Lifetime estimation for a land-fast ice sheet subjected to ocean swell

2001 ◽  
Vol 33 ◽  
pp. 333-338 ◽  
Author(s):  
P. J. Langhorne ◽  
V. A. Squire ◽  
C. Fox ◽  
T. G. Haskell
Keyword(s):  
Sea Ice ◽  
Strain Field ◽  
Field Experiments ◽  
Ice Sheet ◽  
Lifetime Estimation ◽  
Spectral Content ◽  
Fast Ice ◽  
Damage Law ◽  
Number Of Cycles ◽  
Cycles To Failure

AbstractIt is well known that an incoming ocean swell produces a strain field in a land-fast ice sheet. The attenuation and spectral content of this strain field can be calculated and has been measured. The response of the sea ice to this type of cyclic forcing has also been measured, and in particular we are able to estimate the number of cycles to failure for sea ice loaded at constant amplitude. In this paper we consider the response of the land-fast ice sheet or vast floe to a measured ice-coupled wave field of variable amplitude. We use the Palmgren-Miner cumulative damage law and stress-lifetime curves taken from field experiments to predict the lifetime of the sea-ice sheet as a function of significant wave height and sea-ice brine fraction. Calculations are performed to account for the swell entering a land-fast sea-ice sheet at arbitrary angle, and the influence of c-axis alignment and the presence of pre-existing cracks are discussed.

scholarly journals Surface Layer Salinity of Young Sea Ice

1985 ◽  
Vol 6 ◽  
pp. 298-299 ◽  
Author(s):  
Nobuo Ono ◽  
Takashi Kasai
Keyword(s):  
Surface Layer ◽  
Sea Ice ◽  
Surface Temperature ◽  
Laboratory Experiments ◽  
High Salinity ◽  
Ice Sheet ◽  
Surface Salinity ◽  
Seawater Salinity ◽  
Fast Ice

The high-salinity surface layer of young sea ice was subjected to field and laboratory experiments. Artificial pools, in which young ice was formed, were opened within a fast-ice sheet in the Saroma lagoon, Hokkaido, in February of 1983 and 1984. The salinity of 1 mm thick surface layer of the young ice was observed as high as 42.4‰, which exceeds the seawater salinity of 31‰. The surface salinity increased with rising surface temperature. When a load was placed on the fast ice near the pool, seeped brine of salinity 72.5‰ was observed on the surface of the young ice; and when the load was removed, the brine disappeared. Meanwhile, brine permeabilities, both upward and downward, were measured in the laboratory, Both permeabilities decreased logarithmically with lowering surface temperature. A remarkable anisotropy was observed: the upward permeability was greater than downward, and the ratio of upward to downward premeability increased with lowering surface temperature from 5 at -3 °C to 33 at -5°C. Upward and downward permeabilities in ms-1 were respectively 1x10-4 and 2x10-5 at -3°C, 2x10-5 and 6x10-7 at -5°C, and at -10°C upward permeability was 3x10-7.

scholarly journals Surface Layer Salinity of Young Sea Ice

1985 ◽  
Vol 6 ◽  
pp. 298-299 ◽  
Author(s):  
Nobuo Ono ◽  
Takashi Kasai
Keyword(s):  
Surface Layer ◽  
Sea Ice ◽  
Surface Temperature ◽  
Laboratory Experiments ◽  
High Salinity ◽  
Ice Sheet ◽  
Surface Salinity ◽  
Seawater Salinity ◽  
Fast Ice

The high-salinity surface layer of young sea ice was subjected to field and laboratory experiments. Artificial pools, in which young ice was formed, were opened within a fast-ice sheet in the Saroma lagoon, Hokkaido, in February of 1983 and 1984. The salinity of 1 mm thick surface layer of the young ice was observed as high as 42.4‰, which exceeds the seawater salinity of 31‰. The surface salinity increased with rising surface temperature. When a load was placed on the fast ice near the pool, seeped brine of salinity 72.5‰ was observed on the surface of the young ice; and when the load was removed, the brine disappeared. Meanwhile, brine permeabilities, both upward and downward, were measured in the laboratory, Both permeabilities decreased logarithmically with lowering surface temperature. A remarkable anisotropy was observed: the upward permeability was greater than downward, and the ratio of upward to downward premeability increased with lowering surface temperature from 5 at -3 °C to 33 at -5°C. Upward and downward permeabilities in ms-1 were respectively 1x10-4 and 2x10-5 at -3°C, 2x10-5 and 6x10-7 at -5°C, and at -10°C upward permeability was 3x10-7.

An experimental linear cumulative-damage law

1970 ◽  
Vol 5 (3) ◽  
pp. 177-184 ◽  
Author(s):  
K J Miller
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
Constant Strain Rate ◽  
Strain Range ◽  
Cumulative Damage ◽  
Damage Law ◽  
Load Sequence ◽  
Number Of Cycles ◽  
Definition Of ◽  
Cycles To Failure

An hypothesis of cumulative damage is presented that may be expressed mathematically as Σn÷Nf = constant where n is the number of cycles performed at a constant strain range and strain rate and Nf is the number of cycles to failure at the same strain range and strain rate. An initial experimental investigation at room temperature shows that, under constant strain-rate conditions, the load-sequence effect is removed, but the value of the constant is dependent on the definition of failure. If failure is defined as complete rupture the summation term is less than unity whatever the sequence of loading. Should failure be defined as the termination of the steady-state period, that is at the point of crack growth instability, then the summation term is greater than unity. This latter definition therefore leads to a linear law of cumulative damage that gives a doubly cautious prediction of life that is of obvious advantage to engineers.

Fatigue Life of the Human Teeth: A Continuum Damage Approach

2019 ◽  
Vol 43 ◽  
pp. 1-19
Author(s):  
Theddeus Tochukwu Akano
Keyword(s):  
Fatigue Life ◽  
Damage Mechanics ◽  
Stress Amplitude ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Elastoplastic Model ◽  
Human Teeth ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Cycles To Failure

Normal oral food ingestion processes such as mastication would not have been possible without the teeth. The human teeth are subjected to many cyclic loadings per day. This, in turn, exerts forces on the teeth just like an engineering material undergoing the same cyclic loading. Over a period, there will be the creation of microcracks on the teeth that might not be visible ab initio. The constant formation of these microcracks weakens the teeth structure and foundation that result in its fracture. Therefore, the need to predict the fatigue life for human teeth is essential. In this paper, a continuum damage mechanics (CDM) based model is employed to evaluate the fatigue life of the human teeth. The material characteristic of the teeth is captured within the framework of the elastoplastic model. By applying the damage evolution equivalence, a mathematical formula is developed that describes the fatigue life in terms of the stress amplitude. Existing experimental data served as a guide as to the completeness of the proposed model. Results as a function of age and tubule orientation are presented. The outcomes produced by the current study have substantial agreement with the experimental results when plotted on the same axes. There is a notable difference in the number of cycles to failure as the tubule orientation increases. It is also revealed that the developed model could forecast for any tubule orientation and be adopted for both young and old teeth.

Subglacial sediment pathways and deglacial chronology of the northern Barents Sea Ice Sheet

Boreas ◽  
2017 ◽  
Vol 46 (4) ◽  
pp. 750-771 ◽  
Author(s):  
Kelly A. Hogan ◽  
Julian A. Dowdeswell ◽  
Claus-Dieter Hillenbrand ◽  
Werner Ehrmann ◽  
Riko Noormets ◽  
...  
Keyword(s):  
Sea Ice ◽  
Barents Sea ◽  
Ice Sheet

scholarly journals Horizontal Movement of Fast Ice in the North Water Area

1977 ◽  
Vol 19 (81) ◽  
pp. 547-554 ◽  
Author(s):  
Hajime Ito ◽  
Fritz Müller
Keyword(s):  
Sea Ice ◽  
Water Area ◽  
Physical Characteristics ◽  
Stress Strain ◽  
Horizontal Movement ◽  
The North ◽  
North Water ◽  
Fast Ice ◽  
External Forces

AbstractThe understanding of the horizontal movement of fast ice is important for applied sea-ice mechanics. A case study, carried out in conjunction with a polynya known as North Water, is presented in this paper. The displacements of the fast-ire arches which separate the polynya from the surrounding ice-covered sea, were measured and found to be small. It is, therefore, confirmed that these arches prevent the influx of large quantities of sea ice into the polynya. The results are then explained in terms of the external forces (wind and current), the stress- strain situations and some physical characteristics (temperature and thickness) which were measured simultaneously.

scholarly journals Of isbræ and ice streams

2003 ◽  
Vol 36 ◽  
pp. 66-72 ◽  
Author(s):  
Martin Truffer ◽  
Keith A. Echelmeyer
Keyword(s):  
Ice Sheet ◽  
Shear Zones ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Bed Topography ◽  
Ice Stream ◽  
Fast Ice ◽  
Fast Flow ◽  
End Members

AbstractFast-flowing ice streams and outlet glaciers provide the major avenues for ice flow from past and present ice sheets. These ice streams move faster than the surrounding ice sheet by a factor of 100 or more. Several mechanisms for fast ice-stream flow have been identified, leading to a spectrum of different ice-stream types. In this paper we discuss the two end members of this spectrum, which we term the “ice-stream” type (represented by the Siple Coast ice streams in West Antarctica) and the “isbræ” type (represented by Jakobshavn Isbræ in Greenland). The typical ice stream is wide, relatively shallow (∼1000 m), has a low surface slope and driving stress (∼10 kPa), and ice-stream location is not strongly controlled by bed topography. Fast flow is possible because the ice stream has a slippery bed, possibly underlain by weak, actively deforming sediments. The marginal shear zones are narrow and support most of the driving stress, and the ice deforms almost exclusively by transverse shear. The margins seem to be inherently unstable; they migrate, and there are plausible mechanisms for such ice streams to shut down. The isbræ type of ice stream is characterized by very high driving stresses, often exceeding 200 kPa. They flow through deep bedrock channels that are significantly deeper than the surrounding ice, and have steep surface slopes. Ice deformation includes vertical as well as lateral shear, and basal motion need not contribute significantly to the overall motion. The marginal shear zone stend to be wide relative to the isbræ width, and the location of isbræ and its margins is strongly controlled by bedrock topography. They are stable features, and can only shut down if the high ice flux cannot be supplied from the adjacent ice sheet. Isbræs occur in Greenland and East Antarctica, and possibly parts of Pine Island and Thwaites Glaciers, West Antarctica. In this paper, we compare and contrast the two types of ice streams, addressing questions such as ice deformation, basal motion, subglacial hydrology, seasonality of ice flow, and stability of the ice streams.

scholarly journals The North Sea Ice Sheet

Nature ◽  
1894 ◽  
Vol 50 (1282) ◽  
pp. 79-79
Author(s):  
HENRY H. HOWORTH
Keyword(s):  
Sea Ice ◽  
North Sea ◽  
Ice Sheet ◽  
The North ◽  
The North Sea
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