Study On Low Temperature Fatigue Performance Of Steel Used In Polar Icebreaker

Since the beginning of the 21 st century,science and economy have developed rapidly all over the world.The rapid development of the world economy will inevitably bring about a large amount of energy consumption,oil and gas is still the main component of energy.In recent years,the amount of energy collected on land is far from enough to meet the needs of human beings when they cannot leave these fossil fuels.So the development of oil and gas has gradually shifted from inland areas to the blue ocean,from the shallow to the deep sea.With the development of ocean resources becoming a hot spot,there are only two regions left on the earth that are rich in resources due to extreme environmental conditions--the polar regions.As a result,the "arctic route" has been put on the international stage.More and more polar ships,polar research ships and polar submersibles are engaged in the development and expansion of the arctic route.Crushing the ice at the same time the polar structure of low temperature fatigue problem has become the research focus in the experts,scholars,crushing the ice polar structure caused by low temperature fatigue problems because of its working principle,polar icebreaker normally have two ice-breaking ways,one is the method of continuous ice,another is collision type to break the ice.No matter what kind of icebreaking mode the polar icebreaker is in the icebreaking region of the bow,fatigue problem will occur.Because the bow will be hit many times,the fatigue problem is particularly important.Because polar icebreaker sails in the polar cold region,low temperature is sensitive to the fatigue crack growth rate,which is a hot spot being studied now.Therefore,the research on the low temperature fatigue crack growth rate of EH36 steel for polar icebreaker is of great scientific research prospect and practical engineering significance.The main purpose of this paper is to study the low-temperature fatigue performance of the steel used for polar icebreaker.Firstly,the low-temperature mechanical properties of the steel EH36 used for polar icebreaker are explored,including the changes of elastic modulus,yield strength,tensile strength,elongation and section shrinkage with the temperature.Then,the fatigue crack growth rate of polar icebreaker EH36 was investigated,including the influence of different stress ratios and temperatures on the fatigue crack growth rate.Finally,the fatigue crack growth rate of EH36 steel for polar icebreaker is predicted,and titanium alloy is selected for comparative analysis.For this purpose,the main research work of this paper is as follows:(1)Domestic and foreign low temperature fatigue and low temperature fatigue crack growth rate prediction methods were summarized,focusing on the master of low temperature fatigue crack growth rate prediction methods,in order to lay a foundation for this study;(2)Learn and master the basic mechanical properties of the steel for polar icebreaker and the influence of temperature on the fatigue crack growth rate of the steel for this ship according to a large number of literatures;(3)Carry out experimental research on the basic mechanical properties of EH36 steel for polar icebreaker at room temperature and low temperature,and obtain yield strength and elastic modulus of materials at different temperatures,so as to establish the relationship between various mechanical properties parameters and temperature;(4)The experimental study was carried out on the fatigue crack growth rate of EH36 steel for polar icebreaker under different load ratios and temperatures to obtain the fatigue crack growth rate curve of EH36 steel for polar icebreaker under different load ratios and temperatures,so as to obtain the influence of load ratio and temperature on the fatigue crack growth rate of the material.(5)The prediction model of EH36 steel crack growth rate for polar icebreakers was established.The temperature effect was considered in the model,and the model prediction results were compared with the test results,so as to verify the feasibility and reliability of the prediction model and lay a foundation for the prediction of EH36 steel fatigue crack growth rate for polar icebreakers.(6)To the titanium alloy material under low temperature condition,experimental study on fatigue crack growth rate for the effects of temperature on the titanium alloy material fatigue crack propagation rate,using the forecast model to forecast and compared with test results of the study,to verify whether the model is suitable for different materials,for other polar icebreaker steel fatigue crack propagation rate of forecast research foundation.