by downunder
Now over-rev to 40,000 and the piston acceleration increases to over 18,000 G's which is almost double what it had at 30,000. Just where the rod will break depends on the design and it's weakest point. Because it's at an angle to the crankpin at maximum load it's bending first in one direction then the other so it's being flexed at a very high rate and aluminium fatigues fairly quickly.
You're right about the 2 stroke conrods experiencing compressive forces at all times. I was thinking about 4 strokes when mentioning conrod tensional forces.
EDIT: Now that I think of it, a 2stroke engine conrod could see tensional forces. After the exhaust port opens and the pressure on the piston surface drops to zero as the exhuast gases exit, the piston must still drop down further to open the intake ports and still further to BDC. During this arc of the crank travel, the intertia of the rotating moving parts contines to turn the crank abd thus the piston is actually being pulled down at this point. This is where the conrod sees tensional stresses. Is it as significant as the compressive forces from combustion? No, but it is still tension.
As for the conrod experienceing a bending moment, are you referring to Euler buckling? I didnt think the frictional forces at the crank pin and/or piston pin would form a strong enough couple to cause a significant bending moment on the conrod since they are supposed to be lubricated from the fuel. But then, the inertia of the contod itself might cause a bending when very rapidly changing directions inside a very high revving engine.