Inelastic Behaviour of Ice Ih Single Crystals in the Low-Frequency Range Due to Dislocations

Abstract

ABSTRACT. The inelas ti c beh avioW' of ice Ih single crystals has bee n in ves tiga ted by an inverted torsional pe ndulum in the low-freque ncy ra nge. T hree features a re distinguish ed : (i) a relaxation peak prev io usly observed by severa l a uthors in the higher-frequency range, (ii ) a n internal friction in creas ing with tempera ture in the high-te mperature range (230-273 K ), (iii ) within this high-temperatur e ra nge, inte rn a l fri ction becom es a mplitude dependent, and this dependence becomes greater the greater the te mperature. In this case, the intern al fri ctio n h as been interpreted in terms of movements of dislocatio ns. H ence, the experime nta l resul ts a re inte rpreted with a model of in ternal fri ction based on an empiri cal relation fo r the velocity of dislocations. Th is m odel of interna l fri ctio n is in fair agreement with ex perim e ntal data. I t is possibl e then to get a n es tim a te of dislocation de nsi ty. H ence it is sh own that intern al fri ction experiments ca n be useful in the stud y o f th e p lasti c behaviour o f ice single crys ta ls. R ESUME. R ole des dislocatiolls dalls le com/Jortement ineLastique basse Jrtfquence de La glace Ih . L e comportement inelast ique d e la glace Ih mon ocristalline a ete etudie it l'aide d' un pend ul e de torsion in ve rse fonctionn a nt da ns le dom a in e des basses frequences. 11 a ppa rait trois ca racteristiqu es:(i) un pi c de relaxation obser ve precedemme nt p ar d ivers a uteurs d a ns le domaine d es h a utes frequences, (ii ) un fro ttement inter ie ur croissant ra pidem e nt avec la temperatu re dans le domain e 230-273 K , (iii ) d a ns ce domain e d e te mperatures, le fro tte m e nt interieur depend de I'ampli tud e de deformation et ce tte dependance est d 'a utant plus forte q u e la te mpera ture es t plus elevee. Nous nous som mes plus pa rticuli erement interesses d a ns ce travail a u co mportement d e la glace monocristallin e dans le doma in e des h a utes tempera tures e n metta nt en evidence le role des d islocations. La compa ra ison d e nos resulta ts avec ceux obtenus par topogra phie d e rayo ns X nous p erm et d ' interprt: tcr l' cnsembl e d es donn ees a pportees pa r le frotte me nt inte rieur. 11 est a lors poss ibl e d' obte n ir une estimation de la d e nsite d e dislocatio n. II appara it ainsi que les m es ures de fro ttement in terieur peuvent e t re utiles pour I'etud e d e la d eform a tio n p lastique de la glace. Z USAMM ENFASSUNG. Anela stisches Verhalttll VOIl Eis-lh-Einkristalle n im Niedeifrequell z bereich auJgnmd VOIlVersetz llll.gen. D as a nel as tisch e V e rha lten von E is-Ih-Einkrista ll en wurde mit einem umge ke h rten Torsionspendel im N iederfreq uenzbereich untersucht. Drei Merkmale werden h e ra usgeslell t:(i) Ein Rclaxa Li onsdampfu ngsmaximum, d as b e reits frUh er von verschi edenen Ve rfassern im h6heren Frequenzbereich beobachte t wurde. (ii ) E in Anstieg der inne re n R eibun g mit de r T e mperatur im H ochte mpera turbereich (230-273 K ). (iii) Inn...

Anomalous Behaviour of Antarctic ice Cores Studied by Electrical and Mechanical Damping Measurements

“…Thirteen samples cut from blocks situated between depths of 126 and 900 m from Dome C were studied: as the results have been published elsewhere (Vassoille and others 1980), only one example of the anelastic properties of these samples is shown in Figure 1(a) (curve A). The features previously observed with lowfrequency internal friction measurements made on pure ice (Vassoille and others 1974) can again be seen: (i) in the high-temperature range, a peak associated with the movement of grain boundaries (Perez and others 1979), and (ii) at lower temperatures, a relaxation peak generally interpreted in terms of reorientation of water molecules by means of rotational defects (Vassoille and others 1978).

Fig.1(a) Internal-friction spectra versus temperature; curve A: specimen from Dome C 680 m deep, curve B: pure ice.

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Planetary Ices Attenuation Properties

“…Torsional forced oscillation pendulums have also been used to measure dissipation at subresonant frequencies. In such devices, torque is generated by a motor or an electromagnetic drive and angular displacement of the gripped specimen is measured (i.e., Kê 1947;Woirgard et al 1977;Vassoille et al 1978).…”

“…The first low-frequency forced oscillation measurements were obtained during the mid-1970s in the Laboratory of Glaciology of Grenoble (e.g., Vassoille et al 1978;Tatibouet et al 1981Tatibouet et al , 1983Tatibouet et al , 1987. These were torsional measurements obtained over a wide range of temperatures, from 120 to 273 K, and frequencies as low as 10 À4 Hz.…”

“…Studies on single crystal ice have revealed a lowtemperature (or high frequency) relaxation peak associated with this rearrangement of water molecules by rotational defects (e.g. Vassoille et al 1978;Hiki and Tamura 1983;Tatibouet et al 1981). The relaxation is analogous to a Zener relaxation (Zener 1947) in that it occurs because of a change in local atomic order that is affected by the presence of defects (Snoek 1939;Nowick and Berry 1972;p.…”

Détermination du frottement intérieur des systèmes à fort amortissement ; cas des mélanges à base d'eau

“…le cas des monocristaux déformés plastiquement, le mouvement à courte distance des dislocations entraîne une dissipation d'énergie qui peut être très importante [9]. D'autre part, dans le cas des polycristaux, nous avons mis en évidence l'existence d'un pic lié à la présence des joints de grains [10].…”