Investigation And Application On Ductile-to-Brittle Transition Behavior Of Ice

In present research, the extremal ice force and dynamic ice force are the main ice force. When ice and structure interact with each other, non-simultaneous or simultaneous failure is the key research for extremal ice force, it relates to the different results. Ice-induced self excited vibration is the hot spot for dynamic ice force .Whether self exciting vibration existence or not ,how to explain the person and build the corresponding mechanics model and equation is the key studying. Previous studies have demonstrated that non-simultaneous or simultaneous failure, self exciting vibration is relevant with the ducitle-to-brittle (DTB)of ice. The title based on the field observation and the study of DTB of ice , discussed the existence of simultaneous failure and the cause and condition of self exciting vibration.In the second charpter, the result of field monitored is given. By field obversion, when ice and structure interact with each other, with the increasing of ice speed ,there're 3 kinds of ice force forms and respectively corresponding: static state vibration , steady state vibration and random vibration. The first two kind vibration is simultaneous failure, the latter is non-simultaneous failure . Further analysis indicates that steady state vibration is self exciting vibration and the micro crack behavior in ice is the key factor for describing and explaining ice-induced self excited vibration.In the third charpter, the behavior of DTB is studied in detailed by dislocation behavior in ductile areas, the micro crack behavior in DTB areas and the single micro crack behavior in brittle areas. Among them, the mechanisms of crack nucleation and propagation are explained in detailed.In the fourth charpter, based on the study of DTB, the title discussed the condition of simultaneous failure and the mechanism and criteria of self exciting vibration: By the analysis of near field ice Mechanics behavior and coupling process of ice and structure, it point out self exciting vibration take place at DTB of ice and the micro crack behavior is the key factor for describing and explaining ice-induced self excited vibration . And,by the phase analysis of self excited vibration,the title further confirmed the mechanism and criteria of self exciting in quantitative.In the last charpter, driving loading test is introducted. this experiment further confirmed the mechanism and criteria of self exciting produces.