Fracture in the compression of columnar gained ice

Self Cite

As the continental shelves of the Arctic become important as source areas for the oil and minerals required by human society, sea ice becomes an increasing challenge to engineers. The present paper starts with a consideration of the different fields of engineering which require information on sea ice with the tasks ranging from the design of ice-breaking ships to Arctic drilling platforms and man-made ice islands. Then the structure of sea ice is described as it influences the observed variations in physical properties. Next the status of our knowledge of the physical properties important to engineering is reviewed. Properties discussed include mechanical properties (compressive, tensile, shear and flexural strengths; dynamic and static elastic moduli; Poisson’s ratio), friction and adhesion, thermal properties (specific and latent heats, thermal conductivity and diffusivity, density) and finally electromagnetic properties (dielectric permittivity and loss, resistivity). Particular attention is given to parameters such as temperature, strain-rate, brine volume, and loading direction as they affect property variations. Gaps, contradictions in the data, and inadequacies in testing techniques are pointed out. Finally suggestions are made for future research, especially for more basic laboratory studies designed to provide the data base upon which further theoretical developments as well as field studies can be built.

mentioning

confidence: 58%

Section: (D ) Temperaturementioning

confidence: 99%

Engineering Properties of Sea Ice

Schwarz

Weeks

1977

Self Cite

“…The two populations appear to have different dependencies on strain-rate. There is evidence that grain-boundary cracks dominate in brittle fracture (Gold, 1972[a]; Wu and others, 1974). As the majority of cracks are transcrystalline for compressive creep at stress below 2 MN m -2 , there must be a transition in the c ha racteristics of the cracking activity.…”

Section: Ductile To Brittle Transitionmentioning

confidence: 99%

“…This type of failure can be observed in the laboratory if the specimen is constrained in a direction perpendicular to the applied load or if there is little or no friction between the specimen and the load pattern. Information is now becoming avai lable that, it is to be hoped, will allow the appropriate relationships to be established between the strength and deformation properties of ice measured at a laboratory scale and those that determine its behaviour when moving against a structure (Wu and others, 1974;Croasdale, 1974) . As shown by Wu and others, the stress immediately in front of the structure depends on the width of the structure and the thickness of the ice in addition to the properties of the ice under given conditions.…”

mentioning

confidence: 99%

Engineering Properties of Fresh-Water Ice

Gold

1977

132

The principal engineering problems requiring knowledge concerning the properties of ice are prediction of the maximum force that ice might exert on a structure and determination of the load that can be placed safely on an ice cover. The properties of ice relevant to these problems are discussed. Particular attention is given to the dependence of Young's modulus on the frequency of the stress, strain-rate dependence of the yield and fracture strengths, and the ductile to brittle transition. It is shown that the strain-rate dependence of these properties is consistent with information on the stress dependence of dislocation velocity on the basal plane. The tensile and compressive strengths are also shown to be consistent with current theories of crack initiation and propagation.

“…D. J. GOODMAN: IS the author familiar with the paper of Wu and others (1976) who used ice to separate the specimen from the platens? Would he like to comment on this result?…”

Section: Discussionmentioning

confidence: 99%

Measuring the Uniaxial Compressive Strength of Ice

Haynes

Mellor

1977

ABSTRACT. An attempt was made to develop a simple but accurate method for making compressive strength tests on right cir cular cylinders. Compliant loading platens were designed to apply uniform normal stress without introducing signifi cant in terface radial sh ear stresses. The compliant platens gave reproducible results that agree well with results obtained by a precise conven tiona l technique. Accurate results were obtained with simple specimen preparation, a nd with short specimens where the length-todiameter ratio was less than unity. Platens were made from a rubber-like urethane whi ch was molded in aluminum cylinders to provide lateral res tra int. Uniaxial compression tests on cylindrical polycrystalline ice specime ns were made to d e te rmine the characte ristics of the platens. For 21 specimens with ends prepared on a la pping plate to obtain a mirror finish, the m easured strength sh owed a varia tion of only 13 % for lengthto-diameter ra tios from 0.74 to 2.5, with no sys tematic trend. Another 2 1 specimens with le ngth-to-dia me te r ratios of a bout 2. 35 were tested with various platens and vario us methods of specime n end prepa ra tion. The stre ngth for specimens with saw-cut ends and for those with e nds Japped showed ver y little difference when tested with the rubbe r platens. R ESUME. M esllres de la resistance de la glace a llne compression llniaxiale. On a essaye d e m e ttre a u point une me thode simple mais precise pour executer d es essais de resista nce a la compression dans des cylindres circul a ires droits. On a con<;u des platea ux sou pies charges pour produire un effort unifo rm e sans introduire d e cisaill em ent radial significatif a I'intcrface. Les pla teaux sou pies donnent d es res ultats reproductibles qui concord e nt bien avec ceux obtenus par des techniques conventionn ell es precis cs. Des res ulta ts precis peuvent etre obtenus avec la prepara tion d 'echa ntill ons simpl es et sur d es echanti llons courts ou le ra pport de la longueur au diametre est inferieur a l' unite. L es p lateaux etaient faits en une sorte d e gomme en urethan e qui etait moulee da ns des cylindres en a luminium pour les limite r lateralement. D es essais de compression uniaxiales sur des echantillons de glace polycrista llin e cylindrique ont e te faits pour de te rminer les carac teristiqu es d es pla teaux. P our 21 echa ntillons dont les ex tremites e taie nt prepa rees sur un e assie tte a polir pour obtenir un e finition equi valente a cell e d' un miro ir, les res ista nces mesurees mo nu·ere nt une variation d e seule m e nt 13% pour des ra pports longueur/diame tre alla nt de 0,74 a 2,5 sa ns erreur sys te m a tique decelable.Vingt et un a utres echantiLlons avec des rappo rts longeur/diame tre d 'environ 2,35 fut·ent essayes avec d ifferents plateaux et differents modes de preparatio n d es extremites. L es res ista nces mes urees sur les echantillons coupes a la scie et sur ceux soigneuseme nt p olis ne montraient que de tres faibl es differences lorsq ue les mesures e ta ie...