Junkers machine CA 1969 - SAE paper 690055

[Tmoose]

I've read thru the paper a few times, and it seems that when much (or all!) of the admittedly limited fastener testing is done when "the U shaped top part is separated from the bed by flat strips of needle bearings to avoid galling." The U shaped top part is clamped against the bed (and the roller bearings) by the tested bolt's preload and transverse force and displacement is applied.

In my mind that description is not remotely equivalent to two substantial components, with well prepared mating surfaces, clamped together by significant fastener preload, even if powerful eccentric axial loads make a bearing cap nip a bit with micromotions, or significant transverse loading is applied in operation.

The various preload/tranverse Force/displacement figures have also left me somewhat bewildered, but my impression is there is forced lateral displacement of +/- 0.3 mm or more at the outset of the testing.

I will try to find later papers to see if my understanding of this process is correct, and if the testing and tester evolved to something else.

Does anyone know if I have this completely wrong?

 

[Tmoose]

Maybe I probably Should have mentioned that Junkers machines of some description or another are favored by some locking fastener suppliers as proving their products are effective at preventing fastener loosening.

 

[desertfox]

Hi Tmoose
I read this article by Bickford on self loosening:-

https://books.google.co.uk/books?id...oosening of fasteners under vibration&f=false

It highlights the fact that vibration direction is unimportant however if the vibration is sufficient to reduce the friction between the thread surfaces to zero, then the actual bolt tension can physically move the nut and self loosening occurs.

 

[CoryPad]

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