Contact Stress on Sliding Contact Lugs

[Daniel_CD]

Hi team,

I have been designing a quick release coupling which actuates against a force of 430N. The attached image explains the situation; a lever rotates a steel coupling to drive a brass fitting up the slope and engage in a detent at the top.

Bearing stress on each lug comes out ~20MPa based on the detent geometry so that won't be an issue.
Shear stress on each lug is ~7.5MPa, again not an issue.
Peak contact stress comes to 1150MPa (at point of inflection as the lug rolls into the detent at the top of the ramp).

I have seen in other forum posts that a guideline for permissible contact stress is 4*Yield Strength for line contact and 5.5*Yield Strength for point contact but can't find reliable sources to cite these figures from. Formulae related to permissible contact stresses in gears apply various loading factors which aren't directly applicable in this application.

Could anyone provide some insight into how to calculate permissible contact stress? Or point me in the direction of some relevant reading material?

Thanks!

 

[ChadV]

It may not be too much help - Hertz contact stress threads sometimes go in circles, pardon the pun - but there was a previous thread that cited the Italian structural steel code for the 4 and 5.5 values. Several other values from various sources (stated or implied) are mentioned also. Link is below.

http://www.eng-tips.com/viewthread.cfm?qid=95671