【作者】 顾超林；

【导师】 王轲；

【作者基本信息】 南京航空航天大学 ， 工程力学， 2009， 硕士

【摘要】 工程实际中,特别是在航空、航天、船舶、石油化工等领域,结构需要长期承受交变载荷作用,由此引起的疲劳破坏是结构失效的主要形式之一。由于工程结构的疲劳现象往往是由于结构振动引起的,因此,正确评估结构在振动环境中的疲劳寿命已成为工程界的热门研究课题。本文以现代飞机的常用结构铝合金加筋板为研究对象,立足于加筋板结构的疲劳寿命试验,依据疲劳断裂力学、模态分析理论,应用有限元建模、响应、寿命仿真分析等CAE技术,对共振状态下加筋板结构的振动疲劳寿命问题进行了较为系统的分析。本文主要工作包括:1.采用有限元分析软件MSC.Patran和Nastran建立三种不同连接形式的加筋板的有限元模型,并通过对比加筋板自由状态下的模态试验结果对所建模型进行验证修正,在此基础上进行有限元响应分析,为后期的振动疲劳分析做准备。2.为了揭示影响结构振动疲劳寿命的因素,采用激振器直接对结构施加激振力,进行疲劳寿命试验。试验证明在同一载荷作用下的滚焊连接加筋板的疲劳寿命最长。3.采用疲劳分析软件MSC.Fatigue针对结构的不同载荷形式对结构进行寿命分析,通过试验和仿真分析结果对比总结出不同连接形式以及激励方式影响结构疲劳寿命一般规律。4.为了提高寿命预测的精度,从裂纹扩展的角度,采用有限元方法模拟加筋板的裂纹扩展,计算裂纹扩展过程中应力强度因子变化,并据此提出一种新的振动疲劳寿命计算方法,对比试验结果初步证明精度较高。更多还原

【Abstract】 Fatigue failure is the main destroy mode in engineering pratice for most of the components when they work under compexed vibration environments, especially to aircraft, spaceflight, ship industry and prtroleum chemical industry, etc. Therefore, how to properly evaluate the fatigue life of structure under forced vibration becomes a hot research topic now.For obtaining a definite understanding of the mechanism of vibration fatigue, the stiffened structure which is widely used in modern aircraft was employed as a study object. Based on the fatigue life experiment and CAE simulation technology such as finite element analysis and fatigue simulation analysis, the vibration fatigue life of stiffened structure was analyzed systematically combined with damage mechanics and modal analysis theory. For the above purpose, some works were done as follows:Firstly, three finite element models were created for stiffened structure with different type of connection through the FEA soft such as Msc.Patran and Nastran. Modal experiment was carried out for the stiffened structure with free boundary to update the finite model. Finite element analysis was done for the preparation of the future fatigue simulation analysis.In addition, in order to reveal the influence factors on life of structural vibration fatigue profoundly, fatigue life experiments of stiffened structure were done used vibration exciter exerts load on the structure directly. Results indicate that fatigue life of stiffened with rolling weld connection is the longest among the different test piece under the same loading.What is more, structural fatigue life was analyzed used Msc.Fatigue soft with different loading mode and the simulation results were compared with test results. The general rule of structural fatigue life was summarized for different connection mode under different exciting.Finally, the crack propagation of stiffened was simulated through the method of finite element analysis based on fracture mechanics, and the dynamic stress intensity factor was calculated during crack propagation so as to improve the precision of life prediction. A more realistic and accurate calculation method for fatigue crack growth was proposed in the end.更多还原