室温保载对钛合金深潜器载人舱疲劳失效影响研究

Today, the deep sea manned submersible is regarded as a high-tech equipment for the exploration and exploitation of ocean resources. The safety of manned cabin has a decisive effect for the whole systems. So the titanium alloy is used for the manned cabin. Except for the normal cyclic loading, the manned cabin experiences a period of dwell time in each cycle during their service life. However, the titanium alloy will produce room temperature creep strain according to the recent research. So it has both engineering significance and theoretical value to study the effect of cold dwell on fatigue propagation behavior of manned cabin in this thesis. Firstly, the variation of strain with time under room temperature creep, fatigue and dwell-fatigue and the dwell-fatigue propagation behavior under different load ratio, different dwell stress and different dwell time are discussed by experimental method. The mechanism of the effect of cold dwell on the fatigue crack propagation behavior of titanium alloy will be revealed. Secondly, the prediction of dwell-fatigue crack propagation of titanium alloy used for manned cabin will be studied. The saturation stress, saturation time and predicted model of the total fatigue life are studied respectively. And the variation of the propagation rate of dwell-fatigue of titanium alloy with different parameters is obtained. Finally, the relation between the model parameter, dive depth, operation time and the floating model and dwell-fatigue life will be summarized. A dwell-fatigue life prediction method for titanium alloy manned cabin will be developed. And the essential relationship between fatigue life and dwell during their service life. The research results can provide new ideas and methods for the evaluation of the life span of the submersible cabin.

深海载人潜水器是当今深海资源勘探和开发的高技术装备，在整个系统中载人舱安全尤其重要，通常用钛合金材料制作。载人舱除了承受上浮和下潜循环载荷外，还承受水下工作时的恒载作用，而研究发现钛合金室温下将发生蠕变变形，极大影响载人舱结构疲劳性能。本项目通过不同应力水平下钛合金室温蠕变、疲劳和保载-疲劳应变随时间变化规律，及保载-疲劳裂纹扩展行为随载荷比R、保载应力、保载时间变化关系的试验研究，揭示室温保载对钛合金疲劳性能影响机理；其次分别对钛合金保载-疲劳的饱和时间和饱和应力水平及全寿命预报模型进行研究，得到裂纹扩展速率随各个参数变化规律，给出载人舱用钛合金室温保载-疲劳预报方法；最后归纳出典型结构模型参数、下潜深度、作业时间、潜浮模式等与保载-疲劳寿命之间关系，给出钛合金载人舱典型结构保载-疲劳寿命评估方法，揭示其服役期间寿命与保载之间本质关系。研究成果为潜水器载人舱寿命评估提供新思路和新方法。

深海载人潜水器是当今深海资源勘探和开发的高技术装备，在整个系统中载人舱安全尤其重要，通常用钛合金材料制作。载人舱除了承受上浮和下潜循环载荷外，还承受水下工作时的恒载作用，而研究发现钛合金室温下将发生蠕变变形，极大影响载人舱结构疲劳性能。本项目通过不同应力水平下钛合金室温蠕变、疲劳和保载-疲劳应变随时间变化规律，及保载-疲劳裂纹扩展行为随载荷比R、保载应力、保载时间变化关系的试验研究，揭示室温保载对钛合金疲劳性能影响机理；其次分别对钛合金保载-疲劳的饱和时间和饱和应力水平及全寿命预报模型进行研究，得到裂纹扩展速率随各个参数变化规律，给出载人舱用钛合金室温保载-疲劳预报方法；最后归纳出典型结构模型参数、下潜深度、作业时间、潜浮模式等与保载-疲劳寿命之间关系，给出钛合金载人舱典型结构保载-疲劳寿命评估方法，揭示其服役期间寿命与保载之间本质关系。研究成果为潜水器载人舱寿命评估提供新思路和新方法。