高强度钛合金深潜器载人舱在三种不同类型载荷下的裂纹扩展预报（英文）

Prediction of Crack Growth Rates of a High Strength Titanium Alloy for Deep Sea Pressure Hull under Three Loading Patterns

随着安全性要求的提高,深潜器耐压舱的疲劳寿命评估变得越来越重要。对于耐压舱,在其服役期间经历的载荷历程包括扰动疲劳载荷和相对稳定的蠕变载荷,目前尚未有公认合适的模型来描述这一载荷谱历程。传统疲劳寿命预报方法通常忽略蠕变效应导致疲劳寿命预测较大的不确定性。为了更清楚地理解这一机理,该文对深潜器耐压舱用β-退火钛合金TC4 ELI的裂纹扩展率进行了理论分析,分别引入了三种类型载荷作用下的裂纹扩展率模型。并开展了在包含过载和保载载荷的一系列循环三角载荷下的疲劳裂纹扩展试验,对理论模型进行了验证,为合理评估深海载人潜水器的疲劳寿命提供了基础。

Fatigue life assessment of deep sea pressure hull has become more and more important due to the increase in the requirement of the safety. The pressure hull during its service life will experience periods of both fluctuating and steady stresses with creep and fatigue involved. This should be treated reasonably but up to now no proper model was proposed. Large uncertainty of the fatigue life assessment results existed in the traditional fatigue life prediction method which often neglected the creep effect. To obtain a better understanding of the problem, the crack growth rates of a beta-annealed titanium alloy TC4 ELI used for deep sea pressure hull is theoretically analyzed in this paper. The crack growth rate prediction models for the three load patterns are respectively introduced.In order to validate the theoretical assumption, a series of crack growth tests under cyclic triangular loading form with a period of overload and dwell time in the stable crack growth region are conducted, which will provide a basis for developing a proper life estimation method of deep sea manned submersibles.