Fatigue Failure Analysis

[@henzehe]

Bending a wire back and forth to break it struck me as a strange choice of example of fatigue failure. It is an example of repeatedly exceeding yield stress and repeated permanent deformation in a ductile material. When making a structure or device out of ductile/malleable materials the designer should almost always keep cyclic stresses lower than the yield stress (and usually non cyclic stresses too for that matter). Breaking this design rule usually results in a uselessly short lifespan. The value of fatigue failure analysis lies in its ability to predict if/when parts that seem to be working fine initially will crack. This isn't the case with the bent wire. A little research revealed a better analytical tool for the wire bending example exists; the Coffin-Manson relation uses strain rather than stress in order to predict failure in ductile materials that are subjected to repeated deformation.

[@danpt2000]

I think many people go to the metal wire as an example because many high school teachers use that. Which according to more experienced/knowledgeable people, is not really fitting for fatigue failure.

[@josericardotarpani26]

Have u ever heard about low-cycle fatigue? Probably not...

[@tr9036]

Actually it fits to example. High quality phone charger manufacturers claims that their cables lasts for 10.000 bends. Which means this video is a real life example and easy to understand for non expert people.

[@haniie6368]

this is why i dont go to class anymore. a long-winded 1 hour lecture can never beat a well-explained 6 minute video

[@VirendraBG]

0:30 it's *Ratcheting* (cyclic load which results stress more than yield stress in every cycle) and I guess not fatigue. Fatigue is when cyclic load results in stress below yield stress in every cycle, but the system fails because of no. Of cycles. For example pressure vessels. Here is another explanation of fatigue. kzbin.info/www/bejne/pV6Zh5KApLeLZ8k

[@peglor]

Materials such as steel and titanium have a fatigue/endurance limit. Aluminium and most other materials however do not, so it's not possible to design structures in these materials to never fail from fatigue. In this case the number of cycles must be set much higher than the expected number of stress cycles in service. Also the diagram is misleading in that it showed a crack forming and growing inside the material - in all cases of homogeneous materials without case hardening or similar surface property modifications, fatigue cracks always start at the surface.

[@azhaafiikhsan7891]

Perfect explanation. Thank you sir.

[@TheSunshineRequiem]

wow this is very good, you should hire someone to read it out loud though.

[@Vrang89]

Wow. That was easier than I thought. Thank you for taking the time to make this!

[@Shaikhshadat]

awesome work man!!!!!! i respect your hard work :) plz keep uploading more videos, it is helping a lot

[@MegaShriyash]

Fatigue was beautifully explained! Thank you!!

[@MarkKRogalski]

Not all materials show an endurance limit, for example steel and titanium are the only two metals that have one.

[@AS-fm5ew]

great explanation ....giving a good physical understanding of what fatigue is.....

[@obadiahmaxwell8820]

Good day. Please can you explain Double linear Damage (DLD) in contrast to Miner's Rule (Linear Damage)?

[@nilofarpathan665]

Thank you for the simple and effective explaination

[@Medhusalem]

It is wrong, that the material will never fail after reaching the "limit". It is just an assumption because not a high enough number of cycles have been tested. As seen in wind energy components where cycles are over 10^9 this limit is wrong and components are still being damaged by fatigue loads below their assumed limit!

[@igcr1234567890]

there could be coupling with other modes of failure, like wear, stress corrosion, etc.

[@shridharacharya134]

Thank you sir for this valid video😊

[@syedmuhammadtayyeb6994]

!! The example of wire you have given isn't fatigue but it's strain hardening Because we bend the wire permanently that isn't the case in fatigue

[@AS-fm5ew]

ur website is also awesome

[@ikik9469]

How can I calculate how long a machine with a given stress amplitude will break?

[@saiteja3019]

Great video sir like upload videos of mechanical engineering sir

[@crazygirls4491]

Why does soderburg line is most conservative??? Please reply sir

[@bilalsara5809]

Please can you add Turkish subtitles for other videos

[@jasonr5681]

The best visualisation and explanation of fatigue i have seen thanks

[@naviddavanikabir]

great video. I need to do this test on PEEK, a rigid plastic. the standard we follow is ASTM 7791. knowing only the ultimate stress and with limited number of specimen, how should I choose the stress/strain level to find the endurance limit and to waste as little specimen as possible?

[@risingphoenix7670]

why took log s vs log n graph?

[@Kumarvikramgwl]

Both value s and n are exponentially changes when one of those value changes so log scale represents it better.

[@MrSidney9]

You get a straight if you do that instead of exponential curves

[@sln7736]

Google translate

[@utkarshsrivastava938]

can anyone pleasr tell how can i convert rpm into no.of cycles

[@Newbport849]

If you're considering engineering as a major, don't do it. It's not worth it.

[@rohitbhosle6521]

What ??

[@rogeronslow1498]

Nice content but the computer voice is horrible.

[@tabaks]

Roger Onslow, go grab a cold one and get yourself some personality along the way.

[@himg4digu]

U haven't 'seen' horrible then i guess :P, sorry i meant to say heard

[@erickhumalo1913]

You're a dumb ass dude

[@kymattok]

So if the stress is under the endurance limit is the material undergoing stresses that would be in its elastic range on a stress strain graph?

[@prashanttiwari6214]

Yes

[@ahsabhasan4118]

greatly explained ...

[@AS-fm5ew]

Sir please upload videos of Heat and Mass Transfer also please

[@sriramsharma9898]

please,make videos in civil engine...

[@asmaaaq5160]

can you explain the creep-fatigue interaction?

[@lekhrajdewangan8491]

Finally after a long time I got its ans

[@emrekaldrak7203]

nice video

[@atiqahmadjan9175]

what is stress in physical phenomena ?

[@omadhyaru7765]

very good and practical view

[@anuragchandnani8037]

Great Video . Keep up the good work

[@rudhajassim9469]

ty

[@AS-fm5ew]

awesomeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[@lifewonder9033]

Very useful video

[@shashwatpandey1371]

💯💯✔️

[@قيصرالمدينة]

shkrn lak

[@pvnp007]

Why we have to draw the graph in log

[@MrSidney9]

Its for convenience., otherwise you don't get straight lines.

[@jwais3622]

This is amazing thank you so much for the effort U put in this :)!!! Really appreciated!!!

[@kalyanpk2064]

nice lecturee

[@christosdovles3461]

this is really helpfull

[@wahaajali1009]

thanks alot bro!

[@SaiKrishna-vz1up]

Awesome

[@sumitrode6670]

superb!!

[@주영-f5u]

3:40

[@parthbhide7992]

really helped

[@jayasimhanrao3269]

Very nice presentation. Thank you so much