【作者】 赵延广；

【导师】 郭杏林；

【作者基本信息】 大连理工大学 ， 工程力学， 2012， 博士

【摘要】 复合材料网格加筋结构是目前认为有前景的新一代先进复合材料构型,它综合了新材料技术和新结构设计的优点,以可设计性和多种优良性能而得到广泛应用。然而,复合材料网格加筋结构在研制、生产、应用的过程中,会不可预知的产生各类缺陷,这将严重限制其使用性能和应用前景。疲劳破坏是飞机、船舶、汽车以及建筑物等重要的失效形式之一,疲劳破坏经常发生在低应力水平下,而且具有突然性和不可预知性,因此并未得到人们的足够重视。鉴于以上因素,本研究基于锁相红外热成像理论对含不同缺陷类型的复合材料网格加筋结构试件进行了无损检测,并对含缺陷的疲劳试件和焊接接头进行了实时健康检测,在此基础上进而得到了其相关疲劳性能指标。本文的研究工作是基于国家自然科学基金“先进复合材料网格结构共固化工艺与软模成型参数优化分析”(N0.10702012)、工业装备分析国家重点实验室自主研究课题“基于热像法测定金属疲劳特性的实验与机理研究”(S08204)以及国家自然科学基金“基于能量耗散与结构损伤的金属疲劳机理研究与工程应用”(N0.11072045)展开的。本文的主要研究工作如下：1.基于锁相红外热成像理论的复合材料网格加筋结构的无损检测复合材料网格加筋结构由于其自身优良性能得到了广泛的应用,但常规检测方法并不能有效地对其可能存在的各种缺陷进行无损检测,这样就限制了它的适用范围和应用领域。本文基于锁相红外热成像理论,对其可能存在的夹杂、开裂、脱粘等缺陷进行了无损检测,并用法国Cedip公司开发的红外热像系统进行了验证。讨论了检测时选取的加载频率、加载强度等参数对检测结果的影响,并结合拉伸力学实验,对帽型加筋复合材料层合板进行检测,实现了未知缺陷的锁相红外热成像无损检测。2.含缺陷疲劳试件的无损检测及其疲劳性能分析疲劳破坏大量存在于工业生产和人们的日常生活中,疲劳事故的发生危险性和破坏性都很大,然而对疲劳情况进行实时监测并预知其发生是很困难的。本文对含不同缺陷类型的疲劳试样进行了光激励加载下的无损检测,讨论了检测频率、缺陷面积等因素和检测精度之间的关系,指出检测频率是检测成功与否的关键因素。确定了热弹性应力集中系数并分析了加载应力幅对其影响,通过Lung法快速测定了构件的疲劳极限,并讨论了缺陷深度对疲劳极限的影响。3.基于定量热像法的焊接构件疲劳性能评估焊接构件疲劳性能评估是焊接结构设计需要考虑的重要环节,焊缝区存在应力集中和残余应力是焊接结构最危险的区域,目前对焊接结构寿命预测要求准确可靠,需要发展新的有效的评估体系以解决传统方法的不足。作者基于焊接构件的实际工作环境,考虑恒定平均应力的影响,建立了快速预测疲劳参数和残余寿命的模型。通过红外热像仪监测焊接接头表面局部热点的变化,定性分析了损伤演变过程,克服了传统疲劳试验方法的局限性,实现了实时健康检测。更多还原

【Abstract】 The grid stiffened composite structure is the next generation of advanced composite infrastructure with very promising future. Combining advantages of new material techniques and new structure design, it is widely used in industries due of its designable ability and various other advanced features. However, during design, production and implementation processes, unpredictable defects could be generated in grid stiffened composite structures, which seriously restrict their practical applications and the future of implementation. Fatigue failure is one of the most important failure modes for aircrafts, ships, motors and buildings. Fatigue failure often occurs in low stress level and it is unpredictable. Thus, it doesn’t capture as much attention as it should. In this paper, based on lock-in infrared imaging theory, the non-destructive testing is applied to grid stiffened composite specimen with different kinds of defects. We also performed real time detection to fatigued specimen with defects and welded joint. The parameters of fatigue performance are also obtained. The study is supported by National Natural Science Foundation of China (No.10702012), a independent research project State Key Laboratory of Structural Analysis for Industrial Equipment (S08204) and National Natural Science Foundation of China (No.11072045). Major study of this thesis is as follows.1. Non-destructive testing on grid stiffened composite structure specimen based on Lock-in infrared Imaging theoryGrid stiffened composite structure is widely used because of its outstanding capabilities. However, regular testing method can not effectively detect defects inside of the material in a non-destructive way. Hence the application scope of grid stiffened composite structure is limited. In this thesis, based on Lock-in infrared Imaging theory, non-destructive testing is performed to detect potential defects, such as inclusion、crack and deboning. The result is verified by a Lock-in infrared Imaging system developed by Cedip, a French company. The impacts of different loading frequencies and loading strength have been studied. Combined with the tensile mechanical experiment, a testing on hat stiffened composite laminated plates has been performed. The results show that the non-destructive testing based on Lock-in infrared Imaging can successful detect unknown defects in grid stiffened composite structures.2. Non-destructive testing on specimen with defects and analysis of its parameters of fatigue performance Fatigue defects exist widely in industrialized manufacturing and human lives. Accidents caused by fatigue defects are extremely dangerous and destructive. However, it is challenging to predict the fatigue defects and it is difficult to conduct real-time monitoring. In this paper, non-destructive testing is applied to photo-stimulated loading on fatigue specimen with different defects. The relationships between testing accuracy and testing parameters such as testing frequency and defects size are studied. The study concludes that proper testing frequency is the key to success. TESCC is found out and the impact of loading stress amplitude on TESCC is analyzed. The fatigue life of the specimen is calculated using Lung method and the impact of defect depth on fatigue life is studied.3. Evaluation of fatigue performance for welded joints based on quantitative infrared thermographyEvaluation of fatigue performance of welded joints is very important and critical during the design of the welded joint structure, especially for the areas with stress concentration and residual stress. Currently the traditional methods are not able to accurately predict the life of welded joint structures, hence new evaluation system has to be developed. Based on the actual working environment of welded joint and considered the impact of constant mean stress, a model to rapidly predict parameters of fatigue performance and remaining life is developed. From the change of local hot spots detected by infrared camera, the evolution of defects is simulated and analyzed. This new methodology overcomes the restrictions of traditional fatigue testing methods and makes real-time testing possible.更多还原