Finite Element Analysis of Connecting Rods



This is a summary of a discussion we had on The Old One's Discussion Board (Sorry this Board has been removed from the internet.)

rod3fea.jpg

My thanks to somanys (Kelley) who did all the heavy lifting on this. He got me reinterested in FEA as he started to model an "Eagle Like" and a Mechart Rod. He did all the solid modeling and the original ANSYS FEA analysis. He was good enough to share the solid model and I started to play with it in my COSMOS FEA program and made some .avi movies of the rod undergoing cyclic stress.

I exaggerated the deflections so you can see the deflections that "may" happen. This gives you an indication on how the big end distorts at high RPM and a potential view on why you might spin a bearing even if there is enough oil. I was also playing around with the load constraints, and none of these should be taken as a final, accurate analysis of a real rod in a real environment... how's that for a disclaimer?

Maybe right click and save as, then run it. Its an .avi animation.

H Beam Rod. Lots of load with big end distortion with the rod constrained by its lower cap surface.

H Beam Rod. Reasonable load with stress contours with the rod constrained by the big end bore. However the program forced the big end to not distort, hence you see no distortion.

H Beam Rod. Reasonable load with stress contours, and I played with the constraints to put the restraing load where the rod cap bolt heads would be. Notice a learning curve here? Now we have the wrist pin distortion, the stress contours, and the big end distortion. I'm starting to like this stuff!

I Beam Rod. Reasonable load with stress contours, and I played with the constraints to put the restraing load where the rod cap bolt heads would be. Now we have the wrist pin distortion, the stress contours, and the big end distortion. This one is for an I-Beam Type Rod. Not the high stresses near the top of the rib in the "I" by the wrist pin.

The big end is not split, nor constrained with prestressed rod bolts. The deflections are exaggerated, but it gives you a general idea what "sort of" goes on.

Thats all for now...


[Return To Automotive ]