At 06:12 pm 20/08/2005 +0200, you wrote:
>Grimer wrote:
>
>>
>> You could have added Casimir pressure for good measure. 8-)
>>
>> My preferred term is Beta-atmosphere since I find the analogy
>> with atmospheric pressure useful - and it arises naturally if
>> one starts one's analysis with sands and clays which are held
>> together by Alpha-atmospheric pressure in the case of coarse
>> sands (pF < 15 psi) and Beta-atmospheric pressure in the case
>> of clays, say. (pF > 15 psi).
>
> Moin Frank,
>
> So, you are basically changing the baseline for pressure to 15psi, but
> you do still agree with the majority of the scientific community, that
> all pressure is positive with relation to no pressure, and that there is
> no such thing as negative pressure with relation to no pressure.
>
> Knuke
No, no, no, noooooo!
My fault - I'm afraid I expressed things badly.
pF is a log scale of suction, of negative pressure taking
atmospheric pressure as datum.
Normally people think of -15psi as zero pressure (stress) and
anything lower than that they think of in terms of tension.
I am saying that tension is only the absence of some unappreciated
pressure (the Beta-atmosphere pressure in the case of macro
material). Since for me, tension - action at a distance - is a
negation the words pressure and stress are interchangeable.
In the case of steel for example, tension is a reduction in the
EXTERNAL Beta-atmosphere pressure which holds the steel together
in an analogous way to air pressure holds an evacuated plastic
bag of table-tennis balls together.
If you really want to get things straightened out you need to
read the three key publications listed below. which are all
available as .jpeg page scans on various Yahoo sites.
The ideas are very easy to follow, albeit difficult to accept
because of their obvious far reaching implications.
The ideas are certainly not in danger of straining *your* brain. <g>
Jones and Horace seemed to manage OK.
=========================================
REFERENCES
=========================================
GRIMER, F.J. and R.E.HEWITT. The form of the
stress-strain curve of concrete interpreted
with a di-phase concept of material behaviour.
Structure, Solid Mechanics and Engineering Design.
Proceedings of the Southampton 1969 Civil
Engineering Conference. (M.Te'eni, Ed.),
Wiley Interscience, pp 681 - 691, 1972.
CLAYTON, N and F.J.GRIMER. A General Approach
to the Strength of Materials. Speculations in
Science and Technology, Vol.1, No.1, pp5 - 13,
1978.
CLAYTON, N and F.J.GRIMER. The di-phase concept
with particular reference to concrete. Developments
in Concrete Technology, Vol.1, F.D.Lydon, ed,
Applied Science Publishers, England pp.283-318.
================================================
Cheers
Frank
