發(fā)布時間：2018-05-17 23:23

  本文選題：模態(tài)損耗因子 + 頻帶損耗因子��； 參考：《西北工業(yè)大學》2016年博士論文

【摘要】：損耗因子對結(jié)構(gòu)設(shè)計和動力學特性預(yù)測具有重要影響,一般通過試驗方法獲取。本研究重點開展線性系統(tǒng)模態(tài)損耗因子、頻帶損耗因子、剛度非線性系統(tǒng)損耗因子的試驗識別方法研究,旨在提高損耗因子試驗測試精度。本文首先基于高斯-牛頓迭代提出了一種識別模態(tài)損耗因子的擬合法,該方法盡可能多地利用了固有頻率附近的信息計算模態(tài)阻尼,有效消除了試驗測量誤差對損耗因子識別結(jié)果的影響。根據(jù)擬合函數(shù)類型,擬合法可分為直接擬合法、平方擬合法和倒數(shù)擬合法。本文對比分析了頻率間隔、固有頻率附近頻點數(shù)以及試驗重復(fù)次數(shù)等因素對采用線性插值改進的半功率帶寬法和三種擬合法識別精度的影響,結(jié)果表明:三種擬合法的抗噪性均優(yōu)于改進半功率帶寬法,直接擬合法和倒數(shù)擬合法需要的試驗重復(fù)次數(shù)少,精度高,是線性系統(tǒng)模態(tài)損耗因子識別的首選方法,可以有效改進信噪比在10dB~20dB的情況下采用改進的半功率帶寬識別損耗因子誤差較大的問題。在分析初始衰減率法識別頻帶損耗因子誤差的基礎(chǔ)上,論文提出了過程損耗因子的概念,用以描述衰減過程的頻帶損耗因子。分析表明:固有頻率較小的模態(tài)具有較大的模態(tài)損耗因子,是初始衰減率法測試頻帶損耗因子存在較大系統(tǒng)誤差的主要原因。為此,本文發(fā)展了循環(huán)相減法應(yīng)用于頻帶損耗因子識別,提出了時域分離法測試頻帶損耗因子,該方法具有計算過程簡便、應(yīng)用范圍廣并且測試精度高的特點。仿真和試驗結(jié)果均表明,時域分離法的誤差可控制在10%以內(nèi),可用于準確識別頻帶損耗因子;可以有效解決當頻帶中含有多階模態(tài)時,衰減振動曲線出現(xiàn)“分段”現(xiàn)象而導致的衰減法識別頻帶損耗因子難度較大的問題。最后,論文在剛度非線性系統(tǒng)阻尼特性分析的基礎(chǔ)上,基于粒子群優(yōu)化提出了識別系統(tǒng)損耗因子的積分法。研究表明:該方法具有很強的抗噪性,可以利用含噪信號獲取損耗因子,在信噪比低至10dB的情況下,依然可將平均誤差控制在10%以內(nèi),并且信噪比越高,誤差越小。本文提出的識別含多階模態(tài)頻帶損耗因子的時域分離法,彌補了衰減法和輸入功率法的不足,克服了初始衰減率法存在系統(tǒng)誤差的問題,方便工程應(yīng)用。本文提出的積分法測試剛度非線性系統(tǒng)損耗因子,利用積分的方法計算過程量,減小了試驗測試誤差對結(jié)果的影響,并且利用粒子群優(yōu)化求解損耗因子,結(jié)果穩(wěn)定,分析表明該方法具有抗噪性強,精度高等特點。
[Abstract]:Loss factor has an important influence on structural design and prediction of dynamic characteristics, which is generally obtained by experimental method. This study focuses on the experimental identification methods of modal loss factor, frequency band loss factor and loss factor of stiffness nonlinear system, in order to improve the accuracy of the loss factor test. In this paper, based on the Gao Si Newton iteration, a fitting method for identifying the modal loss factor is proposed. The method uses as much information near the natural frequency as possible to calculate the modal damping. The effect of measurement error on the result of loss factor identification is effectively eliminated. According to the type of fitting function, fitting method can be divided into direct fitting method, square fitting method and reciprocal fitting method. In this paper, the effects of frequency interval, frequency points near the natural frequency and the number of repeated experiments on the recognition accuracy of the improved half-power bandwidth method and the three fitting methods by linear interpolation are compared and analyzed. The results show that the noise resistance of the three methods is better than that of the improved half power bandwidth method. The direct fitting method and the reciprocal fitting method need less repeated tests and have high precision, so they are the first choice for modal loss factor identification of linear systems. The SNR can be effectively improved by using the improved half-power bandwidth to identify the large loss factor error in the case of 10dB~20dB. Based on the analysis of the initial attenuation rate method to identify the frequency band loss factor error, the concept of process loss factor is proposed to describe the frequency band loss factor of the attenuation process. The analysis shows that the mode with small natural frequency has a large modal loss factor, which is the main reason for the large system error in the measurement of the band loss factor by the initial attenuation rate method. In this paper, the cyclic phase subtraction method is developed for frequency band loss factor identification, and a time domain separation method is proposed to measure the frequency band loss factor. The method is characterized by simple calculation process, wide application range and high measurement accuracy. The simulation and experimental results show that the error of the time domain separation method can be controlled within 10%, which can be used to identify the loss factor of the frequency band accurately, and can effectively solve the problem when the frequency band contains multi-order modes. It is difficult to identify the frequency band loss factor by the attenuation method due to the "segmental" phenomenon in the attenuating vibration curve. Finally, based on the analysis of the damping characteristics of the nonlinear stiffness system, an integral method for identifying the loss factor of the system is proposed based on particle swarm optimization (PSO). The results show that the method has strong noise resistance, and the loss factor can be obtained by using the noisy signal. When the SNR is as low as 10dB, the average error can still be controlled within 10%, and the higher the SNR, the smaller the error. In this paper, the time-domain separation method with multi-modal frequency band loss factor is proposed, which makes up for the deficiency of the attenuation method and the input power method, and overcomes the problem of systematic error in the initial attenuation rate method, which is convenient for engineering application. The integral method proposed in this paper is used to measure the loss factor of nonlinear system with stiffness. The process quantity is calculated by integral method, and the influence of test error on the result is reduced, and the loss factor is solved by particle swarm optimization, and the result is stable. The analysis shows that the method has the characteristics of strong noise resistance and high accuracy.
【學位授予單位】：西北工業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TB535

【相似文獻】

相關(guān)期刊論文 前10條

1 徐超;張醒;李瑞杰;游少雄;;多粘彈性膠膜夾層約束阻尼梁損耗因子分析[J];宇航學報;2009年02期

2 巨樂;王敏慶;顧金桃;;不可分離結(jié)構(gòu)的損耗因子測量研究[J];噪聲與振動控制;2014年02期

3 張紅亮;孔憲仁;劉源;齊金玲;;寬頻域的內(nèi)損耗因子實驗辨識方法研究[J];振動與沖擊;2013年12期

4 尹幫輝;王敏慶;;基于譜有限元的自由阻尼梁結(jié)構(gòu)損耗因子分析[J];振動與沖擊;2014年04期

5 張永杰;肖健;韋冰峰;王U，

本文編號：1903336