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Technical Term for Bolt Backing Out?
4

Technical Term for Bolt Backing Out?

Technical Term for Bolt Backing Out?

(OP)
Is there a more technical way of saying that a bolt is backing out?

I am writing a service bulletin and want to let the customer know that a bolt tends to back out over time.

RE: Technical Term for Bolt Backing Out?

Why is it backing out?  Reciprocation of adjoined parts, vibration, axial forces, etc.  Customer might appreciate the reasoning behind needing to check a bolt periodically, and could feasibly be more inclined to do so with a valid reason stuck in their mind.

RE: Technical Term for Bolt Backing Out?

Loosening ?

RE: Technical Term for Bolt Backing Out?

Yes, "loosen" does it for me.

RE: Technical Term for Bolt Backing Out?

(OP)
It is backing out due to vibration. We are including a perminate fix we designed  

RE: Technical Term for Bolt Backing Out?

Bolt is loosening itself
Bolt is loose
Bolt is unscrewing
Premature bolt extraction
Bolt doesn't want stay put


Best I can do
 

RE: Technical Term for Bolt Backing Out?

(OP)
I like the last on Mike

RE: Technical Term for Bolt Backing Out?

2
The terms loosening and self-loosening are used in technical journal articles on this subject.  Bickford, in An Introduction to the Design and Behavior of Bolted Joints refers to self-loosening.  Sakai, in Bolted joint engineering, refers to rotational loosening.  And VDI 2230 Systematic calculation of high duty bolted joints uses the term loosening by rotation.

RE: Technical Term for Bolt Backing Out?

2
Yes it can.  The plies in the joint can get thinner due to cold flow, creep or other mechanisms.  This is called embedding.

The fastener can get longer due to creep or yield.

The the length's of things can change due to differential thermal expansion.

Loose bolt without rotation.

 

RE: Technical Term for Bolt Backing Out?

Great answer by MintJulep.  The only other mechanism that I know is wear.

RE: Technical Term for Bolt Backing Out?

How 'bout "decrease in preload" due to ????
 

-Dustin
Professional Engineer
Certified SolidWorks Professional
Certified COSMOSWorks Designer Specialist
Certified SolidWorks Advanced Sheet Metal Specialist
 

RE: Technical Term for Bolt Backing Out?

de-tensioning
relaxation
reversing

RE: Technical Term for Bolt Backing Out?

You gotta write for your audience, not for us.

e.g.:

"Dat dere sumbitch gon' back hissef right outta dere".


 

Mike Halloran
Pembroke Pines, FL, USA

RE: Technical Term for Bolt Backing Out?

And where would that audience be... Compton?
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Technical Term for Bolt Backing Out?

That would be South Louisiana.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Technical Term for Bolt Backing Out?

"in-service vibration causes the bolt to loosen ..." i'd give the reader something of the story,

or you could use Mike's "vernacula" prose ...

RE: Technical Term for Bolt Backing Out?

I have seen bolted joints lose clampload due to fatigue cracks developing in the thread roots of the bolts. Of course, failure was imminent at that point.

RE: Technical Term for Bolt Backing Out?

Just out of curiosity, if the bolts are known to be doing this, has altering them via drilling a hole or replacing them with a predrilled bolt so they can be wire tied to prevent rotation been considered?

RE: Technical Term for Bolt Backing Out?

There are quite a few (self-claimed) bolt locking devices (anti backing due to vibration). You can do a web search to find out.

RE: Technical Term for Bolt Backing Out?

Nordlock washers work very well.  There is also this stuff called "Loc-Tite".  Sorry, too much sarcasm for this late in the week. :>)

RE: Technical Term for Bolt Backing Out?

(OP)
Adalius-

We have found that lock wire doesn't really work as a retention device but more like an indicator (if lock wire is broken you bolt is loose.

Nordlocks do work very well but I don't have the counter bore.

RE: Technical Term for Bolt Backing Out?

And besides, Jake indicated earlier that a permanent fix had been designed.

RE: Technical Term for Bolt Backing Out?

I've used Nordlocks before, I thought they were an incredibly simple yet deviously smart solution.

I must admit I'm surprised you say you've had lock wire breaking from it backing out only under vibration, though, unless these are fairly small fasteners and thereby requiring a small diameter lock wire. Granted my experience mainly lies in gas turbines in regards to lock wire so you're talking a minimum of 1/8" wire.

In any event, as you said you found a permanent solution so its a moot point, I was just throwing a brain dropping out as curiosity often gets the best of me.

RE: Technical Term for Bolt Backing Out?

I like

Quote:

if lock wire is broken you bolt is loose
That says it all!

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Technical Term for Bolt Backing Out?

IRstuff...yes..loosening can come from elongation of the bolt, creep, fatigue, etc....none of which are necessarily rotation.

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