The Incredible Strength of Bolted Joints
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- Опубліковано 17 кві 2023
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Watch my bonus video on joint diagrams: nebula.tv/videos/the-efficien...
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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.
Credit to NASA for the 3d model of the Perseverance Rover: mars.nasa.gov/resources/25042...
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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!
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Did I miss anything interesting about bolted joints? Leave a comment! And remember you can watch the bonus video on joint diagrams on Nebula here - nebula.tv/videos/the-efficient-engineer-understanding-the-joint-diagram
I think double nut method can be also applied to reduce the loosening of bolt joint? I saw them before in some of my local footbridges🤔
Excellent video.
Maybe you could have also covered countersunk holes, purpose, and how they affect tensile and shear calculation.
If you don't mind general requests, i have a couple. 1, metrics...like how do you know the accuracy is ±1% unless you have a more accurate tool to measure that, and then how do you know it's accuracy is even better unless it was directly measured by something even more accurate, etc. This would apply to any base unit (time, length, temp, etc) or truthfully any tool measuring any unit (voltage, pressure, chemical purity, etc.)
2, thermal expansion and various ways to deal with it in various applications, like aircraft, structures, power lines, who knows what else. I've always been fascinated at how it's possible to overcome that thing, to me it seems insurmountable when you think of some regions on earth that get really cold.
@@mcd00080 Agreed. I'm a union ironworker, I've gunned up a bolt or two in my day. We're all taught not to torque the head whenever possible.
I was a little surprised that the humble flat washer was not mentioned. And tho I've rarely had the chance to use them, direct tension washers -the ones that squirt- are a pretty slick system compared to dragging the impact gun around with all that hose. Spline drive are neat too.
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.
Why does the clamping force exist? Is it because of big surface area of contact after the bolt is tightened?
@@himanshusingh5214 it says it in the video. It's because the bolt stretches when you turn the nut. Since the head is fixed in position and the nut wants it closer, the only way to get closer is by stretching the bolt.
That stretching is usually elastic deformation, which produces a tensile force. Although there are some very specific and certainly not reusable bolts that stretch beyond the yielding point and actually use plastic deformation
@@christianlabanca5377 In the video it says that these joints can handle big forces because before the bolt experiences streching force, clamping force takes care of it and he explains it using the example of the bolt representing a small spring and the clamping force representing a big spring.
@@himanshusingh5214 I think it is the elastic deformation of the two plates as the bolt forced them to mate. They act like spring washers as they compress.
@@KayAteChef But spring washer is used to make sure that the bolts don't become lose. It doesn't increase their strength.
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.
yeah this kind of stuff is amazing, look in any direction anywhere in industry and you will see thousands of hours worth of knowledge lying in plain sight when you look close enough. that's why I'm a millwright apprentice, all of this stuff just works somehow and that fascinates me. We are blessed to be able to do the work we do, definitely beats smashing rocks together unga bunga style.
same here. that was a pretty cool video
@@yo64yoskilled labor is awesome! I think the de-skilling of labor is part of what contributes to an attitude of carelessness (like people not caring about torquing to spec for example) because they simply don’t understand *why* it needs to be like that they just know to do the thing.
I used to work in nuclear power and the bolts that hold down a reactor head are about 12" in diameter that need to be torqued to something insane like 1 million ft/lbs. We used a huge hydraulic machine to pre-stretch the bolts and then run down a giant nut. When you release the pre-stretch it generates incredible clamping force, greater than any machine could twist onto the nut!
Thank you for sharing!
😮😯😱
It's not surprising that you would need that much force for a reactor head, but dang, it's still impressive.
What's interesting is the same ft-lb on two different diameter bolts creates different clamping loads.
Seems odd to use a 12" diameter bolt. You're losing a ton of clamping force (which is why the ridiculous 1M ft-lb). Then again, nuclear reactors are not something I've had the good fortune to work on so I'm not even sure what exactly that bolt does.
In my memories those same bolts are hollow, pre-heated by dropped in 440v heaters for many hours, and only then torqued to spec in opposing pairs. The cooling shrinkage does indeed contribute incredible clamping force.
Fun fact: Bolts are much less effective if they are not installed. Looking at you Boeing.
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!
Same here! I graduated from Cal Poly Pomona last year and these videos helped me me out more that I ever Imagined🙌🏻
One of the most underrated channels. I am a Geotechnical Engineer, but I always watch his videos because he explains complex concepts simply.
A good rule in real life engineering ==> It is all made of rubber of varying stiffness.
Well if you look back at how often he posts then you’ll see it takes on average about 3 months
Cal Poly Pomona Architecture grad / lisenced architect here - class of 91' Fully agree with quality asessment. We didn't even have a structural engineering textbook, much less UA-cam back in the day. We just took notes from our engineering professor's lectures.
The hardest part of those classes was staying awake. Luckily, the professor repeated himself constantly.
He was a big believer in redundancy - for his structures and his pedagogy
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.
Whoa! That’s sounds crazy to use hydraulic tensioners and nut them down. Thanks for sharing the info.
I bet if those power plants were privatized and the unions were shut out some genius would go "Hey why can't we just use cheap bolts? Why have all this expensive crap?" Then everything would go to shit like in Texas where their entire power grid failed.
@@nunyabusiness3786 "Hey, that sounds like nunya business" some corpo shill probably
@@greyarea805 b-but I'm an engineer...
"Nope. You are a minimum wage multi-role technician cause umm uhhh I wanna be rich"
Most power plants are private.
Chernobyl was government owned!
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.
It's Science.
@@ThisIS_Insane What drives it is the desire to push the limits of what we can do. Rather than just be satisfied with simple, weak joints, they kept trying to do bigger and bigger things. This required studying in great detail the characteristics of the materials and ways they interact.
@@gblargg No foolin'? 🤔
For many every day situations you don't need to put so much attention into bolt joints. But for some it's super important.
There is and there isn't. It entirely depends on where the system is used. We make engine components where bolt torque can be critical but most of the time it isn't. Many engineering companies like the one I work at develop their own formulas and then simply use a table for guidance or spreadsheets to get quick safe rule of thumb calculations. From there if needed the joint can be further engineered and optimised.
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
What about the 11:47 : Nut Factor
smoking joints?
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).
OMG.
I used to do nuclear outages. The "bolt techs" had those awesome induction heaters.. it was cool just to see how the halves of the turbine were connected together, with such immense force and huge bolts
I wonder how did the makers of steam locomotives a long time ago figure how much to tighten the bolts holding everything together?
@@ninemilliondollars From my understanding it was a process of improvement. As each generation of machine (and machinist) came to be the lessons learned from the last generation would be applied. It's impressive seeing the design changes and improvements in power stations running the same turbines but with more advanced ancillaries.
@@ninemilliondollars They used rivets mainly. Hot pressed rivets have the same shrinkage clamping like bolts.
They used to call me the "nut factor" back in college
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.
I've seen that, it's nice. Isn't that what most animation software nowaddays provides almost automatically?
@@iwilltubeyouall It would have been easier to add those things in some pure video editing software rather than 3D software. I'm saying the fact that he does it the harder way for that extra bit of polish is cool.
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.
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!
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.
i was just about to say this myself! a quick search of comments first led me to yours here so now i am #11 on a thumbs up!
Washers are to reduce wear by transferring bolt rotation to an easily replaceable part, otherwise every time you adjust the bolt, you are digging into the surface of the material. They also reduce pressure by increasing the surface area on softer materials that would be deformed by the preload pulling the bolt end and nut into the materials to be joined. If you have plastic or wooden parts, washers are a necessity. A washer needs to be a certain thickness and hardness to be rigid enough not to bend or deform in the centre, where the nut and bolt ends are. The hole should also not be too much larger than the diameter of the bolt, so that there is plenty of contact area between it and the nut.
One of my professors used to teach a threaded fasteners course and he mentioned that something like 90% of the tension load on a bolt is in the first 3 threads regardless of the number of threads due to the deformation of the bolt when being tightened
My structural engineer colleagues agree with him
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
Incredible as always! This was my favorite part of my Design of Mechanical Systems class. Great work, love the animations
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
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!
Boeing engineers: make a note of that!
A lot of first and second year engineering students are going to be watching these. Really good work.
Im 4th year, with a finals exam on joining technology. This was super useful
visual representation + perfect explanation , really appreciate your hard work 👏
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.
Been an engineer for many year in manufacturing, never specializing this heavily in bolt mechanics, but many times touching on them. Great video!
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.
I liked it before even watching it. Thank you for your hard work and dedication to make engineering so much more enjoyable to learn.
What perfect timing with this video. We're looking at bolted connections in my steel member design class right now. The slip and bearing portions of this video really helped me.
Once again, thank you so much. I just finished this video and it has really kicked open the doors for me. I really understand things I should be including in my analysis package now.
Thank you very much ! as a civil engineer student this video is really helped me understand through this semester. Hope you didn't retired making this kind of videos.
“The common birthing mechanism uses 16 bolts to connect and create a seal between modules on the ISS. Upon docking, each of the 16 bolts mates with a nut…” this has got to be my favorite sentence and might make me become an engineer just so I can use these terms more frequently.
The nut factor had me giggling like a twelve year old lol
*berthing mechanism
@@noodlelynoodle.Nut factor caught me off guard like a brick to the face. It made this the funniest video I've seen in days. 😄
Remember boys and girls, lubrication can affect the nut factor.
Excellent video, mechanical engineer for 20 years and some good refresher info, and some things I didn’t know. I wish they would explain bolted joint design this well in senior mechanical design classes.
Great video! Very informative, and the animations are wonderful.
Keep up the good work!
This was so awesome.. Now you have me excited for a welds video. Excited to see how you do eccentric weld groups with torsion : )
This is an excellent video! The animations, organization, and information are all top notch; such an amazing presentation.
Never thought I'd be so invested in a video about a bolt, good job sir 👏🏾 👍🏾
You are a graphics God ! Those blender animations are certainly taking a lot of time, but the quality is beyond perfect. Keep this up !
I feel like I just took an entire semester's course in mechanical engineering.
Very good explanations, and the visuals are stunning. Perhaps the coolest is that the labels and graphs realistically reflect in the depicted bolts etc
First time on this channel, and I'm mouth wide open from the quality of this video. Every single aspect is perfect. They even added a 'click' to the torque wrench at 11:30.
This was a very informative video, you condensed a whole unit of my post-secondary schooling down to a quarter of an hour. And it all makes sense. This actually makes me want to see your other videos to find out if they're just as enlightening.
Spoiler alert: they are. A quick 1.25 speed watch before you go over it in class will make the topics make so much more sense in lectures
@@johnhartney7576 I could imagine, though I already graduated a few years ago.
I discovered some of the above simply through observation of bolts used in wooden structures, especially when taken apart and put back together again repeatedly. You can frequently see fatigue issues as the bolts are much stronger than the wood. It's fascinating to see what joints are pushing the capability of the wood/bolt joints, and what joints do not show visible fatigue. I learned all this assembling, taking back apart and reassembling, a backyard jungle gym for the kids as we moved around early in our marriage/family. I should also note that we live in the Midwest and the delta temperature and humidity varied throughout the year. I ended up replacing some of the wood and switching to larger bolts in stressed joints that were also roughed up and glued.
The above was used for about 2.5 years before we moved to our newest house which we have lived in now for over a decade. When I took apart the jungle gym the last time, we had to pry the wood apart with a crowbar and no stress was seen in or around the bolts/holes. Thankfully, this was only for those joints that appeared fatigued. I recently inspected the critical joints for visible fatigue and found none. Adults are not allowed to use it, only children, or at this point, grandchildren 🙂
I am a fastener supplier from China, contact me if you need, thanks!
I have been looking for a resource like your channel for so long. I'm so happy to have finally found you!
Thank you for linking to the Nebula video in the description, and for making it its own video instead of "bonus content" at the end! This is so much better it boggles my mind that most creators on Nebula don't do it.
If there's some sort of Nebula creator forum or the like, maybe you could suggest that others do it this way. It's a much more user-friendly crossover between YT and Nebula (and Nebula, for all that I'm sure it's wonderful for the creators, is pretty abysmal for the users, so it needs all the extra user-friendliness it can get!)
Keep up the great content, the amount of effort that goes into these must be immense and we appreciate it greatly.
Anecdotally, the elongation I have measured for a given nominal diameter/girth has always been smaller than I expected. I must have forgotten to account for the nut factor
WOW, my understanding of bolted joints just skyrocketed! Subscribed.
Thank you for this amazing content. Please make more videos about Machine Elements :)
Do note that the use of lubrication may modify the nut factor.
That is one of the reasons that the turn-of-the-nut method of pre-loading is preferred for structural work.
The problem that remains is to decide at what point of loading to begin the turn[of-the-nut process.
The Canadian Handbook of Steel Construction has the starting point after 2 or 3 solid blows of the impact wrench on that bolt.
Lol
This is a great summary about bolted joints. Congrats for your work.
The clarity of the speech and the quality on animations is amazing.
Hey, Awesome video as always.
One comment! Nominal minimum bolt preload for 8.8, 10.9 etc is according to >>>bolt tensile strength
Is that standard freely available?
Brilliant.
While I have an Electrical Engineering degree, the first two years of our course included much stress analysis and mechanical design as a basic foundation.
But ... this video dug into the many nuances of bolted joints which I had either forgotten or not quite grasped at the time, and is a thoroughly enjoyable and informative presentation. 😀
Where'd you do your EE? I went to VPI&SU and none of that was in the curriculum. Too goddamn many programming courses were though. Felt more like a CS major than EE (and I wanted to get into physical chip design so I ended up leaving).
@@ObservationofLimits Queensland Intitute of Technology, Brisbane, Austrslia.
Four year degree. 1969-1972
8 Subjects. 36 hrs/wk lectures. Tutorials and assignments on top of that.
Thesis in fourth year. UHF Stripline solid state amplifier. 5W @ 450Mhz.
Look at the back of any motherboard. All stripline transmission. All the wriggly and bent bits are delay lines, inductors and capacitors.
IT didn't exist then, but 50 step hand-held programmable calculators did. HP and TI. $250 when an Engineer's salary was $6000/pa.
For serious computing we programmed in Fortran and took the punched cards to the mainframe office. Results came back a few days later. 🤣😅😂
Key is to "never" lose curiosity or stop learning.
Years ago I taught myself C++ for a hardware project.
If I have the need I'll learn one of the current coding platforms. Much more readable and less cryptic.
:-)
Never in my life did I think I'd consume an 18 min video on BOLTS! Well-done. It's videos like this that make UA-cam great again.
thank you for the effort putted in the video
It’s 2am and I have work tomorrow, not as an engineer. Why am I watching this.
Rename yourself to The Amazing Engineer.
the amazingly efficient engineer..
+1
I wouldnt want to associate with The Amazing Atheist
@[TV]pp what about the Amazing Jonathan?
The overly effecient engineer 😆
Much awaited video. Thanks and kudos to you for the amazing work!!
Subbed! Needed this a long time ago when i went to engineering school! Very clear explaination. Keep up the good work
Bolt specialist here. As requested, here are my suggestions for improving this video:
1. bolts LOOK simple, but looks are deceiving. There are plenty of subtle details you won't see at first, e.g. bolt-to-joint and nut-to-joint surfaces are often slightly angled to optimize load transfer. Don't call them simple;
2. bolts are not always reusable - see item 8 below;
3. you are correct in mentioning that the joint parts a much less compliant than the bolt. Consider adding that this "much" is typically 3-5 times as stiff for steel parts joined by steel bolts. For aluminium plus steel, the factor smaller - this is one of the reasons why magnesium parts don't combine well with steel bolts;
4. you often say "This is called..." but really, almost all terms you introduce this way have alternate names. E.g. what you call "embedment" is a.k.a. "settling", and the "joint diagram" is often called "clamping diagram". Viewers need to know if they are to learn more;
5. You state that in shear joints, bolts should be "at least two diameters away" from the edge. That assumes typical combinations of materials. On e.g. aluminium parts with 10.9 bolts, I would personally recommend a bit more;
6. I just said "10.9". Bolt strength designations like that one would be a good addition;
7. no, sorry, the turn-of-nut method is NOT easy, at least in mass manufacture. You'll need equipment to measure the angle correctly, especially in safety-critical applications. Plus, it is usually deployed a bit differently than you suggest: first you tighten to a specific torque value, then you add a certain number of degrees of twist. Hence the name "torque plus angle" for this method;
8. you missed the tighten-to-yield method and that's a pity. It works by measuring torque and angle simultaneously, and the bolt is tightened until torque levels off w.r.t. angle. The bolt is now tightened just beyond its yield strength. Second-best possible method out there IMHO, but don't reuse the bolt;
9. best method to date: ultrasonic measurement of bolt lengthening. Dutch company Nedschroef developed this years ago under the name "Nedsonic", taking it from the domain of quality control into line assembly;
10. Final suggestion: take a deep breath now and DON"T FEEL BAD! Your video got quite far, and the points I suggest you add are certainly NOT common knowledge. The assembly industry has a habit of hiding its "secret sauce". Plus, you visualizations are top notch and put almost any textbook to shame. Keep it up buddy ;-)
Thank you for your additional insight, learned several things
The video is clearly meant to simply touch upon these subjects as most videos like this do.
It's an introduction to concepts which the video does perfectly. Adding even half the stuff you suggested would make this a 45-60 minute documentary rather than what it is
This comment, wonderful and informative as it is, is borne from the friction between experts who have deep knowledge on a subject reviewing material that is clearly supposed to give a "20 thousand foot" view of it.
The omissions (like the ones you cite) feel critical to an expert, but to the newbie, they're stuck thinking about the nuances of tension vs. shear. Videos that introduce complex subjects don't have to be one-stop shops for everything about that subject.
A video on "Gell-Mann Amnesia" by acollierastro opened my eyes on this recently. We've all grimaced watching explainer vids on subjects we know a lot about and thought, "thats not how I would put it..." or, "what about [this detail]?"
Thoroughly enjoyed reading your comment. Thanks much for the detailed info
I am a fastener supplier from China, contact me if you need, thanks!
EXCELLENT. very well made video and easy to understand, NOW what I need is a follow up video on the use of washers, lock washers, spring washers, flanged bolts/nuts etc I often see on construction sites of large buildings NO washers are used but a home appliance or small things say a trailer does use them, please explain.
Good question. Building steel joints are sheer joints. The holes for the bolts are made by the steel materials supplier, as specified by engineering. Location, dimensions, tolerances, are all specified by designs which all must conform to standard regulations. So the correct fastener hardware will fit very well in the hole it's designed to go into. Appliances parts are made with very broad tolerances. Precision is expensive. So they add washers and the like to take up the slack in sloppy fitment. And, they use very thin metal and plastics, they don't want to use larger bolts, so they add surface area to the head and nut so it doesn't deform parts.
Thanks for the high quality videos. Better than any textbook available ! Wish these videos were here when I was an engineering student. Keep it up 👍!
In this quarter of an hour I understood more about the topic than in years of working with bolted joints.Thanks for your excellent work.
This is an incredibly informative video. The talk about sheer force being taken on by the joint parts due to friction force was something I've never even considered before.
HOWEVER - please, engineers, please consider renaming K away from 'Nut Factor'
Very good video, i would like to add something though. The clamping force of a bolt or nut acts in a 45 degree angle from the tip of the bolt/nut head down until it reaches the end of the material. This is why adding washers with a bigger diameter than the bolt/nut head increases the clamping force. For the most effective clamping strength across a unit, the clamping force ends should be tip to tip with each other.
Like the double cone looking bolt force diagram?
That's true as long as the washers are thick enough and strong enough. There are plenty of washers out there that are so thin they are virtually worthless.
This was fascinating, thanks for sharing! Your videos are great!
Great video with some great information. One unusual technique I've seen was with very large stud/nut fasteners used to close large pressure vessel heads. The stud actually has a small hole bored down it's length for heating rods. We would insert the heater rods and heat the studs for several hours. Then apply the washers/ nuts and tighten them to a specific angle preload. Afterwards, removing the heater rods and the stud of course would contract a known amount. This made it possible to get a certain elongation (i.e. 'stretch') of the studs without the need for huge torqueing equipment.
Sir please do video on what is thermodynamics, Computational fluid dynamics, heat and mass transfer, strength of materials, Kinematics and Dynamics of machines, CAD/CAM
Yes, the entire mechanical engineering curriculum, please. When you get some free time. 😅
He already has most of these topics covered.
Amazing content! I love seeing engineering concepts so well animated like this. A super cool added bonus would be to include the angled geometry of brittle fracture along shear plane:
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Or necking of ductile fracture:
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Thank you for these videos!
Thank you for taking time out of your day to teach stuff like this to people.
This is a great video, I learned a lot about skew and bolt from it. Thanks a lot!
Great video and animation! You cover many important bits.
But, I would have liked to see
- no preload with a standard nut will cause the nut to loosen
- preload for joints in thin materials is only achieveable with spring washers or bolts with lower Young's modulus
Special case as a sidenote:
- Preload is hard/impossible to keep when boltign plastik parts together. The plastik will literally "flow" away from the stressed area over time, dependant on it's hardness.
I don't understand how pulling the two preloaded sides apart will not directly influence the stress in the bolt. The pulling apart is in the same direction as the preload. If you don't preload the Bolt and Nut at all and pull the two plates apart the load on the bolt increases proportionally to the external force.
EDIT: I get it now... first the preload is reduced and when there is no more preload then all the force goes directly to the bolt. I had to imagine the preload being a lot of small compression springs and the bolt being a tension spring.
Yeah, I dunno. Even treating it like springs I’m having a hard time seeing how a bolted assembly has more tensile capacity than the bolt itself just due to preload… It just doesn’t make sense to me.
Clear, concise, easy to understand. Well made video!
Very interesting and clear information provided through the excellent diagrams, animations and well delivered narrative. I just stumbled onto this video and enjoyed it thoroughly so thank you very much.
Through it all I kept thinking about how this applies to rivets....
I don't think you have enough subscribers so I added one of my own with a white notification bell. And a thumbs-up, of course because this analytical mind appreciates this kind of precision when information is being imparted. Well Done.
A couple of related topics that might fit in (and I didn't see in the preview images for nebula) are: how washers affect the load application (during fastening) and load distribution, and types of washers
Especially split lock washers
i dont know why im watching this at 1am
the explanation and visualization is brilliant
I'm also an engineer and this video is a better explanation of the nuts and bolts of nuts and bolts (so to speak) than anything I've heard or seen before. Good work!!!
Your explanation of clamping force is totally wrong. When you tighten the bolt, the clamping force is equal to the tension in the bolt. if you then try to separate the clamped parts, the parts won't separate until the acting force is becoming larger than the clamping force, but the extra force applied is transferred to the tension in the bolt from the start. So when parts begin to separate, the tension in the bolt is already twice the initial preload.
I disagree - see the graph in the Bolt Load vs Applied Load section of this page, for example - mechanicalc.com/reference/bolted-joint-analysis.
Preloading doesn't affect tension joints though! Any tension load applied to the joint must eventually be transmitted to the bolt, so a 10kN load will result in 10kN force in the bolt regardless of how strong you preload it, it's a simple case of following the load path really
You're generalizing the case of piping (which require preloading for the sealing of the joint rather than actual structural requirement) to all bolted joints
This should be higher up
What he means in the video is that the *change* in tension in the bolt is far less than the *change* in tensile load. This is because the tension on the bolt due to the contact force of the joint members is *replaced* with the tensile load. Without preloading the change in tension on the bolt would be equal to the change in tensile load.
@@JWQweqOPDH still, the change in tension doesn't govern failure at all
If you preload a bolt that's rated for 100kN with 90kN then introduce a 10kN change then it'll fail just like it would from a 10kN preload with 90kN change
So all in all whatever he meant it was wrong
Don't get me wrong I love the channel and this is the first time I've seen him make a mistake, but it is nonetheless a mistake
@@architunnel thanks, I hope it does just so that people don't get this fact wrong
I myself really like and trust this channel and I was starting to doubt all my engineering career from this lol
@@Truth4thetrue While *static* failure depends upon absolute tension and not change in tension, *fatigue* failure absolutely does depend upon change in tension. The mechanics of fatigue failure is what makes older parts less reliable than new/unused parts.
Thank you this video was unbelievable. So well explained.
This was SO INTERESTING. Thanks!
This video is very clear straight to application point of view yet covering the majority of science of clamping force from fastening. Far better than what one can understand reading whole semester engineering on fastening.
This was super interesting and very well animated, loved the video!
Exellent video with very good description, to analyse the mechanics of fasteners. It is useful for every engineer who is working on designing clampings systems for a product.
Thanks for a fascinating and comprehensive insight into which on the surface appears to be a simple subject. Duly liked and subbed.
This video deserves way more views. It's a hidden gem on UA-cam!
That part about the clamping force taking part of the load is counterintuitive and might confuse some people. I would put it this way: When the preloaded bolt is put under load, it elongates. At the same time, the clamped members spring back (expand/decompress). As a result, the members remain clamped together since the elongation of the bolt is cancelled by the expanding members. As the load is increased some more, the bolt elongates further. At some point, the members are fully decompressed and can longer cancel the bolt elongation. At this point, the members move apart.
I get why the parts only separate after a certain total load. But I don't get how the bolt only takes a part of the additional load. After all the bolt is the only thing holding the parts together.
@@superdau That is the part I could not get either. And I bet it's wrong because it goes against all intuition and physics.
@@superdau same. and I'm really glad some here are pointing it out. all the comments about how amazing the video is but it's got this glaring problem - maybe it's just being very unclear, but it sounds like it's just flat out wrong about an absolutely central bit of reasoning.
@@vincentpribish5103 I'm also surprised that people who seem to have had work experience with bolts could not detect the anomaly.
@@bluekenya4825I thought this was wrong at first too, but I think I figured it out. Consider this, when there is no load applied there is still tension in the bolt, so the tension is GREATER than the applied load. But if you apply enough load, at some point the bolt will be stretched enough for the two parts to separate, as you pointed out. And at this point the tension in the bolt has to be EQUAL TO the applied load because that load is now the only force acting on it. So that means that as load is added, the tension in the bolt is NOT just increasing by the amount of the applied load!!!
Without a load, the force on the bolt is coming from the compression of the clamped material between the head and the nut, but as load is added and the bolt elongates, that material decompresses which means that source of tension gets reduced as the tension due to the load increases.
Great material to refer and refresh about bolted joint. Appreciate your efforts and knowledge sharing.
Super Good, thanks for all your hard work. Visualizing it made things so much clearer.
This has been very informative, thanks!
I'm studying this rn at university, and I realized I never gave a deep thought about this apparently simple element. Nicely explained
I know nothing of these things, but I'm glad it popped up and look forward to learning more.
Excellent video. Beautiful to watch and very detailed and well explained. Thanks!
What a great video. I had no idea. Super interesting! Thank you!
Excellent video.
I've been using CAE to analyse bolted joints for a number of years now.
Some of the engineers in the teams I worked in knew nothing about how bolted joints work. One of the chief engineers thought i was talking another language when I told him that the bolt sees near no load when a joint is in tension and doesn't open.
I had to draw him a joint diagram before he was finally convinced.
Bolt Science is a good website that I've used in the past.
Some of this stuff is stuff I somehow knew intuitively but this confirms my intuition so thank you.
New sub. great visual explanations. I enjoy the straight to the point explanations and no unnecessary comedy or meming.
I enjoyed this way more than I expected