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Science Forum Index » Materials Forum » Energy absorption of foam
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| JB |
 Posted: Tue Aug 19, 2003 8:44 am |
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Guest
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Hi,
I am faced with a little problem.
I have a pyramid (or another shape) in foam. I know its impact
compression (stress-strain curve) and as a consequence the energy it
can absorb.
Now, the problem:
I want to absorb a certain amount of energy with a pyramid of foam.
What is the size of the pyramid I can use? How can I easily use the
characteristics of the first pyramid for the new one?
Let me know what is your point of view.
Thanks
Jb |
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| Jack Ferman |
| Posted: Tue Aug 19, 2003 3:03 pm |
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Guest
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In article <178dfb8d.0308190644.7f610828@posting.google.com>,
jbrodel@ifrance.com (JB) wrote:
Quote: Hi,
I am faced with a little problem.
I have a pyramid (or another shape) in foam. I know its impact
compression (stress-strain curve) and as a consequence the energy it
can absorb.
Now, the problem:
I want to absorb a certain amount of energy with a pyramid of foam.
What is the size of the pyramid I can use? How can I easily use the
characteristics of the first pyramid for the new one?
Let me know what is your point of view.
Thanks
Jb
I have never had to do this kind of problem, but would not a
correspondence approach work. My first guess would to be scale the
crossectional area up (or down) in proportion to the energy difference
provided the deformation in the direction of the principal forces do not
vary. But I am not a sress analyst. |
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| Gregg |
| Posted: Tue Aug 19, 2003 7:49 pm |
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I remember an article in Scientific American quite a few years ago about
explosives- They showed foams being used to absorb explosive energy .
You may want to find the article (I think it's pre 1999) and take a look at
the references.
Good luck
"JB" <jbrodel@ifrance.com> wrote in message
news:178dfb8d.0308190644.7f610828@posting.google.com...
Quote: Hi,
I am faced with a little problem.
I have a pyramid (or another shape) in foam. I know its impact
compression (stress-strain curve) and as a consequence the energy it
can absorb.
Now, the problem:
I want to absorb a certain amount of energy with a pyramid of foam.
What is the size of the pyramid I can use? How can I easily use the
characteristics of the first pyramid for the new one?
Let me know what is your point of view.
Thanks
Jb |
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| John Spevacek |
| Posted: Wed Aug 20, 2003 5:41 am |
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Guest
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jbrodel@ifrance.com (JB) wrote in message news:<178dfb8d.0308190644.7f610828@posting.google.com>...
Quote: Hi,
I am faced with a little problem.
I have a pyramid (or another shape) in foam. I know its impact
compression (stress-strain curve) and as a consequence the energy it
can absorb.
Now, the problem:
I want to absorb a certain amount of energy with a pyramid of foam.
What is the size of the pyramid I can use? How can I easily use the
characteristics of the first pyramid for the new one?
Let me know what is your point of view.
Since you are taking the energy absorption characteristics of the foam
to be a function of strain only (I would also consider strain rate as
another primary variable) then you must scale your pyramids so that
strain is conserved. I can't tell you how to do that since it would
depend highly on the geometry of the object impacting the foam.
John |
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| JB |
| Posted: Thu Aug 21, 2003 4:16 am |
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Guest
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I found at this adress:
http://www.foamstudies.bham.ac.uk/packaging/pyramid.html
a little computational program that can solve my problem. You define a
geometry for the pyramid, choose a material and the energy to absorb
and then you get the stress-strain curve!
The only question is: what are the equations beyond that program!
If someone knows, let me know.
Thanks
JB
jspevacek@msn.com (John Spevacek) wrote in message news:<38c9b55b.0308200341.49608673@posting.google.com>...
Quote: jbrodel@ifrance.com (JB) wrote in message news:<178dfb8d.0308190644.7f610828@posting.google.com>...
Hi,
I am faced with a little problem.
I have a pyramid (or another shape) in foam. I know its impact
compression (stress-strain curve) and as a consequence the energy it
can absorb.
Now, the problem:
I want to absorb a certain amount of energy with a pyramid of foam.
What is the size of the pyramid I can use? How can I easily use the
characteristics of the first pyramid for the new one?
Let me know what is your point of view.
Since you are taking the energy absorption characteristics of the foam
to be a function of strain only (I would also consider strain rate as
another primary variable) then you must scale your pyramids so that
strain is conserved. I can't tell you how to do that since it would
depend highly on the geometry of the object impacting the foam.
John |
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