【正文】 an AE signal consisting ofx [0]， x [1], …… , x [N?1] , its rms value is 機(jī)電 工程學(xué)院 機(jī)械系機(jī)械設(shè)計(jì)制造及其自動(dòng)化班 學(xué)生 毛祖慶 畢業(yè)設(shè)計(jì) 第 3頁 共 13頁 井岡山大學(xué)外文翻譯用紙 The advantage of energy measurement is that the energy content of the AE signal can be directly related to important physical parameters associated with the energy release at the AE source [14]. The above parameters have been used to describe AE signals in a variety of applications [11, 17, 18]. The aforementioned parameters are measured in the time domain. Besides, parameters measured in the frequency domain are also of interest, such as the frequency and magnitude of the dominant frequency ponent and the energy contained within frequency bands. For the continuoustype AE, these parameters can be obtained through spectral analysis using Fourier transform. The power spectral density (PSD) of AE signals can be puted using the following equation [19]: where P[ k ] is the power spectral density, X [k]] is the discrete Fourier transform (DFT) of an AE signal x[n], andT is the sampling period. The PSD represents the distribution of the signal power over frequencies. Some studies of AE signals in the frequency domain can be found in Refs. [10, 13, 20, 21]. 3. Experimentation Due to the plexity of AE phenomena, analytical methods are not well established. Therefore, experimental methods are introduced to investigate AE. In order to study the characteristics of AE signals generated by internal leakage in water hydraulic cylinders, experiments were deliberately designed, as described below. For each record of AE signal, the AE count rate, denoted as _N AE was calculated by dividing the AE counts by the signal duration. Both a fixed threshold and a floating threshold were used for counting. Since there was no welldefined procedure to choose the threshold value, a wide range of values were tried. For the fixed threshold, a value of yielded the best results, as shown in Fig. 6a. It is noted that the AE count rate drops fast as the internal leakage rate decreases. For the floating threshold, the threshold value was set to be proportional to the rms value of the signal. The resulting AE count rate remained at a constant level, no provide a desirable simulation of the dynamic processes existing in a cylinder subject to internal leakage. Thus in the present work, efforts have been made to simulate the real internal 機(jī)電 工程學(xué)院 機(jī)械系機(jī)械設(shè)計(jì)制造及其自動(dòng)化班 學(xué)生 毛祖慶 畢業(yè)設(shè)計(jì) 第 4頁 共 13頁 井岡山大學(xué)外文翻譯用紙 leakage in hydraulic cylinders. In the following, the leakage mechanism is first studied。 yrynen, S. Kesanto, J. Varrio, Using a high resolution thermograph in predictive maintenance and fault diagnosis of fluid power ponents and systems, in: Proceedings of the Fourth Scandinavian International Conference on Fluid Power, Tampere, Finland, September 26–29, 1995, pp. 719–725. 機(jī)電 工程學(xué)院 機(jī)械系機(jī)械設(shè)計(jì)制造及其自動(dòng)化班 學(xué)生 毛祖慶 畢業(yè)設(shè)計(jì) 第 8頁 共 13頁 井岡山大學(xué)外文翻譯用紙 機(jī)械系統(tǒng)與信號處理 , 2020, 21: 1115–1126 液壓密封完整性調(diào)查研究 P. Chena, . Chua, . Lim 摘要： 本文中所涉及在液壓缸的上線檢測密封缺陷 . 一個(gè)明顯的影響密封的缺陷是內(nèi)部泄漏。 結(jié)果表示，基于能量的 AE 參量，特別是均方根值，是更加適當(dāng)解釋內(nèi)部漏出引起的 AE 信號。其中最常見的問題是比較大的內(nèi)部滲漏水液壓元件。 本文提出的是打算開發(fā)一個(gè)定量模型通過 AE估計(jì)在水液壓缸的內(nèi)部漏出流速項(xiàng)目的一部分。 2. 聲發(fā)射 AE 被定義作為由迅速能量的釋放從局部性引起的瞬變彈性波。 在機(jī)電 工程學(xué)院 機(jī)械系機(jī)械設(shè)計(jì)制造及其自動(dòng)化班 學(xué)生 毛祖慶 畢業(yè)設(shè)計(jì) 第 9頁 共 13頁 井岡山大學(xué)外文翻譯用紙 液壓缸的內(nèi)部漏出情況下， AE 信號主要?dú)w因于內(nèi)部漏出導(dǎo)致的動(dòng)蕩。 圖 1： AE 信號所產(chǎn)生的內(nèi)部滲漏水液壓缸 一般來說，直接觀察的連續(xù)聲發(fā)射信號很少關(guān)于 AE 信號源資料。以下簡單地描述有些用途廣泛的參量連續(xù)式 AE 發(fā)信號。均方根 (rms)是常用的測量 AE 信號能量內(nèi)含。 其外，在頻域測量的參量也是利益，例如在頻帶內(nèi)和巨 大包含的統(tǒng)治頻率組分和能量的頻率。 AE 信號的有些研究在頻域的可以在 Refs 找到。人工介紹的內(nèi)部漏出流經(jīng)了閥門而不是液壓缸。 因此，在當(dāng)前工作，努力被做了模仿在液壓缸的真正的內(nèi)部漏出。 這些封印帶領(lǐng)內(nèi)部漏 出 0–70 酒吧的壓力范圍的小于 升 /分鐘。 沿比分的邊緣，五個(gè)關(guān)鍵被選擇了，并且測量了他們的座標(biāo)。 機(jī)電 工程學(xué)院 機(jī)械