compaction of cans and bottles in pet

[cris1972]

hi, I'm almost about to graduate and what tease I decided to design what in question through the use of an electric actuator. After the first calculations from the data from various tables, I learned that by applying, through the actuator, a force greater than 9,7 kn is reached the breaking load (sigma r 85 n/mm2) of the pet and therefore the crushed bottle should, according to logic, maintain the crushed form assumed. Is that correct?
thanks to the attention

 

[MBT]

hi, I'm almost about to graduate and what tease I decided to design what in question through the use of an electric actuator. After the first calculations from the data from various tables, I learned that by applying, through the actuator, a force greater than 9,7 kn is reached the breaking load (sigma r 85 n/mm2) of the pet and therefore the crushed bottle should, according to logic, maintain the crushed form assumed. Is that correct?
thanks to the attention

Meanwhile welcome... .
and well presented... :tongue:

look, I would say that with 9700 n (which are 990 kg, to be practical) exceeds the breaking sigma also of a glass bottle. but also a can.. .
My wife crushes pet bottigles, but I assure you that she does not embrace me with 990 kg... :biggrin:

 

[cris1972]

Of course, the bottles are clearing them, but considering that the bottles must remain deformed to reduce the space of encumbrance even once they have removed the action of force, it seems to me that the latter is just higher than the neccessaria (at least mathematically) to deform them stably. Right?
if you do not mind I will continue to involve you in my adventure as I will certainly need help on someone who surely knows more about me!!! Thank you.

 

[MBT]

Now I understand...
But I believe that in this case the best answer comes from practical evidence.
the thickness of the pet used and also the mixture of pet (if loaded or not, for example) it is more necessary to change much the force necessary, in addition to the shape of the bottle itself.

 

[cris1972]

Meanwhile welcome... .
and well presented... :tongue:

look, I would say that with 9700 n (which are 990 kg, to be practical) exceeds the breaking sigma also of a glass bottle. but also a can.. .
My wife crushes pet bottigles, but I assure you that she does not embrace me with 990 kg... :biggrin:

Of course, the bottles are clearing them, but considering that the bottles must remain deformed to reduce the space of encumbrance even once they have removed the action of force, it seems to me that the latter is just higher than the neccessaria (at least mathematically) to deform them stably. Right?
if you do not mind I will continue to involve you in my adventure as I will certainly need help on someone who surely knows more about me!!! Thank you.

(excuse me of the answer procedure but I'm learning now to use my first forum)

 

[myface]

hi, I'm almost about to graduate and what tease I decided to design what in question through the use of an electric actuator. After the first calculations from the data from various tables, I learned that by applying, through the actuator, a force greater than 9,7 kn is reached the breaking load (sigma r 85 n/mm2) of the pet and therefore the crushed bottle should, according to logic, maintain the crushed form assumed. Is that correct?
thanks to the attention

It is not a correct statement and the reasoning behind it does not follow any logic, at least that on the resistance of materials.

 

[cris1972]

I took an average diameter of the bottles normally on the market and by means of an average thickness I calculated the pressure-resistant surface. with this value and the average value of the breaking load of the pet, I calculated the neutral force to the compression with exceeded for the purpose of the pet sigma. the bottle should be deformed and considered the overcoming of its breaking load, should also lie it. as well as for cans that have a resistant surface less than bottles and the breaking load is equal to the pet

 

[Fulvio Romano]

hi, I'm almost about to graduate and what tease I decided to design what in question through the use of an electric actuator. After the first calculations from the data from various tables, I learned that by applying, through the actuator, a force greater than 9,7 kn is reached the breaking load (sigma r 85 n/mm2) of the pet and therefore the crushed bottle should, according to logic, maintain the crushed form assumed. Is that correct?
thanks to the attention

I think reasoning is quite wrong.
If I have a tube along a meter, stuck in the wall and hangs me, I do the lifts, if the tube is ten meters long, I deform it plastically. Does that mean that ten meters I weigh more? No, of course not.

How do you connect a push of a press with internal tension to the bottle? you can't do it by letting the position of the various bottles, whether or not they are capped (this is very important, if you can't make them "disappear" you'll never be able to deform them plastically, the air inside you will swell them immediately) etc.

a good engineer would go to a warehouse of vans of the urban cleanliness and would go to read the plate data, which should be exposed on the car.
In the case of a plum... I don't know, it depends on the professor.

 

[Fulvio Romano]

I took an average diameter of the bottles normally on the market and by means of an average thickness I calculated the pressure-resistant surface. with this value and the average value of the breaking load of the pet, I calculated the neutral force to the compression with exceeded for the purpose of the pet sigma. the bottle should be deformed and considered the overcoming of its breaking load, should also lie it. as well as for cans that have a resistant surface less than bottles and the breaking load is equal to the pet

We talk about yielding and not breaking, but in any case, all cans and bottles are crushed by buckling and not by material collapse.

 

[cris1972]

I'm sorry if I allow myself! from data taken from various tables found on the internet, I said that the breaking load of the pet amounted to 85 n/mm2. As the two litre commercial bottles contain 2 dm3 h2o, I calculated the average diameter of the ideal bottle to contain this liquid. I then measured the thicknesses of some bottles and prepared that they took values of about 0.3 mm, I deduced the outer diameter of the ideal medium bottle. subtracting the surface of the diameter min from the max one, I am traced back to the resistant surface. from the relationship f=sigma r x hard surface I calculated the neutral force to win this breaking load. used a congruous safety coefficient (n=2) in the application of such force by the electric actuator, came to the fatefuls 9,7 kn. Of course the bottle must be empty, tinned and contained within a cylinder at the time of application of force. Am I wrong?

 

[myface]

you are considering compression behavior based on a fact that it is tensile strength are two different things

 

[cris1972]

what is buckling?

 

[cris1972]

excuse me but the breaking coefficient to the traction, is not also used for compression dimensionalities?

 

[Fulvio Romano]

what is buckling?

instability. if you snap a can does not deform at the loading point, because instability is a global feature of the piece, and not local. I don't know how to explain. It's a somewhat delicate concept, and it's absolutely not possible to evaluate it quantitatively in your case, unless the plum was asked by the nose.

excuse me but the breaking coefficient to the traction, is not also used for compression dimensionalities?

Of course, but only for trespass and von mises, which apply well to steels. For example, cement has a scarcity tensile strength, an excellent compression. soils (sand, gravel, clay) have excellent compression resistance, and nothing at traction. depends on the material.

Moreover, just to put other meat on fire, "scratch" a can, does not mean to stress it compression. when instability generates a fold, this will have compression on the intradox and traction on the extremity, as in any butterfly characteristic of bending stress.

I mean, if you don't study engineering, I don't know if it's the case of getting into this field... you'd fill your head with notions, without theoretical bases, you'd make an immense effort to achieve a useless result.

 

[myface]

It is different to talk about plastics rather than metals, it is not that if you spray the bottle of pet over the ribbing (at traction) this remains as you deformed it, it has more memory than a can, for example

 

[Fulvio Romano]

I'm sorry if I allow myself! from data taken from various tables found on the internet, I said that the breaking load of the pet amounted to 85 n/mm2. As the two litre commercial bottles contain 2 dm3 h2o, I calculated the average diameter of the ideal bottle to contain this liquid. I then measured the thicknesses of some bottles and prepared that they took values of about 0.3 mm, I deduced the outer diameter of the ideal medium bottle. subtracting the surface of the diameter min from the max one, I am traced back to the resistant surface. from the relationship f=sigma r x hard surface I calculated the neutral force to win this breaking load. used a congruous safety coefficient (n=2) in the application of such force by the electric actuator, came to the fatefuls 9,7 kn. Of course the bottle must be empty, tinned and contained within a cylinder at the time of application of force. Am I wrong?

Of course!
Take a plastic cylinder and crush it, what force do you use?
take a tube, with the thick wall 0.3mm, but that has the same section, you will be a diameter of a few meters...crash it. use the same strength?
No. How is that possible? Here, I introduce you to the attic instability, one of the many ways of buckling

 

[cris1972]

I think it's more complicated than I thought!

 

[myface]

This is the concept!:smile:

 

[Fulvio Romano]

I think it's more complicated than I thought!

Yes, but don't break down. to design it is not necessary to calculate and model everything. Comparative design works, the wool was born like this and now she's making us shoes!

 

[gerod]

I would do like this:
make a test equipment to press (use a scale, a dynamometer or invent something) and see what you get.
to make a calculation I would say that you should invest a lot of time and money, I would say that it is better to study an empirical/experimental system.
I had followed something similar in 2000 and had been made to "nase".
on terminology and reasoning I would say that you have already been told by the forum colleagues.
However follow what he told you about lightning in the last post and welcome in the forum.
Hi.