Accumulated Damage and Miner's Rule

Here the concept of accumulated damage is presented in the context of fatigue. Miner's rule is presented and some types of stress histories are outlined. An example problem is demonstrated wherein a smaller stress wave is interspersed within a larger stress wave. The cumulative damage is found (using Miner's rule) resulting from applying 100,000 cycles of this complex stress wave. The expected number of additional cycles allowable before expected failure for a different fully-reversed stress magnitude is then computed.
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This lecture was presented on February 19, 2018. All retainable rights are claimed by Michael Swanbom.
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[@soheilmohammadi5876]

I am studying in an Italian university the subject of Fundamentals of machine design and drawing and Sir your videos are amazing !

[@forsakenV12]

Well done ! You attacked miner's rule and rainflow quite nicely.

[@TheBomPE]

Thanks! Glad you enjoyed it!

[@majidebrahimi8890]

Thank you Professor, It was quite good for me to have an overall view on this subject

[@TheBomPE]

Glad it was helpful!

[@ehosseinnn]

Thanks but I believe you had one mistake: that one pattern that repeats for 100000 times has TWO cycles for each of frequencies so in 32:31 numerator should be doubled (if you draw rain flow you will see that count of each cycle is 2). Let me know what you think.

[@learnwithistiaque3736]

this video is life saving for me..

[@TheBomPE]

Glad it helped! Thanks for watching!

[@TheAran123456]

Your videos are amazing and are really helpful for me. The way you explain makes it more interesting and intriguing. I have one question. Is there any modified miner's rule, to get rid of the issue of order of cycles (if plastic deformation comes first in cycle it can make more damage).

[@prashantbits]

This is pure art... the way you explain the things sir. what tools do you use for writing during video? please... tell me...

[@TheBomPE]

Thanks for the great review! I use a Fujitsu T901 (gen 2 i7, 16GB ram, discrete NVIDIA graphics, wacom "penabled" active digitizer). I use microsoft onenote 2007 (last version with customizable toolbars) for the writing.I use camtasia 9 for the screencapture and editing. I can use just about any video camera to record myself...I believe in this video I used my Canon 80D. Rather than getting camtasia to capture it, I just record it separately and sync it up in editing. Thanks for watching!

[@michaelswanbom6023]

If you found this video useful, consider helping me upgrade the old tablet PC I use to create these videos! Thanks! www.gofundme.com/help-replace-my-2011-tablet-pc

[@Marcelo-he8gf]

Thanks for sharing, really helps :) keep up the good work

[@TheBomPE]

Thanks for the positive feedback, I'm glad it helps! Thanks for watching!

[@sdsssdd1987]

GOOD video! l've learned a lot.

[@TheBomPE]

I'm glad you enjoyed it! Thanks for watching!

[@venkatv6550]

Fantastic explanation on damage accumulation. In the miner rules you mentioned # of cycles before failure at that load level. How you define before failure . In the example cycle1 Sf is 47 ksi which is more than the material se 40 ksi. Is this a failure of the material which you accounted in damage calculation?

[@TheBomPE]

Se is called the endurance limit, and it is the stress level below which it is assumed the material will last infinitely (i.e. no limit on the number of stress cycles before failure). At stress levels above the endurance limit, we expect that there will be a finite number of cycles that the part can withstand before failure. If parts fail in fatigue it looks a lot like brittle fracture, because fatigue failure mechanics involve tiny voids forming due to tiny amounts of plastic deformation occurring at tiny locations of material imperfection. Eventually voids coalesce together and there are too many of them for the part to survive, and the part will fracture. Since the stress of 47ksi is higher than the Se of 40ksi, it means there will be a finite number of cycles that we expect can occur; eventually the part will fracture if stress cycles persist at that magnitude.

[@dogansahutoglu2073]

Dr. Micheal, what does Fully-reversing load mean? Thank you, sir.

[@TheBomPE]

Fully reversing means that the stress element in question experiences cycles of stress that go from some magnitude in tension to the same magnitude in compression, back to the same magnitude in tension, and so on. A fully reversing load is similar.

[@johanmoens1825]

Is there a written course available of this topic ?

[@abdulmalakabdullah7374]

Very good

[@TheBomPE]

Glad you enjoyed it!

[@mvarun10]

Hello Sir , COuld you please tell me what is the a & b values mean that you use a fomula to calculate ?

[@surferitoful]

Minute 35:30 the number is 180,838***

[@ciaraw3185]

Where is the graph for f vs Sut from? I have a value of 40MPa (=approx 5.8ksi) so I’m not able to get the F value from the graph

[@TheBomPE]

That relationship is presented in Shigley's Mechanical Engineering Design, but it is applicable only to ferrous materials. I think you must have some other kind of material if you have Sut=40MPa. So I think you'll have to try to locate (or generate experimentally) a S-N curve for your material.

[@tesfamicaelyohannes]

Sir, can I find the book in amzon? what is the title of the book and who is the author of the book? I am refering to the book you are using during the lecture time in all these videos you showed us. Thank you beforehand. Tesfamicael yohannes Oslo, Norway

[@TheBomPE]

It's called Shigley's Mechanical Engineering Design, 10th ed. Thanks for watching!

[@daginganindonesia4814]

@@TheBomPE i just want to ask about the book, thank you

[@dejannikolic4647]

Is there any software for calculation damage sum or doing miners rule?

[@KIMIRAIKKONE198N4]

Manson's rule is way better and describes better the situation

[@acloudatlas]

what is ksi ? we use(Mpa) MEGA PASCAL as stress unit

[@TheBomPE]

ksi stands for kips per square inch. A kip is 1000 pounds (lb), so ksi = 1000 psi = 1000 lb/in^2 A lot of people outside the US are bilingual; inside the US, engineers have to be bilingual WRT units!

[@acloudatlas]

@@TheBomPE thank you so much for replying sir ?

[@capturingmylife001]

what is f/

[@KIMIRAIKKONE198N4]

fatigue strength fraction

[@albertjerin5]

Hi Professor, what is the Graph Sut vs F, Where do I find for a material A356 Aluminium Alloy

[@TheBomPE]

What is the name of the parameter you call "F"?

[@jamesonkeeton9170]

Hi professor - What text are you referencing in this video?

[@TheBomPE]

I'm using Shigley's Mechanical Engineering Design, 10th ed. Thanks for watching!

[@adiraaz7736]

very noice ,

[@TheBomPE]

Thanks! I'm glad you liked it! You might like some of the others in this series as well: kzbin.info/aero/PL1IHA35xY5H5AJpRrM2lkF7Qu2WnbQLvS Thanks for watching!

[@conor1577]

why are you using ksi

[@TheBomPE]

It is important to be familiar with both systems if you work in my beloved home country!