > Setting Up Part 2 > Nonlinear Analyses > Analyses Parameters >
Define Load Curves". And lucky you, there is already a written example of using the results based loads for a crank shaft analysis.

The MES analysis will not provide the buckling multiplier, unless you run multiple analyses with increased loads until you make the rod buckle or yield. But I would think that you can compare the calculated stress with the stress from the "Linear > Critical Buckling Load" analysis, and then calculate what multiplier for the MES analysis would give the stresses shown in the Critical Buckling Load.

Does this make sense? I am not an engine designer, so use your experience and that of others on this group to "do it correctly".

Sincerely,
John Holtz, P.E.
Senior User Experience Designer, Simulation
Autodesk, Inc.

Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)