Understanding Fatigue Failure and S-N Curves

[@petercalow1028]

HELLO, I have an exam in 2 and a half hours. Can you tell me why the initial fatigue results are scattered? Cant find the answer anywhere. Great video otherwise!! Thankyou!!

[@TheEfficientEngineer]

Hi Peter! Most of the scatter will typically arise in the crack initiation phase, where there is more variability, than in the crack growth phase. This initial phase will be sensitive to things like the surface conditions of the test piece. Of course there will also be some variability associated with the test, e.g. the equipment that is used. Hope that helps - good luck with the exam!

[@petercalow1028]

@@TheEfficientEngineer Ahhh yes, thank you so much for replying so quickly. Will need the luck!

[@Tranefine]

peter calow How did you do in your exam? :)

[@hamz4977]

hqhhahahHAHAHAHAHAHAHAHHAHAA

[@ashwinpande7095]

i cant believe he actually replied just in time before your exam

[@kingz.a1918]

my professor spent tens of hours to deliver what you have delivered in less than 10 minutes

[@babajungLA]

That's because the professors need to justify their jobs and therefore have to drag out lectures when in reality they can be explained in much easier terms as seen in the video.

[@ziheng666]

If the professor use the video method to teach u in the first time, May you not understand the content.

[@shakirobaid2895]

if you have no idea what stress is or what stress strain chart is or what fatigue is .. what stress amplitude is .. it could take a while to get here and for you to understand it .. however going through semester and thn filling up gaps in understanding from youtube videos work really welll

[@CluckYou21]

This guy spends tens of hours creating this video.

[@mikimikito-mc5mr]

This man is God

[@mathiasbruunchr]

These vidoes are the best i have seen on the topic of mechanical engineering. Keep up the great work.

[@albanopietro3173]

What a video! That is one of the best explanations I've ever seen in my whole engineering life! Congratulations to you all! And, please, don't stop posting subjects like that

[@bpring21]

I would love it if you kept making amazing videos. You do a great job breaking down the fundamentals without overloading in the theories behind them. The annotations...pristine!

[@honzco]

I wish there was a channel like yours explaining engineering facts when I was an Engineering student. Complicated engineering concepts are easier to understand and remember with multimedia like your channel. Thanks

[@elnuryus]

+

[@sultanhassanieh7546]

Make a video on creep pleaseeee

[@aravindvissamsetty]

That was basically my entire Masters level Fracture Mechanics course condensed into just over 8 minutes. Great job!

[@donshaffer4169]

Where was KZbin in 1982?!

[@javier987]

I love these graphics! what software is being used?

[@khaidirandromeda]

these is what i needed for so long, representaive animation, simple and easly understanding for those who are not english native speakerr, keep it up broo.. attending college cant make me understand about material engineering :') , may u blessed..

[@irtesamnasrat9866]

thank you for making the nights before exams this much easier. the graphics, animation, voiceover and the scripts are very well thought and well put down. please don't stop producing such useful video lectures, the planet needs good people like you. 🙏

[@GeniusEngineering]

I like how your videos explain these Engineering concepts in an understandable and visually engaging manner.

[@ShayanAsim]

I am super impressed by your way of summarizing the S-N curve. I was just looking for a video to refresh my concepts and this is perfect. Keep up the good work! Subscribed and expecting even more from you guys now! :D

[@The92gopal]

Hi. Huge fan of your service. It isn't easy to eat an entire sugarcane but it can be easily consumed as a juice. As part of an engineering community, we are grateful for your work. Can you please do a video on Fracture mechanics as a follow-up to this?

[@andrisberzins9053]

Great video introducing fatigue! Could mention that damage summation by Miner is only approximation as for variable loading actual loading history can make huge difference. Fun fact initial high loading (even partial yielding) for steels can improve high cycle fatigue.

[@nareshvangari2021]

Randomly found a video.....In two days completed his entire playlist. Now addicted to his videos. Waiting for my bell icon notification.

[@ozgun228]

I love the efficiency in your videos. No need to waste hours to have a solid understanding of important principles.

[@danielbadel1226]

This video and all your videos in general are really cool, educational and cristal clear. I wish you made a couple of lecture about LEFM and fatigue approach for multiaxial state of stress criterions or non proportional mixed loadings. Greetings and thank you!

[@sairaj7914]

Completing this video marked my reaching the end of your Strength of Materials playlist. What an intense but great wrapping up of all core concepts! I feel so much more confident learning this. I already work as a machanical engineer and this is seriously better than whatever I was taught (but did not understand) back in college.

[@ACDroneDesignforPerformance]

Hi, could I use part of this animation inside of my next video? It will deal with the engineering aspect of aircraft Panavia Tornado and I would introduce a short explanation of the fatigue aspect. Thanks

[@yusufberk460]

paris erdoğan denklemi ?? :D

[@hemanthtandaganagaraju2943]

Fantastic video, I have a question. At 2:06 , isn't the number of cycles to failure 600,000?

[@tanmayeheblekar2162]

Can't wait for the Strain Life video. Outstanding presentation of the concepts as always! Thanks a ton mate

[@louisavelino9323]

Thank you so much! Sending good vibes for this.. Very well made video.

[@thesuperkat943]

On the stress amplitude graphs at 4:15, you should’ve plotted some of the other theories, especially since the Goodman line and Gerber Line do not guarantee infinite life, as they can fail from going past the yield point of a material, giving them finite life. This is true for most theories, but especially true for these

[@akhilpatil-jain7644]

The video is great n pretty crisp...keep up the great work

[@sozharajanb3713]

Hi,kindly provide videos for SN approach and EN approach based on analytical solution.Also chose which theory (Soderberg, Goodman ,Gerber, ASME elliptical, SWT and Morrow theory in strain life) better for corresponding application.

[@titorotod]

Hi, I'm wondering, to calculate a stress range, the stresses you are using are the principal stresses? or is it the equivalent von Mises stresses? Thanks for such an amazing video!

[@Uzumaki998]

This playlist is great!!! Whenever i feel like revising my basics i just go though your playlists. Can you make some vids on manufacturing process and theory of machines...would be of great help

[@samuelcarvalho3691]

Best Channel for understanding Engineering concepts. The visuals does the world of good.

[@smith101.9]

my professor just showed this in its entirety during a lecture

[@MrJohnHughesHimself]

Great videos. What do you use for the animations?

[@TheEfficientEngineer]

Thanks Ivan! I use Blender for the animations.

[@smeetashar]

Can you please suggest some books or material for further reading? And thanks for this awesome video.

[@TheEfficientEngineer]

Hi Smeet, glad you enjoyed the video! Dieter's Mechanical Metallurgy has a well written chapter on fatigue of metals that I would recommend as further reading.

[@smeetashar]

@@TheEfficientEngineer Thank you!!

[@saverrosuseno6712]

These videos are so good!! could you do one on stress concentrations??

[@AnilVerma-uh2np]

Simple and details explain action.. thank you...👍😀

[@safooh94]

I like the quality in your video and your explanation. Keep up the good work 👍

[@sowhatdane7942]

When I get a job, you'll get a new Patreon.

[@cussyrichards6121]

What counts as a 'fatigue cycle'? Is it ANY loading - however infinitesimally small? For example, if I stroke a brick of aluminium with a feather - does that count as a 'fatigue cycle'? If yes, since aluminium has no fatigue limit, does that mean after the aluminium brick is stroked by the feather billions of times, eventually the feather will break the aluminium brick?

[@mangeshdeshmukh2140]

Superb sir , Greetings from INDIA !

[@enjoymfs9715]

If you help me to understand that sitiuation, i would be appreciated a lot. lets say that we designed our mechanical part with minumum stress concentration. No initial crack, hole or something that inreases or causes stress concentration. What would be the key factor occuring fatigue failure ? since we dont have anything against stress concentration which will cause crack eventually. I have read some articles which mentions that stress amplitude is the reason of fatigue failure? Btw, you did a great job. Waiting a similar video regarding creep failure

[@mohammadkhanafer4847]

please , do not stop blowing our minds with this amazing videos, keep it up and you can really do much better and download more videos on different topics in engineering, man it’d be amazing for all of us in the industry

[@flemirbingo6185]

Sir, could you tell me how to find the models you presented in the video? For example, bolts in an office chair, how did you find the pictures with the highlighted bolts?

[@8mybcur]

i learnt more in this video than i did in 3 weeks worth of lectures

[@jbkamehameha]

How do you shift the fatigue curve downwards, you consider the two standard deviation of the fatigue limit?

[@vohoangquannguyen7706]

Hi, many thanks for the videos! It help me to get overview of the engineering methods regarding this topic!

[@pavanvinay1874]

10 pages concept in 10 min 🖐️ thanks

[@jeysrether]

best explantion for fatigue failure thank you very much

[@sahandsoltanieh5186]

May I ask which programs do you use for making these animations?

[@TheEfficientEngineer]

Hi Sahand, I use Blender for the animations.

[@DineshKumar-ts1vq]

Awesome. Thanks for putting your time and effort for this brief and elegant explanation. Expecting more videos from this channel. Subscribed :)

[@ceciliamoncada3224]

Explain why old buildings structures collapse?

[@itsagoal182]

Endurance limit is king, and everything I’ve designed, where possible, has been within this limit. For steel, I try to design to Tensile/3 and apply a good surface finish, and touch wood I’ve not had a failure in over 20 years.

[@nyquist_control]

yup, factor of safety always important to use irl.

[@itsagoal182]

@@nyquist_control not so much a FOS with fatigue, but typically for steel, fatigue really only becomes an issue at Tensile/2, although there are mitigating circumstances!! That’s why working to Tensile/3 means your design is typically free from fatigue failure.

[@technicalknowledgesharing6701]

Hi, Can you please provide a good reference book list for fatigue analysis (Example, for Mechanics of materials - Beer & Johnson book)

[@manshi1028]

Hello, can you provide such videos on concrete fatigue failure as well.

[@josephaonno5684]

great video, very clear and all, but the music?!! it makes me want to slap s.one

[@hal9000svk]

Very good intro to problematic. Just what I needed. Thank you!

[@dhrubotara3284]

Thank you a lot sir❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤ Alhamdulillah.. Allah bless upon you in sha Allah

[@captainclone1367]

It might be good to mention that fatigue general occurs with tensile structure.

[@mahmoudtrimech1309]

Thank you for the amazing informative video on such a complex topic. I have one question: What stress to consider to assess fatigue life? (is it Von Mises, Normal stress (to the weld for example), Maximum principal stress etc.) ??

[@TheEfficientEngineer]

Hi Mahmoud, great question! You would usually consider the normal stress in the direction you are interested in. Sometimes you might have to calculate the fatigue life in more than one direction (e.g. both perpendicular and parallel to a weld) to figure out which has the shortest life, because they might have different S-N curves.

[@andrisberzins9053]

Depends on the problem, for 1D loading maximum principal stress would be used. For loading in 2D things start become complicated and especially if maximum principal stress changes direction. At work for 3D stress state for steel with changing maximum principal stress direction we use signed von Mise. It is not entirely correct, but close enough. As we have understood then "correct" would be calculating critical plane by summing damage from principal stress in every direction, but that is easier said than done. For welds building codes give simple guidelines by using nominal or hotspot stress with corresponding detail categories.

[@abhh-ok4jq]

Is there any book reference for endurance limit of several materials

[@kashty103]

My material science instructor put the link to this video in his slides.

[@CaesarBro]

I had a poorly packaged pipe shipped to me crack from either reaching tensile strength, cycle fatigue, or both because it wasn’t strapped down and it was fully constrained at one end. So while riding on the truck it freely bounced up and down, like a spring until failure. Now I’m writing the FMEA report. Calculations showed it may have reached plastic deformation elsewhere if tensile strength was reached, let alone ultimate strength. Now have to measure crack size for comparison. Thank you for the useful review!

[@sahandsoltanieh5186]

awesome explanation, awesome animation! Thanks a lot!

[@TahinaFelisca]

Any recs on where to find fatigue data for spring steel?

[@Kornet104]

About so known 'endurance limit'. Actually there is no such thing in real life even for ferrous materials. It is shown that at number of cycles about 10^9 failure still happens (such numbers can be obtained in low-stressed high-frequency parts as gas turbine engine blades, reduction gear teeth and etc.). Look for 'Gigacycle Fatigue in Mechanical Practice' by Claude Bathias for the initial acquaintance. It is said at 3:10 that at low stress levels we are dealing with only elastic deformation, but this is a complete nonsense, because it contradicts the definition of elastic deformation (!). Nevertheless, I am very pleased with the quality of the material and am grateful for the popularization of engineering knowledge.

[@jorgeserrada1810]

Hello, I think ENDURANCE LIMIT is mixed up WITH FATIGUE LIMIT. Could anyone confirm this please? Thank you.

[@cwong1229]

Thank you very much for the video!! After I watched your video, I realized that most of the professors at a 4-year research university don't know how to teach!!! I cry 😢 because videos like this didn't exist when I attended college. P.S. I graduate from college back in the year 2010 by the way. Back then KZbin was just 5 years old in my graduating years, meaning it was still relatively new, and learning engineering concepts from youtube back then weren't as common as today. There weren't that many videos that are educational and can teach me engineering either back then. All I can say is: college students nowadays are such a group of lucky fellows.

[@updatedotexe]

The end of the video had way too much information about too many different topics. Did you make videos explaining things like Miller's Rule or the crack grow thingy in more detail?

[@arunal5726]

Superb explanation..Thank you so much.................🙏🙏🙏

[@bozhenwang5493]

wow, such an informative lesson!

[@Sarcophagus_666]

Near perfect video 👌 you just didn't explain why fatigue occurs. The crack is the result, not the cause, speaking from a chemical viewpoint tho 🤔

[@xuxu119]

@4:43 two standard deviation is not 1%, more like 5%

[@yuanzhou3368]

Hello, I have an interview tomorrow. Do you mind tell me in practical what are some solutions can extend the time to fail? And what should I be thinking about when deciding what materials to use during designing process? Thank you!!!!!!

[@vivekgupta9829]

Please make a dedicated video on low cycle fatigue

[@aiseymen90]

Hello.. can you do a video explaining difference between ratcheting and shakedown? Thanks😊

[@malikmuhammadawais]

can you create a detailed video on Rainflow cycle counting with respect to fatigue counting ? how this complex loading is simplified by this counting and how the fatigue useful information is retained by this counting ? when MATLAB gives an output table of Rainflow, how and what is to be interpreted ?? any response is highly appreciated

[@Chr0nalis]

Music is unneccesary.

[@marcoskrupiczer6595]

How do you account for negative (compressive) mean stresses? And if you have a biaxial or triaxial stress state, is it correct to apply these concepts to the equivalent stress? (Calculate the equivalent mean and range stresses, and use Soderberg's law for example)

[@jankafka6731]

Excellent job, very explanatory a easy to understand. I wish this had exist during my msc study 20 yrs ago. thumbs up!

[@bijibijmak]

Very nice and informative videos. I only have one constructive feedback: the music doesn't really fit the content. The Ukulele and Bells music reminds me of HowCast how-to videos on how to get that annoying grease stain out of your shirt or a Kickstarter videos about a glow in the dark dog leash.

[@tonyoak2230]

Impossible to learn from such a brief and superficial presentation. Want to learn? Read books.....

[@GamingShiiep]

I'm studying geosciences in my masters. I still can't believe how much of other disciplines we have to know (like engineering, physics and chemistry. It's insane.

[@achirabdirzak8010]

amaziiiinnnggg

[@belakhdarmedslimane8946]

Such a great explanation......We need an episode on VMEA/FMEA analysis

[@mohammadhoseinrivandi5657]

I am totally grateful for ur videos!!! KEEP GOING!💥

[@amiraboodi2075]

Thank you very much. This video helped me a lot to understand what is fatigue failure. Your explanation is fantastic.

[@matiracciatti]

Why are fully-reversing loads worse than zero-to-max-to-zero loads, even when te max values are the same? Thanks!

[@PastaCountry]

Is it possible to derive the Poisson's ratio from a S-N curve? I heard this was possible from a friend but was really curious if anyone knew how.

[@karthicmanoharan9776]

Can you do a video on EN curve approach as well please

[@RajeshGupta-kn2vs]

Sir We are very lucky to have your lectures. Kindly start a full course of RCC Structure design from very basics to become a fully professional Structural Engineer who can design bridges, buildings perfectly like professional structural engineers. I am in India, Haryana state. I am a Civil Engineer in Haryana PWD and was surching lectures like you who can teach us like you teaches. Sir I would be very happy if I can associate with you in any thing in your lectures or preparing the full course of RCC design as per Indian Standards. My mobile number is 9729829995 Er Rajesh Gupta

[@ceciliamoncada3224]

What about the building that just collapsed? Could this be a combination of fatigue failure, overload, there was also a mayor construction to the left?

[@rezaahmadi1492]

hi, infinite life doesn't exist in reality and it is a theoretic term

[@muhammadzakky7618]

MES231003 - MUHAMMAD ZAKKY AL YAMINY

[@alexnicolas9486]

OMG this video just help me figure out the answer for my assignment question, thank you!

[@sher.5027]

This is completely Gold. Can't appreciate more. Thanks for making this. You will Reach 1M soon.

[@dremr2038]

@5:30 why tensile stress result in a shorter fatigue life?

[@cck0728]

Excellent video. At 8:07 of this video, what is "E" and "G"? Thanks.

[@ivandoan8405]

Hello. I would like to know how to predict the sample is in warranty time or out of warranty time of product. The product like push belt in the car

[@pavanyeluri7557]

Does application of constant load(not constant amplitude) which is below the material strength affect the failure in anyway?

[@akshaypawashe7043]

Please please please please add more such videos and for complete mechanical engineering. I am requesting you🙏🙏

[@ambidixtrs7111]

Wow, a video like this can clear up the whole concept that one were struggling to understand during its semester. That one would be me 😅.