Effects of Hydrodynamic Forces on Ice Plate Bending Failure

Research Project

Project/Area Number	01460167
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	船舶抵抗・運動性能・計画
Research Institution	The University of Tokyo
Principal Investigator	KATO Hiroharu The University of Tokyo Professor, 工学部, 教授 (00010695)
Co-Investigator(Kenkyū-buntansha)	MAEDA Masatsugu The University of Tokyo Assistant, 工学部, 助手 (60219277) KOMURA Takashi The University of Tokyo Assistant, 工学部, 助手 (10010894) YAMAGUCHI Hajime The University of Tokyo Assistant Professor, 工学部, 助教授 (20166622) MIYATA Hideaki The University of Tokyo Assistant Professor, 工学部, 助教授 (70111474) KAJITANI Hisashi The University of Tokyo Professor, 工学部, 教授 (80010693)
Project Period (FY)	1989 – 1990
Project Status	Completed (Fiscal Year 1990)
Budget Amount *help	¥6,800,000 (Direct Cost: ¥6,800,000) Fiscal Year 1990: ¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1989: ¥4,700,000 (Direct Cost: ¥4,700,000)
Keywords	Icebreaker / Ice Plate / Ice Resistance / Ice Piece / Bending Test / Rigid Body Spring Model / 砕氷パタ-ン / 実船実験 / 氷海試験水槽 / 模型実験 / 模形氷 / 氷海 / 砕氷現象
Research Abstract	The results obtained in this research are summarized as follows : 1. Three kinds of model ice plate flexural property tests were performed at an ice model basin. Those were cantilever bending test, 3 point bending test and plate deflection test. Calculations using Rigid Body Spring Model were also made to investigate the problems in the cantilever bending test. The results showed that the generally adopted cantilever bending test gave significantly smaller Young's modulus mainly because of the deflection of the plate connected with the root of the cantilever while it gave proper values of the flexural strength. 2. Fundamental theoretical analyses using two-dimensional flow calculation and beam theory were made to investigate the effect of water pressure due to ship advance on the size of the broken ice pieces. The results showed that the pressure increase under the ice plate due lessened the ice piece size. This tendency agreed with the observations on the full-scale and model ships. The force to break the ice increased in proportion to the square of the ship speed. This fact has not been taken into account in the existing ice resistance prediction methods. 3. Full-scale and simplified ship model experiments on the icebreaker "Soya" were performed to measure the icebreaking patterns. The ratio of the ice piece depth to its length was in the range of 0.17 - 0.27. Thicker ice plate enlarged the broken ice pieces for both the full-scale and model ship cases. The size of the ice pieces were significantly different between the full-scale and the model ; the ice pieces in the model were some times larger than those in the full-scale. This discrepancy was considered due to the difference in the ice mechanical properties between the fullscale and the model.