A-Arm Buckling end conditions?

[getafix0]

Hi I was wondering what the proper Euler Buckling end conditions would be for a individual tubular a-arm link would be. The links are welded to a steel boss with a spherical bearing. The other end of the link has a threaded rod end attached to it. I am thinking that you can assume that the end with the rod end is a pinned joint (no moment support) and the end at the ball joint is fixed. Therefore the effective length would be .7L. Or would a model with both ends fixed be more accurate (ie. effective length of .5L)?
Thank You

 

[GregLocock]

The effective length will be more than 1L - in a buckling case the outboard end of the arm will not be providing much vertical resistance.

Shouldn't really matter unless you have an extraordinary design, I've worked on very few suspension parts where buckling was a big design issue (two, from memory, neither were A arms).





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[getafix0]

I want to check the buckling loads because this suspension due to packaging constraints has rather long trailing links (SLA type setup). The suspension is also using a good amount of anti lift as well. I also wanted to be able to reduce the weight of arms by reducing the wall thicknesses from my buckling calculations.

 

[GregLocock]

Since it is a safety critical part then for a road car use L of at least 2. For a circuit car 1 is probably OK.

Given that arms do occasionally get bent it pays to be ultracautious.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[sreid]

Also, rod ends and spherical joints can require a fair amount of torque to move when under load.