A Study on Incipient Damage Monitoring in Rolling Contact Fatigue Process Using Acoustic Emission

Acoustic emissions (AE) technique was applied to rolling contact fatigue tests of two radially loaded rollers running under constant load and velocity to detect the incipient damage and damage location. Signals detected from contacts were processed using signal conditioning and enhancement techniques by an AE source locator to bring out the difference between the signals from the sound and damaged rollers. It was found that AE hit count pulse observations by the AE source locator can provide an indication of the damage at its initial stage. The conventional AE parameters and the AE signal features were studied and correlated with the AE source locator counts. The results demonstrated the successful use of the combination of the AE monitoring and the AE source locator as a new technique for detecting the incipient damage and forecasting the position of the damage in the roller, and this technique could allow the user to monitor the rate of deterioration of the rolling elements.     

Incipient damage detection and its propagation monitoring of rolling contact fatigue by acoustic emission

The acoustic emission (AE) technique was applied to rolling contact fatigue tests using a test-rig running under constant load and speed for detecting the incipient damage and damage location. This incipiently-damaged roller was investigated in detail and monitored by further running to determine the damage severity and to understand the surface damage propagation process by applying the AE techniques. The conventional AE parameters and AE signal features were studied, and their relation with the AE source locator hit count rate were correlated. The results demonstrated the successful use of the AE measurement unit, which is principally, consists of the AE data analyzer and the AE source locator as a new system for detecting incipient damage produced by fatigue. Moreover, the system is able to forecast the position of the damage in the roller, capable of providing an indication of the severity of damage i.e. damage size, and thus it could allow the user to monitor the rate of further degradation of the rolling elements.     

声发射监测切屑状态的可行性研究

金属切削过程中产生丰富的声发射。用声发射技术监测切屑状态是一个很有潜力的新方法。本文通过实验研究了车削时切屑状态和声发射信号间的相互关系,结果表明：1.声发射DC包络信号脉冲能准确反映断屑情况;2.声发射加权计数率波形和包络信号均值能反映切屑形状和异常切屑状态;3.不同类型切屑的形成过程具有不同的声发射信号波形。     

Analysis of acoustic emission in precision and high-efficiency grinding technology

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.     

刀具磨损监测中信号特征值的提取与聚类分析

声发射是近年刀具监测研究中采用的新技术之一,本文用包络分析法求取刀具磨损中声发射信号的包络线,用其时序模型参数作为特征值,采用神经网络对刀具磨损状态进行分析,试验表明效果良好。     

基于小波分析的声发射源定位技术

声发射全波形采集技术为基于波形分析的声源定位方法提供了可能。在板状构件中声波的传播模式较为复杂,且不同模式的波到达时间和波速均不相同,从而带来了声源定位误差。将时频幅度分析方法引入声发射源定位技术：从接收到的信号中提取出某一频率的柔性波随时间变化的规律,在理论分析的基础上证明,这个分离信号的最大幅值点所对应的时间就是该频率柔性波群速度的到达时间。根据这个到达时间,以及实际测量出的群速度就可以实现声发射源更精确的定位,试验结果也证明了这种方法的可靠性。     

Acoustic Emission Method for Testing Oil and Gas Tanks

Results of practical hydraulic tests of railway tanks owned by Altaivagon Corporation by the method of acoustic emission (AE) are given. A new technique for localization of AE signals and an appropriate software package have been developed to detect with a high certainty both internal and penetrating flaws in tanks under a load of 0.5 atm. A technique for estimating the hazard presented by the flaws in railway tanks based on detection of AE signals is discussed.     

加工过程刀具破损的声发射传感监测新技术

主要介绍一种适合加工过程刀具破损的声发射传感监测新技术,论述了新型传感器的结构、工作原理及信号处理方法。同时还介绍了适合自动化加工过程的新型刀具破损实时监控系统及其应用效果。     

加工过程刀具破损监测的声发射传感新技术

主要介绍一种适合加工过程刀具破损监测的声发射传感新技术,论述了新型传感器的结构、工作原理及信号处理方法。同时还介绍了适合自动化加工过程的新型刀具破损实时监控系统及其应用效果。     

复合绝缘子压接质量监测仪的研制

复合绝缘子越来越广泛地应用于输电线路中，但其压接过程中的质量一直没有有效的方法进行监测。由于复合材料在变形过程中会出现声发射现象，并且随着变形或损伤的程度不同，其声发射信号的特征有所不同．分析这些特征可以对压接过程中绝缘子的压接质量进行判断根据此原理，构建了复合绝缘子的压接质量监测仪器，并且重点描述了系统软、硬件设计中的关键问题现场测试表明：基于声发射技术的监测仪在复合绝缘子压接质量判别上有着良好的效果。     

基于中值滤波-SVD和EMD的声发射信号特征提取

针对随机噪声和脉冲干扰对经验模态分解(EMD)质量的影响,提出中值滤波和奇异值分解(SVD)联合降噪方法,并将其与EMD分解相结合形成一种新的声发射(AE)信号特征提取方法.首先对原始AE信号进行中值滤波,去除幅值较大的异常值;其次对去除异常值的信号序列进行相空间重构和SVD分解,并针对难以确定重构阶数这一问题,提出奇异值能量差分谱概念,利用谱峰的较大值位置来确定重构阶数,以进一步降噪;最后对降噪信号进行EMD分解,以本征模态函数(IMF)的能量占比作为表征各损伤信号的特征向量.数值仿真和5层胶合板损伤的实测数据表明,该方法不仅能够滤除噪声干扰,提高EMD分解的时效性和准确性,而且能够有效地提取出胶合板AE信号特征,对其损伤类型进行有效地识别.     

A comparative experimental study on the diagnostic and prognostic capabilities of acoustics emission,vibration and spectrometric oil analysis for spur gears

Prognosis of gear life using the acoustic emission (AE) technique is relatively new in condition monitoring of rotating machinery. This paper describes an experimental investigation on spur gears in which natural pitting was allowed to occur. Throughout the test period, AE, vibration and spectrometric oil samples were monitored continuously in order to correlate and compare these techniques to natural life degradation of the gears. It was observed that based on the analysis of root mean square (rms) levels only the AE technique was more sensitive in detecting and monitoring pitting than either the vibration or spectrometric oil analysis (SOA) techniques. It is concluded that as AE exhibited a direct relationship with pitting progression, it offers the opportunity for prognosis.     

液体雾化状态的声发射检测

为检测液体雾化状态,基于声发射检测技术,通过采集雾化液体撞击挡板产生的声发射信号,结合功率谱分析、小波分析和重标极差分析,得到雾化液体撞击挡板产生声信号的机理和特征,获得表征液体雾化状态的特征声信号尺度(J1尺度)。根据特征信号尺度能量分率与液体雾化状态间的规律性变化关系,提出雾化质量的判断方法,即液体雾化质量随特征信号尺度能量分率的增大而提高,当特征信号尺度能量分率快速上升时,液体进入充分雾化状态。判断方法得到照相法的验证。利用声发射检测发现液体雾化质量随轴向距离增大而提高,与事实相符。由此获得一种快速、实时、便捷和安全的液体雾化状态检测方法,其可用于雾化机理研究、喷嘴设计选型和工业生产监控。     

A method of functional invariants in problems of strength assessment based on acoustic emission

A new technique is developed to estimate the dynamics of developing acoustic emission (AE) processes on the basis of phenomenological models and experimental data through detection of a disturbance of the Poisson distribution of AE pulses that indicates the onset of development of a structural fracture process. This approach has some advantages due to processing of amplitude information.     

基于光纤光栅阵列和MVDR算法的声发射定位

基于光纤光栅(FBG)传感器网络构建了声发射检测系统,并提出了最小方差无失真响应(MVDR)的声发射源定位方法。构建的系统由7个FBG传感器组成传感器线阵列,采用未经平坦的放大自发辐射(ASE)光源边缘滤波实现信号解调。利用Shannon小波变换从频散复杂的声发射信号中提取窄带信号,并基于MVDR算法扫描整个监测区域获取空间谱。根据空间谱函数计算输出值,并将计算的输出值作为像素值。最后,通过提取空间谱中的最大值的坐标确定声发射源的位置。在LY12铝合金板上进行了实验验证。结果表明,该方法在400mm×400mm的区域内,声发射定位的最大误差为9.4mm,平均误差为7.2mm,耗时小于3s。该系统具有较高的实时性和定位精度,是一种声发射源定位的新方法。     

Acoustic-emission testing of solebars with boxlike cross sections

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.     

A probabilistic neural network applied in monitoring tool wear in the end milling operation via acoustic emission and cutting power signals

Tool condition monitoring, which is very important in machining, has improved over the past 20 years. Several process variables that are active in the cutting region, such as cutting forces, vibrations, acoustic emission (AE), noise, temperature, and surface finish, are influenced by the state of the cutting tool and the conditions of the material removal process. However, controlling these process variables to ensure adequate responses, particularly on an individual basis, is a highly complex task. The combination of AE and cutting power signals serves to indicate the improved response. In this study, a new parameter based on AE signal energy (frequency range between 100 and 300 kHz) was introduced to improve response. Tool wear in end milling was measured in each step, based on cutting power and AE signals. The wear conditions were then classified as good or bad, the signal parameters were extracted, and the probabilistic neural network was applied. The mean and skewness of cutting power and the root mean square of the power spectral density of AE showed sensitivity and were applied with about 91% accuracy. The combination of cutting power and AE with the signal energy parameter can definitely be applied in a tool wear-monitoring system.     

A study of the tribological behaviour of piston ring/cylinder liner interaction in diesel engines using acoustic emission

The novel use of non-intrusive acoustic emission (AE) measurements to provide information pertaining to the interaction between piston rings and cylinder liners in a range of diesel engines is investigated in this paper. In doing so, this technique is shown to offer a new method of investigation into this important interface in engine operation.AE generated during normal engine operation is known to consist of contributions from a number of different sources such as injector and valve activity. A recent finding has been the identification of AE signals associated with the ring/liner interface which presents the opportunity for in-service monitoring. This work discusses the possible AE source mechanisms, such as asperity contact, lubricant flow and/or blowby, through reference to a number of tests on motored and in-service small HSDI diesel engines and large, 2-stroke, marine diesel engines. The influence of various factors such as engine speed, load and lubrication is considered.     

Acoustic emission method for research and control of friction pairs

One of the new physical methods that provides much information about the processes going on in a friction contact zone in real time is acoustic emission (AE). Basic experimental results of AE in friction are presented and analysed. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surfaces in real time, sometimes about intensity of wear, changing of wear and friction regimes and so on. The influence of sliding velocity, load, roughness and some physical and mechanical properties of the body on the parameters of AE are also given. Some attention to the practical implementation of these techniques for control of capability for work of friction pairs in real conditions are given. Modern methods and devices enable condition monitoring of sliding and rolling bearings.     

储罐的声发射在线检测技术与研究进展

根据承压和常压储罐的声发射检测与评价技术的研究成果 ,以及综合分析不同发展阶段的有关文献 ,介绍了在用储罐结构完整性检测与综合评估的意义 ,分析其合理性和难度 ,并对这种动态检测技术在评价储罐结构完整性方面的研究进展作了较全面的评述。