All structural bolts are tested for their stretch limits. We don't push that in the field, that goes back to the 70% ultimate tensile strength I talked about a few posts ago.
Granted some of that is assumed, As all bolts will be different. And you trust that your test sample is good enough to represent all bolts in the lot.
The manufacturer of the bolts will test that in the lab for a given lot number of bolts.
Of course metallurgy testing is part of that as well.
No, that bolt isn't a torque to yield type fastener. Having one hand in the auto world and one in the construction industry, I have asked those questions myself. And only get answers when I run across another car guy.
But the construction guys look at you funny.
So those two technologies don't cross over.
Those bolts were bolts I personally tested back in '13/'14ish they were at the bottom of the barrel. Full of oil. Actually had to wipe off the oil off first.
The tension is calculated off the correct amount of lube that is slightly oily but not soaked like those were.
When they broke, I knew what happened. But as I inspector I can't just toss out two broken bolts and say fu©k it, that doesn't matter.
The fact is , I tested the bolt and they broke. While my education kicked in said. It's of no consequence, I'm ethically obligated to report it. So course when I reported this and it started a whole mess.
Why did they fail, how many bolts failed, what was I doing when they failed. How many bolts where in the lot, and how many barrels were in that lot, etc,etc.
Well unfortunately, there ended up being alot of barrels. And alot of bolts in the lot. (I can't recall how many)
So when it happened, Nucor Steel sent one of their QA reps out to Colorado from Indiana.
The problem was, if the failure happened, all the bolts would from the lot would have to be found and replaced. Some bolts being in service in buildings.
Anyway the next day we tested bolts and tested and tested. We tested with my machine and his machine.
Then they took the failed bolts for destructive metallurgy testing.
It was quite the thing.
It was also one of those "ah shit!" Moments where I realized how important my job can be. Lol.
In short the answer is-(I don't have the testing results anymore) over lubricated bolts. I do understand what your saying about tension being calculating off of dry bolts, friction from the threads, etc.
But they calculate off of properly oiled bolt.
(As a side note, I'm the only inspector that's I know that has first hand experience with this type of failure and everyone else I've met has only read about it in the textbooks. So it's rare.
I was actually asked to talk about it at an AWS conference once.)
Yep I've seen that about ARP before. If I recall to my automotive training, some OEMs do that as well.
My only thought is, how do they measure the tension on the bolt in the real world?
If your tighting a main cap you can't check that in the real world. But a rod bolt you can usually put a stretch gauge on it. But even a stretch gauge doesn't give you a real value. Just a known amount of stretch to calculate back into your chart, that you made up from Lab testing of tension.
I'm not going to weld on a hardened bolt for my axle. Even a small amount of heat can possibly destroy the metallurgy.
You know the flat-earthers, that talk about how jet fuel doesn't burn hot enough to melt steel. But yet, somehow jet fuel took down the twin towers on 9/11.... Yeah those people are idiots, steel weakens at a much lower temperatures. Steel melts at 2800 but the affects of weakening steel starts at 400 degrees.
@tRustyK5 knows this, when you had a temp stick in your tool box, you probably had a 70,150,400,800 degree temp stick? (Possibly others depending on what kind of steel fabrication you were doing)
I have a trick up my sleeve for those axles. I'll post it up in the next few days. Unfortunately, it's not a clear cut as just cutting threads in the axle flange.
Lastly, (whew!)
The bolt that broke is a TC bolt.
(Tension control bolt)
Those are the bolts that look like rivets on one side.
And lastly anyone that bothered to read all that.... Here a picture of the bolts on my bridge I'm building now. Hot off the presses, I took this pic this morning.
