裂纹管结构的振动分析与裂纹识别.pdf

大连理工大学博士学位论文裂纹管结构的振动分析与裂纹识别姓名：胡家顺申请学位级别：博士专业：水工结构工程指导教师：周晶;冯新20090601大连理工大学博士学位论文摘 要管道普遍应用于化工、核电和油气储运等领域，是一种重要的工程结构随着海洋油气资源的开发，海底管道已成为海洋油气集输的重要手段，被誉为海上油气田生命线工程，其安全性和可靠性日益受到重视然而，由于材料老化、腐蚀和各种环境荷载的长期作用，海底管道不可避免产生凹痕和裂缝等损伤损伤的累积和扩展导致结构抗力衰减，突发情况下甚至引起海底管道破裂因此，采取有效的技术手段对海底管道进行结构分析、监测诊断以及安全评价具有重要的理论意义与实用价值本文围绕海底悬跨管道的振动分析以及结构状态与裂纹识别中的关键科学和技术问题，系统开展了理论和试验研究，其主要内容包括：(1)获得了裂纹管结构在复杂荷载联合作用下的局部柔度系数基于应变能释放原理和线性断裂力学理论，推导了管类结构在轴力、剪力和弯矩作用下由非贯穿直裂纹、圆周非贯穿及贯穿裂纹等三种典型裂纹所引入的附加局部柔度方程，通过数值积分方法进行局部柔度系数求解，发展了较为完善的裂纹管局部柔度系数求解方法。

研究结果表明，本文所建立的裂纹管局部柔度能够较为准确地反映裂纹的局部力学行为，弥补了现有模型局限于特定荷载模式或非空心截面的不足，为裂纹管结构的动力分析和损伤识别提供了基本参数2)基于以上局部柔度系数，建立了裂纹管结构的有限元模型和弹簧铰模型为了验证裂纹管局部柔度系数及裂纹模型的合理性，进行了裂纹管的动力模型试验，通过对比裂纹管固有频率理论计算值与试验测试值分析了本文裂纹模型的合理性在此基础上，进行了悬臂裂纹管和简支裂纹管的固有振动分析，系统研究了裂纹位置、裂纹深度与裂纹管固有频率变化之间的关系，并且发展了管类结构裂纹识别的等值线图法3)分析了边界土体性质变化对悬跨管道固有振动特性的影响，并提出了悬跨管道的状态识别方法首先，建立了以三向土弹簧约束模拟悬跨管道边界条件的数值模型，讨论了边界土体性质、外部环境荷载、轴向力以及悬跨长度等参数变化对结构固有频率的影响；其次，根据悬跨管道频率结构的内瘭特征，构建了结构状态敏感的特征矢量，提出了一种基于核判别分析(Kernel Discriminant Analysis，简称KDA)的悬跨管道状态识别方法；最后，进行了悬跨管道状态识别的模型试验，利用模型试验数据验证了该方法的有效性。

研究结果表明，本文方法能够有效挖掘悬跨管道状态矢量的本质特征，实现了结构状态的正确分类，适合工程应用4)进行了“呼吸"裂纹结构的非线性谐振分析，提出了一种基于谐振特性的疲劳裂纹识别方法首先，引入“呼吸"裂纹模型描述疲劳裂纹的非线性时变特性，使用接裂纹管结构的振动分析与裂纹识别触分析方法建立了裂纹梁的动力接触模型，研究了裂纹梁在简谐荷载激励下的非线性动力特性，分析了激励频率、裂纹位置、裂纹深度对谐振现象的影响，在此基础上提取了一种“呼吸’’裂纹识别的损伤敏感特征；其次，建立了含疲劳裂纹悬跨管道的三维动力接触模模型，进行了疲劳裂纹悬跨管道的非线性谐振分析和裂纹识别；最后，开展了疲劳裂纹识别的模型试验研究，使用三点弯曲疲劳试验预制了不同裂纹程度的裂纹管模型，进行了裂纹悬跨管道的无水和水下动力测试，根据疲劳裂纹管的真实振动信号验证了本文方法的有效性关键词：管道；振动分析；局部柔度；裂纹识别；状态识别大连理工大学博士学位论文Vibration Analysis and Crack identification forCracked Pipe—like StructuresAbstractAs important engineering structures，pipes are widely met in many applications，e．g．chemical plants，power plants，and gas and oil transportation,et a1．Submarine pipelines playan important role in the process of oil and gas仃aIlsportation’regarded as the lifeline ofmarine oil and gas fields．Therefore，the structural security and reliability of submarinepipelines have received more attention in practice．However，dent,crack and damages areinevitably occurred in structural components of submarine pipelines due to material aging，corrosion and environmental loads．111e damage accumulation and performance deterioratonwould seriously reduce the resisting capacity of the structures against the disaster,even resultin collapse．Thus，the safe operation and the prolongation of the service life urgently motivatethe research on the structural vibration analysis，health diagnosis and safety assessment forsubmarine pipelines．硼1e key issues of the above problems，i．e．crack modeling，structuralcondition recognition and crack identification et al，are stressed in the study．nle mainachievements of the dissertation are summarized in the following：(1)m equations of local flexibility for cracked pipes are theoretically proposed．仉local flexibility coefficients for typical crack sections，due to the straight part-through，thecircumferential part-through crack and the straight through crack were deduced by linearfracture mechanics and the theory of strain energy mlease rate．The local flexibility matrixWas numerically by the adaptive Simpson algorithm．111e results show that the presented localflexibility of cracked pipes Can be used to simulate the local mechanics behavior precisely，which．provides required parameters for dynamic analysis and crack identification forpipe—like structure谢nl open crack．111e presented method overcomes the shortcoming of thetraditional crack model．(2)Based on the proposed local flexibility matrix，the analysis models for cracked pipesare presented by finite element and torsional spring approach．The scaling model Was used tovalidate the proposed local flexibility and cracked pipe model by comparing the theoreticalresults to experimental data．，nle measured frequencies of the craked pipes show goodagreements诵nl the calculated results，which indicates that the proposed flexibility equationsand crack models are reasonable． Moreover，the vibration characteristics analysis forcantilever cracked pipe and simple support cracked pipe are conducted respectively．Theeffects of crack location,crack depth on natural frequency are discussed in detail．n地Il，crack—III—裂纹管结构的振动分析与裂纹识别in the pipe—like structure was proposed to be identified by contour diagram of crack locationsversus crack depth．(3)m effects of boundary constraints on the vibration characteristics is presented bytaking consideration of the ambient loads，and an effective approach of structural conditionidentification for free span(CIFS)is proposed Firstly，an interaction model of the contactbetween the pipeline and seabed Was established、衙廿l respect to boundary constraintvariations，which Can be simulated by means of altering dynamic stiffness of soil spring．Based on the proposed model，the vibration characteristics of free spanning pipeline underdifferent environmental factors，such as oil property，environmental load，axial force and spanlength,were studied．Secondly，a methodology to identify the operational conditions of freespan based on nonlinear kernel discr。