Tightening against incomplete threads
Tightening against incomplete threads
(OP)
Hello guys,
Is there any effect on static of fatigue behavior of fasteners if the nut is tightened against the incomplete threads of the screw? Is there any studies that was performed to study this configuration?
Perhaps I am not clear..., please see attached the definition of incomplete threads .
Thanks
Is there any effect on static of fatigue behavior of fasteners if the nut is tightened against the incomplete threads of the screw? Is there any studies that was performed to study this configuration?
Perhaps I am not clear..., please see attached the definition of incomplete threads .
Thanks





RE: Tightening against incomplete threads
Quando Omni Flunkus Moritati
RE: Tightening against incomplete threads
The effects of insufficient preload are well documented.
RE: Tightening against incomplete threads
RE: Tightening against incomplete threads
Tension bolts usually do not control the thread length/runout as tightly as shear bolts do. With tension fasteners, it is common practice to allow the addition of washers under the nut to prevent the nut from "bottoming out" on the bolt threads. With shear fasteners, it is common practice to allow the substitution of a bolt with the next higher/lower grip dash number to ensure that there are no threads in shear and that the nut/bolt threads do not bottom out.
In terms of fatigue, bottoming out the threads of a tension bolt will likely produce a significant local stress concentration, and this would have an adverse effect on fatigue life.
Hope that helps.
Terry
RE: Tightening against incomplete threads
Thanks for your explanations, I fully agree with you on the effect of this tightening on preload. But Can you explain to me what can happen in theroritical conditions : assuming a non preloaded joint? I know that this application may not exist in industrial conditions, but I need to have more details about the creation of "stress concentration" as you said.
Shingouz
RE: Tightening against incomplete threads
Quando Omni Flunkus Moritati
RE: Tightening against incomplete threads
RE: Tightening against incomplete threads
The geometry is uncontrolled, and you don't know what you will get.
The primary purpose of bolts is to clamp things together. If you are bottoming out before the required preload is developed then the joint is failed before it's even assembled.
However now you have introduced the term "non preloaded joint". What does that mean to you?
RE: Tightening against incomplete threads
B.E.
You are judged not by what you know, but by what you can do.