The Incredible Strength of Bolted Joints
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- เผยแพร่เมื่อ 20 ธ.ค. 2024
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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/...
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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.
Love it when professionals are interested in constantly learning and getting better. Respect! 🙏
This is particularly important because people will often take shortcuts or otherwise deviate from the plans without realizing why the plans where written that way in the first place.
In engineering, we studied the Hyatt Regency walkway collapse of 1981. The jist of it is that the engineer's plan called for attaching the walkways in a method that was cumbersome and time-consuming, so the assemblers modified the assembly into a way that was faster and simpler, but they didn't realize the effect this would have in the stresses on the floors, causing them to fail under their own weight. One reason we study that is because it wasn't entirely the assemblers' fault. The engineers plans called for an assembly that was impractical, which is why the assemblers modified the approach.
Us engineers always need to consider how something will be assembled to make sure it's possible and practical. It's far too common to end up with a design where a bolt head is inaccessible because of a lack of clearance, for example. Vehicle mechanics regularly complain about the engineers who designed the vehicles because the clearances are so close that it's quite difficult (though not impossible) to access the fasteners.
2:30 Note: With a joint in tension like that, the bolt is resisting the entire load. The stress that the bolt experiences is not reduced because it has been preloaded unless the two surfaces are bonded in some way. In the case of two unbonded surfaces, the stress that the bolt can take before it breaks (the bolt's ultimate strength) is unchanged by how you preload it. The only thing that preloading does is increase the amount of external force you can apply before a gap opens in the joint (which may be considered a failure of the joint). The ultimate strength of the bolt doesn't increase because you preload it as implied in the video.
Thank you, that was the only point that was bothering me, very well worded, another way to think about it is as: the joined members are in compression (by the bolt) and the bolt is in tension (by the members). If the tensile and compressive forces don't balance, then you have a result of movement and possible failure, this is true of any structure. When those forces fall out of balance things move.
To the maker of this video, it is very good and I like that you have used accurate grade markings on the fasteners.
Yeah, a whole bunch of people are getting the takeaway that compressive forces between the joint members are load-bearing - but they can’t be since they are already nullified by their corresponding normal forces.
Preload seems like it’s just for rigidity and sealing/mating surfaces.
Though thinking on this again, there is a factor that having the faces of the members in contact, that does decrease the load on the bolts:
The gravitational pull between bodies, though I would be amazed if it had any notable influence, let alone be measurable. It would be possible to calculate it, but you would never rely on it.
But as an engineer, I would greatly appreciate being corrected if these views are wrong.
@@seanmance7499 I don’t think so, the electrostatic and atmospheric forces between them would be orders of magnitude higher.
Thank you for bringing this up. I thought I was alone. There is no way, without adhesion between the two bolted members, for the total preload between the members to be anything but equal to the total load on the bolt. As soon as the members are loaded the bolt begins to lose preload. A simple free body diagram is all it takes.
The stress in the materials may be different but the total load and preload is the very same.
Without the bolt there is no preload between the two members.
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.
I also make my living making GTEs
80% of the struggle in repairing old cars is getting rusted bolts out without stripping or breaking them. Sure would be nice if they'd use stainless.
@@dekutree64 Its purely a cost issue. The extra Nickel and Chromiun in stainless steel makes the stainless steel bolts a dollar or two more expensive than steel bolts. Multiplied by a few hundred bolts bolts per car, the OEM's would lose about $300/per car of profit times 4.4 million cars (what Ford made in 2023). That comes out to about $1.32 billion of lost profit per year for Ford.
@@dekutree64 stainless springs, galls, and is weaker than other forms of steel.
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 TH-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
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.
@@paris_marsto be frank, 3d is easier for channels, they can reuse those assets, not saying it's bad or less effort, 3d will take a lot of pre allocated time to finish. But it's doing the hard work first.
lol. Settle down nerd
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.
@Nunya Business "Hey, that sounds like nunya business" some corpo shill probably
Most power plants are private.
Chernobyl was government owned!
Thank you for sharing!! I wouldn’t want my fingers in the way when the bolt was still tensioned😂
@@MrAstrojensen bolts for traffic lights are bigger
I was in disagreement about the tension joint at first, but I worked out a way to explain it in layman’s terms. Could you paraphrase me in a pinned comment to help everyone else?
Bolts stretch in tension. If you add enough load to the joint, the bolt will stretch enough to remove the clamping force entirely. At that point, the preload is gone.
Every amount of applied load less than that, the bolt is bearing the *whole applied load* plus *whatever preload is left.* The clamping force is equal to that preload, and I think it was too distracting to bring in when making that point.
In the end, the tensile strength of the *joint* is still the same as the tensile strength of the *bolt,* and I think that needed emphasized.
The use of preload in a tension joint is in *rigidity, sealing surfaces, and cyclic fatigue reduction.* The way the video was worded seemed like there was a change in overall load capacity, though there never was.
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?
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
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.
Fun fact: Bolts are much less effective if they are not installed. Looking at you Boeing.
Planes use rivets 😜
@@MichalKolodziejczak-tf1yk You think there are no threaded fasteners in airplanes? Ok there champ.
@@MichalKolodziejczak-tf1ykthey use ductape
At least Boeing is inclusive and LGBQblabla friendly.
@@abdou.the.heretic Are you telling me that it wasn't just the hopes & dreams of the workers at Boeing that were holding those aeroplanes together
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.
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.
>>Browsing TH-cam, 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
Lol 😂 same exact thing
Cheers!
same 🤣 bed time
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 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!
tysm for making of the background black/dark. Makes watching this in bed so much easier on the eyes
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!
I love how every time you show a bolt breaking, it gets replaced instead of animating it rejoining because it's just a picture.
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.
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 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
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!
They used to call me the "nut factor" back in college
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.
You are a graphics God ! Those blender animations are certainly taking a lot of time, but the quality is beyond perfect. Keep this up !
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
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!!!
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
First three threads on which side?
@@WIentertainment The three that are closest to the head as that’s where the tension is when you torque the bolt.
When you put tension on a bolt, you are actually stretching it and deforming the threads.
Grip a rubber band in one hand and slowly pull with the other and feel for how the tension changes from the side you’re pulling from to the opposite side.
Iirc it's 40% on the first turn, 30%, 20, & everything else, do the rest of the bolt, is in that last 10%.
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 TH-cam great again.
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
Hi, I'm a mechanical engineering student, and I'd like to make a small correction. Fatigue is actually slightly correlated with the magnitude of the stress (4:30). It is usually discounted during calculations because it doesn't make a huge difference, and it would be impossible to run tests on all the average stresses the part might experience. So if someone wishes to account for the effect of average stress on fatigue, one of the things you can use is the Haigh Diagram, where the average stress and the stress amplitude define a triangle where operation is safe.
I liked it before even watching it. Thank you for your hard work and dedication to make engineering so much more enjoyable to learn.
Any chance you plan on doing a follow up video on fitted bolts? This video was great!
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.
Boeing engineers: make a note of that!
Incredible as always! This was my favorite part of my Design of Mechanical Systems class. Great work, love the animations
I'm studying this rn at university, and I realized I never gave a deep thought about this apparently simple element. Nicely explained
These videos are so brilliant, but when I heard about "the Nut Factor" at 11:46 I just lost it. I am still a child despite having a graduate degree..
In most aerospace applications the frictional force between the plates is ignored as most joints are not designed to be in tension. These shear joints are designed with tight tolerance holes, that way the joint is "fully effective" in transferring all the load from the first plate by bearing on the fastener, and to the second plate through bearing contact. The example from the video shows a loose fit fastener, as the the hole is much larger than the fastener diameter, causing the force to be transferred through friction rather than bearing.
visual representation + perfect explanation , really appreciate your hard work 👏
You have packed more knowledge into these 18 minutes than any book or reference material I have ever read. Absolute gold for anyone starting on bolted connections.
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.
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.
At 2:50 : I don't understand. The only force holding the upper half down, against the load, is the bolt. This clamping force that is mentioned is not a real force, as the bottom half of the jint piece does not really pull on the upper half.
5:50 This is a concept the general public is woefully ignorant of. People think that if there is a shear loading on the joint, the bolt must be in shear. It isn't. It's the friction between the two plates that prevents movement and the bolt is just there to increase the normal force to cause higher friction.
“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.
The main reason I love this channel is that how easily and brilliantly u make non engineers love engineering
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?
I'm not an engineer and I probably won't ever use this knowledge in my life, yet I still watched this 18 minute video for some reason
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 😆
I'm a mere DIY'er, but your demonstration was extremely useful in helping me understand more about some of the practices I've learned over the years. One thing I wish you had addressed is how the use of washers (e.g., of different thicknesses/diameters) affects (or not) the joint. I know you talked just a bit about "special" washers as a means to help address long-term slipping, but it looked to me like the ones you illustrated were just simple flat washers, not the spring or lock washers I've seen most commonly used to prevent loosening from vibration or simple aging. At any rate, this was a most welcome presentation, so THANKS!
Great video! Very informative, and the animations are wonderful.
Keep up the good work!
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.
This was so awesome.. Now you have me excited for a welds video. Excited to see how you do eccentric weld groups with torsion : )
I'm not even close to being an engineer, but I've been doing a lot of handy man work lately and just today had to do a simple installation involving some 1/4" bolts. my main concern was making sure the nut didn't strip, but watching this video afterwards made me appreciate the sturdiness of the final product even more. Didn't even know bolts were designed to stretch and apply a clamping force, although it makes perfect sense why they would be.
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.
I appreciate how the information is condensed and consolidated so as to deliver high efficiency that the viewer may easily absorb. Appropriate name for the channel.
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'
7:50 This answers my life-long question of why bolts don't just have threads all the way to the base.
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!
Toolmaker here.......this should be mandatory in any manufacturing apprenticeship program. Fantastic vid!
WOW, my understanding of bolted joints just skyrocketed! Subscribed.
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
As a structural steel fabrication shop owner/project manager, this is awesome for training guys on the use of shop installed bolts: type n joints-snug tightened bearing joints, vs pretensioned, vs slip critical. So good
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.
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.
It’s 2am and I have work tomorrow, not as an engineer. Why am I watching this.
Im an ordinary guy who's been using bolts all my life. This video has taught me much more than I ever knew about bolts, especially pre-load
i dont know why im watching this at 1am
You yearn for knowledge
As a normal person laying in bed watching this at 4:40 in the morning I got no clue what’s happening
Could be a physics thing (because that’s my background) but at 5:30 shouldn’t the normal force be pointing up?
I am a lawyer and watched this in full...amazed how much significance lies in seemingly simple things...the considerations that go into figuring out the correct torque/tensioning are just amazing...
0:54 Really, THAT wrench?
😂
What about it?
You use an adjustable wrench only if you really don't have the right size wrench, one of the reasons is that it will make nut round after a while
Once tightened, there is really only one way to do quality control on with how much torque a bolt or nut has been tightened, and that is by retorqueing: applying torque and measuring when the bolt or nut starts to turn further. The torque curve will show a sharp drop when that happens, which provides the measurement. It's used a lot in automotive quality control (bolt conditions remain constant there so variables that would influence measurements such as lubrication and surface friction don't change). Nice work.
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.
The most basic and the finest start for anyone keen to engineer. I would have liked to have watched this, er, sixty years ago. Cheers.
11:38 ah yes, the nut factor
so fun fact, I'm a philly ironworker and because we cant use a torque wrench large enough on the bolts that hold tower crane sections together we use a giant micromotor to measure the bolt stretch to know we have enough preload on the bolts.
That method is the only method actually precise enough to ensure preload was achieved.
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.
It's been almost 20 years since my graduation and I had remembered nothing about bolt joints till I watched this video. Thank you for this brief great illustration
Keep up the great content, the amount of effort that goes into these must be immense and we appreciate it greatly.
This was SO INTERESTING. Thanks!
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!
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.
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.
This makes so much sense, I’ve always wondered how ironworkers/steel erectors are so confident with assembling steel beams for skyscrapers using just a few bolts
She torque on my wrench till I preload with nut force.
That sounds like the nut factor right there.
Dude! Keep the torque under check it might break your wrench.
Right
I had the course of bolt calculation for 2 days and had read a lot things from the internet, But I am able to understand after watched this video. Thanks a lot. Please keep it for engineers. Best Regards
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 think I've watched this video like 10 times already lol, as a suggestion, I'd really love one dedicated to welded joints, since that is a topic not many people talk about, yet it is ond of the most common types of joint
BTW, if it wasn't clear, this is a great video
Hehe... joined members
Your shear and especially double shear diagrams blend in with the background
Nut factor, lmao
Teşekkürler.
The nut factor 😂😂😂
When reinstalling my axles/suspension on my jeep, I was told by an old timer to go back and re torque every nut after about 250 miles due to settlement and creeping. All but 3 were out of torque.. going back and re torqueing is now on the to do list when replacing parts.
12:11 "friction under the nut and in front of the bolt and the use of lubrication, all introduce a lot of uncertainty..." must... hold back... penis joke...