【正文】 nd the internal leakage rate Qi is obtained using the least squares method, given by Qi=+. For a measured AE rms value, the internal leakage rate may be predicted with Eq. (7). Suppose the measured AE rms value is Vrms0. A 95% prediction interval for the true value of the internal leakage rate,denoted as Qi0, is given by where ^Qi is the internal leakage rate predicted by Eq. (7) based on the measured Vrms0 and d is a measure of the width of the prediction interval. Note that d is not a constant but varies with the measured AE rms value Vrms0. For the range of the internal leakage rates smaller than L/min, d is about L/min. Eq. (8) means that for the measured AE rms value Vrms0, the true value of the internal leakage rate Qi0 lies inside the intervale ^Qi d。機電 工程學院 機械系機械設計制造及其自動化班 學生 毛祖慶 畢業(yè)設計 第 1頁 共 13頁 井岡山大學外文翻譯用紙 Mechanical Systems and Signal Processing, 2020, 21: 1115–1126 A study of hydraulic seal integrity P. Chena, . Chua, . Lim Abstract: The work described in this paper involved online detection of seal defects in a water hydraulic cylinder. An obvious effect of seal defect is internal leakage. Therefore, the approach used was to detect the internal leakage using suitable technique. The technique used involved detecting the acoustic emission (AE) due to the internal leakage. This paper evaluated various parameters of AE signals in terms of their capability in estimating the internal leakage rate in a water hydraulic cylinder. Experiments were carried out to study the characteristics of AE parameters at different internal leakage rates, the parameters including the rootmeansquare (rms) value, the count rate, the peak magnitude of power spectral density and the energy. The correlations between these parameters and the internal leakage rate were analysed carefully. The results show that energybased AE parameters, especially the rms value, are more suitable to interpret AE signals generated by internal leakage. Keywords: Acoustic emission。 ^Qi t dT with 95% confidence. 6. Conclusions This paper analysed the characteristics of AE signals generated by internal leakage in a water hydraulic cylinder. Experiments were carefully designed, including the simulation of the internal leakage across the piston seals in a water hydraulic cylinder and the measurement of the internal leakage rate. AE signals obtained from the experiments were analysed, in which several AE parameters were extracted from the AE signals and their effectiveness for predicting the internal leakage rate were the analysis results,some conclusions can be made, as follows: (1) AE signals are sensitive to small internal leakage in a water hydraulic cylinder and AEbased methods are able to predict the internal leakage that is smaller than L/min. (2) Energybased AE parameters, whether measured in the time domain or in the 機電 工程學院 機械系機械設計制造及其自動化班 學生 毛祖慶 畢業(yè)設計 第 7頁 共 13頁 井岡山大學外文翻譯用紙 frequency domain, are more suitable than the AE count rate and the peak PSD magnitude to interpret AE signals generated by the internal leakage. References [1] . Krutz, . Chua, Water hydraulics—theory and applications 2020, in: Proceedings of the Workshop on Water Hydraulics, Agricultural Equipment Technology Conference (AETC ’04), Louisville, KY, USA, February 8–10, 2020. [2] E. Trostmann, Water Hydraulics Control Technology, Marcel Dekker, New York, USA, 1996. [3] W. Backe′ , Water or oilhydraulics in the future, in: Proceedings of the Sixth Scandinavian International Conference on Fluid Power, Tampere, Finland, May 26–28, 1999, pp. 51–64. [4] J. Watton, Condition Monitoring and