外文翻譯---液壓密封完整性調(diào)查研究-液壓系統(tǒng)-免費(fèi)閱讀
【正文】 分析了從實(shí)驗(yàn)得到的 AE 信號(hào)，幾個(gè)參量從 AE 信號(hào)提取，并且研究了他們預(yù)測的內(nèi)部漏出率。 δ 的值反映在估計(jì)內(nèi)部漏出率的錯(cuò)誤。 假設(shè)被測量的 AE 均方根值是Vrms0。由此產(chǎn)生的 AE 計(jì)數(shù)率保持在一個(gè)恒定的水平，不管漏出率變化。每條記錄的 AE 信號(hào)載 4096 點(diǎn)采樣 5 兆赫，從哪個(gè)聲發(fā)射參數(shù)計(jì)算。 16 個(gè)得分沿封印的圓周平等地被分布了。 這種的優(yōu)點(diǎn)是模仿漏出率可能容易地是受控的。 使用傅立葉變換，對(duì)于連續(xù)式 AE，這些參量可以通過光譜分析得到。 AE 計(jì)數(shù)用途廣 泛，是作為 AE 活動(dòng)一項(xiàng)實(shí)用措施。 聲發(fā)射信號(hào)可分為兩種基本類型。它集中于內(nèi)部漏出小于 L /min。 關(guān)鍵詞： 聲發(fā)射 ； 液壓缸 ； 內(nèi)部泄漏 ； 聲發(fā)射計(jì)數(shù)率 ； 均方根功率譜密度 ； AE能 量 1 引言 現(xiàn)代水利使用自來水作為液壓油，在過去幾十年中，由于液壓油其固有的優(yōu)勢相比。 then, the simulation of the leakage is presented. In order to simulate scores created by the abrasive action of solid particulates, a file was used, in the present work, to make scores on the piston seal surfaces of a water hydraulic cylinder. Fig. 2 shows the scored piston seals used in the experiments. These seals lead to an internal leakage smaller than L/min for the pressure range of 0–70 bar. Sixteen scores were equally distributed along the circumference of the seals. The dimensions of these scores were measured with a noncontact optical measurement system. shows the profile of a score taken by the measurement system. Along the edge of the score, five key points were selected and their coordinates were measured. The width and depth of the score were then measured. In addition, a circular arc fit to these five points was calculated. Thus, an approximate radius of the score could be obtained. Fig. 2. The 16score piston seals. Fig. 3. The profile of a score. 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 5頁 共 13頁 井岡山大學(xué)外文翻譯用紙 4. Experimental results In the experiment, 100 sets of data were acquired at different internal leakage rates, with each set consisting of 40 records of AE signals measured at a certain leakage rate. Each record of AE signal contained 4096 points sampled at 5 MHz, from which AE parameters were calculated. For each AE parameter, results obtained from the 40 records were then averaged. In the following, all the results are the average values. 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. 4a. It is noted that the AE count rate drops fast as the internal leakage rate decreases. Fig. 4. AE count rate versus internal leakage rate 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, nom atter how the leakage rate varied. This is shown in Fig. 4b, where the AE count rate was obtained with the threshold equal to the rms value of the signal. It can be seen that there is no desirable trend in the AE count rate with respect to the leakage rate. 5. Predict the internal leakage rate As has been shown in the above, the energy content of AE signal is closely 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 6頁 共 13頁 井岡山大學(xué)外文翻譯用紙 related to the internal leakage rate in the water hydraulic cylinder. Therefore, it may be used to predict the internal leakage rate. The error of prediction, then, is of interest. In the following, an empirical model is built to predict the internal leakage rate based on measured AE signals and the error of prediction is analysed with statistical methods. Due to the simplicity in calculation, the rms value Vrms is chosen instead of the energy Ef to characterise AE signals. From the previous experimental data, the relationship between the AE rms value Vrms a
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