×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Calculation of female thread strength

Calculation of female thread strength

Calculation of female thread strength

(OP)
A colleague in Sweden is in the process of designing a new flange joint bolted together with bolts (M30 to M100). Current calculation methods within the department are 10+ years old and are limited to typically 45% of the yield stress of the bolt shank, this limitation is due to the stripping of the female threads within the flange (blind tapped holes used as opposed to nuts).

The method in use is a crude approximation based on just a proportion of the thread shear area and material yield stress. It is known (and has been completed for certain customer orders) that the threads can take a preload equivalent up to 70% of the bolt yield without any problems, but simple methods to prove this are not known.

Does anyone have any experience with bolting technology and knows of a method that models the female thread strength to a greater accuracy and thus will allow a greater utilisation of the bolt preload? Any help or references would be greatly appreciated.

RE: Calculation of female thread strength

While that is a fascinating academic question, utilization of bolting and allowable stresses for pressure retaining parts is very strictly dictated by codes such as ASME B16.5, B16.34, and B31.1 in the US.  Other countries have adopted similar codes.  If your colleague develops a new method for calculating stresses it will be necessary for him to prove its validity and have it adopted by the certifying agencies before he can implement it in service.  In most areas, codes have the force of law. If an accident happens and it is found that a bolted joint violated existing codes, this presumes guilt and exposes a lot of parties to liability if not criminal prosecution.  

Do your research and get it incorporated into the codes before you dare to sell the new flange joint.  

RE: Calculation of female thread strength

(OP)
Sorry, wrong group - its not a pressure boundary application but part of a marine propulsion drive.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources