| With the exploitation of the offshore oil and gas resources, the problem rises seriously by sea ice. The investigation to the interaction of ice and flexible cylindrical structures is the key to solve the problem. By field observations, offshore platform will produce self -excited vibration and damage during the ice speed at which ice fails in ductile-to-brittle transition (DBT) range. In order to further investigate the mechanism and build model of self-excited vibration, it is necessary to study the mechanism of DBT and the feedback to self-excited vibration.Firstly, the paper reviews the research about DBT and ice mechanics. Then the three DBT model accepted by most people is discussed.Secondly, experiments and mechanism on DBT have been studied. In the uniaxial compressive experiment, 6 columnar ices are compressed with the strain rate between 10-3 ～10-5 /s. Typical ductile and brittle failure mode is observed and the strain rate on DBT is got.Thirdly, interaction of ice and flexible cylindrical in the process of self-excited vibration has been studied. Self-excited vibration and ice frequency locking have been described. Interaction process has been discussed by different phases. Input and output stability in ice vibration system is analyzed quantitatively. In conclusion, this ice vibration system possesses certain stability, which can return to the energy balance state under little disturbance. It is a stability system.Last, saw-tooth force functions are discussed and proved. The response under periodical excitation is clculated and improved. Then transition velocity of self-excited vibration and continuous crushing is got bu the model of saw-tooth force function.
|
PDF Full Text Request