The Incredible Strength of Bolted Joints

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This video takes a detailed look at bolted joints, and how preload, the tensile force that develops in a joint as it is torqued, can significantly improve the performance of a joint.

The video covers tension joints, shear joints, and joints that are subjected to combined tensile and shear loads.

It also explores the different methods that can be used to control the amount of preload applied to a joint, including the torque, turn-of-nut and ultrasonic measurement methods.

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This will allow me to create more high quality videos covering a range of engineering topics.

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The Efficient Engineer is a channel aimed at mechanical and civil engineers. The mission is to simplify engineering concepts, one video at a time!

[GHohn]

I make a living as an engineer and I can tell you these videos are higher quality than any textbook I had, probably better than any BSME curriculum out there. EXCELLENT work.

[zoeylamant]

As an ironworker, a lot of this goes under our daily radar, but it’s awesome to see the science behind the stuff aside from just slapping the bolt in and walking away. Knowledge like this allows me to do my job better and understand why things need to be done in a particular way to achieve the end goal. Well done.

[HansCSchellenberg]

Fun fact: Bolts are much less effective if they are not installed. Looking at you Boeing.

[NickDanzinger]

>>Browsing YouTube, about to go to bed.
>>Sees 17 minute youtube recommendation: "The Incredible Strength of Bolted Joints"
Me: You son of a b*tch, I'm in

[ryant]

Don’t know how long it takes to make these videos, but I imagine it takes quite a while because the quality is beyond excellent. Thank you for helping get through Cal Poly Engineering!

[charlesthomas]

Some of the coolest bolted connections were the slip critical joints in powerplants that have to meet seismic code. Things are massive, took forever to rattle them right.
The neatest bolts are on the turbine case, feedwater pumps and boiler piping. We don't even use torque wrenches, you can't really because it just takes too much force. Instead we used hydraulic tensioner to stretch the bolt and then spin the nut down. It's at the correct preload when you let the hydraulic pressure off. Another one is really weird. It had a hole drilled down the center for an heating element. Since you can calculate how much the stud will lengthen at a specific temperature you can determine the clamping force when it cools and shortens. Essentially you use heat to make the.bolt grow to loosen and let it cool to tighten. Crazy stuff in powerplants.

[gblargg]

Watching this gives me great respect for the amount of work that goes into seemingly simple things like bolt joints. I would have never imaged so much nuance.

[paris_mars]

Dude, there are so many subtle details in the animation that are kind of amazing. Like at 10:48 when the little windows with the bolt details cast light on the bolts themselves, meaning they are actual objects in the 3d scene with some alpha and emission and they are themselves being animated in and out. Awesome! A lot of people might not consciously register these details but they're really cool.

[kingkottah]

Exceptional video. I used to work on Toshiba 660 and 720 MW steam generators and this video has given me more of an appreciation for the countless weeks stoning flanges. We used a combination of turn of nut for applying the actual force and measuring the elongation. To turn the nuts we would use an induction heater to stretch the bolt and tap them around with a flogging spanner and I would use an extensiometer (essentially a rod and a dial indicator mounted to a sleeve) to measure the stretch after the bolts had cooled down (usually 12+ hours later).

[summatim]

0:01: Introduction to nuts and bolts
0:34: Assembly process of bolted joint
1:42: Tension joints
4:50: Shear joints
6:45: Bearing joints
8:23: Combined effect of tensile and shear loads
11:04: Controlling preload
13:47: Example of bolted joint in space
14:04: Bolted Joints
14:27: Preload in bolts
15:57: Joint diagram
16:01: Nebula

[rocketscience]

Great video. As a designer of gas turbine engines, we never use a critical bolt in shear. The flange is always piloted so that the bolt is only in tension. Also, the bolt should have a lower coefficient of thermal expansion than the flange so the bolt gets tighter when the flange heats up. Bolts are the most over-looked part of mechanical design. I have heard that 80% of the problems at car dealerships are realated to poor bolted joint design. Also, in critical applications, we use a hydraulic bolt stretcher that stretches the bolts the exact amount needed to get the desired pre-load and is much more accurate than using a torque wrench.
If you use 4D spacing between bolts (the center to center distance is 4 bolt diameters), you will almost never have a leaky joint. Most engine oil leaks on cars are the result of much larger than 4D spacing because they want to save the cost of the extra bolts and reduce assembly time. Next time you go to Walmart, look at all the oil spots in almost every open parking spot.

[kurtrowland]

This is amazing. I'm not even a mechanical engineer, but a computer engineer. But I found this captivating and informative. Thanks you for broadening my knowledge base!

[jpennin]

Awesome video! As a few others have said, I would love to see a follow-up episode about washers since now I'm not sure how they work, what they accomplish and what their limitations are.

[peanuts]

Glad you mentioned vibration because I work in aircraft maintenance and sometimes we have to torque check components after the aircraft has flown predetermined cycles numbers. The secondary torque values are noted and sent off to engineering monitoring to establish a resolution, if any

It's incredible how you managed to converge information that I have gathered and understood for 3 years in such short video! Absolutely fantastic information well done!

[nickbell]

They used to call me the "nut factor" back in college

[CalyGamer]

I started watching your videos for studying, but now I watch them for entertainment, they are so good. The animation quality and the information is amazing! I have to present in mechanical design on Wednesday and I based my presentation in your video about fatigue and SN curves

[ykyjohn]

this is a very well made educational video not just for the subject. The way it is made, the richness of content, the pauses, the way to speak, how clear and well pronounced words are, the amazing display with visual representation, the list goes on. Every aspect of the video is well done.

[ivanj]

I've been working in structural steel for a while now and this is by far the best explanation I've seen about how bolts work. Even what was tought in school did not come close to the quality if this video ! Thanks for making such understandable videos so people can learn complex topics easier.

[Strykenine]

A lot of first and second year engineering students are going to be watching these. Really good work.