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MechaTomics
Добавлен 9 мар 2009
spring buckling
Buckling is another design consideration for compression springs. We discuss the displacement criteria, show FEA buckling, show buckling failure maps, and how the slenderness ratio plays a key role.
Просмотров: 204
Видео
spring lecture 4
Просмотров 279 месяцев назад
We cover some basic information in spring design with the goal of making clear some of the info we have already covered.
Spring Design Lecture 3 Comparing FEA and Castigliano's theorem for spring stiff
Просмотров 133Год назад
We discuss how to count coils, how to estimate spring stiffness, and how that estimate is strongly dependent upon the coil count.
Spring Design Class 2 Estimating spring stiffness using Castigliano's theorem
Просмотров 157Год назад
We use Castigliano's approach to estimate the spring constant for a helical coil spring loaded in compression. This allows a simple formula for calculating spring stiffness for a given coil diameter, D , and wire diameter, d.
Spring Design Lecture 1
Просмотров 171Год назад
Intro to springs and calculating the stress that drives failure in compression springs.
gear meshing
Просмотров 1,2 тыс.2 года назад
Overview of meshing equations to assure that gear pairs can work together. I provide the basic equations for both Spur and Helical gears and show how the equations for helical gears suffice for both helical and spur. Also, once you know the minimum pinion to mesh with a rack, you know that all sizes above that minimum will mesh. It is small gears that give us problems.
Intro to Gear Trains
Просмотров 3962 года назад
Brief intro to gear train calculations, including the basics of train values and how you calculate torque and speed ratios
FEA of simplified diesel engine to evaluate gasket pressure
Просмотров 1742 года назад
A quick run through of how one can use FEA to evaluate gasket/contact pressure at the head/block gasket in a diesel engine. The basic idea is good for any IC engine. Though it is a simplification, it captures the essentials of the problem.
head bolt lifetimes and gasket failures in the Ford 6 0L powerstroke diesel
Просмотров 3342 года назад
We apply our understanding of tension loaded bolted joints to the failure of the head gaskets on the Ford 6.0L powerstroke diesel
Sample problem showing factors of safety for a bolted pressure vessel
Просмотров 4832 года назад
Steps that one must take to determine factors of safety for a bolted joint loaded in cyclic tension. This includes static and fatigue factors of safety and the steps one takes to calculate them.
Climbing robot demo
Просмотров 992 года назад
This is an embodiment of a climbing robot we imagined, designed, built and tested. My grad student on this was a beast! He is now at SpaceX.
Lecture 27c Sample gear tooth contact calculation
Просмотров 5742 года назад
Sample problem showing how to find the contact stress acting between spur gear teeth at the pitch point.
Lecture 27b Gear Tooth Contact Stress
Просмотров 1 тыс.2 года назад
We discuss how to model gear tooth contact stresses using equivalent cylinders for the involute profiles. This allows us to use existing solutions from contact mechanics to find the contact stress in meshing gears.
Lecture 27a Comparing Lewis Bending Stress with FEA
Просмотров 5202 года назад
We step through a comparison of FEA and the Lewis Bending Stress results for tangential loading at the outer extremity of a spur gear tooth. The difference can be accounted for using a root fillet stress concentration factor.
Lecture 26 Lewis Bending Stress in Gears
Просмотров 2 тыс.2 года назад
An overview of the Lewis bending stress for stress in a gear tooth. This forms the basis of both yield and fatigue limited design of gears. We develop the equations and then apply them, prior to learning the AGMA for gear design. Bottom line is that gears fail either by bending driven fatigue at the tooth root, or contact fatigue on the tooth faces.
Lecture 25 forces between gears and intro to gear trains
Просмотров 8952 года назад
Lecture 25 forces between gears and intro to gear trains
Lecture 22 More info on Journal bearings
Просмотров 5662 года назад
Lecture 22 More info on Journal bearings
Lecture 21a intro to Journal bearings
Просмотров 9152 года назад
Lecture 21a intro to Journal bearings
Lecture 20b Sample problem for tapered roller bearings
Просмотров 2,4 тыс.2 года назад
Lecture 20b Sample problem for tapered roller bearings
Lecture 20a Intro to Tapered Roller bearings
Просмотров 18 тыс.2 года назад
Lecture 20a Intro to Tapered Roller bearings
Lecture 19 variable loading of bearings and intro to damage mechanics
Просмотров 8242 года назад
Lecture 19 variable loading of bearings and intro to damage mechanics
Lecture 18 Combined axial and radial loads on bearings
Просмотров 17 тыс.2 года назад
Lecture 18 Combined axial and radial loads on bearings
lecture 14 welds under bending and shear
Просмотров 4162 года назад
lecture 14 welds under bending and shear
Lecture 12 Shear loading of bolted joints subjected to moments
Просмотров 1,3 тыс.2 года назад
Lecture 12 Shear loading of bolted joints subjected to moments
Lecture 11b example problem for bolts in shear
Просмотров 5742 года назад
Lecture 11b example problem for bolts in shear
ME 329 Design of Machine elements: Lecture 11a intro to shear loading of bolts
Просмотров 4792 года назад
ME 329 Design of Machine elements: Lecture 11a intro to shear loading of bolts
Lecture 10 Fatigue factors of safety for bolted joints in tension
Просмотров 5572 года назад
Lecture 10 Fatigue factors of safety for bolted joints in tension
Loving the classes. Its so much detailed and good
you are a sexy boy
tnx
What a gem of a video! Thank you very much for the clear, concise explanation.
This is absolutely incredible.
so valued video, thanks
Thank you! I visited your channel and saw a number of wonderful machines!!
This was an excellent explanation
Thanks! Glad it resonated.
hi sir, where's the example from? from which textbook or source? could you say? thanks.
Brilliant video, thanks a lot.
Sir, what is the physical meaning if the contact pressure ges negative ?
Hello.Nice video!!But I have a question. How to calculate safety factor using Gerber theory, when my load cycle is symmetrical (mean stress is zero)?
If the mean stress is zero you are intersecting the stress amplitude axis where all lines converge...so the factor of safety is just equal to the stress amplitude divided by the endurance strength. Thank you for asking this question, because the Gerber formula does not work when the mean is zero!!
Thanks, you just stopped my mate from having a breakdown in the engineering forum. Brill video. My hero
It's funny to think that something imaginary would be so concrete to base stability on
Well how do you find this correction constant for the cross-sectional area?
Professor, I stumbled on the same question. Need help!
The chart I show is just a portion of the bearing catalog. You would need to go to a comprehensive catalogue from the supplier you want to use. For instance, you could go to the SKF online catalogue and enter the dimensions of your shaft and it directs you to a bearing. The lecture here, is showing you a procedure that you can use to double check what the suppliers suggest when they point you to an online calculator. You could also go to the online pdf catalogue for Timken, or NSK, or Fersa or Schaeffler. There are many sites you can choose from. Pick the supplier that offers the best combination of price and reliability that can deliver to your location.
What if my diameter is 2.125? What should I do when looking at the catalog?
What a surprise!! I had the same problem
Great
Sir, could you share the excel file that you programmed, thanks.
There is a tutorial video that explains what to do. I don't share the files because I often assign this task to my students!!
Grateful to you, thank you so much
sir what happens if it is a compound shaft of varying diameter, i have a overhang shaft which is thicker at centre and has two mass components at the end of thicker section ,how can i approach it
You have 2 main options: 1: Just build the shaft and run an FEA analysis in the manner I showed; or (2): Use a lumped mass model in the basic equation. You can choose the smallest diameter section and treat that as a uniform shaft the entire span...then add lumped masses to that uniform shaft that are associated with the changes in diameter and combine the uniform shaft and the lumped masses using Dunkerly's equation. The more 'lumps' you use, the better the approximation. Remember to not include the uniform shaft in the 'lumped' masses. Imagine those shoulders as extra weight added to the uniform shaft. Does this make sense to you? Regardless, I would compare a hand calc to an FEA to make certain you are getting similar answers.
I want to caution you on using the approach I recommended above...it will give you answers that are well below the reality. If you do what I suggested, you are going to add mass to the smallest 'effective ' diameter shaft...this will be much more compliant than the true shaft, and will give a whirling frequency much lower than the true answer. I am currently writing code in Excel to partition the shaft into segments but account for the changing diameters as part of that partition. It is pretty tricky code, but I will press on with it. I am doing it in Excel, not because I like VBA, but because nearly everyone has it. Your best option is to use FEA code to analyze the whirling.
is this bearing alone water leak resistant? i have diy project that contain shaft with bearing mixing the liquid on a container. can I use this bearing alone to prevnt water leak fro mixer?
No...it is not naturally leak resistant. You can, however, purchase a sealed bearing that will incorporate a polymer seal that also slides against the shaft. They increase friction and will, eventually wear out. Water resistant is also a lot different from water proof. If all you need is water resistance, then you could probably use a sealed bearing. Your best bet is to go to the SKF or Timken or other manufacturers site and open a chat to discuss options. There are seals, alone, that are designed to isolate locations on the shaft...but these are different from bearings...think of a crankshaft seal on a car, for instance, or seals that are required for prop shafts in boats/submarines. Sealing against pressure is a tough proposition that gets expensive.
why do you apply a fixed support to bearing B and a pin support to bearing A?
Pramath...good question. I want to constrain translation, but allow rotation. that is why I chose this approach. So I fixed the x,y,z coordinates of one end, and just the in-plane coordinates at the other. But there is a better way...if you put a small hemispherical impression at each end, then use a frictionless constrain, it fixes the location of the shaft ends, but allows for rotation. It is always a challenge to find appropriate constraints, I must say. So, whatever you choose to do, do not analyze the results near those constraints...also, just change the constraints and observe how it changes the results. This is an eye opening experience for all of us, students especially. In fact, I love that FEA allows one to run a host of 'experiments' that help you develop understanding.
@@MechaTomics I'm getting the bearing loads very high near the split faces, and I think it's because the area is very small, causing it to fail unreasonably. Should I increase the width of split face or is it a different problem causing. Also, I very much appreciate your last reply, learning a lot from your videos. Thank you! :))
@@pramathbhat6423 You will definitely have extremely large bearings loads at the split faces...you can not trust those numbers, because they are a poor representation of how the loads are actually applied. As usual, you need to keep you analysis away from the points where you apply constraints. It does not mean that you can not do it differently to get what the actual distribution of the bearing loads happens to be, but you can not get it from what I proposed doing here. You would need to actually sort out the contact area for a real bearing...it can be done, but that is not what I was trying to do here. Bottom line is that you've got the correct intution...your bearing loads are high because of the artificial area you are choosing to support those loads! So, I would say, good job! It is very important to look at your results and check them for reasonableness. You found them to be unreasonable, so you know that the answer is incorrect. I repeat: good work!
thankyou
This is the most comprehensive video on fracture mechanics I've seen
The video is very useful! It teach me about the meaning of the exceedance probability.❤ from China
could you tell me the reference or the handbook from which you got these photos, please.
Shigley's Mechanical Engineering Design text has the images, otherwise I imported CAD drawings into Fusion 360 using the import part menu item. I import the CAD drawings from McMaster Carr,
Thank you so much Sir. What statistical distribution do you use for tropical cyclone windspeed? E.g. I have a wide range of choices (i.e., Weibull, gamma distribution, etc). Also, how can I convert EP to Return Period?
Hi can you share the excel document
Hi, Can you also make a video on how to make the singularity function for the deflection of a stepped shaft? Shafts in real life almost always have steps in them.
You are quite right! They are rarely, if ever, a single diameter. I will do it.
@@MechaTomics Thank you so much!
thanks for solving doubts
Sir . I have a doubt , shall we will do ansys fluent in ansys work bench
Darshan. I do not use ANSYS, so I am not qualified to comment. However, any FEA program would work well. I now use COMSOL for most of my FEA, and just use Fusion 360 for a first look. This is a solid mechanics problem, so it is a pretty good problem for any FEA package. I thought Fluent was a fluid program (CFD)? IF so, you do not need it for this sort of problem.
Super sir
What we are going to do if we have only spur gears on our shaft, therefore there is no axial force acting on the bearings? As long as I understand we need to have axial force and calculate Fa/C0 ratio in order to continue with the bearing selection process.
You needn't make a correction if you do not have an axial load.
So glad I found this channel. A 💎
5:19 How they get the value of (Fe)/(V*Fr) though we don't know the equivalent radial load(Fe)? or can you explain process of experiment? from 5:19 to 6:02
Yet more info for you. You start with a guess. I always start with Fe=Fr. Then you select a C10. get the C0, and find an updated e by computing Fa/C0. You then select the X and Y values and update your bearing selection....you keep iterating until you get no change in the selected C10 value.
why we don't use vector addition to get equivalent load?
It would be totally sensible to do as you say if fatigue was not so emperical. But there are threshold loads below which your part will last indefinitely. So, the approach presented here is a 'design' approach to determine an equivalent radial load that would have the same lifetime. It comes about from a large number of experiments, not a first principles calculation. That said, you could do a thorough analysis and determine the contact loads in the bearings, then determine the endurance strength and compare the loads. The approach presented is just a simple, time-tested, approach to make it easier to design the bearing. It incorporates a fairly significant factor of safety, as do nearly all of our simplified design calculations. I encourage you to keep thinking as you do, question everything, and determine which topical areas you would like to pursue. It may be that you advance the field in a meaningful way.
I also forgot to mention that the selection tables are based entirely upon radial loads applied to the bearings. So, to use the bearing selection tables when you have a combined axial and radial load, you need to find an equivalent radial load. Think of this in the same way you use the von Mises criterion to find an equivalent uniaxial load from a multi-axial loading state. But in this case, you are using equations that are based upon experiments and curve fitting, not some meaningful mechanics calculation.
Hello I don’t understand how to get C10 search if the Fe is 2.876 how do you get 21.6622 I would really appreciate it if you explain !
This does seem a bit odd, I admit. But you need to select a dramatically over-rated bearing if you want a high lifetime with a high reliability. The tabulated values are only good for a 50% reliability. So, if I want, for instance, a 98% reliability of the bearing for the given lifetime, I need to select a much 'stronger' bearing. If you watch the lecture on bearing reliability shifting, it will begin to make sense. I hope!
I tried to replicate your excel sheet however my hoop stress values for the last 5 results out of 50 always become regative crossing over the radial stress plot, why would this be?
Aidan: If you look at the hoop stress equation the only negative value is the last term, so the answer can only become negative if that last term dominates. I am guessing that there is a numerical error in how that last term is calculated. That pre-factor that contains the Poisson ratio. If you do this in excel you have to be very careful about placing parentheses around the correct terms so the order of operations is what you want it to be. You need to calculate like this: ((1+3*nu)/(3+nu))*r. If you aren't very careful you end up with operator orders that change the answer. The other problem is that you need to fix the cell number where you have Poisson's ratio, or just numerically enter Poisson's ratio into the equation...because excel tries to move down the column for every element in an equation.
good video
what is r supposed to be? the explanation doesn't make sense
r is the distance from the axis of rotation out to any location, radially, that is in the disk
Can you share the catalogue you are looking into in this video ?
could you share the excel chart to do the calculations plis!!!
I have another video that shows this with much better resolution! I will look through my files to find it, and will get back to you.
Victor...this video does a better job of explaining and setting up the spreadsheet...it should help a lot. I apologize for the poor quality of this current video...it is from my early tries at doing these things. ruclips.net/video/8F2cgmp-UV8/видео.html
Amazing
Man, this video is seriously great and is the first one that solves the mystery of the mean stress. Thanks!
Have you ever experienced a failure in which the outer ring of a tapered roller bearing begins to rotate within the housing ?
This is not good, and I have never encountered that problem. If the outer ring, known as the cup, is rotating, it means that the rollers are not sliding properly on the cone and the race. The outer ring is supposed to be secured by a set screw or a press fit or otherwise locked into the housing. Also, you should be using these bearings in pairs ( not required, but advisable) so the induced axial load does not 'push' the shaft/cone out of the cup...that could also be happening. Bottom line, you need to fix that, but be advised that it may have been induced by excess friction in the bearing itself. Sounds like it is time for a new bearing. As an intro guideline to mounting, watch the SKF training video at ruclips.net/video/JugU6NHgqVY/видео.html
@@MechaTomics thanks for your response. The machine was run with lubricant below the required amount therefore having insufficient lubrication. However in skf literature they indicate that the only causes for this to happen would be shaft unbalance and incorrect fit during assembly. However I also believe that a higher frictional force would cause this as well as "bearing creep".
Sir, can u please give the name of the book u r referring to? Thanks.
Thank you Owen Wilson for teaching this :D
Shigley which edition
What a great channel with great content. Thank you so much for taking the time to share these lessons for free!