Corrections: at minute 7 and a half, the integral should be [-2/sqrt(a)], not [-1/sqrt(a)]. Therefore, the final answer should be 203,132 for the number of cycles to fracture failure.
What program are you using to present your lectures? They are pleasing to the eyes, but i also see how robust they can be as you shift from one area to another, use of the ruler, etc..
Really great video!! Do you have any details on how the initial micro crack forms ? I have read things like that small amounts of dislocation movements happens near the surface (even if loading is below the yield strength), causing the surface to roughen and hence cause micro-notches, turning later into cracks. I just don't understand why we are having dislocation motion underneath the yield strength...?
hello, I've a question, isn't the Beta coefficient supposed to vary with respect to a ? I don't understand why beta is a constant since it depends on a, when a grows, beta is supposed to vary ? thanks for reading
You are totally correct. ß does vary with a. The proper use of the Paris Equation requires you to write ß as a function of a, which can easily be done creating a regression from data-points in the ß plots that you find in textbooks (for whatever type of crack you have). HOWEVER, almost no instructor or textbook teaches it that way, and the big (and in my opinion, not-accurate-at-all assumption/simplification) is that ß doesn't vary much as the crack grows. So for this video, I stuck to explaining it the basic, most-commonly-used way. But again, you are indeed right.
They cover a good amount of real world cases. The other two modes are still important for other applications (brittle metals and ceramics), but their nature is more complex than that of K_I, generally relying on experimental results, and not just analytically derived models.
These are usually included in textbook tables, around the crack propagation chapters, but you can also look them up online as the fracture strength (KIC) and the crack propagation coefficients of steel (or any other material).
Corrections: at minute 7 and a half, the integral should be [-2/sqrt(a)], not [-1/sqrt(a)]. Therefore, the final answer should be 203,132 for the number of cycles to fracture failure.
Awesome video. Thanks Sensei
What program are you using to present your lectures? They are pleasing to the eyes, but i also see how robust they can be as you shift from one area to another, use of the ruler, etc..
Really great video!!
Do you have any details on how the initial micro crack forms ? I have read things like that small amounts of dislocation movements happens near the surface (even if loading is below the yield strength), causing the surface to roughen and hence cause micro-notches, turning later into cracks. I just don't understand why we are having dislocation motion underneath the yield strength...?
Great content and explanation. Thanks!
yeah..yeah....delicious... It took me a 3,14 centuries to understand this
Thank you so Much....
very cool, thanks so much
good video sir
Isn’t the solution to the integral -2x^(-1/2) in 7:35?
hello, I've a question, isn't the Beta coefficient supposed to vary with respect to a ? I don't understand why beta is a constant since it depends on a, when a grows, beta is supposed to vary ? thanks for reading
You are totally correct. ß does vary with a. The proper use of the Paris Equation requires you to write ß as a function of a, which can easily be done creating a regression from data-points in the ß plots that you find in textbooks (for whatever type of crack you have). HOWEVER, almost no instructor or textbook teaches it that way, and the big (and in my opinion, not-accurate-at-all assumption/simplification) is that ß doesn't vary much as the crack grows. So for this video, I stuck to explaining it the basic, most-commonly-used way. But again, you are indeed right.
@@LessBoringLectures thank you so much for you reply, it's much more clear now :)
How useful is leaning fracture mechanics for the other loading modes? Or does using K_I vs K_IC and the Paris equation cover most cases?
They cover a good amount of real world cases. The other two modes are still important for other applications (brittle metals and ceramics), but their nature is more complex than that of K_I, generally relying on experimental results, and not just analytically derived models.
@@LessBoringLectures Thanks
Why doesn't a crack always go in a straight line?
because a crack always follows the path of least resistance as defined by the local microstructure of the material and it's imperfections
How to get KIc steel and C? at 6:01
These are usually included in textbook tables, around the crack propagation chapters, but you can also look them up online as the fracture strength (KIC) and the crack propagation coefficients of steel (or any other material).
@@LessBoringLectures Thank for yours explanation, its very helpfull, but maybe I have another question, can I ask you some day?