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Indentation Calcs

I won't comment on this as I understand very little about calculating, but I will point out, for the purpose of this thread, that we must always attempt to achieve the closest to a real result, but at the end of the day we simplify many things, with assumptions and not over-analyzing the calculations involved. Which is actually quite normal in engineering, from my understanding of it.

I'll be keeping up with this thread just to see where it goes. If my input becomes useful for some reason, I'll comment on it.
 
StretchSebe said:
The fictional feats all seem to be at 9-B, and converting the newtons to joules seems consistent in that.

I'm sorry the irl guy is too strong, I guess.
Click to expand...
If the IRL guy is 10x stronger than he should be, why would we expect that error to suddenly stop at 9-B? I don't want calcs that are that far off from reality. My personal tolerance is around the 1.5x off end, and even that's only for cases where there's no room for improvement.
StretchSebe said:
We've already discussed converting newtons to joules earlier in the thread, and at this point multiple times. Yes:

Convert the Newtons to Joules if it's a striking/ap feat. Use Newtons if it's slow-twich fiber muscles and a LS feat.

With all due respect, I would assume as an admin and calc group member you'd not need this repeated to you...
Click to expand...
You're saying that I don't know that Joules are used for striking feats, and Newtons are used for feats of slower pushing/lifting. Lets retrace the conversation to see whether the posts in this thread support that claim.
  1. You said that Pascals can not be converted to Joules. That the issue with these feats is that they're finding the Joules to do the damage, and that such a thing is impossible.
  2. You repeated that, saying that one could not use the dent made in a door to find the energy of the explosive yield.
  3. You then said that the 6.6e6 Newtons I got from multiplying the pressure needed to dent steel by the surface area dented was actually the value in Joules. And that such a Joule value for that feat (which was a real-world human denting a real car) makes sense. You also said here that Newtons aren't used for AP or SS.
  4. I responded that the most recent posts were grossly incorrect; that the 6.6e6 value is Newtons, and that 6.6e6 Joules would be nonsense for a real human.
  5. You responded, saying that the IRL one was almost 7000 Joules, which is fine for a real human.
  6. I then jumped back to your earlier posts (here, posts 1 and 2), saying that the idea of just using force for these feats is still bad, since it would give this real human Class K LS.
  7. You responded that Newtons shouldn't be used for SS or AP, and that the wiki already doesn't do that.
  8. I responded that our wiki already converts from Newtons to Joules for a bunch of AP feats, and that changing this would require a lot of revisions. And that there is still the issue of this giving a real human Class K LS.
  9. Your latest response is that it should only be converted from Newtons to Joules if it's a SS/AP feat, and for slow-twitch muscles it should be a LS feat.
First, as credit to you, I see how one could interpret my mentions of that feat involving Class K LS as endorsing that striking feat being used for lifting. But I'm more concerned with how extreme of a value is, and the possibility that someone could have an actual LS feat calculated with the same method. Due to the differences between lifting and striking, performing such a feat with slow-twitch muscles would be harder, and therefore get a lower value, but I don't think it'd be on the order of >300x lower that it'd need to still be a realistic LS rating for such a feat. Especially since we consider jumping and throwing to be LS.

But there were still other issues. You saying that Pascals could not be converted into Joules (done in posts 1, 2, and 7) has only just now been retracted. You saying that my conversion from pressure to force was actually joules (post 3) and that 6.6e6 joules would be fine was, although not retracted, just sort of dropped as if you never said it in post 5.

So like, I do appreciate the move from "These feats cannot be anything but LS. Pressure exerted cannot be used to find the Joules." to "They can be AP or LS, and they need to be converted appropriately depending on their source", but I think it's weird to frame things as if I'm not understanding the distinction.
 
Agnaa said:
If the IRL guy is 10x stronger than he should be, why would we expect that error to suddenly stop at 9-B? I don't want calcs that are that far off from reality. My personal tolerance is around the 1.5x off end, and even that's only for cases where there's no room for improvement.

So like, I do appreciate the move from "These feats cannot be anything but LS. Pressure exerted cannot be used to find the Joules." to "They can be AP or LS, and they need to be converted appropriately depending on their source", but I think it's weird to frame things as if I'm not understanding the distinction.
Click to expand...
Alright. Sure man.
 
I just have to say this:
Are you absolutely SURE he was bending steel? As it sure as hell seems to me, that he only bent the polymer covering (specifically in the fender) over the chassis (which is the metal frame of a car).

Which, is likely made out of either polyethylene or polypropylene, NOT steel.

And funnily enough, you can actually fix those dents with boiling water if it is made out of polypropylene, as the strength of polypropylene weakens when heated past 180°F.

In fact, here is a video of this exact thing:


And if you want to know the UTS of polypropylene...it is 71.1 MPa on average.

Or a mere 42.66 MPa for shear strength.
 
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I've edited your posts together, and deleted the extras. Please don't spam posts like that.

Anyway, that is a great point! But I'd expect changing the material there would also entail changing some of the materials in some of those car calcs.

If we move to that value of shear strength instead, the value gets dropped to 1/7th, which still makes the LS entirely unrealistic, and still has the SS be a bit suspect. Especially if the thickness turns out to be greater than the one I used.
 
Agnaa said:
I've edited your posts together, and deleted the extras. Please don't spam posts like that.

Anyway, that is a great point! But I'd expect changing the material there would also entail changing some of the materials in some of those car calcs.

If we move to that value of shear strength instead, the value gets dropped to 1/7th, which still makes the LS entirely unrealistic, and still has the SS be a bit suspect. Especially if the thickness turns out to be greater than the one I used.
Click to expand...
I mean, sure.
It still has pretty high LS and SS, but least the SS is somewhat within human capability now.

(Also kicks are biomechanically stronger than punches, think by like a factor of around 3-5x for an average person, which would make a baseline human's (at 60 joules) kicks around 180 to 300 joules; 10-A to baseline 9-C, since the baseline for 10-B is based on the punch of an average person)

And I also want to say...you can actually push in the polymer cover with your hands. I only know this, because I used to do it as a kid on my grandmother's car.

Now, it wouldn't permanently bend it, as it will just spring back immediately, but you can still push in the polymer cover of a car.
 
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Agnaa said:
If we move to that value of shear strength instead, the value gets dropped to 1/7th, which still makes the LS entirely unrealistic, and still has the SS be a bit suspect. Especially if the thickness turns out to be greater than the one I used.
Click to expand...
Could I ask you to elaborate as to why you're considering the "Lifting Strength" of a strike? Obviously the divide we make in the website doesn't exist IRL, but the kg of force behind a strike you deal are still not the same as your ability to lift things. Trained boxers can deal upwards of 350 kgf with a punch, which I highly doubt they can lift. Obviously this guy isn't one but kicks are much stronger than punches, and they happen over a smaller surface area.

The calculation might still be wrong but if the result that is directly obtaining (Striking Strength) is reasonably acceptable, while the extrapolated LS isn't, then the flaw is likely in the way the latter is obtained, rather than the calculation method as a whole. Otherwise, they'd both be similarly high.
 
Agnaa said:
I'm more concerned with how extreme of a value is, and the possibility that someone could have an actual LS feat calculated with the same method. Due to the differences between lifting and striking, performing such a feat with slow-twitch muscles would be harder, and therefore get a lower value, but I don't think it'd be on the order of >300x lower that it'd need to still be a realistic LS rating for such a feat. Especially since we consider jumping and throwing to be LS.
Click to expand...
 
I don't really know that, since LS is done on the way to Joules.
 
Okay what is happening here?
KLOL506 said:
Uhhhhhhh... guys, I thought we treated Striking Strength and LS as separate. My query was more so about calculating LS for bending metal with your hands by grabbing it like in those power-lifting thingies.
Click to expand...
I've said two times that I know that AP and LS are different. Why are you saying that as if I don't know that?
Armorchompy said:
But the joules result is acceptable, or at least closer to acceptable, so those aren't the issue.
Click to expand...
I know.

But the LS method is used on the way to the AP method.

If the force involved in the feat is not being derived correctly, then the energy needed to exert that force over a certain distance would also be inaccurate.

Like, idk, if we found a method of calculating a feat which found that ordinary real-world humans can flick the tip of their fingers at 300 m/s. But only the tip of the finger, weighing 20 grams, moves, such that the KE is only 900 Joules. I wouldn't find that end-value comforting given that an intermediary step involves a human body part almost breaking the speed of sound.

These sorts of errors at intermediary steps carry over, even if the final result seems fine.
 
Ah okay.

Re-reading that comment, I think it may also be useful to point out that using shear strength of polypropelyne, the IRL human in the video above would be kicking with 136,546 kgf. 390x above that of the boxer's punch.

As I said before, if it was in that boxer-punch sort of range, I wouldn't have an issue with it as an intermediary step. But a random dude dishing out a force 390x above that of a trained boxer indicates that something has gone horribly wrong.
 
Agnaa said:
I've edited your posts together, and deleted the extras. Please don't spam posts like that.

Anyway, that is a great point! But I'd expect changing the material there would also entail changing some of the materials in some of those car calcs.

If we move to that value of shear strength instead, the value gets dropped to 1/7th, which still makes the LS entirely unrealistic, and still has the SS be a bit suspect. Especially if the thickness turns out to be greater than the one I used.
Click to expand...
That's basically what I was talking about :cry: . Why wasn't I given attention? But yeah there is something at play here.
 
Serlock_Holmes said:
That's basically what I was talking about :cry: . Why wasn't I given attention? But yeah there is something at play here.
Click to expand...
Yeah I figured that the entire painted surface would be made out of metal. Whoops.

Anyway, in another way of approaching this issue...

Tanks can crush cars by driving over them.

Lets do a ludicrous lowball and say that cars are just 1m^2 of steel.

Using shear strength (60% UTS), and the values accepted in these calcs (350 MPa UTS), that would require 2.1e8 Newtons of force to dent.

Dividing by 9.81 to convert to kgf, involves 21,400,000 kgf.

Tanks aren't pushing down with anything but their own weight, so that implies that these tanks weigh at least 21 million kilograms.

The heaviest tank ever built weighed 188 tons. 113x less than this method implies most tanks should weigh.

Doing better to incorporate realism (counting up the total surface area of metal in the car, incorporating the fact that the tanks in that video often were only putting a part of their weight on the cars) would imply even heavier weights. But if we move into the method of assuming that such cars are always made out of plastics, that'd cut this down by 1/7th, to only weighing 20x more than the heaviest tanks ever built.

now that I write this up I kinda feel like I'm belaboring the point
 
Last edited:
Agnaa said:
Yeah I figured that the entire painted surface would be made out of metal. Whoops.

Anyway, in another way of approaching this issue...

Tanks can crush cars by driving over them.

Lets do a ludicrous lowball and say that cars are just 1m^2 of steel.

Using shear strength (60% UTS), and the values accepted in these calcs (350 MPa UTS), that would require 2.1e8 Newtons of force to dent.

Dividing by 9.81 to convert to kgf, involves 21,400,000 kgf.

Tanks aren't pushing down with anything but their own weight, so that implies that these tanks weigh at least 21 million kilograms.

The heaviest tank ever built weighed 188 tons. 113x less than this method implies most tanks should weigh.

Doing better to incorporate realism (counting up the total surface area of metal in the car, incorporating the fact that the tanks in that video often were only putting a part of their weight on the cars) would imply even heavier weights.

now that I write this up I kinda feel like I'm belaboring the point
Click to expand...
So what's the most likely issue? That an equation used is being used way to simply and thus not taking things into account that would make the result lower? I feel this looks to be needed. Might turn out to be a big thing.

Also don't tanks push down through their speed or is power not applied downwards using that?

Seeing the video yeah I believe this needs to be looked at more. Maybe tagging every cgm and brainstorming?
 
Serlock_Holmes said:
So what's the most likely issue? That an equation used is being used way to simply and thus not taking things into account that would make the result lower? I feel this looks to be needed. Might turn out to be a big thing.
Click to expand...
As said before, my best guess is that the tests to find these values aren't cross-applicable to these situations. I expect that the materials in these examples are both thinner, and less supported, than the materials used in such tests. These things may be relevant to, like, pure steel beams, but not to sheet metal.
Serlock_Holmes said:
Also don't tanks push down through their speed or is power not applied downwards using that?
Click to expand...
Actually that's fair, but I don't think it's a significant enough factor. I think the tank would have to be accelerating faster than gravity for its push on the objects below it to be more from speed than from weight.

And still, in the grand scheme of things I don't think it matters too much. I don't think a car would be completely un-dented if a tank was gently lowered onto it, then released.
 
Agnaa said:
As said before, my best guess is that the tests to find these values aren't cross-applicable to these situations. I expect that the materials in these examples are both thinner, and less supported, than the materials used in such tests. These things may be relevant to, like, pure steel beams, but not to sheet metal.

Actually that's fair, but I don't think it's a significant enough factor. I think the tank would have to be accelerating faster than gravity for its push on the objects below it to be more from speed than from weight.

And still, in the grand scheme of things I don't think it matters too much. I don't think a car would be completely un-dented if a tank was gently lowered onto it, then released.
Click to expand...
So should all these feats be banned for always giving exaggerated values?
 
As I said, I think a thickness minimum is a good idea. But I'm not sure exactly where it should be.
 
I'd think so, yeah.

Fundamentally it is pretty weird that we'd consider denting a 1mm thick steel plate as requiring the same amount of force as denting a 2m thick steel plate. So maybe it is actually an equation issue.
 
Actually can't you find Force from Work?

Work (j) = Force (N) x Displacement (m)
So if you do: Work / Displacement, you will get Force.

Displacement would the the depth on the dent.

NVM, just did it and result is still absurd.
 
Last edited:
Agnaa said:
pointed out to me by Vapourrr
Click to expand...
988.jpg

(More seriously, being in an actual car crash has made me acutely aware how easy it is on a relative scale to bend metal, so I agree)
 
So I found this calc for bending a piece of sheet metal (though I assume it can be used for other materials as you can adjust the UTS)
With sheet thickness being the depth of the bend (0.625 mm), bend length being the diameter of the bend (20cm), and UTS of course being the UTS of polypropylene in psi.
Die Ratio and Die Opening is auto calced with other values inserted.

So, that would equal 1,450.119 N (Athletic Human LS) and an energy of...0.000625 joules.
Huh.
 
Last edited:
StrymULTRA said:
Those aren't Tons in TNT, they're in Short Tons.
Click to expand...
I...didn't use that value AT ALL.
I converted the lb-force to Newtons (1,450.119 N), then used that value to find Work in joules.
Work = 0.000625 joules

Edit: Oh wait, the calc I used saw the comma as a decimal for some reason.
Work actually equals 0.906 joules.
 
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What I think you guys are forgetting is strikes are instantaneous. The 4096 newtons of force Frank Bruno exerted, for example, lasted only 14 ms. Pretty sure lifting requires a LOT more time than that.
 
Last edited:
Flashlight237 said:
What I think you guys are forgetting is strikes are instantaneous. The 4096 newtons of force Frank Bruno exerted, for example, lasted only 14 ms. Pretty sure lifting requires a LOT more time than that.
Click to expand...
Firstly, I'd refer you to the three times where I've made it clear that I understand that.

Secondly, I'd refer you to this calc I whipped up, which doesn't have that issue, but still demonstrates the dissonance of the force values in these indentation calcs:
Agnaa said:
Anyway, in another way of approaching this issue...

Tanks can crush cars by driving over them.

Lets do a ludicrous lowball and say that cars are just 1m^2 of steel.

Using shear strength (60% UTS), and the values accepted in these calcs (350 MPa UTS), that would require 2.1e8 Newtons of force to dent.

Dividing by 9.81 to convert to kgf, involves 21,400,000 kgf.

Tanks aren't pushing down with anything but their own weight, so that implies that these tanks weigh at least 21 million kilograms.

The heaviest tank ever built weighed 188 tons. 113x less than this method implies most tanks should weigh.

Doing better to incorporate realism (counting up the total surface area of metal in the car, incorporating the fact that the tanks in that video often were only putting a part of their weight on the cars) would imply even heavier weights. But if we move into the method of assuming that such cars are always made out of plastics, that'd cut this down by 1/7th, to only weighing 20x more than the heaviest tanks ever built.

now that I write this up I kinda feel like I'm belaboring the point
Click to expand...
 
Agnaa said:
Firstly, I'd refer you to the three times where I've made it clear that I understand that.

Secondly, I'd refer you to this calc I whipped up, which doesn't have that issue, but still demonstrates the dissonance of the force values in these indentation calcs:
Click to expand...
I think I can see why the results of the car calc are a bit high. Cars are hollow, so I believe the thing you should be accounting for is the cross-sectional area of the "supports", in the car's case, that would start at the window frames. Another possible way to make the results seem more realistic would be the thickness of the car's hull (or whatever you call the painted part).
 
Agnaa said:
Yeah I figured that the entire painted surface would be made out of metal. Whoops.

Anyway, in another way of approaching this issue...

Tanks can crush cars by driving over them.

Lets do a ludicrous lowball and say that cars are just 1m^2 of steel.

Using shear strength (60% UTS), and the values accepted in these calcs (350 MPa UTS), that would require 2.1e8 Newtons of force to dent.

Dividing by 9.81 to convert to kgf, involves 21,400,000 kgf.

Tanks aren't pushing down with anything but their own weight, so that implies that these tanks weigh at least 21 million kilograms.

The heaviest tank ever built weighed 188 tons. 113x less than this method implies most tanks should weigh.

Doing better to incorporate realism (counting up the total surface area of metal in the car, incorporating the fact that the tanks in that video often were only putting a part of their weight on the cars) would imply even heavier weights. But if we move into the method of assuming that such cars are always made out of plastics, that'd cut this down by 1/7th, to only weighing 20x more than the heaviest tanks ever built.

now that I write this up I kinda feel like I'm belaboring the point
Click to expand...
So here's a real life reference of something that can actually crush cars: a car crusher used in scrap yards: https://bestsellingcarsblog.com/2018/09/media-post-whats-the-deal-with-car-crushers/
auto.howstuffworks.com

How Car Crushers Work

The hydraulic press is at the heart of almost all modern car crushers. Find out how the hydraulic press works and learn about car crusher hydraulics.
auto.howstuffworks.com auto.howstuffworks.com

Based on this, the force needed to crush a car is more along the lines of 150+ tons.
 
Flashlight237 said:
I think I can see why the results of the car calc are a bit high. Cars are hollow, so I believe the thing you should be accounting for is the cross-sectional area of the "supports", in the car's case, that would start at the window frames. Another possible way to make the results seem more realistic would be the thickness of the car's hull (or whatever you call the painted part).
Click to expand...
Yeah I think that's one of the main issues, but it's more to demonstrate how our standards don't currently account for that.

With our current calcs, we'd consider denting a sheet of metal propped up by supports, no matter how thin the sheet or spread apart the supports, to get the same rating.

Cross-sectional area of supports sounds more promising, but still pretty strange in terms of methods. Especially in cases where those supports aren't even getting dented.

EDIT: Especially when there are material differences. If we've dented a piece of rubber supported by some steel rods, no combination of those really makes sense other than rubber-force and rubber-area.
 
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Hopefully.

I did my best to explain the unusual approach of calculating for shear strength: Finding ultimate tensile strength of material (60% of that UTS value to find shear strength), the general formula of stress and (non-comprehensive) outcomes for the fictional examples, and converting pascals to newtons per meter squared, multiplying that by surface area (as Agnaa pointed out and corrected, to isolate the newtons), and then convert newtons to joules given indentation often does not involve volumetric damage, but is still striking strength or ap (the fictional examples would seem to still be around street-wall level iirc).

That's a pretty reductionist summary, but still.
 
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