Thickness of aluminum cans, part 2

[Nickrz]

Dangit! I accidentally deleted Mr. J's thread. Luckily I copied off my cache version the following:

Mr J. Speaking:
Well that didn't quite work I will try again and then contact mr nick. (all sorts of strange stuf has been happening to me ever since i did NOT discover and did NOT go to the private forums,which do Not exist. Almost as if THEY{who also do NOT exist} are trying to discourage me.) Here we go:
Sorry to start another thread,but search's WAGs are totally without foundation. i can't find the original. here is an Email i sent to two engineers at alcoa. and the answer one of them sent.
Gentlemen;
It is a debate I am involved in. Given that soda cans are harder to crush than beer cans; Is there a difference in the wall thickness of a beer can and a soda pop can? Or another structural difference that would make a soda can harder to crush? If so why? My hypothesis is that soda cans are thicker due to more pressure from the carbonation. If you shoot me down I won't mind. If either of you can help me, I promise to drink even more beer, thereby increasing the amount of aluminum recycled. In closing I would like to remind you of some words from the movie "The Graduate", "Mrs. Robinson, you're trying to seduce me.....Aren't you?" thanx, Al

Well, yes and no. (now that i see that in juxtaposition it seems real strange,mj)
Yes, soda has more carbonation than beer. Typically about 3.5 volumes of CO2 for soda (sprite is higher, Fanta is lower), and only 2.7 for beer.This means on a hot day in the back of a delivery truck soda cans will have higher pressure than beer cans, perhaps 90 psi compared with 60 psi.But the crush load of a can (resistance to standing on it) is a requirementof the necking and filling operations, not the product inside. Necking is the metal forming operation on the can to allow the lid diameter to be smaller.(So that's what necking is.What were my parents so worried about?mj) Beer and soda cans have the same requirements in this regard.My guess is that you buy good quality beer and lousy quality soda. Lots of
soda bottlers buy cans strictly on price, and those outdated can designs and equipment have much higher performance (and in many cases performance requirements) than the newer, more highly-engineered cans.
Of course, these comments are my own and do not reflect the opinions of my gracious employer.
Cheers,
abt

Turns out every body was right and wrong. At least those of us on the more pop in pop were right, but the entire thick can theory was bogus. To paraphrase ,some cans are thick some are thin,some have wide necks some narrow but not because of the pressure.It's because of the machine they use to pour the stuff in. At least the research involved in comparing neck sizes was interesting, even if it was a lot of work to empty all those (burp,'scuse) beer cans ,so i wouldn't strain myself holding them against the soda cans.

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"Pardon me while I have a strange interlude."-Marx



pmh
Member posted 08-24-1999 02:04 AM
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quote:
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But the crush load of a can (resistance to standing on it) is a requirementof the necking and filling operations
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Is that the answer? MechEs please translate. My statics class was a long time ago.

FTR, the original thread is at

http://www.straightdope.com/ubb/Forum3/HTML/001959.html

[Strainger]

pmh, look at the top of a Coke can. Notice the taper from the body of a can to the mouth. That's the neck. Now, assume a vertical load evenly distributed around the rim. This will result in bending + axial stresses in the neck which greatly exceed the compressive stresses in the body (P/A). Therefore, that's where failure will initially occur. Once the neck fails, you'll end up with an eccentrically applied load in the body, resulting in bending moments there, greatly increasing the stresses and resulting in can crush.

[Strainger]

Hmmm, I have yet to do a buckling analysis using a finite element modeler (I just do static and thermal analyses), but I may just have to give it a shot with this. Stay tuned.

[mr john]

you done good nick. that's what I wanted.
I have a reply from the other engineer now. These two guys are working on making the cans ever more thinner! They each received the same mail from me BTW the other guy is Andrew Trageser, I gotta go buy some more canned beer to pay them back. The letter;

Probably the biggest difference is that soft drink companies have a minimum
sidewall thickness specification whereas most beer companies do not. Thus beer cans tend to be lighter. Both still have minimum requirements for axial column strength. Thank you for the inquiry.

Bob Dick
Technical Specialist
Rigid Packaging Design and Development Division

me again' Axial column strength','crush load' ain't scientifical talk cool? I used to work in flexible package art design,we didn't have no axial column strength, about the biggest problem we had was that we never did find a good substitute for real potato chips in a package mockup,specialy if there was a window. For cheeto type things styrofoam peanuts were great,if there was a window we just backed it up with a piece of amber tintscreen, looked like the real thing. ( Tasted like some of the products I designed for too) Iam still not satisied by all his technical jargon,I am going to buy another case of beer and continue the research. Maybe a bag of pretzels too, I always buy the ones in a package that I designed. I have no resistance to that subliminal stuff hidden all over them.

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"Pardon me while I have a strange interlude."-Marx

[Strainger]

I have some empty pop cans at my desk, full beer cans in the fridge (Bud and MGD, left over from my b-day party. "Normally I drink out of bottles, but for this I'll use cans, eh"), a knife, and access to a digital Vernier caliper. If y'all are interested, I'll cut open some empties and measure the pop can wall thinknesses vs. the beer can wall thicknesses. All in the name of science. I need to see if the OP specified specific brands of pop and beer.

Sorry I'm so late posting, I haven't been following this thread until today.

[Lumpy]

I was under the impression that higher internal pressure (from carbonization) actually made it possible for cans to be thinner. The main stress pop and beer cans are under is stacking weight- those cases stacked eight feet high at the supermarket. "Inflating" the cans with internal pressure helps them resist buckling under external loads. If this is not so, I stand corrected. But it does seem that products that aren't carbonated (fruit juice, etc) still come in those thick sturdy cans.

[pmh]

Strainger, I know what the neck is, What I want to know is: What effect (if any) does the diameter of the top / angle of the neck (wrt vertical) have on the "crush load" of the can? (see the original thread for the argument)

If y'all are interested, I'll cut open some empties and measure the pop can wall thinknesses vs. the beer can wall thicknesses. All in the name of science.

I tried this in the original thread (and w/ 9 different beers and 11 different soda varieties since). Found they are the same (to within .0005"). But more data is always useful.

Hmmm, I have yet to do a buckling analysis using a finite element modeler (I just dostatic and thermal analyses), but I may just have to give it a shot with this. Stay tuned.

Please do! My attempts to figure it out with a bathroom scale and freeweights is pitiful.

Now? Now am I taking this too seriously?

WOTSB

[Strainger]

pmh, after reading through the original thread, I realized that I had totally misunderstood your question. Sorry about that. A larger angle wrt vertical would be worse with regard to yield strength, but I admit I still have some things to learn about structural instability.I tried this in the original thread (and w/ 9 different beers and 11 different soda varieties since). Found they are the same (to within .0005"). But more data is always useful.Sounds like you have plenty of data points. I'll just measure the dimensions I need to create a FEM. samclem, was there a prevalent brand among the beers and pops? If so, let me know and I'll model based on the dimensions of those cans.Now? Now am I taking this too seriously?Hey, it's what us geeks consider "fun!"