[Homeroast] Poisson's ratio WAS: Re: Compak vs Macap vs Rocky Grinders

David Liguori liguorid at albany.edu
Wed May 19 11:50:46 CDT 2010


I'm splitting hairs too, but ten to one Poisson didn't know jack about 
molecules.  As late as the beginning of the 20th century, the very idea 
of their existence was mached.

On 5/18/2010 10:34 AM, Mike Koenig wrote:
> I'm probably splitting hairs here, but Poisson's effect happens on the
> molecular level, with bonds elongating under pressure or strain.  I'm not a
> geoscience guy, but I imagine the effect effect would happen in rocks, dense
> clays and shale, etc,  but what you are seeing in a coffee puck is
> interactions between discrete non-uniform particles.
>
> I'm not arguing at all that you don't get some lateral expansion during
> tamping, since that certainly does happen, but it's not necessarily uniform,
> and dependent on the distribution (and re-arrangement under force) of the
> particles, as opposed to poisson's effect, which describes a predictable
> amount of lateral expansion based on the change axial length.  If the
> expansion was due to poisson's effect, the puck would spring back when you
> let go of the tamper.   What you are getting is some re-arrangement of the
> particles under force (like when you step in sand, and it moves out of the
> way under your foot).
>
> --mike
>
>
>
> On Tue, May 18, 2010 at 3:01 AM,<raymanowen at gmail.com>  wrote:
>
>    
>> Then I don't know why the grounds would press out and seal against the
>> sides
>> of the basket when you are only applying axial force with the tamper.
>> Hydrostatic?
>>
>> I hope I don't owe a refund of all our pay at the Geophysics Research
>> Institute at CSM. Please don't tell Dr. Levent Ozdemir or Dr. Russ Miller
>> we
>> were doing bad oil shale research. Damn!
>>
>> What supports you when you walk on a sandy beach?
>>
>> Teach me, please. -ro
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