机翼蒙皮结构多部位损伤研究

发布时间：2018-01-31 12:33

本文关键词： 机翼蒙皮多部位损伤发生概率内力再分配剩余强度　出处：《哈尔滨理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：广布疲劳损伤是指多个元件或者多个相似细节中存在大量的细小裂纹,这些细小裂纹在疲劳载荷的作用下发生连通,而引起结构的剩余强度不能继续承受载荷作用导致结构失效。广布疲劳损伤广泛存在于飞机蒙皮结构中,广布疲劳损伤的存在降低了飞机蒙皮结构的承载能力,严重影响飞机的安全和寿命,尤其是老龄飞机。广布疲劳损伤分为多元件损伤和多部位损伤两种形式,本文主要研究广布疲劳损伤中的多部位损伤问题,基于机翼蒙皮结构和机翼蒙皮常用的2024铝合金材料,根据多部位损伤发生和发展过程研究多部位损伤发生的概率、多部位损伤内力再分配问题和多部位损伤的剩余强度。本文的研究对深入了解多部位损伤的形成及发展过程具有重要的参考价值,也为飞机结构的安全设计和寿命评估提供有力的参考依据,对我国的航空以及国防建设事业也具有重大的现实意义。在研究多部位损伤发生概率方面,首先给出多部位损伤发生的判定依据,然后在假设各个细节具有相同疲劳特征和产生裂纹随机独立性的条件下,根据概率断裂力学当量初始裂纹分布的理论和数理统计中的三参数威布尔分布建立了预测多细节结构发生多部位损伤概率的数学模型,具体建立了载荷循环次数和发生概率之间的函数关系。最后,通过2024铝合金薄板单细节和三细节的疲劳试验对模型的合理性进行验证。经验证,模型可以很好地预测多细节结构在一定载荷循环次数下发生多部位损伤的概率,但预测结果偏于保守。在研究多部位损伤内力再分配方面,首先对复杂的多部位损伤问题进行简化处理,根据某民机机翼蒙皮结构得到多部位损伤结构的两个基本简化模式,再运用Abaqus和Franc3d建立裂纹有限元模型研究两个基本多部位损伤结构的应力强度因子中结构综合修正因子,在得到结构综合修正因子中的组合修正因子和局部载荷再分配因子与主裂纹长度存在函数关系的结论后,通过这种函数关系研究了组合修正因子和局部载荷再分配因子与主裂纹长度的变化规律,间接研究了多部位损伤内力再分配的变化规律。得出一定载荷情况下,多部位损伤结构的内部载荷是不断进行分配的,分配的规律与结构形式和裂纹分布等因素有关等的结论。在多部位损伤剩余强度研究方面,首先根据前文对多部位损伤内力再分配问题研究的结论和试验标准设计了两类同细节不同裂纹分布的含有多部位损伤结构的试验件,试验件材料采用2024铝合金材料。通过两类多部位损伤结构试验件的剩余强度试验,讨论了净截面屈服计算方法、基于Swift连通准则的计算方法和线弹性条件下断裂力学的计算方法这三种常用的剩余强度计算方法在多部位损伤结构剩余强度计算方面的适用性。最后得出结论:同细节不同裂纹分布对多部位损伤结构剩余强度有影响,净截面屈服计算方法较其他两种计算方法更准确。
[Abstract]:Widespread fatigue damage refers to the existence of a large number of small cracks more elements or more similar details, these small cracks in fatigue load under the effect of connectivity, caused by the residual strength of the structure can not continue to bear the load may cause structure failure. Widespread fatigue damage is widely existed in the aircraft structure, widespread fatigue the existence of damage reduces the bearing capacity of aircraft structure, seriously affect the safety and life of aircraft, especially aging aircraft. Widespread fatigue damage is divided into multiple components damage and multiple site damage in two forms, this paper mainly studies the widely distributed multi site damage fatigue damage, skin structure and wing wing skin commonly used 2024 Aluminum Alloy based material according to the occurrence and development process of multi site damage probability of multiple site damage, multiple site damage redistribution problem and multiple site damage The residual strength. This study has important reference value for understanding the formation and development process of multiple site damage, but also provide reference for the safety design and life assessment of aircraft structure, also has great practical significance for China's aviation and national defense construction. The probability of occurrence in the study of multiple site damage firstly, multiple site damage criterion of the conditions and have the same characteristics in detail and fatigue crack random assumption of independence, according to the three parameter Weibull distribution model was established to predict the detail structure of the probability of occurrence of multiple site damage probability fracture mechanics equivalent initial crack distribution theory and mathematical statistics. How to establish the function relationship between the load cycles and occurrence probability. Finally, by 2024 Aluminum Alloy details and the details of the three single sheet The fatigue test of the rationality of the model is verified. Verification results show that the model can well predict the probability of multiple details structure occurs in certain load cycles under multiple site damage, but the prediction result is conservative. The internal force redistribution in study of multiple site damage, the multiple site damage complex problem is simplified, according to the basic a simplified model of a civil aircraft wing skin structure structure with multiple site damage two, then use Abaqus and Franc3d to establish the finite element model of crack two basic structure with multiple site damage stress intensity factors in the structure of comprehensive correction factor is a function of a combination of correction factor and local load redistribution factor and the main crack length in structure the comprehensive correction factor in the conclusion, through this function relationship of combined correction factor and local load redistribution factor and main crack Changes of the length of the variation of the indirect multiple site damage redistribution. The load conditions, the structure of multi site damage is ongoing internal load distribution, distribution regularity and conclusion structure and distribution of cracks and other factors. The residual strength of the multiple site damage, according to the study the redistribution of internal force on the above conclusions and multiple site damage testing standard test piece is designed with the structure of multi site damage two similar details different crack distribution, the test materials using 2024 Aluminum Alloy material. By two kinds of multiple site damage residual strength test structure of the test piece, the net section yield calculation method, method damage in many parts of the calculation method and the linear elastic fracture mechanics criterion Swift connected under these three kinds of commonly used based on the residual strength Finally, it is concluded that different crack distributions with the same details affect the residual strength of multi site damaged structures. The net section yield calculation method is more accurate than the other two methods.

【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V215

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