无须测量声速的声发射源定位方法研究

为消除声速测量偏差给声发射系统带来的定位误差，本文提出一种多探头定位方法。从理论上导出了该方法的线定位和平面定位计算公式，并用AE21C型四通道声发射仪在碳钢管道和平板上以铅笔芯折断产生信号为模拟源进行了实验验证，结果表明用这种新的方法具有较高的定位精度，且定位时只要利用原系统的门槛跨越技术测量各探头接收到信号的时差即可，不必测量传声媒质的声速。     

Method of coupled dipoles for localization of the sources of acoustic emission

A technique for minimizing errors in location of the sources of acoustic emission in bedrock via the use of the method of coupled dipoles is considered. Specific calculations are made to show that, if the system of equations is selected improperly, the method does not have any practical value.     

Locating acoustic emission sources in complex structures using Gaussian processes

A standard technique in the field of non-destructive evaluation is to use acoustic emissions to characterise and locate the damage events that generate them. The location problem is typically posed in terms of the times of flight of the waves and results in an optimisation problem, which can at times be ill-posed. A method is proposed here for learning the relationship between time of flight differences and damage location using data generated by artificially stimulated acoustic emission (AE)—a classic problem of regression. A structure designed to represent a complicated aerospace component was interrogated using a laser to thermoelastically generate AE at multiple points across the structure's surface. Piezoelectric transducers were mounted on the surface of the structure, and the resulting waveforms were recorded. A Gaussian process (GP) with RBF kernels was chosen for regression. Since during AE monitoring not all events can be guaranteed to be detected by all sensors, a GP was trained on data for all possible combinations (subsets) of sensors. The inputs to the GPs were the differences in time of flight between sensors in the set, and the targets were the locations of the source of ultrasonic stimulation. Subsequent (test) data points were located by every possible GP, given the active sensors. It is shown that maps learned on a given structure can generalise effectively to nominally identical structures.     

Identification of sources of acoustic emission on casting flaws in cast parts

Peculiarities of the estimation of the state of sections with casting flaws in cast parts using acoustic-emission (AE) method are considered. The dynamics of variations in AE parameters for developing flaws during mechanical tests is analyzed. The methods for distinguishing useful information of AE signals from the regions of localization of casting flaws are revealed.     

Studying sources of acoustic emission during the cooling of a weld seam with the use of cluster analysis

Acoustic-emission (AE) signals localized during cooling of a weld seam were analyzed. The hazard degree of flaws (faulty fusions, cracks in the root of a weld seam, etc.) was studied using cluster analysis in the parameters of AE signals. Flaws were simulated via introduction of titanium and duralumin inserts into a weld seam. The results of metallographic investigations of specimens with artificial and actual flaws were analyzed. Localization of AE signals was performed for the specimens studied, and a time distribution taking into account the clustering of the total count and energy of AE signals was constructed.     

灌装机灌装精度概率模型与可靠度计算模型

推导出了控制液位定量式灌装机的实际灌装时间与实际灌装量的理论计算公式。描述了实际灌装量随机误差的特性。针对实际存在的各种随机变量对实际灌装量的影响,提出基于灌装量随机误差的灌装精度概念以及灌装精度可靠度概念,并相应建立出灌装精度概率模型与灌装精度可靠度计算模型。     

Utilization of electromagnetic acoustic conversion to estimate microstress in steels

Results of studies on the influence of microstress on the parameters of electromagnetic-acoustic transduction (EMAT) in thermally treated and cold-worked steels are presented. It is shown that in thermally treated steels, except high-alloy corrosion-resistant austenite-martensite steel 1Kh15N5AM3Sh, the amplitude of the EMAT signal decreases linearly with an increase in the microstress. In this situation, the propagation velocity of normal elastic waves also decreases monotonously; this is also the case for 1Kh15N5AM3Sh steel. In pearlitic steel that is cold-worked by drawing, the dependences of the EMAT amplitude and the propagation velocity are linear only at the initial stage of deformation. After that, the parameters of the EMAT are affected most strongly by the phenomena that occur during the drawing: the turning of ferrite and carbide plates and the decrease in the dispersion angle of the axial crystallographic structure.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 26–33.Original Russian Text Copyright © 2004 by Gorkunov, Zadvorkin, Solomein.     

How to estimate the reliability of a weld joint under conditions of cyclic loading according to the results of a nondestructive check

The problem of how to determine the reliability of thin-walled structures as a function of the number of loading cycles and degree of inspection of the weld joints with blind cracklike holes, whose depth and length are independent random values, is solved. The reliability is characterized by the probability of whether the defect sizes belong to the admitted region, whose boundary is determined by the set of the initial sizes of the defects, which rises past the limit state of the predetermined number of loading cycles.     

车削过程异常智能化声发射(AE)监视系统的研究

本文阐述了一种车削过程异常智能化监视系统的。作原理。根据这一原理建立的专家系统型车削过程异常声发射监视装置，有效地提高了识别成功率，降低了误报率。     

声发射技术在起重机无损检测中的现状

对起重机械常规无损检测技术(目视检测、磁粉检测、超声检测、应力测试、振动测试等)和声发射技术进行了比较,归纳了声发射技术在起重机械无损检测中的研究现状,提出了研究的基本思路,讨论了起重机械声发射技术中的几个关键问题,即典型声发射源信号的获取、声发射信号处理技术、声发射源的模式识别。最后,对起重机械声发射检测技术的研究前景进行了展望。     

Using fuzzy sets to estimate the geometric parameters of surface damage

This paper considers the influence of the variable parameters of a surface defect detection algorithm on the result of its operation. A method for estimating the influence of the variable parameters on the recognized geometric characteristics of the surface defect network is proposed. This method is based on representing the basic zones of the skeleton of the surface damage network in the form of compact fuzzy sets in two-dimensional space (fuzzy quasi-points). The set of points of the recognized object obtained for various combinations of the test algorithm parameters is represented in the form of a fuzzy set with a certain membership function. A method for calculating the geometric parameters of the damage network (length and slope) by means of fuzzy geometry is considered, and its use for determining the geometric parameters of the damage network of a continuous casting roller is demonstrated.     

A review of acoustic emission as a biotribological diagnostic tool

ABSTRACT

Acoustic emission (AE) testing has been used in the detection of the onset and progression of mechanical flaws. It has also proven advantageous in the tribological assessment of mechanical systems and human joints as well as for implant condition monitoring. Current modes of diagnosing implant failures are becoming less effective and time consuming calling for the development of a more effective and dynamic diagnostic method. This review aims to provide an overview of the current tribological applications of AE and to highlight how this can be instrumental in the development of a more effective failure diagnosis method. It can be concluded that AE has potential capabilities as a tool for monitoring the tribological phenomenon of artificial joints which would not only allow for a more effective way of diagnosing implant failures but also for diagnosing natural joint diseases such as back pain and arthritis.     

A quantitative model to estimate rail surface failure

This paper is concerned with the formulation of an approximate analytical model describing the total wear on both high and low rails as a function of the angle of attack ψ. The rail life γ(ψ) is obtained in this model as follows as: γ(ψ) = l(ψ?m)²+ nψ? 0.0058 radγ(ψ)=Pψ+qψ ? 0.0058 rad where l,m, n, p and q are constants which can be determined for a specific set of boundary conditions. The results of applying this equation to various values of ψ are compared with field data and good agreement is observed.     

Estimating tool properties on the basis of acoustic emission

Estimation of the operational properties of metal-cutting tools on the basis of acoustic emission is considered.     

民用航空器维修可靠性的模糊综合评价

这里研究民用航空器维修可靠性的模糊综合评价问题。论述了航空器维修可靠性的含义;建立了评价指标体系及评价模型;分析了如何运用模糊数学对航空器维修的可靠性进行综合评价;并给出了评价过程的完整算法。     

TPMS发射模块的强度可靠性设计

利用有限元分析软件对轮胎压力监测系统(Tire Pressure Monitoring System,TPMS)的发射模块进行了强度可靠性设计.具体包括材料选择、产品成型分析、结构强度分析与优化3个方面,再借助振动、冲击和疲劳破坏试验来验证产品的强度可靠性.文中所采用的强度可靠性设计方法也不失为同类产品的一般性设计方法.     

Influence of operational variables in a hydrodynamic bearing on the generation of acoustic emission

Detecting mechanical faults of rotating machines particularly in hydrodynamic bearings has been recognised as important for preventing sudden shut downs. This technical note presents an experimental investigation that is aimed at understanding the influence of operational variables (speed, load, etc) on generation of acoustic emission in a hydrodynamic bearing. It is concluded that the power losses of the bearing are directly correlated with acoustic emission levels.     

Identification of the acoustic emission source during a comparative study on diagnosis of a spur gearbox

Condition monitoring of gears with vibration analysis is well established whilst the application of acoustic emission (AE) to gear defect diagnosis and monitoring is still in its infancy. This paper details results of an experimental programme to ascertain and validate the applicability of AE to seeded gear defect identification. Furthermore, comparisons are made to vibration diagnosis. As a direct consequence of the experimental programme, the relationship between temperature, oil film thickness and AE activity were investigated. It is shown that similar to the lubricant film thickness between non-conforming surfaces under isothermal conditions, AE activity is not influenced by load. Limitations of applying AE to seeded defect identification are presented and it is concluded that the source of AE activity is attributed to asperity contact.     

An investigation of acoustic emission to monitoring flat lapping with non-replenished slurry

Lapping is a precision manufacturing process. However, the material removal rate and surface roughness show significant variation between trials for repeated experiments and, thus, the repeatability of the results depends on the machine operator’s skill. Acoustic emission (AE) seems to be capable of monitoring the process. Therefore, an understanding of AE generation during lapping is important to predict the performance of the grains and hence the lapping results. Based on a theoretical analysis and experimental results collected during flat lapping, the AE signal was investigated for the situation when slurry is supplied without replenishment. The experiments were carried out with a wireless rotating AE sensor mounted in the middle of the lapping plate. Three parameters related to the AE curve are proposed to monitor the process. The influence of process parameters (lapping pressure, velocity, average grain size, concentration of grains in lapping compound and the number of conditioning rings) on the characteristics of the AE curve was investigated.