stress calc's for threads
stress calc's for threads
(OP)
I need to do an analysis of loading on 2-12UN threads. How can I calculate the bearing, shear, and bending stresses?
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
stress calc's for threads
|
stress calc's for threadsstress calc's for threads(OP)
I need to do an analysis of loading on 2-12UN threads. How can I calculate the bearing, shear, and bending stresses?
Red Flag SubmittedThank you for helping keep Eng-Tips Forums free from inappropriate posts. Reply To This ThreadPosting in the Eng-Tips forums is a member-only feature.Click Here to join Eng-Tips and talk with other members! |
ResourcesWhat is rapid injection molding? For engineers working with tight product design timelines, rapid injection molding can be a critical tool for prototyping and testing functional models. Download Now
The world has changed considerably since the 1980s, when CAD first started displacing drafting tables. Download Now
Prototyping has always been a critical part of product development. Download Now
As the cloud is increasingly adopted for product development, questions remain as to just how cloud software tools compare to on-premise solutions. Download Now
|
RE: stress calc's for threads
RE: stress calc's for threads
As for bearing (tensile?) stress and shear stress you could look in ASME B1.1, it has a section on design.
RE: stress calc's for threads
I was following some calc's. left to me from a retired engineer (see attachment), but am unsure as to where the factor "23/24" is from.
I will also look in ASME B1.1.
Thanks.
RE: stress calc's for threads
http://www.turula.com/bolt.html
You might also check www.boltscience.com
rmw
RE: stress calc's for threads
Dan
www.eltronresearch.com
Dan's Blog
RE: stress calc's for threads
RE: stress calc's for threads
RE: stress calc's for threads
To avoid this it is usually fairly easy to re-design a joint.
A downloaded sketch coiuld be useful in this connection.
RE: stress calc's for threads
RE: stress calc's for threads
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: stress calc's for threads
1) The analysis was not of "bearing, bending and shear" of the bolt, rather it is bearing, bending and shear of the threads.
2) I don't know where the 23/24 factor comes from. Your attached calculations look like it is the loaded height of material at the root of the thread. That would probably be within the realm of reason for a vee-thread, which is what a 2-12UN is, though the drawing throws you since it appears to represent an acme/trapezoidal thread. Assuming that it is a vee-thread, I still don't know where the 23/24 comes from, though it seems like it probably isn't completely unreasonable.
Regardless of all that, my experience has been that all of my fastener failures were broken bolts (either at the nut or the transition from threaded to unthreaded shank), not sheared/stripped threads except for the cases when I have fine threads (which you have in a 2-12UN fastener) along with repeated assembly/disassembly. Though it never hurts to be thorough and do the calcs anyway. (And I suggest that you do.)
Engineering is not the science behind building. It is the science behind not building.
RE: stress calc's for threads
Engineering is not the science behind building. It is the science behind not building.
RE: stress calc's for threads
looking on the diagram you uploaded the (23/24)*P is shown on the sketch where the bending stress is and it looks to me as it represents the thickness of a single thread at the base and its being treated like a cantilever beam.
Just looking through some old books now but thats what I believe it to be.
desertfox
RE: stress calc's for threads
Just to confirm the 23/24 * 0.25 pitch is to give the thickness of the single thread at the root and then to use this in the formula that I have from "Schaums Outline Series
theory and problems of Machine Design" to calculate the bending stress at thread root:-
stress (bend) = 3*W*h/(2*pi*n*Rm*b^2)
where W=load
h= thread depth
Rm= mean thread radius
n = number of thread turns taking the load
b = width of thread section at the root
in your example you posted b= ((23/24 )*P)^2
I calculated the root width of your thread and it agrees
to within 8% of ((23/24 )*P)^2
hope this helps
desertfox
RE: stress calc's for threads
Generally, if you have sufficient engagement, the threads will not be the long pole in the tent. As a matter of fact, best practice is to have enough engagement to ensure that they are not. A mechanic is less likely to notice a failed thread than, for example, a broken screw or bolt.
Bickford gives a simple formula for determining the static shear strength of threads: F = Su*Ats
Su = Ultimate Shear Strength of the Nut or Bolt Materials
Ats = Cross-sectional Area Through Which Shear Occurs
He then gives several formulas for calculating Ats based on the strengths of the respective nut and bolt materials. His chapter on the strength of threads can be found at this link.
RE: stress calc's for threads
How many screw are you using?
what is the clamping plates thickness?
Is it tapped hole or bolted with nut?
What is the force to be clamped or weight to be with stand
Mark the pitch or the location of the bolts
Then I can help you to figure out the strength of the bolts whether it withstand or not?