SHOCK COMPRESSION OF SNOW AND ICE

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Submitted on 1 Jan 1987

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SHOCK COMPRESSION OF SNOW AND ICE

E. Gaffney

To cite this version:

E. Gaffney. SHOCK COMPRESSION OF SNOW AND ICE. Journal de Physique Colloques, 1987,

48 (C1), pp.C1-655-C1-655. �10.1051/jphyscol:1987195�. �jpa-00226461�

JOURNAL DE PHYSIQUE

C o l l o q u e C1, s u p p l 6 m e n t a u n o 3, Tome 48, m a r s 1987

SHOCK COMPRESSION OF SNOW AND ICE

E.S. GAFFNEY

L o s Alamos, NM 87545, U.S.A.

Abstract : Shock wave data have been obtained i n snow and i c e a t s t r e s s e s up

to

450 MPa and temperatures a s low a s 249 K. The experiments were conducted using

a

200 mn diameter, single-stage gas gun. Data were taken i n t h e form of Lagrangian shock p r o f i l e s measured by carbon piezoresistive f o i l s a t several locations in each target. A l l samples were constructed by assembling successive l a y e r s with t h e gauges placed between the l a y e r s . Construction was m p l e t e d i n a cold room, and the samples were aged a minimum of four days a t the design

test

temperature. After removal from the cold roam f o r mounting on the gun, the t a r g e t s were cooled with cold, dry nitrogen g a s flowing through circumferential cooling c o i l s and t h e tenqerature

was

monitored by t h e r m u p l e .

Snow t a r g e t s tested to date have a l l been constructed by recompacting f i n e l y crushed i c e

to

the desired density (about 400 kg/m3) i n l a y e r s in the sample holder. W e plan t o conduct

test

on naturally precipitated snow

in

t h e winter of 198586. I n i t i a l r e s u l t s on snow for peak s t r e s s e s near 10 MPa show t h a t snow loads nearly along a Rayleigh l i n e to d e n s i t i e s within a few percent of those reached by q u a s i s t a t i c compression a t s i m i l a r peak s t r e s s e s . The l o a d i n g wave

is,

however, q u i t e dispersive.

Release is

very s t i f f compared to loading, but

it is

much s o f t e r t h a t release i n dense ice.

Preliminary analysis of

ice

shocked to about 450 MPa a t 249 K indicates t h a t t h e e l a s t i c wave (about 3700

m/s)

may be a s l a r g e a s 400 MPa. I f Poisson's r a t i o

is

equal to its zero-pressure value, t h e shear s t r e s s . f o r a uniaxial s t r a i n wave of t h a t amplitude

is

about 210 MPa o r about 7.5 percent of c44. This

is

only s l i g h t l y larger than t h e 6 percent value a t 263 K derived by Gaffney (1) from Larsen's data (2). The

s m a l l

difference between experiments conducted above and below the minimum melting point of the

ice

phase diagram (251 K) supports the contention t h a t melting

is

n o t involved a t t h e e l a s t i c l i m i t , even a t 263 K. Rather, yielding a t t h e Hugoniot e l a s t i c l i m i t (HEL) is probably related to fundamental l o s s of strength by t h e l a t t i c e . Abwe the HEL, further deformation

is

accompanied f i r s t by m v e r s i o n to a hydrostatic s t a t e and l a t e r by p a r t i a l t r a n s i t i o n to some high pressure phase.

References

(1) Gaffney, E.S.

,

Ices i n the Solar System, J. Klinger (ed.) Reidel, Dordrecht (1985), 119-148.

(2) Larsen, D.B. J. Qaciol.

2

(105) (1984), 234-240.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987195