共查询到20条相似文献,搜索用时 31 毫秒
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Xuesong Han Tianyu Wu 《The International Journal of Advanced Manufacturing Technology》2013,67(9-12):1997-2006
Current demands of machining hard and brittle materials at very small tolerances have predicated the need for precision and high-efficiency grinding. In situ monitoring systems based on acoustic emission (AE) provide a new way to control the surface damage and integrality of the components. However, a high degree of confidence and reliability in characterizing the manufacturing process is required for AE to be utilized as a monitoring tool. The authors established AE based online monitoring system and studied technique parameters versus the waveforms of AE under different working conditions. The results show that there are obvious mapping relations between the technique parameters of grinding and the effective values of the AE signals. Grinding along different directions would result in different strength of AE signal. Comparing with grinding along first longitude, fewer AE signal is released when grinding along latitude and better surface quality is generated. Similar variation tendency is observed no matter between AE root mean square (RMS) and linear speed or between surface roughness and linear speed which justify some kind of correlation may exist between AE RMS and surface roughness. The distance between the AE transducer and the AE source should be less than 80 mm while monitoring the process of grinding composite ceramics. 相似文献
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L. N. Stepanova S. A. Grassman S. I. Kabanov A. L. Bobrov S. A. Bekher A. A. Bolchanov 《Russian Journal of Nondestructive Testing》2011,47(3):158-163
The changes in the design of the 18–578 solebar with a boxlike cross section required the development of a new scheme of arrangement
of acoustic-emission (AE) transducers and improvement of both technique and software. All sources that were detected during
AE testing were divided according to their degree of hazard into passive and critically active ones. Location grids that specified
the rejection levels were imposed on the tested zones under study. In the refined technique, linear location was used, which
made it possible to preserve the reliability of the investigation results and reduce the labor intensiveness of the AE testing. 相似文献
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Yiyo Kuo Kuo-Ping Lin 《The International Journal of Advanced Manufacturing Technology》2010,50(9-12):1243-1251
Overall equipment efficiency (OEE) is widely used in industry. OEE is the combination of availability efficiency (AE), operation efficiency (OE), rate efficiency (RE), and quality efficiency (QE). In general, OEE, AE, OE, RE, or QE are only calculated as part of a management consultancy exercise. In the present research, a group of washing machines from a TFT-LCD manufacturing company was used for the case study. Because AE is strongly related to the reliability of a machine, this research aims to use collected AE data for predicting the reliability of the machine. Four methods are proposed for predicting the machine’s reliability. The results show that the combination of neural networks and decision trees based on the previous eight AE values has the best performance in predicting the reliability of TFT-LCD washing machines. 相似文献
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The operating principle and design of an eddy-current transducer intended for in-service measurement of the wall thickness of light-alloy drill pipes are described. The block diagram and algorithm of conversion are provided for measurement-data signals from the eddy-current thickness gauge. The main technical specs are listed for a thickness gauge prototype. 相似文献
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静压轴承轴瓦座磨损严重,需加工处理,为此设计一套大型工装。该工装采用主轴带动镗套和镗杆及刀杆的结构来完成球面加工的切削运动,已取得了良好的使用效果。 相似文献
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Seyed Ali Niknam Victor Songmene Y H Joe Au 《The International Journal of Advanced Manufacturing Technology》2013,69(9-12):2679-2689
Bearings are known as the vital parts of machines, and their condition is often critical to the success of an operation or process. Presence of a film of lubricant such as grease between the bearing surfaces minimizes the friction and surface wear. Contaminated grease or lack of lubricant may lead to an ineffective bearing performance or malfunction of the machinery parts. Therefore, in order to avoid unexpected breakdowns, reliable and robust bearing condition monitoring techniques are demanded. According to previous studies, acoustic emission (AE) signals contain valuable information that can be used for bearing condition monitoring and fault detection. The main objective of this study is to evaluate the effectiveness of AE signal parameters to distinguish between lubricated and dry bearings under similar operating conditions. To this end, a low-speed rotating test rig is manufactured and used. Eight levels of rotational speeds and four levels of radial loads were applied to the test rig shaft end, which is connected to the testing bearing. In each test, seven time domain AE parameters were computed. The statistical tools were also used to present the dominant experimental variables on AE signal parameters. According to experimental results, it was found that four AE parameters can be used to distinguish between dry and lubricated bearings. 相似文献
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针对声发射技术对金属结构损伤的检测可靠性问题,以金属疲劳裂纹检测试验为基础,利用声发射特征参数的趋势分析和关联分析法,首先根据贝叶斯理论,计算了声发射对一定长度疲劳裂纹的检测概率;其次,研究了检测结构起裂时对应声发射幅度参数的阈值及其对损伤判断的影响。该研究可为减少声发射检测中的金属疲劳损伤信号误判,提高检测效率,以及确定复杂航空结构疲劳寿命提供支持。 相似文献
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In a nuclear power plant, a loose part monitoring system (LPMS) provides information on the location and the mass of a loosened or detached metal impacted onto the inner surface of the primary pressure boundary. Typically, accelerometers are mounted on the surface of a reactor vessel to localize the impact location caused by the impact of metallic substances on the reactor system. However, in some cases, the number of accelerometers is not sufficient to estimate the impact location precisely. In such a case, one of useful methods is to utilize other types of sensor that can measure the vibration of the reactor structure. For example, acoustic emission (AE) sensors are installed on the reactor structure to detect leakage or cracks on the primary pressure boundary. However, accelerometers and AE sensors have a different frequency range. The frequency of interest of AE sensors is higher than that of accelerometers. In this paper, we propose a method of impact source localization by using both accelerometer signals and AE signals, simultaneously. The main concept of impact location estimation is based on the arrival time difference of the impact stress wave between different sensor locations. However, it is difficult to find the arrival time difference between sensors, because the primary frequency ranges of accelerometers and AE sensors are different. To overcome the problem, we used phase delays of an envelope of impact signals. This is because the impact signals from the accelerometer and the AE sensor are similar in the whole shape (envelope). To verify the proposed method, we have performed experiments for a reactor mock-up model and a real nuclear power plant. The experimental results demonstrate that we can enhance the reliability and precision of the impact source localization. Therefore, if the proposed method is applied to a nuclear power plant, we can obtain the effect of additional installed sensors. 相似文献
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L. N. Stepanova I. S. Ramazanov K. V. Kanifandin 《Russian Journal of Nondestructive Testing》2010,46(9):676-683
A method for detecting hazardous sources of acoustic-emission (AE) signals by the level of their energy activity using clustering
by digitized signal shape was considered. The influence of the distance between a source and an AE transducer on the energy
of recorded AE signals was analyzed. The energy distribution median of signals in a cluster was proposed for evaluating the
hazard of an AE signal source. The application of the developed method was tested based on the example of the analysis of
AE inspection data on the welding of steel specimens with incomplete fusion and a crack at the root of a weld seam. This testing
confirms the results of the fractographic inspection of a defective weld seam. 相似文献
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这里将深入探讨真空助力器回程速度的问题。对影响真空助力器回程速度的结构设计,密封性能,技术参数等几个方面分别作了详细的阐述,提出并详细阐述了最后平衡位置的原理。同时,给出了真空助力器的特征曲线是如何反映助力器回程速度的方法。 相似文献
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Changqing Su Yimin Zhang Qunchao Zhao 《Journal of Mechanical Science and Technology》2011,25(12):3123-3133
The vibration problem of the general system is the main object of research. The material properties and geometry of general
system are random parameters because of the manufacturing environment, technical conditions, manufacturing and installation
errors, multiphase materials, features and other factors. According to the relation criterion that the difference between
the natural frequency and the driving frequency of general systems is not beyond a specific value, the vibration reliability
mode and vibration reliability of general systems are defined considering the correlation of the multi-order natural frequency
and the random characteristics of structure size and material, and the vibration reliability analysis method for avoiding
the resonant is carried out. The second-order joint failure probability is obtained by using the numerical integration method.
Based on the reliability design theory and sensitivity analysis method, the vibration reliability sensitivity of the general
system with correlation failure modes is extensively discussed and a numerical method for vibration reliability sensitivity
design is presented. The variation regularities of vibration reliability sensitivity are obtained and the effects of random
parameters on vibration reliability of the general system are studied. The presented method provided the theoretic basis for
the reliability design of the general system. A numerical example demonstrated that the proposed method is effective. 相似文献
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车门系统是地铁列车的关键子系统,对其进行可靠性评估从而确定危害性较大的故障模式有助于提高车门的可靠性和改善车门维修决策。由于车门故障数据的不足,难以对风险因子及其权重进行准确评价而导致车门可靠性评估存在模糊性,故引入模糊理论构建模糊TOPSIS方法并应用于车门故障模式的可靠性评估中。对风险因子进行模糊评价得到加权决策矩阵,应用加权决策矩阵计算每一个故障模式到正负理想方案的相对贴近度,得出了EDCU功能失效、螺母组件破损和行程开关S1破损对车门危害性较大的评估结果。分析结果与专家经验一致,为车门的设计与维修决策提供了技术支持。 相似文献
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A method for the recognition of dispersion curves on the spectrogram of acoustic-emission signals has been developed based on the Hough transform. The method was successfully tested in an experiment using a Hsu-Nielsen source. It has been determined that the suggested method can determine the distance from the source of a signal, even when the signal arrives only at one acoustic emission transducer. This enables one to perform AE testing only with one-sided access to any dimensional object or when there is a sufficiently large distance between transducers, when an AE signal reaches only one of them. 相似文献
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This paper presents a laboratory study on the Acoustic Emission (AE) generated during railway wheel–rail track interaction, with a view to developing methods of in situ rail–wheel interaction monitoring using rail-mounted sensors. It is known that the physical processes of impact and wear generate AE and it was therefore expected that axle loads, speed and traction would influence the AE generated by an interaction and that the characteristics of “normal” interaction would be affected by wheel and/or track defects and/or any misalignment between rail and track.A set of laboratory experiments were carried out on a scaled test rig to characterise the continuous AE generated by a wheel rolling on a rail and, secondarily, to assess the effect on the AE characteristic of the natural defects present on the contact profile of the rail. The natural defects were of a relatively minor nature and their assessment serves as part of the calibration of background AE for experiments with more significant simulated defects.A simplified analytical model, devised for AE waves propagating from a moving source, based on “vehicle” speed and wave damping coefficients, has been developed for the test track and fitted to the measured results. As a wheel rolls towards a sensor and then away from the sensor the measured AE generally rises and falls in a predictable way. The effects of wheel and rail surface features were found to introduce deviations from this “background”, and a method to identify the location of surface defects, based on identifying peaks above the background is also demonstrated. 相似文献