• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.423-428
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• 2014

Ice loads may be conveniently categorized as local ice loads and global ice loads. Local ice loads are often defined as ice pressures acting on local areas of shell plates and stiffeners. Therefore, local ice loads are defined in all ice class rules. However, directly measuring the local ice pressure using the actual ice class vessel is a very difficult task because appropriate instruments for direct measurement must be installed on the outer hull, and they are easily damaged by direct ice contacts/impacts. This paper focuses on the estimation of the local ice pressure using the data obtained from icebreaking tests in the Arctic sea in 2010 using the Korean icebreaking research vessel (IBRV) ARAON. When she contacted the sea ice, the local deformation of the side shell was measured by the strain gauges attached to the inside of the shell. Simultaneously, the contact area between the side shell and sea ice is investigated by analyzing the distribution of the measured strain data. Finally, the ice pressures for different contact areas are estimated by performing a structural analysis.

• Journal of Ocean Engineering and Technology
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• v.28 no.1
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• pp.28-33
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• 2014

The Korean icebreaking research vessel "Araon" performed four sea trials in the Arctic and Antarctic Seas. The ice properties, such as the ice thickness, floe size, ice strength, and power of the vessel were quite different in these trials. To compare the speeds of ship with the same ice strength and power, the AARC (Arker Arctic Research Center) method is used with a vessel power of 10 MW and an ice strength of 630 Pa in this paper. Based on the analysis results, the speed of the ship was 1.62 knots (0.83 m/s) with a 1.02-m ice thickness and 2.5-km floe size, 5.3 knots (2.73 m/s) with a 1.2-m ice thickness and 1.0-km floe size, and 13.8 knots (7.10 m/s) with a 1.1-m ice thickness and 200-m floe size. The analysis results showed that the ship speed and floe size have an inversely proportional relationship. Two reasonable reasons are given in this paper for the final result. One is an ice breaking phenomenon, and the other is the effect of the ice floe mass. For the breaking phenomenon, the ice breaking force is very small because the ice floe is not breaking but tearing when a ship is passing through a small ice floe. Regarding the effect of the ice floe mass, it is impossible for a ship to push and tear an ice floe if the mass of the ice floe is too large compared to the mass of the ship. The velocity of the ship decreases when the ice floe has a large mass and a large size because the ship has to break the ice floe to move forward.

• Journal of Ocean Engineering and Technology
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• v.16 no.1
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• pp.27-35
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• 2002

The interaction of grounded ice ridges with underlying seabed is one of the major considerations in the design of Arctic pipeline system. Previously several ice scour models were developed by researchers to describe the ice scour-seabed interaction mechanism. In view of possible improvements, a comparative study of those ice scour models is performed and their limitation in modeling is discussed. Simple laboratory tests are carried out and then the shape pattern of deposited soil around the ice model is newly defined. Unlike the rectangular idealization of an ice block, in this modified ice scour model, trapezoidal cross sections are assumed to represent the typical shape of an ice ridge based on the field observation data. With the horizontal and vertical motion of ice model, the ice scour depth and soil reacting forces on seabed are calculated with varying the keel angle of an ice ridge.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.5
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• pp.421-425
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• 2011

To know the speed performance of "ARAON" in Arctic ice field, the measurement of ice properties which is ice thickness & strength, snow depth and free board were performed on July 2010. The measuring method of nautical signals such as heading angle, power of engine, wind & current information etc. was described in this paper. The speed sea trials in ice were performed on the four different positions with different ice properties and engine powers because the uniform level ice is not detected in the Chukchi Sea. The test field was partially constrained ice floe with hummocks and it was superposed with small broken ice pieces each other. All of the measured ice properties were compared and evaluated according to the results of sea trial. The relations between speed, ice thickness, strength and power were summarized. Consequently according to the sea trial results, the speed of ARAON is 2.78knots at the 2.49m ice thickness with 6.55MW engine power.

• Journal of Ocean Engineering and Technology
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• v.26 no.1
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• pp.1-8
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• 2012

To correctly estimate ice load and ice resistance for a ship's hull, it is essential to understand the material properties of sea ice during ice field trials and to use the proper experimental procedure for gathering ice strength data. The first Korean-made icebreaking research vessel (IBRV), ARAON, had her second sea ice trial in the Arctic Ocean during July and August of 2010. This paper describes the test procedures used to properly obtain sea ice strength data, which provides the basic information on the ship's performance in an ice-covered sea and can be used to estimate the correct ice load and ice resistance on the IBRV ARAON. The data gathered from three sea ice field trials during the Arctic voyage of the ARAON includes the ice compressive strength, flexural strength, and failure strain of sea ice. This paper analyzes the gathered sea ice data in comparison with data from the first voyage of the ARAON during her Antarctic Sea ice trial in January 2010.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.414-417
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• 2008

We have extracted a surface deformation map of a part of Canisteo Peninsula on Amundsen Sea in West Antarctica by applying 4-pass DInSAR technique to two ERS-1/2 tandem pairs obtained on October 21-22, 1995 (diff-pair) and March 9-10, 1996 (topo-pair), and analyzed changes of glaciers, sea ice, ice shelves, and their kinematic interactions. We observed fast motion of glaciers pushing the adjoining sea ice. Some interferometric phases indicate the up-rise of sea ice of which type is thought to be land-fast ice to exert repulsive force against the pushing glacier. There were other glaciers and sea ice that moved to the same direction, suggesting that the sea ice in these regions was land-fast ice weakly harnessed to sea bottom or pack ice not harnessed at all. Several small circular fringes in ice shelves suggested that islands or seamounts on the bottom of ice shelves deterred the movement of ice shelves, resulting in the rise of ice surface.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.796-808
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• 2019

In this paper, a Smoothed Particle Hydrodynamics (SPH) method is extended to simulate the ice failure process and ice-ship interactions. The softening elastoplastic model integrating Drucker-Prager yield criterion is embedded into the SPH method to simulate the failure progress of ice. To verify the accuracy of the proposed SPH method, two benchmarks are presented, which include the elastic vibration of a cantilever beam and three-point bending failure of the ice beam. The good agreement between the obtained numerical results and experimental data indicates that the presented SPH method can give the reliable and accurate results for simulating the ice failure progress. On this basis, the extended SPH method is employed to simulate level ice interacting with sloping structure and three-dimensional ice-ship interaction in level ice, and the numerical data is validated through comparing with experimental results of a 1:20 scaled Araon icebreaker model. It is shown the proposed SPH model can satisfactorily predict the ice breaking process and ice breaking resistance on ships in ice-ship interaction.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.1
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• pp.15-22
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• 2020

Understanding the strength characteristics of model ice is an important issue for model testing in an ice model basin to estimate the ship performance in ice. In particular, the mechanical properties of the model ice including elastic modulus, flexural strength and compressive strength are key consideration factors. In order to understand the characteristics of the model ice during warm-up phase at KRISO's ice model basin, the strength properties are tested in this study. The infinite plate-bending method, in-situ cantilever beam test and ex-situ uniaxial compressive test are conducted to determine the strength properties of model ice. The strength characteristics of the model ice are then analyzed in terms of the warm-up phase and seasonality. These results could be valuable to quality control of the model ice characteristics in KRISO's ice model basin and to better understand the variations in strength properties during the ice model tests.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.104-109
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• 2015

The Korea Research Institute of Ships & Ocean Engineering (KRISO) has an ice tank to make a test environment similar to the real ice in the polar sea in order to carry out model tests. One of the most important task of the ice tank is to generate the model ice to have similar material properties as sea ice. The primary properties of sea ice which influence the ice performance of ice breakers and ice-strengthened vessels traveling in the polar sea are ice thickness, flexural strength, density, modulus of elasticity and crystal structure etc. Among them, since the density of model ice influences the buoyance resistance of ice for the ship model, the accurate measurement of ice density should be used to obtain the accurate analysis results from the model test. In this paper, some existing methods to measure the density of model ice are reviewed and a new one is proposed to measure it accurately and easily as possible. In this study, the measuring system including an UTM and several measuring devices was established to obtain the model ice density. Polyethylene and ice specimens are used for a series of repeatable measurement tests. From the results, it was recognized that both of the displacement method and the weight/weight methods gave the stable and favorable tendency.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.85-91
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• 2016

The most important factor in the structural design of ships and offshore structures operating in arctic region is ice load, which results from ice-structure interaction during the ice collision process. The mechanical properties of ice related to strength and failure, however, show very complicated aspect varying with temperature, volume fraction of brine, grain size, strain rate and etc. So it is nearly impossible to establish a perfect material model of ice satisfying all the mechanical characteristics completely. Therefore, in general, ice collision analysis was carried out by relatively simple material models considering only specific aspects of mechanical characteristics of ice and it would be the most significant cause of inevitable errors in the analysis. Especially, it is well-known that the most distinctive mechanical property of ice is high dependency on strain rate. Ice shows brittle attribute in higher strain rate while it becomes ductile in lower strain rate range. In this study, the simulation method of ice collision to ship hull using the nonlinear dynamic FE analysis was dealt with. To consider the strain rate effects of ice during ice-structural interaction, strain rate dependent constitutive model in which yield stress and hardening behaviors vary with strain rate was adopted. To reduce the huge amount of computing time, the modeling range of ice and ship structure were restricted to the confined region of interest. Under the various scenario of ice-ship hull collision, the structural behavior of hull panels and failure modes of ice were examined by nonlinear FE analysis technique.