低温和腐蚀环境与载荷联合作用下航空复杂连接结构疲劳与裂纹扩展性能测试及模型表征技术

The focus of this proposal has been to present new measurement and characterization techniques on the behaviours of fatigue crack formation and propagation of complex bolt/rivet fastened structures in airplane under a combination of low temperature or corrosion and cyclic load. Particular novel features are four-fold: 1) From enginering mechanics point of view, based on the sub-structuring technique, three-dimensional Finite Element (FE) models are established to predict uneven transfer load and stress pattern of complex bolt/rivet fastened structures in airplane. 2) New measurement techniques and test systems are developed to determine the behaviours of fatigue crack formation and propagation of complex bolt/rivet fastened structures in airplane under a combination of low temperature or corrosion and cyclic load. 3) On the basis of experimental observations, by considering the effects of low temperature, corrosion, loading ratio and load sequence on fatigue crack formation and propagation, novel S-N and da/dN-?K surface models are developed to characterize the behaviours of fatigue crack formation and propagation of complex bolt/rivet fastened structures in airplane under a combination of low temperature or corrosion and cyclic load. 4) New approach is presented to predict fatigue life of complex bolt/rivet fastened structures in airplane from fatigue behaviour of representative bolt/rivet fastened panels. And practical algorithm is developed to calculate stress re-disbution between interaction cracks. Thus new techniques are established to assess fatigue life and damage tolerance of complex bolt/rivet fastened structures in airplane under a combination of low temperature or corrosion and cyclic load. All models mentioned above are verified with experimental data.

从工程力学的角度，以飞机复杂螺栓/铆钉连接结构典型件作为研究对象，利用计算机仿真技术，建立静力学分析有限元分区模型，分析载荷传递机理和应力分布；研究低温和腐蚀环境与载荷联合作用下的螺栓/铆钉连接结构的疲劳和裂纹扩展性能试验测试原理和技术，并研制其试验测试系统；在试验研究的基础上，综合考虑低温和腐蚀环境、加载应力比及高低载效应，建立典型环境下航空螺栓/铆钉连接结构S-N曲面和da/dN-?K曲面表征模型；提出由简单连接件疲劳性能估算复杂连接件疲劳寿命新方法和考虑多裂纹相互作用的应力再分布的新算法，发展复杂螺栓/铆钉连接结构疲劳寿命与损伤容限评估技术，并通过试验验证评估技术的有效性。

在国家自然基金的资助下，项目（51375033）开展了腐蚀/高低温环境与载荷联合作用下航空金属材料/结构疲劳及裂纹扩展性能试验测试与模型表征技术研究，完成了项目计划书规定的全部研究内容，达到了预期的研究目标。（1）建立了腐蚀/高低温环境与载荷联合作用下航空金属材料/结构疲劳及裂纹扩展性能试验测试方法，并搭建了测试系统；（2）测试了腐蚀/高低温环境与载荷联合作用下，11种铝合金、4种钛合金、4种合金钢，13种铝合金连接件和4种飞机飞控系统作动器的疲劳/裂纹扩展性能；（3）提出考虑环境、应力比、载荷顺序效应的疲劳/裂纹扩展性能表征模型；（4）发展了上述材料/结构疲劳寿命估算与评估技术。研究成果已成功应用于我国打飞机（C919和运30）研制，为大飞机设计提供了基础数据和技术支持。