coefficient of friction of fasteners

[evmundo2003]

Hi,

I have an issue, while testing the break load of a fastener in Plated form, black self colour and greased forms, I experienced an unusal result in that the greased bolt actually produced a higher break load than the other two bolts. Can somebody explain the reasons why this may occur, for information the jig did not contain a blind hole so the effets of hydraulics can be excluded.

Evmundo2003

 

[kenvlach]

Possibly, the plated and black oxided(?) bolts suffered some hydrogen embrittlement during processing.
Was this a 'torque-to-failure' or some type of tension test?

I suggest that posting your question in the 'Welding, Bonding and Fastening' forum:
forum725