考虑小裂纹和保载时间效应的疲劳可靠性分析

大深度载人潜水器的载人舱材质是高强度金属，不可避免地会受到疲劳损害现象的挑战。实际的载人舱结构中存在着由外部因素和内部因素引起的不确定性，其疲劳寿命将受到这些不确定性的影响。在前期的研究中，课题组基于统一的疲劳裂纹扩展率模型进行了疲劳可靠性分析方法的探讨，可作为进一步进行载人舱疲劳寿命预报的基础。但是，该模型无法反映小裂纹和保载时间的影响，而这正是载人舱结构和所受载荷的重要特征，应进行深入研究。所以，课题组提出了一个小裂纹扩展率模型和两个反映保载时间效应的裂纹扩展率模型，以更好地解释载人舱用钛合金金属的蠕变疲劳特性。文中基于这三个模型，结合不同的理论方法，进行了疲劳可靠性分析，考察了可靠度分析方法之间的不同、输入参数以及不同的裂纹扩展理论模型对结构的疲劳可靠性的影响。

Fatigue Reliability Analyses Considering Short Crack and Dwell Time Effects

Proper fatigue life prediction is important for the deep-sea manned cabin made of high strength metal. In real practice, many uncertainties both intrinsic and extrinsic properties affect the fatigue behavior of the manned cabin. In the former research, the fatigue reliability analysis was con-ducted based on a unified crack growth rate model, to provide a basis for fatigue life prediction of manned cabin. However, it could not consider the short crack effect and dwell time effect, both of which are essential in structure and load characteristics of manned cabin, and should be studied fur-ther. In this paper, a short crack growth rate model and two kinds of dwell fatigue crack growth rate models newly proposed by the authors’ group aiming to better describe the dwell-fatigue behavior of the titanium alloys, will be analyzed combined with different reliability analysis methods. The differ-ence of several fatigue analysis methods as well as how the input variables and the crack growth models affect the structural fatigue reliability will be analyzed and demonstrated.