interfence fit effect on fatigue life -- recommend sources

[JJuhlin]

I am seeking recommendations for source materials on the effect of interference fits on the fatigue life of a cantilevered pin subjected to reversed bending.

I recall this as a topic when I was a student (a long time back) and I am designing a device that will include cantilevered pins subjected to reversing loads on the pin ends. The loads are perpendicular to the pin axis, resulting in bending stress at the point where the pin emerges from the base material.

We have been doing rotating beam testing on a prototype of the joint that suggests that the pin fatigue life is influenced by compressive stress resulting from the interence fit. But I'd like to improve my understanding of the effect beyond simply considering superposition. In particular I suspect that there is an optimum degree of interference / strain hardening.

Any suggested works that include discussion of this topic?

Any students out there that recall this as a lecture topic?

Jon Juhlin

 

[rb1957]

somethng else to consider with your application ... the transverse (shear) loads causing bending of th ebolt, there'll be a significant local effect at the shear face.

I'd research FTI ... Fatigue Technologies Inc ... their Forcemate is something like you're doing. Also Hi-Lok fasteners.

i'd've thought there'd be a ton of reports out there on this topic.

 

[Tmoose]

many machine design texts are concerned about fretting that will occur at the edges of the captured surface. The resulting surface finish murders the endurance limit/fatigue strength.

 

[dhengr]

JJ:
Depending on the pin dia. vs. the canti. length vs. the loading; more likely than not you are dealing primarily with high shear stress and strains at the root of the pin. Your pin is probably a short, deep, canti. beam and shear predominates in the load transfer. Then you can add some secondary surface tension/compression stress reversals due to bending, too. If I could, I would go from a 1" pin at the press fit, to a .5" pin at the tip/load; with a generous transition radius in terms of its transition length. Polish this pin transition in an axial direction, not in a circumferential direction. Don’t overdue the press fit. While it adds compression stress and strains in the pin which would probably be O.K. for a normal (tension dominant) stress fatigue problem, the press fit strains are additive to shear strains, one way or another. I’d also clean up the corner (edge) of the hole in the base material. What does this thing look like in terms of dimensions, loads and material properties? Have you had failures yet in your testing, and what life are you looking for? While I normally rail against over dependance on FEA, this is a problem well suited for it.

 

[electricpete]

I am not sure if it's exactly what you're looking for, but see Machine Elements Life and Design section 2.1.2 starting at bottom of the page here:

http://books.google.com/books?id=B0...&resnum=1&ved=0CCgQ6AEwAA#v=onepage&q&f=false

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