Calculate pin in double shear with repetitive impact or vibrational loading.

[nateconn]

I'm looking through my Shigley's Machine Design text and I don't see anything specifically for a pin in double shear that has to endure repetitive loading/impact loading. Not sure exactly what it would be called.

The pin is not tight, think of it like a quick release pin from the image below. There is some small clearance between the OD of the pin and the ID of the holes. So I don't think I can calculate it as a simple alternating sheer stress fatigue life. As when the load is being applied then reversed, the pin slams into the other side of the hole.

Is there a way to estimate the life of the pin in this situation? Or is there a spot in Shigley's I should be referring to. I've looked through Chapter 6 (Fatigue Failure Resulting from Variable Loading) but I don't see anything that covers impact.

 

[berkshire]

Look in Section 2
B.E.

You are judged not by what you know, but by what you can do.

 

[robyengIT]

why not to refer to knuckle joint (paragraph 12.12 of attached doc) ?

 

[tbuelna]

A cyclic reversing load condition in a clevis/pin joint having radial clearance like you describe can get ugly in a hurry. It only takes a small amount of radial clearance to produce large dynamic impact forces at the pin/clevis bore contacts. This loading condition will quickly produce fretting damage to both the pin body and clevis bore surfaces. As the fretting damage to the contact surfaces accumulates, the radial clearance increases, and the failure process becomes self-perpetuating.

I don't think there is any reliable method to predict fatigue life with the joint arrangement and loading conditions you describe, since the failure mode will likely be due to fretting. The best approach would be to re-design your joint to have a proper shear fit.