Tighten bolt beyond yield point - Preload the bolt in the plastic area 2

[KenoFr]

Hello everyone, I'm new here, let me quickly introduce myself.

I'm a research engineer, and I'm working on "the behavior of an assembly subjected to tightening beyond its elastic capabilities"

To do this, we will carry out tensile tests with different stages of pre-load/tightening. However, before starting all this, I'm looking for articles on the tightening of bolts beyond their elastic limit and haven't found many. It's been about a month now that I've been searching, and apart from a small list of 9 articles, I have nothing else. So, if anyone has information/articles on this subject, I would be happy to discuss it with you.

 

[KenoFr]

No problem, I'll keep you posted. What's more, on the bolts we're going to test, we're going to study the influence of bolt design, whether the bolt is rolled and then heat-treated, or heat-treated and then rolled. On the one hand in tension with centered loading, and on the other hand with eccentric loading, always with different tightening levels up to a plastic tightening level.

These will be fatigue tests to determine the endurance limit.

But to do this, I also need a database of tests of this type that have already been carried out, so that we can compare them with the various results in the literature. (This has never been done in the plastics field, however).

For the moment, I have 3 articles in my possession, as follows:

- Fatigue of High Strength Bolts Rolled Before or After Heat Treatment with Five Different Preload Levels (R. I. Stephens, N. J. Bradley, N. J. Horn, J. J. Gradman, J. M. Arkema and C. S. Borgwardt 2005, DOI: 10.4271/2005-01-1321 )

- Influence of Cold Rolling Threads Before or After Heat Treatment on High Strength Bolts for Different Fatigue Preload Conditions (Nathan J. Horn and Ralph I. Stephens, 2006 DOI:10.1520/JAI13069 )

-

https://www.researchgate.net/public..._Thread_Bolts_for_Multiple_Preload_Conditions

( This one I can't get with the legal means, but if someone can help me to find the full article for free, that would be awesome ! )

To conclude, if you have any articles on the subject, I'd love to read them!

 

[desertfox]

Hi KenoFr

What will be your prime method of tightening? I ask because Torquing bolts is highly variable and to get an accurate preload +/- 5% you need to use a tensioner or something similar.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[dik]

Way back in first year engineering (in '65)... in one lecture about bolted connections, being a bit of a 'smart*ss', I asked the prof what would happen if someone added oil to a slip critical connection... The rest of the lecture was spent on friction values... It wasn't really a 'dumb' question.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[FacEngrPE]

Shigley's Mechanical Engineering Design (4th ed i think) has a discussion about the behavior of bolted assemblies. My take on this discussion is that a benefit of torque to yield is better fatigue service life. The variable load on the assembly is mostly transferred by the stiffest part of the assembly (the clamped stuff) while the bolt behaves as a clamping spring, so it's load is almost unchanging.

Torque to yield will not usually have this benefit on gasketed joints due to the softness of the gasket.

Shigley's Mechanical Engineering Design is now at the 11th ed, so millage may vary.

 

[TugboatEng]

In cylinder head applications TTY bolts are standard. Foil reinforced graphite compressible gaskets were common initially. Manufacturers have moved to shim gaskets that do result in a rigid assembly when compressed. TTY works well in both applications.

 

[PersonalProfile]

The following may be of interest, despite that you may be aware etc:

Guide to Design Criteria for Bolted and Riveted Joints

https://www.boltcouncil.org/files/2ndEditionGuide.pdf