【摘要】：由于材料、連接和變形等因素的非線性導(dǎo)致實(shí)際結(jié)構(gòu)都不同程度地存在非線性行為。特別是當(dāng)結(jié)構(gòu)遭受損傷時(shí)，損傷可能導(dǎo)致結(jié)構(gòu)非線性加劇，并造成結(jié)構(gòu)動(dòng)態(tài)響應(yīng)不滿足平穩(wěn)性假定。結(jié)構(gòu)的損傷和非線性行為導(dǎo)致基于線性、平穩(wěn)性假定的結(jié)構(gòu)損傷識(shí)別方法不再適用。本文基于經(jīng)驗(yàn)?zāi)B(tài)分解和Hilbert-Huang Transform（HHT），研究了基于HHT的非線性系統(tǒng)損傷識(shí)別方法。主要內(nèi)容包括： 對(duì)非線性系統(tǒng)識(shí)別方法進(jìn)行了比較系統(tǒng)的歸納和綜述，主要包括時(shí)域方法、頻域方法、時(shí)頻域方法和基于混沌的方法。本文研究采用時(shí)頻域的HHT方法。 采用集成經(jīng)驗(yàn)?zāi)B(tài)分解方法，針對(duì)模態(tài)分解過(guò)程中篩選次數(shù)恒定，可能會(huì)導(dǎo)致分解結(jié)果不精確、信號(hào)分解過(guò)程缺乏自適應(yīng)性的缺點(diǎn)，基于Huang提出的改進(jìn)差值和函數(shù)方法，并結(jié)合篩選信號(hào)極值點(diǎn)與過(guò)零點(diǎn)數(shù)目差最大為1的要求，對(duì)集成經(jīng)驗(yàn)?zāi)B(tài)分解方法的篩選停止條件進(jìn)行了改進(jìn)。通過(guò)算例分析，驗(yàn)證了改進(jìn)方法增加了信號(hào)分解的精確性及自適應(yīng)性。 分析比較了端點(diǎn)效應(yīng)影響范圍和時(shí)間特征尺度大小之間的關(guān)系，，信號(hào)的高頻分量時(shí)間特征尺度小，低頻分量時(shí)間特征尺度大。驗(yàn)證了端點(diǎn)效應(yīng)對(duì)于信號(hào)的高頻分量相對(duì)于低頻部分影響較小，因此提出在不需要整個(gè)信號(hào)特征時(shí)，可以選取高階固有模態(tài)函數(shù)分量作為分析對(duì)象。 采用改進(jìn)的希爾伯特-黃變換分析方法，并以基于系統(tǒng)輸出信號(hào)第一階固有模態(tài)函數(shù)分量的瞬時(shí)頻率作為損傷指標(biāo)，對(duì)地震波作用下的二維雙線性框架結(jié)構(gòu)的損傷進(jìn)行識(shí)別。通過(guò)瞬時(shí)頻率的時(shí)域變化，能夠有效識(shí)別結(jié)構(gòu)非線性損傷及損傷時(shí)刻。 通過(guò)在三維框架模型底層引入非線性元件來(lái)模擬非線性，桿件截面變化模擬損傷，將改進(jìn)的HHT變換用于非線性框架結(jié)構(gòu)的損傷識(shí)別。利用結(jié)構(gòu)頂層輸出信號(hào)來(lái)進(jìn)行損傷識(shí)別，將系統(tǒng)輸出信號(hào)第一階固有模態(tài)函數(shù)分量的瞬時(shí)頻率及瞬時(shí)能量作為損傷指標(biāo)。結(jié)果表明：根據(jù)結(jié)構(gòu)對(duì)稱性選擇合適的信號(hào)，利用響應(yīng)第一階固有模態(tài)函數(shù)分量的瞬時(shí)頻率和瞬時(shí)能量可以有效檢測(cè)出損傷的存在，并能進(jìn)行損傷的程度識(shí)別。
[Abstract]:Due to the nonlinearity of material, connection and deformation, the nonlinear behavior of the actual structure exists in varying degrees. Especially when the structure is damaged, the damage may lead to the aggravation of the nonlinearity of the structure, and the dynamic response of the structure does not satisfy the assumption of stationarity. Due to the damage and nonlinear behavior of structures, the method of structural damage identification based on linear and stationary assumption is no longer applicable. Based on empirical mode decomposition (EMD) and Hilbert-Huang Transform (HHT), a method of nonlinear system damage identification based on HHT is studied in this paper. The main contents are as follows: the methods of nonlinear system identification are summarized and summarized systematically, including time domain method, frequency domain method, time and frequency domain method and chaos based method. The HHT method in time-frequency domain is studied in this paper. Based on the improved difference and function method proposed by Huang, the integrated empirical mode decomposition method is used to solve the problem that the filtering times are constant in the process of modal decomposition, which may lead to the imprecision of decomposition results and the lack of adaptability in the process of signal decomposition. According to the requirement that the maximum difference between the extreme point and the zero crossing point of the filter signal is 1, the screening stopping condition of the integrated empirical mode decomposition (EMD) method is improved. An example is given to verify that the improved method increases the accuracy and adaptability of signal decomposition. The relationship between the influence range of the end point effect and the size of the time characteristic scale is analyzed and compared. The time characteristic scale of the high frequency component is small and the time characteristic scale of the low frequency component is large. It is verified that the endpoint effect has little effect on the high frequency component of the signal compared with the low frequency part, so it is proposed that the higher order inherent mode function component can be selected as the object of analysis without the need of the whole signal feature. Using the improved Hilbert-Huang transform method and the instantaneous frequency of the first order natural mode function component of the system output signal as the damage index, the damage of the two-dimensional bilinear frame structure subjected to seismic waves is identified. The time domain variation of instantaneous frequency can effectively identify the nonlinear damage and damage time of the structure. The nonlinear element is introduced into the bottom layer of the three-dimensional frame model to simulate the nonlinearity and the change of the member section is used to simulate the damage. The improved HHT transform is applied to the damage identification of the nonlinear frame structure. The structural top output signal is used to identify the damage. The instantaneous frequency and instantaneous energy of the first order natural mode function component of the output signal of the system are taken as the damage index. The results show that the existence of damage can be effectively detected by using the instantaneous frequency and instantaneous energy of the component of the first order natural mode function according to the symmetry of the structure and the degree of damage can be identified.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU317

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