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Breaking Something in Half

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Flashlight237

Flashlight237

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So here's the thing. Through our current methods, breaking a 12x12x1 board (measured in inches) would sit at 17408.72534 joules (2359.737216 cm³ at 7.3774 j/cc for white oak), yet according to this, to do the same thing, you only need 500 newtons of force, which would equate to 375 joules for a 75-centimeter punch, to break the same board in half: https://daily.jstor.org/the-physics-of-karate/

Have we been using the wrong measurements this whole time thinking they were right? Or is there something we aren't fundamentally understanding about the concepts of strain, stress, and modulus?
 
Flashlight237 said:
So here's the thing. Through our current methods, breaking a 12x12x1 board (measured in inches) would sit at 17408.72534 joules (2359.737216 cm³ at 7.3774 j/cc for white oak), yet according to this, to do the same thing, you only need 500 newtons of force, which would equate to 375 joules for a 75-centimeter punch, to break the same board in half: https://daily.jstor.org/the-physics-of-karate/

Have we been using the wrong measurements this whole time thinking they were right? Or is there something we aren't fundamentally understanding about the concepts of strain, stress, and modulus?
Click to expand...
17408.72534 joules is for fragmentation of the entire board's volume- or breaking every single cubic centimeter of the board- while the 500 newtons of force (375 joules for a 75 centimeter punch) is for simply splitting it in half.

Obviously turning a board into woodchips is gonna require more energy than splitting it in two pieces.

Additionally, the current "material destruction value" system is hyper-simplified compared to actual stress/strain/deformation physics, but since basically every website uses the simplified system it's fine that we use it too.
 
Flashlight237 said:
Sure. I feel trying to see what's up would help more in the future when we would have to calc breaking stuff in half and such.
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Cutting things is gotten via- assuming a rectangular cross section- length of the cut * depth of the cut * blade thickness * pulverization value of the material. Not sure how splitting things in half is done though.
 
ElajRuengies said:
Cutting things is gotten via- assuming a rectangular cross section- length of the cut * depth of the cut * blade thickness * pulverization value of the material. Not sure how splitting things in half is done though.
Click to expand...
Cutting is very much the easy part. But yeah, trying to figure out how splitting something in half blunt-forcing it worked would help wank-proof feats like this:



Which is a prime example of blunt-forcing a table in half.
 
With regular breaking its MPa since MPa measures pressure or yield strength of a material which you'll need to break it. Not necessarily the same as regular destruction calcs but is kinda similar.

Your volume (surface area) in m^2 is multiplied by the MPa value of the matieral and then the by displacement of the material (the displacement I'm pretty is the width of the broken portion and measures the area broken) for the yield

Sorry I kept rewriting this It wasn't satisfactory to me at first
 
Flashlight237 said:
Have we been using the wrong measurements this whole time
Click to expand...
Yes
Flashlight237 said:
thinking they were right?
Click to expand...
No, we've been aware for a while that it's not how material fragmentation works in real life at all.

It's not even because the real method is too conplicated so we have to use an oversimplified one. I even know an almost equaly simple yet way more realistic method. The truth is it's just too late to roll everything back at this point.
 
Ugarik said:
Yes

No, we've been aware for a while that it's not how material fragmentation works in real life at all.

It's not even because the real method is too conplicated so we have to use an oversimplified one. I even know an almost equaly simple yet way more realistic method. The truth is it's just too late to roll everything back at this point.
Click to expand...
Too late? If I can somehow got a calc group member to read over concrete's shear and compressive strength values from a university and make a suggestion on how to incorporate its info, then I can surely try and patch this up at least. What is this "more realistic" method you speak of?
 
Flashlight237 said:
Too late? If I can somehow got a calc group member to read over concrete's shear and compressive strength values from a university and make a suggestion on how to incorporate its info, then I can surely try and patch this up at least. What is this "more realistic" method you speak of?
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Toughness. Unfortunately, it didn't fly as concluded in this thread.

A more appropriate method would be powder factor, but that didn't work out either, it was limited to rocks only.
 
Flashlight237 said:
Cutting is very much the easy part. But yeah, trying to figure out how splitting something in half blunt-forcing it worked would help wank-proof feats like this:



Which is a prime example of blunt-forcing a table in half.
Click to expand...

I'd recommend measuring the length and height of the cracked portion and then figuring out the crack width. It would be prolly 1 cm or less. That'd nerf the feat, but bring it closer to reality.
 
KLOL506 said:
I'd recommend measuring the length and height of the cracked portion and then figuring out the crack width. It would be prolly 1 cm or less. That'd nerf the feat, but bring it closer to reality.
Click to expand...
Sounds like the best we can do here for now.
 
ElajRuengies said:
Is it a "necro" if it's been less than a month?

Anywho, where in the video is the yield of 350 joules?
Click to expand...
It's with regards to the displacement (Compressing distance before the block cracks) and the force being applied.
 
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Anyway, we've already discussed this many times in a row, and I think the original question by OP's been answered. Don't see a point to keeping this thread open any longer.
 
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