Kt for filled theaded hole...

[krt222]

thread2-106068

Referencing the above thread, I wanted to extent the discussion to not a net fit fastener, but to a standard or clearance fit preloaded fastener in a threaded hole. What sentiment or knowlegde is out there for Kt's or Kf's for such a configuration.

Thanks.

 

[rb1957]

that's odd ... this is the 2nd thread today on hte Kt of a threaded hole, and the 1st one has been deleted (RF'd?) ?

ream off the thread, and fill with an interference fit plug

 

[krt222]

Yea, I apologize for multi-posting. I was just trying to reach a larger audience.

I concur that reaming and filling more soundly with an interference fit plug is more advantageous at reducing local stress magnitudes.

Regardless, I want to understand what knowledge exists on Kt's for standard or clearance fit preloaded fastener in a threaded hole...

Thanks.

 

[StAnalysis]

Usually a threaded hole isn't good design practice. As was stated, an open hole has a Kt of 3 and for a hole with a fastener, the Kt can go much higher (see Michael C.Y. Niu's books for stress at a loaded hole. Such as "Airframe Structural Design"). A threaded hole would probably have an even higher Kt since there would be the combined effect of the hole and the additional stress riser of the threads.

 

[krt222]

Understood. How about asking it this way - relatively speaking, what would be the difference in expected Kt for an open threaded hole in a thick plate seeing bending versus the same threaded hole filled with a preloaded clearance fit fastener (ignoring mean stress effects of fastener preload)? I'm trying to discern whether there i merit to the possibility of 'filling' an open threaded hole with a preloaded net fit fastener and thereby extending fatigue life at that location.

Thanks.