Can you please tell me that which test will show more strength- a 3 point or a 4 point bending test and why? Can we do some modifications in these tests to obtain purely shear cracks and not the flexural cracks? Furthermore, can you please explain me again the lines from 4:39 to 4:52?
Within reason... it depends. What properties of your material are you attempting measure? In general, using a larger diameter will increase the contact area at each roller. As a result, you will decrease contact stress directly around where the rollers touch your sample. Assuming you're 'far enough' away from the rollers, you should see little impact (i.e., Saint-Venant's principle should take over). If you need to know exactly how much impact the choice has (and quantify things like 'far enough'), then you can get a good estimate with a 2D elastostatics model. A 2D linear elastic FEM (or BEM) model of 3 point bending should converge almost instantly (even on an old laptop). This is likely a tutorial model in most commercial software. I'd also be surprised if a few minutes of googling didn't reveal matlab code you could download, at which point you'd just need to setup the problem.
jasper schuringa For some reason it appears the 1/2 isn't showing up in the video, and left a nice gap in its place (there's also a good chance I just forgot it!). However, the subsequent equation does take that 1/2 into account.
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
your moment summation for region B-C at 2:44 should be 1/2Fx + F(x-L/2), i think
You're correct, but his final moment equation (below the summation equation) is correct
thank you! I thought i was going crazy for a second.
Can you please tell me that which test will show more strength- a 3 point or a 4 point bending test and why? Can we do some modifications in these tests to obtain purely shear cracks and not the flexural cracks?
Furthermore, can you please explain me again the lines from 4:39 to 4:52?
Does the roller diameter have an influence (varied "within reason")?
Within reason... it depends. What properties of your material are you attempting measure?
In general, using a larger diameter will increase the contact area at each roller. As a result, you will decrease contact stress directly around where the rollers touch your sample.
Assuming you're 'far enough' away from the rollers, you should see little impact (i.e., Saint-Venant's principle should take over).
If you need to know exactly how much impact the choice has (and quantify things like 'far enough'), then you can get a good estimate with a 2D elastostatics model. A 2D linear elastic FEM (or BEM) model of 3 point bending should converge almost instantly (even on an old laptop). This is likely a tutorial model in most commercial software. I'd also be surprised if a few minutes of googling didn't reveal matlab code you could download, at which point you'd just need to setup the problem.
@@jdomann Trying to measure fracture, force and displacement just before it occurs, and calculate the max stress at that moment.
Really good explanation
Very well explained. Thank you.
Thank you so much for these videos!!!!! :D
thank you man
excellent
It is very useful. Thanks so much.
Can we determine Young's modulus from bending test?
ASTM D790 - 10
Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
ASTM C1161 - 13
Standard Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature
I think you made a mistake in your calculation at 2:48, shouldn't the sum of the moments at the cut be ..+F(x-1/2L)+M?
jasper schuringa For some reason it appears the 1/2 isn't showing up in the video, and left a nice gap in its place (there's also a good chance I just forgot it!). However, the subsequent equation does take that 1/2 into account.
at 2:50 sum M_cut = 0 = -0.5Fx + F(x-0.5L) + M
Marc C thanks for catching that! Fortunately I corrected that mistake by the next line.
Thank you.
Thanks!
I love you