ไม่สามารถเล่นวิดีโอนี้
ขออภัยในความไม่สะดวก
ฝัง
- เผยแพร่เมื่อ 2 ก.พ. 2018
- Here several corrections to the endurance limit are presented and discussed, as well as fatigue stress concentrations and their relation to theoretical stress concentration factors via notch sensitivity factors. An example is completed in which a non-rotating hot-rolled rectangular plate with a hole is subjected to fully-reversed bending. A fully-corrected endurance limit is found by applying Marin factors, including a surface finish factor, a size factor (including an accounting for non-rotating bending using an equivalent diameter technique), a loading factor, a temperature factor, and a reliability factor. A fatigue stress concentration factor (Kf) is computed from the theoretical stress concentration factor (Kt) by computing the Neuber constant (sqrt(a)) to then compute a notch sensitivity factor (q). The nominal stress in the plate is computed and the fatigue stress concentration factor is applied to determine the maximum stress. The fatigue factor of safety for infinite life is determined by taking the ratio of the fully corrected endurance limit to the maximum stress.
Playlist for MEEN361 (Advanced Mechanics of Materials):
• MEEN 361: Advanced Mec...
Playlist for MEEN462 (Machine Element Design):
• MEEN 462: Machine Elem...
This lecture was presented on February 2, 2018. All retainable rights are claimed by Michael Swanbom.
Please subscribe to my TH-cam channel and follow me on Twitter: @TheBom_PE
Thank you for your support!
the best lectures series on youtube
Thanks for the review, and thanks for watching! I'm glad I could help!
Dear Professor, thanks for your valuable videos on fatigue that I started to follow to review my engineering background. I am responsible for design on a Company that manufactures big equipment for heavy industry, and needless to say, I’ve been using these methods (on a slightly different flavour, but substantially the same) for many years. Most of the time we use FEM to get theoretical Von Mises stresses, sometimes we mitigate with q factor if we feel that it is significant, and we come out with a fatigue stress.
Many times we deal with large welded structures and we consider them as solid to figure out what the stresses could be at the weld itself. You may imagine that it is quite difficult to treat these weldings with the “classic” formulas when the structure is highly hyper static and needs to be solved numerically.
Most of the time our stresses are pulsating (from the zero) so we need to figure out Se with the Marin factors.
My questions are:
- the ultimate tensile strength of the materials usually varies with the thickness or diameter of the part. If we consider actual UTS of our part, already reduced with respect to conventional 10mm test part, do we need to consider as well the Kx related with the size?
- are you aware of some literature that explains how to use FEM and compute fatigue safety factor, maybe focused in case of weldings? FEM (we use Ansys) does not take into account Neuber factor, so it might overestimate especially with low resistance ductile steels, usually applied in welded structures.
I know that I’m asking a lot, but it is a very interesting topic and I find very few people competent on this.
Thanks!
This was so much better than my Asian lecture I couldn't understand. God bless you.
Thanks for watching! Glad I could help. May God bless you too!
O MY! This lecture helps me a lot! Such a meaningful job! Thank you very much!
I'm glad I could help! Thanks for watching!
thank you sir for uploading the video
Glad you liked it! Thanks for watching!
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
My only confusion is that in Finland we use different notations and of course SI units. I enjoy your videos. They are fantastic!
Thank you! I'm glad you enjoy them! Thanks for watching!
Extraordinary teacher!
You are very kind! You might also be interested in my other course I teach out of the Shigley text: th-cam.com/play/PL1IHA35xY5H5KqySx6n09jaJLUukbvJvB.html
He is GOD.
Thank you...............from South Africa
You're welcome! Glad it helped!
I love your contents. I find them very useful for engineering students.
Thank you! I'm glad they are helping! Thanks for watching!
Thanks for this video and thanks for perfect teaching style.
You are always very kind! I appreciate the encouragement!
Thank you very much. Great Job.
Thanks! I'm glad you liked it! In case you haven't seen them yet and might be interested, here are some of my playlists:
ENGR122 (Statics & Engr Econ Intros): th-cam.com/play/PL1IHA35xY5H52IKu6TVfFW-BDqAt_aZyg.html
ENGR220 (Statics & Mech of Mat): th-cam.com/play/PL1IHA35xY5H5sjfjibqn_XFFxk3-pFiaX.html
MEMT203 (Dynamics): th-cam.com/play/PL1IHA35xY5H6G64khh8fcNkjVJDGMqrHo.html
MEEN361 (Adv. Mech of Mat): th-cam.com/play/PL1IHA35xY5H5AJpRrM2lkF7Qu2WnbQLvS.html
MEEN462 (Machine Design): th-cam.com/play/PL1IHA35xY5H5KqySx6n09jaJLUukbvJvB.html
(MEEN 361 & 462 are taught from Shigley's Mechanical Engineering Design)
Thanks for watching!
Hey man how do I be so intelligent like you? you are the best professor
from Minnesota state university
Thank you, that is very flattering! Anything you cultivate interests in will naturally drive you to read, study, and learn. I'm sure you are already on your way. BTW, I'm not sure if you were saying that you are from Minnesota State or me... if you are speaking of yourself, then greetings to you in Minnesota! If you were speaking of me, then let me send my greetings instead from Louisiana Tech University!
Sir, is there a chart to find surface factor for machined shaft with steel of ultimate strenght of S_ut=108ksi? also, how to modify endurance strenght in soderberg criteria for this shaft? thanks in advance.
Thanks Professor
Glad I could help!
Awesome lecture
I'd like to know what you do for zero based
Have u got the lecture of that ?
These Marin factors can be used for the aluminum alloy ?
Thanks for your video, I am trying to find out how to use the formula for the size factor with a hollow circle cross section with a diameter of 200 and 600 mm.with an area of 0.282m^2 but I can not get an equivalent diameter to use the formula. Can you help with this?
Thanks for sharing this, you do it great! I am a teacher too, may I ask which software and hardware are needed to make nice colorful notes on the screen during teaching?
I use a Fujitsu T901 as my computer. It is a convertible tablet PC with a Wacom active digitizer. I use Camtasia for screencapture and video editing. I use Microsoft OneNote 2007 to write the notes (that was the last version that had user-customizable toolbars). Thanks for watching, and thanks for the positive feedback!
मजा आ गया, सर 👌👌
Glad you enjoyed it! Thanks for watching!
what book does he use in his class. Great lectures btw
Nice video! One question professor, what valor of Kb is used when we are sizing a cilyndrical shaft and we don't know the diameter? Suppose it's not rotation, just alternating forces like the problem that you solved. Regards
When you say alternating force, I assume you mean causing flexure like the example here. Table 6-3 in Shigley says round members in non-rotating bending have effective diameters de=0.370d. You could do an iterative solution where you assume a size and solve for factor of safety, then revise your assumed size based on that result and go on until you are pleased with the outcome. Good luck, and thanks for watching!
@@TheBomPE ok, I supossed to do iterations, thank you very much!
May I asked what book is used as references? I’m currently doing my undergraduate thesis on remaining fatigue life. Thank you in advance.
I use Shigley's Mechanical Engineering Design, 10th ed. (US version). Good luck on your thesis!
Which book you are referring, eq. 6-19.
And how to get endurance limit for metal matrix composites
Which book and which edition are you referring to?
I'm using Shigley's Mechanical Engineering Design, 10th ed. I have not done a lot of reading about how to find endurance limits for the composites you reference. I'm sorry, I wish I could contribute more!
Thank you professor for this information. I would like to ask a question I need your answer .. can this be applied to fragile materials like PMMA? Is it possible to get the book you use ?
I use Shigley's Mechanical Engineering Design as the basis for these lectures. I do not have specific experience with fatigue in PMMA, but some relatively recent papers appear to be available based on a cursory search. The idea of plotting cyclical stress magnitude against number of cycles to failure is pretty standard. The specifics of how various factors influence the fatigue strength are somewhat similar in concept across material groups, but are likely to vary in how specific scenarios are to be evaluated. For instance, the relationship between temperature and the associated Marin factor will be very dependent on what kind of material you are considering. You won't be able to just use the table I used in the video or the equations in the text. If no data is available for the type of material & loading scenario you are trying to use, it means you have an opportunity to do some experiments and write a paper! I hope this helps!
Hi Sir, when calculating Neuber number, should we plug in S_ut = 68 ksi (from table A-20) or the operating ultimate strength which is kd*S_ut?
I tend to use the plain ultimate strength since that leads to a calculation of higher notch sensitivity since the material has lower strength at high temperatures. This makes it more conservative, generally. I don't think it is wrong to adjust for temperature though, if you are confident about the nature of the material behavior at elevated temperatures.
@@TheBomPE thanks for your clarificafion!
When i put the values of a and b in the equation of K sub a, i get some odd value with some odd units in Mathcad. what can be reason?
That is an empirical equation based on experiments and not theoretically derived. Because of that, units should be stripped before performing the calculation in mathcad. Those equations assume you are plugging in a numerical value associated with specific units, but not the actual units.
Thanks. It worked after stripping off the units.
Please provide Text book details used in this Vid
I'm using Shigley's Mechanical Engineering Design, 10th edition.