Tapped Thread Yield Limit 2

[ZMalik2k8]

Hi All,

I'm trying to calculate the yield strength of a tapped hole but I can't find it any where as the importance is on stripping/shearing the threads. Does anyone have any knowledge on it?

Any help is appreciated. Thanks

ZMalik2k8

 

[burningDiesel]

If I understand you correctly, you just want the yield strength of whatever material your hole is tapped in?
And for shearing, just divide by sqrt(3).

 

[desertfox]

Hi

Try this

http://www.engr.sjsu.edu/youssefi/me154/notes/Threaded Fasteners.pdf

 

[ZMalik2k8]

Basically, its an M2 tapped hole and the material is aluminium. What i'm trying to find out is at how many newtons does the thread yield at. Any thoughts?

 

[braddles90]

I found this online when searching for a similar thing, where it outlines the length of engagement to prevent the internal hole stripping (Section 8):

prod.sandia.gov/techlib/access-control.cgi/2008/080371.pdf

I haven't compared that section to anything yet to check it, but the other more basic bolt relations gave similar results to what I've previously used. Could be useful to you.

 

[ZMalik2k8]

Thanks braddles90,

I've had a scan through the above link and it mentions length of engagement to prevent thread stripping and factor of safety /margin of safety. I can't change the design but what I would like to find out is at how many newtons or torque would the internal/female threads yield at.

 

[TVP]

Internal threads under load do not yield the same way that a tensile specimen yields. I suggest you review some references on threaded fastener failure modes. Here are some links that have good technical information on this subject:

http://www.boltscience.com/pages/Thread Stripping Background.swf

http://www.boltscience.com/pages/strength.htm

https://www.fastenal.com/content/feds/pdf/Article - Screw Threads Design.pdf

http://www.ajaxfast.com.au/downloads/Technical notehowmanythreads.pdf

 

[desertfox]

Hi ZMalick2k8

Look on page 11 of the link I gave you and it gives a formula for internal thread stripping of nuts.
To calculate the thread stripping you need the yield stress of the aluminium in question, then divide that figure by 2.
Use the formula on page 11 and transpose it to give you the (P) value which is your load.

 

[Tmoose]

"I've had a scan through the above link and it mentions length of engagement to prevent thread stripping and factor of safety /margin of safety. I can't change the design but what I would like to find out is at how many newtons or torque would the internal/female threads yield at."

Steel fastener? What grade?
How much relative thread engagement?
If I know the thread engagement I would compare it to one of the sources that rate such things. Strength approximately proportional to relative lengths.

pages 66-68 here by no less a source than SPS Unbrako

http://www.dalecompany.com/pdf/UNBRAKO.pdf

As to the clamping force (Tension) vs torque there have been many threads on that topic.