Tension Clip Yield Allowable Stress

[StevenKatzeff]

When calculating the tension allowable on an extruded angle clip and for Ultimate conditions I often use the Lockheed graphs and the Niu angle bathtub fittings where applicable. However these are all for Ultimate conditions (test data) and give much more allowable tension load than just comparing to the My/I using the Plastic Bending allowable- Fbu. My question is this: For yield conditions, is there a similar correlation like the graphs that would give one more allowable load than Fby would yield?

 

[bf109g]

Flabel has the best section on tension clips that I know of, but it's based on calculated Fby. Don't know of any testing to yield that would have generated tables like you mention.

 

[stresscalcs]

I believe that the Lockheed graphs are based upon values determined from deflection criteria not strength, hence the values are not true ultimate values but ultimate values that ensure the yield to ultimate load of 1.5 is maintained.

This suggests that the yield values are the graph values divided by 1.5.

 

[palomc]

The note on the Lockheed graphs says "The ultimate load P is defined as 1.5 times the load at 0.005 inch permanent set."

If you accept the Lockheed definition of limit allowable being that which gives 0.005" permanent offset then Lockheed gives you the limit capability (just divide by 1.5). So many people use this method that its definition of limit capability could be considered a de facto standard.

Flabel has the same graphs but he gets into fastener prying which Lockheed ignores (the Lockheed SM 89 sketches show P at the bolt the same as P at the flange).