Acoustic monitoring of gas emissions from the seafloor. Part II

Aabortion ---n.故障｀失灵｀失事abortive----v.失败abruption n 裂断｀中断。

断路absolute adj 绝对的｀纯粹的absolute sensitivity 绝对灵敏度absolute value 绝对值absorb 吸收`减震absorbance 吸收absorb dose 吸收计量absorbent 吸声材料，吸收体。

吸收性的。

Abutment joint 平接缝`对接缝。

对接。

AC yoke demagnetization 交流磁轭去磁，交流磁轭退磁AC yoke magnetization 交流磁轭磁化。

accept n 接受acceptable defect level 缺陷合格等级。

Acceptable emergency dose 容许的事故计量。

acceptable quality level(AQC)指验收等级，象指验收表准。

acceptance 接收，验收。

认可，肯定Acceptance certificate 验收证明书Acceptance criterion 验收准则` 验收Accessory device 辅助装置Accessory equipment 附属设备Accident 偶然事故，偶然损伤。

Accident condition 事故情况Accident error 偶然错误。

Accident prevention 安全措施Accidental exposure 偶然曝光Accidental radiation injury偶然辐射伤害。

Accumulate dose 总剂量，累计剂量。

Accumulator battery 蓄电池Accumulator cell 蓄电池Acetic acid 醋酸，乙酸。

ACDS（acoustic crack detection system）声裂纹检测系统，声裂纹检测装置，声裂纹检测仪。

第32卷 第4期Vol.32, No.42013年7月 Applied Acoustics July, 20132013-05-07收稿; 2013-05-20定稿*国家自然科学基金重点项目(10834010)、面上项目(11074268)和863课题(2006AA06Z413)作者简介: 何世堂 (1958- ), 男, 湖南平江人, 研究员, 博士生导师, 研究方向: 声表面波传感器、声表面波滤波器组、声表面波低插损滤波器及其在移动通信中的应用。

王文 (1976- ), 男, 研究员。

刘久玲 (1976- ), 女, 副研究员。

刘明华 (1978- ), 男, 副研究员。

李顺洲(1953-), 男, 副研究员。

†通讯作者: 何世堂, E-mail : heshitang@纪念应崇福院士诞辰95周年声表面波气体传感器研究进展*何世堂†王 文 刘久玲 刘明华 李顺洲（中国科学院声学研究所 北京 100190）摘要 基于声表面波技术的气体传感器包括采用敏感膜和结合气相色谱两种方式。

比较而言，采用敏感膜的声表面波气体传感器体积小、功耗低，适应小型化毒气报警器的发展要求，但可检测的气体种类少、灵敏度低、存在交叉干扰问题；声表面波与气相色谱联用的气体分析仪灵敏度高、可检测气体种类多、很好地解决交叉干扰问题，特别适合于复杂大气背景条件下的气体成分分析。

本文从传感器响应机理分析与物理功能结构两方面出发介绍了两类声表面波气体传感器的研究进展情况。

关键词 声表面波，气体传感器，敏感膜，气相色谱，灵敏度 中图分类号：O429文献标识码：A文章编号：1000-310X(2013)04-0252-11Research progress of surface acoustic wave based gas sensorsHE Shitang WANG Wen LIU Jiuling LIU Minghua LI Shunzhou(Institute of Acoustics , Chinese Academy of Sciences , Beijing 100190, China )Abstract Two approaches are used for gas sensing of the surface acoustic wave (SAW) based gas sensor, one is using the sensitive film coated onto the SAW device directly, interacting with the target specifics by absorbing; the other way is joint detection using the naked SAW sensor and gas chromatography (GC). The first one is characterized by small size, low power in the practical application, and it adapts to the development of miniaturization poison gas sensor requirements. However, it still suffers from some problems as low sensitivity, few detectable gas types and crossed-interference. It is fortunate that these problems can be solved just right by the joint detection using the naked SAW sensor and GC, the method is especially suitable for the gas composition analysis in the complicated atmosphere background. This paper reviews the development of the SAW gas sensor using the two detection methods.Key words Surface acoustic wave, Gas sensor, Sensitive film, Gas chromatography, Sensitivity第32卷第4期何世堂等:声表面波气体传感器研究进展2531 引言声表面波（Surface acoustic wave，SAW）是在压电材料上淀积叉指电极通过压电效应所激发的沿基片表面传播的一种表面声波，对表面扰动的物理、化学或者其他机械参量相当敏感，由此可实现各种具有高灵敏度的传感器。

现代电子技术Modern Electronics Technique2022年7月1日第45卷第13期Jul.2022Vol.45No.13压力容器气体泄漏中WOA⁃VMD与SVM 联合检测方法李鹏1，2，3，常思婕1，2，杨佳康1，2（1.南京信息工程大学江苏省气象探测与信息处理重点实验室，江苏南京210044；2.南京信息工程大学江苏省气象传感网技术工程中心，江苏南京210044；3.南京信息工程大学滨江学院，江苏无锡214105）摘要：从声信号特征分析的角度，提出一种引入鲸鱼算法的变分模态分解（WOA⁃VMD ）和支持向量机的气体泄漏故障诊断新方法。

首先，引入鲸鱼算法应用于变分模态分解，对参数α和K 进行全局寻优，得到最优()α,K 组合，并将优化后的变分模态分解方法应用于时频分析；然后，提取23个可以用来表征气体泄漏信号的时域、频域及时频域特征，构成了特征参数矩阵输入支持向量机；最后，选择识别率最高的特征组合作为支持向量机的输入矩阵，并对气体泄漏情况进行识别。

经实验分析：提出的引入鲸鱼算法优化后的VMD 方法能够有效地自适应获取最优参数组，且该方法在抗模态混叠和抗噪声干扰方面具有明显优点；利用优化后的VMD 方法及其他时、频域分析方法对压力容器气体泄漏声波信号进行特征提取，选取最优的特征组合输入支持向量机，得到泄漏与否判别准确率高达99.18%，有助于对后续泄漏源定位及实时监测系统开发的进一步研究。

关键词：气体泄漏检测；压力容器泄漏；变分模态分解；鲸鱼优化算法；时频分析；气体泄漏识别；参数寻优；特征提取中图分类号：TN06⁃34；TP391.4文献标识码：A文章编号：1004⁃373X （2022）13⁃0104⁃07WOA⁃VMD and SVM combined detection method for gas leakage in pressure vesselsLI Peng 1，2，3，CHANG Sijie 1，2，YANG Jiakang 1，2（1.Jiangsu Key Laboratory of Meteorological Observation and Information Processing ，Nanjing University of Information Science and Technology ，Nanjing 210044，China ；2.Jiangsu Provincial Meteorological Sensing Network Technology Engineering Center ，Nanjing University of Information Science and Technology ，Nanjing 210044，China ；3.Binjiang College of Nanjing University of Information Science and Technology ，Wuxi 214105，China ）Abstract ：A new gas leakage fault diagnosis method based on the variational mode decomposition optimized by whale optimization algorithm （WOA ⁃VMD ）and the support vector machine （SVM ）is proposed in the perspective of acoustic signal feature analysis.The whale optimization algorithm （WOA ）is introduced to the VMD.The parameters αand K are subjected toglobal optimization to obtain an optimal ()α,K combination.The optimized VMD method is applied to time⁃frequency analysis.And then ，23time⁃domain ，frequency⁃domain and time⁃frequency domain features that can be used to characterize gas leakage signals are extracted to form a feature parameter matrix ，which is then input to the SVM.The feature combination with the highest recognition rate is selected as the input matrix of the SVM ，which is used to identify the gas leakage.The experimental analysis shows that the proposed VMD method optimized by the WOA can adaptively obtain the optimal parameter set effectively ，and hasobvious advantages of anti ⁃modal aliasing and anti ⁃noise interference.The optimized VMD method and other time ⁃domain and frequency ⁃domain analysis methods are used to extract the acoustic signal features of the gas leakage of pressure vessels.The optimal feature combination are selected and input into the SVM ，and the obtained accuracy of judgement whether there is a leakage or not is as high as 99.18%，which is helpful for the subsequent location of leakage sources and the further research on the real⁃time monitoring systems.Keywords ：gas leak detection ；pressure vessel leakage ；VMD ；WOA ；time⁃frequency analysis ；gas leakage recognition ；parameter optimization ；feature extractionDOI ：10.16652/j.issn.1004⁃373x.2022.13.020引用格式：李鹏，常思婕，杨佳康.压力容器气体泄漏中WOA⁃VMD 与SVM 联合检测方法[J].现代电子技术，2022，45（13）：104⁃110.收稿日期：2021⁃11⁃03修回日期：2021⁃11⁃22基金项目：江苏省重点研发计划社会发展项目（BE2015692）；无锡市社会发展科技示范工程项目（N20191008）104第13期0引言以压力容器为载体的化工产品在人类日常生活中得到广泛应用，但由于制造、保管和运输过程中操作不当，极有可能泄漏并引发安全事故，这不仅会给国家带来巨大的经济损失，还会破坏泄漏现场的生态环境，甚至危及周围人们的生命安全。

1.B ackgroundAcoustic emission occurs when most materials deform and break, but the acoustic emission signal strength of many materials is so weak that it cannot be heard directly by the human ear and needs to be detected with the help of sensitive electronic instruments. The technology of detecting, recording, and analyzing acoustic emission signals with instruments and inferring the acoustic emission source by using acoustic emission signals is called acoustic emission technology. Acoustic emission instruments are known as stethoscopes for materials.After entering the 21st century, with the rapid development of computer technology and communication technology, the application of acoustic emission technology is more extensive and can complete more complex detection content.2.T heoretical foundationAE is a naturally occurring phenomenon within materials and the term AE is used to define the transient elastic waves that result from a sudden strain energy release within a material due to the occurrence of micro-structural changes. If enough energy is released, audible sounds are produced. Acoustic emission in the proper sense covers the audible frequencies up into the high ultrasonic range.Figure 23.12 shows the operating principles of the acoustic emission test method. The component is subjected to an applied elastic stress; usuallyjust below the design load limit. When cracks and voids exist in materials, the stress levels immediately ahead of the defect are several times higher than the surrounding material. This is because cracks act as a stress raiser. Any plastic yielding and micro-cracking that occurs ahead of the defect owing to the stress concentration effect can generate acoustic stress waves before any significant damage growth. The waves are generated by the transient release of strain energy owing to micro-cracking. The waves are detected using sensitive acoustic transducers located at the surface. Several transducers are placed over the test surface to determine the damage location. Certain defects have a characteristic sound frequency value and this is used to determine the type of damage present in the material. For example, delaminations in carbon–epoxy composites have a characteristic frequency of about 100 kHz whereas damaged fibres emit sound at around 400 kHz.Acoustic emission has several advantages, including rapid inspection of large components and the capability to determine the location and type of damage. The downside is that the component must be further damaged to generate the acoustic emission signal.3.E ngineering applicationAt present, acoustic emission technology, as a mature non-destructive testing method, has been widely used in many fields, mainly including the following aspects:Material test:material performance test, fracture test, fatigue test, corrosion monitoring and friction test, etc.Civil engineering: inspection of buildings, bridges, cranes, tunnels, dams, continuous monitoring of the generation and development of cracks in cement structures, etc.We will explain one of these applications in detail:Identification and Analysis of Acoustic Emission Signal of Pressure Pipeline Leakage:The acoustic emission test system of pressure pipeline leakage is as follows,1-sensor;2-preamplifier;3-acoustic emission instrument;4-pressure pipeline;5-leak pointPlace two sensors on both sides of the leak point, first collect the signal during normal operation of the pipeline without leakage, and then open the leakage valve to simulate the pipeline leakage. After the signal is stable, collect the signal when there is a leakage, so as to obtain the normal operation and leakage acoustic emission signals.The left picture is the signal when the pipeline is operating normally, and the right picture is the signal when the pipeline is leaking. It can be clearly seen from the two time-domain waveform diagrams whether a leak has occurred.For further quantitative analysis, the experiment will be performed in the following two aspects:①Keep the sensor position unchanged and change the pressure in the pipeline.① Maintain pipeline pressure and a certain leakage state, and change the distribution of sensor spacing.The experimental results are as follows:①The rule of signal as pressure changeAs the pressure increases, the intensity of the signal from the acoustic emission sensor increases linearly. When the pressure increases to a certain extent, the slope decreases, but still changes linearly.①The rule of signal as distance changeAs the propagation distance increases, the total energy and signal strengthof the acoustic emission signal decreases.4.C onclusion and outlookAfter entering the 21st century, with the rapid development of computer technology and communication technology, the application of acoustic emission detection technology is more extensive, and it can complete more complex detection content. At present, extensive research and exploration have been carried out in the diagnosis of various materials processing and the manufacture of acoustic emission equipment. However, the research on acoustic emission detection and safety evaluation on large cranes is still a relatively new subject, which needs the research results of previous researchers. On the basis of further exploration.。

Vehicle gearbox fault diagnosis using noisemeasurementsSameh M. Metwalley, Nabil Hammad, Shawki A. Abouel-SeoudFaculty of Engineering, Helwan University, Cairo, Egypt.Abstractmeasurement is one of many technologies for health monitoring and diagnosis of rotating machines such as gearboxes. Although significant research has been undertaken in understanding the potential of noise measurement in monitoring gearboxes this has been solely applied on any types of gears (spur, helical, ..etc.). The condition monitoring of a lab-scale, single stage, gearbox, represents the vehicle real gearbox, using non-destructive inspection methodology and the processing of the acquired waveform with advanced signal processing techniques is the aim of the present work. Acoustic emission was utilized for this purpose. The experimental setup and the instrumentation are present in detail. Emphasis is given on the signal processing of the acquired noise measurement signal in order to extract conventional as well as novel parameters potential diagnostic value from the monitoring waveform.The evolution of selected parameters/features versus test time is provided, evaluated and the parameters with most interesting diagnostic behavior are highlighted. The present work also reports the results concluded by long term (~ 6.0 h) experiments to a defected gear system, with a transverse cuts ranged from 0.75 mm to 3.0 mm to simulate the tooth crack. Different parameters, related by the analysis of the recording signals coming from acoustic emission are presented and their diagnostic value is discussed for the development of a condition monitoring system.Copyright © 2011 International Energy and Environment Foundation - All rights reserved.Keywords: Diagnostic, Geared system, Sound pressure level, Stationary signal, Faulty gear, Measuring devices, Condition of gear, Monitoring, Maintenance action.1. IntroductionAcoustic emission is defined as the range of phenomena that results in the generation of structure-borne and fluid-borne (liquid, gas) propagating waves due to the rapid release of energy from localised sources within and/or on the surface of a material. The application of the acoustic emission technology in research and industry is well-documented. In relation to gearboxes, a few investigators have assessed the application of acoustic emission technology for diagnostic and prognostic purposes. Others applied acoustic emission in detecting bending fatigue on spur gears and noted that acoustic emission is more sensitive to crack propagation than vibration and stiffness measurements. Again, AE was found to be more sensitive to the scale of surface damage than vibration analysis [1-3].In automotive gearboxes and power drive trains in general, gear damage detection is often very critical and can lead to increased safety in vehicle, aviation and in industry as well. Thus the interest for their periodic non-destructive inspection and/or on line health monitoring is growing and effective diagnostic techniques and methodologies are the objective of extensiveresearch efforts over the last 50 years. Few research teams have published experimental data coming from long-term testing to see the effect of natural gear pitting mostly upon vibration recordings. In [4, 5], some excellent experimental work at GRC/NASA and published interesting results from extensive gear testing at a special test-rig utilizing vibration and oil debris measurements. With the clear goal to improve the performance of the current helicopter gearbox health monitoring systems, they have tested gears at high shaft speed for multi-hour periods (up to 250 h) and correlated special features extracted from the vibration recordings with the Fedebris mass accumulated during the tests.The interest for applications of acoustic emission for condition monitoring in rotating machinery is relatively new and has grown significantly over the last decade. Acoustic emission in rotating machinery is defined as elastic waves generated by the interaction of two media in motion, i.e., a pair of gears.Sources of acoustic emission in rotating machinery include asperities contact, cyclic fatigue, friction,material loss, cavitations, leakage, etc. Acoustic emission technique has drawn attention as it offers some advantages over classical vibration monitoring. First of all, as acoustic emission is a non-directional technique, one acoustic emission sensor is sufficient in contrast to vibration monitoring which may require information from three axes. Since acoustic emission is produced at microscopic level it is highly sensitive and offers opportunities for identifying defects at an earlier stage when compared to other condition monitoring techniques. As acoustic emission mainly defects high-frequency elastic waves, it is not affected by structural resonances and typical mechanical background noise (under 20 kHz). In [6],acoustic emission to spur gears in a gearbox test rig has been applied. It is simulated pits of constant depth but variable size and acoustic emission parameters such as energy, amplitude and counts were monitored during the test. Acoustic emission was proved superior over vibration data on early detection of small defects in gears. Also, acoustic emission technique in condition monitoring of test-rig gearboxes has been applied, while vibration methods was used for comparative purposes by placing accelerometers on the gearbox casing [7, 8]. The influence of oil temperature and the oil film thickness on acoustic emission activity and on acoustic emission RMS varied with time as the gearbox reached a stabilized temperature and the variation acoustic emission activity RMS could be as much as 33%.The effect of oil temperature on the acoustic emission was discussed in [9, 10] and concluded that the source of acoustic emission mechanism that produced the gear mesh bursts was from asperities contact. Moreover, some interesting observations on acoustic emission activity due to misalignment and natural pitting, where the acoustic emission technique is applicable for monitoring gear damage.Researchers in the field have focused mainly on advanced signal processing techniques applied on acoustic recordings coming mainly from artificial gear defects in short tests rather than including gear pitting damage in multi-hour testing. However, the condition monitoring of a lab-scale, single stage,gearbox, represents the vehicle real gearbox, using non-destructive inspection methodology and the processing of the acquired waveform with advanced signal processing techniques is the aim of the present work.2. Stationary signal data analysisThere are numerous signal processing techniques in the literature for fault diagnostics ofmechanical systems. Case-dependent knowledge and investigation are required to select appropriate signal processing tools among a number of possibilities. The most common waveform data in condition monitoring are vibration signals and acoustic emissions. Other waveform data are ultrasonic signals,motor current, partial discharge, etc. In the literature, there are two main categories of stationary waveform data analysis; time-domain analysis and frequency-domain analysis.3. Time-domain analysisTime-domain analysis is directly based on the time waveform itself. Traditional time-domain analysis calculates characteristic features from time waveform signals as descriptive statistics such as mean, peak, peak-to-peak interval, standard deviation, crest factor and high order statistics (root mean square, skewness, kurtosis, etc.). These features are usually called time-domain features. A popular time-domain analysis approach is Time Synchronous Average (TSA). The idea of TSA is to use the ensemble average of the raw signal over a number of evolutions in an attempt to remove or reduce noise and effects from other sources to enhance the signal components of interest.More advanced approaches of time-domain analysis apply time series models to waveform data. The main idea of time series modelling is to fit the waveform data to a parametric time model and extract features based on this parametric model. The popular models used in the literature are the Auto Regressive (AR) model and the Auto Regressive Moving Average (ARMA) model [11].In this paper, only high order statistic of root mean square (RMS) is used. This feature is usually called time-domain features. RMS is a kind of average of signal, for discrete signals, the RMS value is definedas:4. Frequency-domain analysisFrequency-domain analysis is based on the transformed signal in frequency domain. The advantage of frequency–domain analysis over time-domain analysis is its ability to easily identify and isolate certain frequency components of interest. The most widely used conventional analysis is the spectrum analysis by mean of fast Fourier transform (FFT). The main idea of spectrum analysis is to either look at the whole spectrum or look closely at certain frequency components of interest and thus extract features from the signal [12].5. Constant percentage bandwidth (CPB)The basic choice to be made is between constant absolute bandwidth and constant proportional(percentage) bandwidth where the absolute bandwidth is a fixed percentage of the tuned centre frequency. Constant percentage bandwidth gives uniform resolution on a linear frequency scale, and this for example, gives equal resolution and separation of harmonically related components and this will facilitate detection of a harmonic pattern. However, the linear frequency scale automatically gives a restriction of the useful frequency range to (at the most)two decades.It is worth paying particular attention to two special classes of constant percentage bandwidth filter, viz.octave and third octave filters since these are widely used, in particular for acoustic measurements. The former have a bandwidth such that the upper limiting frequency of the pass band is always twice the lower limited frequency, resulting in the band width of 70.0%.6. Measuring system and test procedureFigure 1 shows the experimental setup used for the gearbox testing. The gearbox consists of two helical gears with a module of 2 mm, pressure angle 20°, which have 64 and 26 teeth with 40 mm face width.The axes of the gears are supported by two ball bearings each. The entire system is settled in an oil basin in order to ensure proper lubrication. The gearbox is powered by an electric motor and consumes its power on a hydraulic disc brake, while the speed is measured by photo electric probe. Bruel & Kjaer(B&K) portable and multi-channel PULSE type 3560-B-X05 (Figure 2) with condenser 1/2- microphone and preamplifier type 4189A-021 was positioned in the center of gearbox front casing away from the casing and the ground by 1.0 m and 0.50 m respectively [13]. The B&K PULSE labshop is the measurement software type 7700 is used to analyse the results (Figure 3). In terms of various parameters evolution during the test –from a representative test on a gear system with a cut of root thickness to simulate the tooth crack (Figure 4) will be presented and detailed in this study. Many tests were conducted on the same configuration yield similar parameters behaviour. Small cracks were made artificially with wire electrical discharge machining at the root of gear of one tooth to create a stress concentration which eventually led to a propagating crack. The crack depths are ranged from 0.75 mm to 3.0 mm with thickness of almost 0.5 mm. Recordings every 15 min were acquired and a total of 24 recordings (~ 6.0 h of test duration) were resulted until the termination of the test. This type of test was preferred in order to have the opportunity to monitor bath damage modes, i.e., the natural crack propagation. Damage is assured by increasing the test period to the point of where the remaining metal in the tooth area has enough stress to be in the plastic deformation region. Careful monitoring of the SPLresponses reveals some subtle and increasing changes in responses. When the gear tooth is brought under load, all the response are seen declining slightly over initial few hours, or 'break-in period'. Break-in period is followed by a long period with little or no change in the responses, 'or stable period'. Finally,often several hours prior to failure, one generally sees the responses decrease during the 'divergence period [14].Figure 1. Experimental setup Figure 2. Bruel & Kjaer (B&K) portable andmulti-channel PULSEFigure 3. The B&K PULSE labshop Figure 4. Gear tooth crackFive gear wheels with one pinion whose details mentioned in Table 1 have been used. One was a new wheel and was assumed to be free from defects (g o). In the other four gear wheels, defects were created using EDM in order to keep the size of the defect under control. The details of the various defects are depicted in Table 2 and its view is shown in Figure 4. The size of cracks is a little bigger than one can encounter in the practical situation. The sound pressure level signal from the microphone mounted on front of the test structure was taken, after allowing initial running of the system for sometime.Table 1. Gear and pinion wheels specificationsTable 2. Details of gear wheels various defectsAt crack size (g4), Table 2, recordings every 15 min were acquired and a total of 24 recordings (~ 6.0 h of test duration) were resulted until the termination of the test. This type of test was preferred in order to have the opportunity to monitor bath damage modes, i.e., the natural crack propagation. Damage is assured by increasing the test period to the point of where the remaining metal in the tooth area has enough stress to be in the plastic deformation region. Careful monitoring of the SPL responses reveals some subtle and increasing changes in responses.7. Results and discussionIn Figure 5, where the speed is 400 rpm, and load is 10 Nm for healthy gear, the sound pressure level(SPL) measured at a location of 1.0 m away from the gearbox face in time domain (Figure 5a) and in frequency domain (Figure 5b). This indicates high levels in the frequency ranges of 200 Hz-300 Hz, 400Hz-500 Hz and 600Hz-700 Hz (Figure 5b), while the levels of the remaining frequency are lower and almost constant. The influence of the load on the measured SPLs at speed of 400 rpm is presented in Figure 6, where the 1/3-octave SPL is increased with the increase of the load dispite some small discrepancies exsited in the 1/3-octaves up to 63 Hz (Figure 6b). This may be attributed to the influnce of gear meshing frequencies, rotating shafts frequencies and structure rigidity resonance frequencies.In Figure 7, where the speed is 400 rpm, and load is 10 Nm for faulty gear, the sound pressure level(SPL) measured at a location of 1.0 m away from the gearbox face in time domain (Figure 7a) and in frequency domain (Figure 7b). The whole spectrum levels are higher when compared with those presentin Figure 5b, particularly towards the higher harmonics of tooth-mesh of the output gear, indicating crack. Furthermore, for healthy gears (Figure 5b), the averaged signal is normally dominated by tooth meshing harmonics modulation by the rotation of the gear shaft. When a localized tooth defect, such as tooth crack (g4) of dimension of 3.0 x 0.5 x 40, the engagement of the cracked tooth will induces an impulsive change with comparatively low energy to the gear mesh signal. This can produce some higher shaft-order modulations and may excite structure resonance.The influence of the crack size on the measured SPLs at speed of 400 rpm and load 10 Nm is presented in Figure 8, where the 1/3-octave SPL is increased with the increase of the crack sizes stated in Table 2 dispite some small discrepancies exsited in the 1/3-octaves up to 63 Hz (Figure 6b).Figure 5. Sound pressure level spectra: (a) time history of sound pressure level; (b) frequencydomain of sound pressure levelFigure 6. 1/3-Octave sound pressure level spectra: (a) 1/3-octave sound pressure level; and (b)1/3-octave sound pressure levelFigure 7. Sound pressure level spectra: (a) time history of sound pressure level; and (b)frequency domain of sound pressure levelFigure 8. 1/3-Octave sound pressure level spectra: (a) 1/3-octave sound pressure level; and (b)1/3-octave sound pressure levelTo highlight the noise signal components generated by crack damage only, the influence of the regular sound pressure levels (SPL) components are to be removed for obtaining the residual SPL signal. When there is no crack in the gear, the obtained noise signal can be considered to be regular signals. Thus, if the sound pressure signals with 0% crack has been selected as a reference signal and remove it from each set of cracked gear SPL signals, the information contained in the remaining part is supposed to be only related to the gear crack. The aforementioned equation (1) for RMS is applied to the residual signal,where their results are shown in Figure 9. The influence of load and crack size on the RMS SPL averages are present in Figure 9a and b respectively. It is clearly seen that the SPL in terms of RMS value increased as the increase of load output gear tooth crack size. This significant increase indicates the deterioration in condition.However, when analyzing the noise signal measured from the single-stage gearbox structure in frequency-domain (Figure 10), firstly, each gear's shaft rotating frequency and meshing frequency are calculated. Table 3 tabulates them at motor speed of 400 rpm and load of 2.5 Nm, where their shaft rotating frequencies, ƒpr and ƒgr and meshing frequencies, ƒpm and ƒgm are listed. The spectrum of healthy gearbox is shown in Figure 10a which can be considered to represent the new condition, while Figure 10b represents the faulty gear at crack size (g4) with the dimension of 3.0 x 0.5 x 40 mm. It is found that the spectra are dominated entirely by these frequencies as shown by the arrows. The other significant components in the spectra are an inter-modulation sideband with the same spacing from the first tooth-mesh harmonic as that of the ghost frequency from the fundamental tooth-meshing frequency. Some sidebands are presented but at a relatively low SPL levels.Table 3. Gearbox shafts frequencies at motor speed of 400 rpm and load of 2.5 NFigure 9. RMS sound pressure level: (a) influence of load; and (b) influence of crack dimensionFigure 10. Locations of tooth meshing and shaft rotation frequencies: (a) healthy gear; and (b)faulty gear (g4), 3.0 x 0.5 x 40 mmSamples from SPL responses at speed of 400 rpm, load 15 NM and 330 min for faulty gear with crack dimension of 3.0 x 0.5 x 40 mm in terms of time history and frequency domain are shown in Figure 11a and b respectively, while Figure 12a and b show the 1/3-octave RMS averages for different testing time up to 6.0 hours. The evaluation of RMS average parameter with respect of testing time ranged from 0.0 min to 360 min (6.0 hours) is depicted in Figure 13. To assist the more accurate observation of this parameter evaluation during the range of testing time, a magnification was seen in the Figure 13, where the first transition period is obtained at the end of testing time near 135 min, while the second transition period is observed from 135 to 360 min. These transition periods are important and possess diagnostic value as they can be used to define and characterize critical changes of the gears damage accumulation and evaluation.Figure 11. Sound pressure level spectra: (a) time history (g4), 3.0 x 0.5 x 40 mm; and (b)frequency domain (g4), 3.0 x 0.5 x 40 mmFigure 12. 1/3-Octave sound pressure level spectra: (a) 1/3-octave sound pressure level; and (b)1/3-octave sound pressure levelFigure 13. Relationship between RMS of SPL and testing time8. Conclusion1- The experimental methodology capability developed in this work could be utilized for diagnostic regime. Furthermore, the obvious periodical impulses caused by the cracked tooth appear in time history,frequency domain and in 1.3-octave band averages signals as the crack level increases, these carry diagnostic information which is important for extracting features of tooth crack damage.2- The FFT technique and the high order statistic of RMS reflect in the Sound pressure level (SPL)responses of the gearbox. This can be an effective way to carry out the predictive maintenance regime and consequently to save money and look promising.3- The identification of gearbox noise in terms of SPL is introduced. When applied to thegearbox, the method resulted in an accurate account of the state of the gear, even, when applied to real data taken from the gear test. The results look promising. Moreover, the proposed noise in terms of sound pressure level (SPL) signature methodology has to be tested on the other test rig also. RMS average value analysis could be a good indicator for early detection and characterization of faults.4- In order to study the development of damage in artificially induced cracks in the gearbox, multi-hour tests were conducted and recordings were acquired using noise in terms of SPL monitoring, where the RMS average was calculated. In the recordings, the transitions in the RMS values with the recording time were highlighted suggesting critical changes in the operation of the gearbox.References[1] Singh A, Houser DR. and Vijayakar S. "Detecting gear tooth breakage using acoustic emission: a feasibility and sensor placement study" J Mech Design Trans. ASME 1999;121(4):587–93, 1999.[2] Miyachika K., Zheng Y. and Tsubokura K. "Acoustic Emission of bending fatigue process of super car burized spur gear teeth" Progress in Acoustic Emission XI. Anonymous. The Japanese Society for NDI; 2002. pp. 304 310, 2002.[3] Singh, A., Houser, D.R. and Vijayakar, S. "Detecting gear tooth breakage using acoustic emission:a feasibility and sensor placement study" Journal of Mechanical Design 21(1999) pp. 587–593,1999.[4] Tandon N. and Mata S. "Detection of defects in gears by acoustic emission" J. Acoustic. Emission 1999;17(1–2):23–7.1999.[5] Kramberger, J., Sraml, M., Glodez, S. Flasker, J. and Potrc, I."Computational model for the analysis of bending fatigue in gears", Computers and structures 82 (23-26), pp 2261-2269, 2004.[6] Loutas, T. H., Sotiriades, G.,Kalaitzoglou, I. and KOstopoulos, V."Condition monitoring ofa single-stage gearbox with artificially induced gear cracks utilizing on-line vibration and acoustic emission measurements" Applied Acoustics 70, pp. 1148-1159, 2009.[7] Tan,CK., Irving, P. and Mba, D. "A comparative experimental study on the diagnostic and prognostic capabilities of acoustic emission, vibration and spectrometric oil analysis for spur gears" Mechanical System signal Process, 21(1), pp. 208-233, 2007.[8] Toutountzakis, T., Tan, C. K. and Mba, D. "Application of acoustic emission to seeded gear fault detection" NDT&E Int. 2004;37, pp. 1-10, 2004.[9] Tan, C. K. and Mba, D. "Identification of the acoustic emission source during a comparative study on diagnosis of a spur gearbox" Tribology Int. 2005;38, pp. 469-480, 2005.[10] Eftekharnejad, B. and Mba, D. "Seeded fault detection on helical gears with acoustic. Emission "Applied Acostic 70, pp. 547-555, 2009.[11] Abouel-seoud, S. A., Hammad, N., Abd-elhalim, N., Mohamed, E. and Abdel-hady, M. "Vehicle Gearbox Condition Monitoring Using Vibration Signatural Analysis" SAE Paper No. 2008-01-1654, 2008.[12] Yuan, X. and Cai, L. "Variable amplitude Fourier series with its application in gearbox diagnosis-Part II: Experimental and application" Mechanical Systems and Signal Processing 19, pp. 1067-1081, 2005.[13] Rebbechi, B., Howard, C. and Hasen, C."Active control of gearbox vibration" ACTIVE 99, Fort Lauderdale, Florda USA, December 02-04, 1999.[14] Mille, R.K. and McIntire, P. "Acoustic Emission Testing, vol. 5, second ed" Non- destructiveTesting Handbook, American Society for Non-destructive Testing, 1987, pp. 275–310,1987.基于噪声测量的车辆变速箱故障诊断摘要噪声测量的方法是众多对旋转机械的健康监测和诊断的技术之一，比如变速箱的监测和诊断。

绿色星球读后感600字英语作文The Green Planet: An Exploration of Earth's Most Remarkable Ecosystem.Sir David Attenborough's latest documentary series, "The Green Planet," is a visually stunning and thought-provoking exploration of Earth's most vital ecosystem: the rainforest. Spanning five episodes, the series delves into the intricate relationships between the rainforest's diverse flora and fauna, showcasing the incredible adaptations and resilience of life in this remarkable habitat.Attenborough's trademark narration weaves a captivating tale of survival and interconnectedness, as he guides us through the rainforest's various layers, from the towering canopy to the teeming forest floor. From the smallest insects to the largest mammals, each organism plays a crucial role in maintaining the rainforest's fragile balance.The opening episode, "The World Above," introduces us to the rainforest's most iconic inhabitants: the giant trees that form the canopy. These towering behemoths create a dense overhead layer that filters sunlight, creating an ideal environment for a multitude of plant and animal species. The canopy is home to a vast array of epiphytes, such as orchids and bromeliads, which have adapted to life high above the ground by drawing nutrients from the air and rain.The second episode, "Tropical Treasures," explores the extraordinary diversity of life found in the rainforest's understory. Here, a plethora of plants and animals compete for light and resources, leading to an array of ingenious adaptations. From the camouflage of stick insects to the mimicry of poison dart frogs, the understory is a testament to the power of evolution in driving survival."Jungles Under Attack," the third episode, confronts the urgent threat facing rainforests worldwide: deforestation. Attenborough highlights the devastatingconsequences of human activities, such as logging and agriculture, which are destroying these vital ecosystems at an alarming rate. The episode emphasizes the interconnectedness of life on Earth, demonstrating how the loss of rainforests not only affects the species thatinhabit them but also has far-reaching implications for the planet's climate and biodiversity.The fourth episode, "Rainforest Symphony," celebrates the incredible symphony of sounds that fills the rainforest. From the chorus of birds to the rhythmic beat of insects, Attenborough reveals how sound plays a vital role in communication, courtship, and territorial defense among rainforest species. The episode highlights the importanceof preserving the rainforest's acoustic environment and the detrimental effects of noise pollution.The final episode, "The Edge of Life," explores the fringes of the rainforest, where it meets other ecosystems such as rivers, savannas, and oceans. These transitional zones are equally rich in biodiversity and provide unique habitats for a wide range of species. The episodeunderscores the importance of protecting the integrity of these interconnected ecosystems and their role in maintaining the planet's ecological balance.Throughout the series, Attenborough highlights the crucial role that rainforests play in regulating theEarth's climate. These vast ecosystems absorb immense amounts of carbon dioxide, helping to mitigate the effects of greenhouse gas emissions. They also play a vital role in the water cycle, releasing moisture into the atmosphere and helping to distribute rainfall across the globe."The Green Planet" is not merely a nature documentary; it is a powerful call to action. Attenborough urges viewers to recognize the importance of rainforests and to take steps to protect them. He emphasizes the need for sustainable practices, the reduction of our carbon footprint, and the restoration of degraded forest areas.By showcasing the incredible beauty, diversity, and importance of rainforests, "The Green Planet" serves as a timely reminder of our responsibility to protect thesevital ecosystems for the benefit of both present and future generations. It is a must-watch for anyone who cares about the future of our planet.。

气体绝缘开关设备局部放电特高频在线监测技术及应用李兴旺;卢启付;吕鸿;王宇;王流火【摘要】分析了各种气体绝缘开关(gas insulated switchgear,GIS)局部放电检测方法,认为特高频(ultra high fre-quency,UHF)法抗干扰能力较强,检测效率较高,可实现在线监测、故障模式识别及定位.以一起UHF在线监测系统发现的GIS设备缺陷为例,分析并总结运行经验.运行经验表明,时连续性的局部放电信号要重点关注,应监测24 h局部放电的发展情况,必要时利用便携式设备进行复测,排除现场干扰,确定故障位置,进行解体处理.通过安装GIS设备局部放电UHF在线监测系统,可发现GIS设备隐患,有效保证电力系统的安全稳定运行.【期刊名称】《广东电力》【年(卷),期】2012(025)006【总页数】5页(P91-95)【关键词】气体绝缘开关;局部放电;特高频法;在线监测【作者】李兴旺;卢启付;吕鸿;王宇;王流火【作者单位】广东电网公司电力科学研究院,广东广州510080;广东电网公司电力科学研究院,广东广州510080;广东电网公司电力科学研究院,广东广州510080;广东电网公司电力科学研究院,广东广州510080;广东电网公司电力科学研究院,广东广州510080【正文语种】中文【中图分类】TM595气体绝缘开关(gas insulated switchgear，GIS)设备具有可靠性高、占地面积小、安全性高等优点，在电力系统中被广泛应用。

进行GIS设备局部放电在线监测可及时发现存在的隐患，是保障电网安全运行的重要措施。

国际大电网委员会(International Council on Large Electric Systems，CIGRE)于1998年统计了1967—1992年投入运行的不同电压等级的GIS设备绝缘故障情况，故障率均超过了GIS设备绝缘所要求的0.1次/年的指标[1-2]，电压等级升高导致绝缘故障率随之增大。

热力透平THERMALTUR BINE第49卷第3期2020年09月VO. 49 No. 3Sep. %0%0文章编号：1672-5549(2020)03-0206-06F 级重型燃气轮机燃烧室热声振荡分析研究和宏宾，陈明敏,刘晓佩（上海电气燃气轮机有限公司，上海200240）摘要：目前，为了进一步适应环境保护的要求，燃气轮机采用了贫预混燃烧技术来降低NO ”的排放。

热声振荡是燃气轮机稳定运行面临的一个主要问题。

采用三维有限元方法对重型燃气轮机热声振荡特性进行建模分析:首先，分析了在无非稳定热源状态下燃烧室的固有频率；其次，加入非稳定热源，分析有热源情况下燃 烧室的频率特性&最后，对比分析了有无非稳定热源的差别。

通过分析发现了影响燃烧室热声振荡的主要模态和传播形式，为后续设计优化提供指导。

关键词：热声振荡；非稳定热源；频率；模态中图分类号：TK472 文献标志码：A dot ： 10. 13707/j. cnki. 31-1922/th. 2020. 03. 008Research on Thermal Acoustic Oscillation of CombustionChamber in F-Class Heavy Duty Gas TurbinesHE Hongbin , CHEN Mingmin , LIU Xiaopei(Shanghai Electric Gas Turbine Co. , Ltd. , Shanghai 200240,China )Abstract : At present , in order to further meet the requirements of environmental protection , the lean premixedcombustion technology is used to reducc NO ” emissions in gas turbines . Thermae acoustic oscillation is a majorproblem in the stable operation of gas turbines . A three-dimensional finite element method was utilized to model andanalyze the thermal acoustic oscillation characteristics of a certain type of gas turbine. First, the natural frequency of thecombustoon chamberwasanaazed wothoutan unsteadNheatreaease.Second , theunsteadNheatreaeasewasaddedto analyze the combustion chamber's frequencc characteristics. Finally, the dbferences between the presencc andabsFncFoounstaba hFatrFaasFwFr comparFd and anaayzFd.Through anaaysos , thFmaon modFsand propagatoonmodFsa o ctongthFthFrmaaacoustocosco a atoon ooacFrtaon combustoon chambFrwFr oound , whoch can proeodF guodancFooroo a owongdFsogn optomozatoon.Key woc I s ： thermal acoustic oscillation ； unsteady heat release ； frequencc ； mode燃烧室是燃气轮机的重要部件，为了保证燃 气轮机能够安全可靠的运行，最为重要的是保证在不同工况下燃烧室都能稳定工作。

八年级英语第七单元作文,保护鲸鱼1. Whales are magnificent creatures that inhabit our oceans.2. They are the largest animals on Earth, with some species growing to over 100 feet long.3. Whales play a crucial role in maintaining the health of marine ecosystems.4. Their movements help mix ocean waters, promoting nutrient circulation.5. Whales also contribute to carbon storage in the ocean.6. Protecting whales is essential for preserving marine biodiversity.7. Many whale species are threatened or endangered due to human activities.8. Commercial whaling has led to significant declines in whale populations.9. Whales are often caught accidentally in fishing gear, leading to injury or death.10. Pollution in the oceans impacts whale health and reproduction.11. Climate change affects the habitats of whales, disrupting their migratory patterns.12. Noise pollution from ships and industrial activities interferes with whale communication.13. Many organizations work diligently to protect whale populations.14. They promote legislation against whaling and habitat destruction.15. You can help by supporting these organizations through donations or volunteering.16. Educating yourself and others about whale conservation is also vital.17. Learning about the different species of whales can deepen our appreciation for them.18. Each species of whale has its unique characteristics and behaviors.19. Humpback whales are famous for their complex songs.20. Blue whales are the largest animals to have ever existed.21. Orcas, or killer whales, are known for their intelligence and social structures.22. Sperm whales have the largest brain of any animal.23. Beluga whales are easily recognized by their white color and vocalizations.24. Protecting whales requires international cooperation and commitment.25. Many countries have enacted laws to protect whales from hunting.26. Marine protected areas can help safeguard their habitats.27. Community involvement in conservation efforts is crucial.28. Beach clean ups can help reduce ocean pollution affecting whales.29. Reducing plastic use is essential for cleaner oceans.30. Supporting sustainable seafood choices can lessen the impact on marine life.31. Awareness campaigns can help inform the public about the plight of whales.32. Documentaries and films can highlight the beauty and intelligence of whales.33. Schools can incorporate whale conservation into their curricula.34. Young people can be powerful advocates for environmental issues.35. Organizing events can raise funds and awareness for whale protection.36. Art can also be a strong medium for promoting whale conservation.37. Participating in wildlife watching can be beneficial if done responsibly.38. These activities can help generate funds for conservation projects.39. Responsible tourism ensures that whales are not disturbed.40. Respecting marine wildlife means observing them froma distance.41. Whale watching tours should follow guidelines to minimize disturbances.42. Learning to identify different whale species can enhance your experience.43. Engaging in citizen science projects can contribute to whale research.44. You can report whale sightings to help track their populations.45. Support for legislation aimed at reducing greenhouse gas emissions is crucial.46. Addressing global warming is essential for preserving whale habitats.47. Many whales are migratory, traveling vast distances each year.48. These journeys can take them through international waters.49. Collaboration between nations is necessary for effective whale protection.50. International treaties like the IWC aim to regulate whaling activities.51. Each whale species has specific conservation needs.52. Research on whale populations can inform better protection strategies.53. By understanding their behavior, we can create safer marine environments.54. Health assessments of whale populations can track the impact of pollutants.55. Technology has improved our understanding of whale communication.56. Acoustic monitoring helps researchers listen to and track whales.57. Many communities depend on healthy whale populations for their livelihoods.58. Indigenous communities have longstanding relationships with whales.59. Respecting these traditions is an integral part of conservation.60. Education and outreach programs can help bridge cultural knowledge.61. The growth of eco tourism has helped raise awareness about whales.62. Sustainable practices in tourism can promote whale conservation.63. The impact of climate change on oceans affects food availability for whales.64. Krill, a primary food source for many whales, is sensitive to temperature changes.65. Protecting the ocean means protecting its inhabitants.66. Public awareness can lead to changes in consumer behavior.67. Reducing our carbon footprint is vital for long term conservation.68. Engaging with local communities can foster supportfor whale protection.69. Collaboration among scientists, governments, and activists is essential.70. Volunteering for local organizations can make a difference.71. Individuals can influence policymakers through advocacy.72. Writing letters and using social media are powerful tools for change.73. Supporting bans on single use plastics can help reduce ocean debris.74. Small lifestyle changes can collectively have a significant impact.75. Recycling helps reduce the amount of waste entering the ocean.76. Education should start at a young age to foster respect for nature.77. Field trips to marine sanctuaries can inspire future conservationists.78. Engaging in discussions about marine conservation can generate interest.79. Schools should promote programs focusing on ocean literacy.80. A healthy ocean supports diverse marine life, including whales.81. Awareness of overfishing is critical for maintaining whale populations.82. Sustainable fishing practices can help protect whale food sources.83. Each individual's actions contribute to a larger movement for change.84. Whale watching can inspire passion for marine conservation.85. Observing these animals in their natural habitat is a profound experience.86. Conservation efforts require time, patience, and dedication.87. Documenting whale sightings can contribute to scientific knowledge.88. An informed public can drive changes in policy and behavior.89. Protecting whales benefits humanity by ensuring healthy oceans.90. Whale conservation is linked to broader environmental issues.91. Healthy oceans contribute to a stable climate and food security.92. We must act now to protect these incredible creatures for future generations.93. Each step taken towards conservation counts.94. Collaboration can lead to innovative solutions for conservation challenges.95. The future of whales relies on our commitment to change.96. We have the responsibility to ensure that whales continue to thrive.97. Knowledge is power when it comes to conservation efforts.98. Working together, we can create a better future for whales.99. Each voice raised for whale protection adds to the chorus of change.100. The beauty of whales can inspire awe and wonder in everyone.101. Together, we can make a difference in the fight for whale conservation.102. Every action counts, no matter how small it seems.103. Raising awareness about whales encourages others to care.104. Protecting whales also means protecting the health of our oceans.105. We are stewards of the Earth and must safeguard its treasures.106. The legacy we leave behind should include thriving ecosystems.107. Let us unite in our efforts to protect whales and our oceans.。

噪音对海洋影响英语作文Title: The Impact of Noise Pollution on the Ocean。

The ocean, a vast expanse of life and mystery, is not immune to the effects of human activity. Among the various forms of pollution it faces, noise pollution stands out as a significant but often overlooked threat. In this essay, we will delve into the detrimental effects of noise pollution on the ocean ecosystem and explore potential solutions to mitigate its impact.Firstly, it is crucial to understand the sources of oceanic noise pollution. Anthropogenic activities such as shipping, construction, offshore drilling, and naval exercises are primary contributors. These activities introduce sounds ranging from low-frequency hums to deafening blasts, disrupting the natural acoustic environment of the ocean. Additionally, the proliferation of maritime transportation has led to an increase in vessel traffic, amplifying noise levels in marine habitats.The consequences of noise pollution on marine life are profound and multifaceted. One of the most affected groupsis marine mammals, particularly cetaceans like whales and dolphins, which rely heavily on sound for communication, navigation, and foraging. Excessive noise can interferewith their ability to echolocate, locate prey, and communicate with conspecifics, leading to disorientation, stress, and even strandings.Furthermore, noise pollution impacts various other marine organisms, including fish, invertebrates, and plankton. Studies have shown that prolonged exposure to anthropogenic noise can disrupt fish behavior, such as feeding and reproduction patterns, ultimately affecting population dynamics. Invertebrates with sensitive auditory structures may suffer from direct physical damage oraltered behavior due to noise-induced stress. Even plankton, the foundation of the marine food web, can experience changes in distribution and abundance in response to noise disturbance.The ecological repercussions of noise pollution extend beyond individual species to entire marine ecosystems. Changes in animal behavior and population dynamics can disrupt trophic interactions, leading to cascading effects throughout the food web. For example, declines in fish populations due to noise disturbance can affect the abundance of their predators, ultimately impacting higher trophic levels, including marine birds and mammals.In addition to ecological impacts, noise pollution poses socio-economic challenges, particularly for coastal communities dependent on marine resources. The disturbance of fish populations and alteration of habitat due to noise pollution can jeopardize livelihoods reliant on fishing and tourism. Furthermore, noise pollution from maritime activities can degrade the quality of recreational experiences, diminishing the aesthetic value of coastal environments.Addressing the issue of oceanic noise pollution requires a multi-faceted approach involving collaboration among governments, industries, scientists, and conservationorganizations. Implementing regulations to limit noise emissions from shipping, offshore construction, and military exercises is essential. This can include measures such as the use of quieter vessel designs, speed restrictions in sensitive areas, and the establishment of marine protected areas where noise levels are controlled.Furthermore, technological innovations can play a crucial role in reducing noise pollution. Advancements in ship design, propulsion systems, and underwater construction techniques can help minimize noise emissions without compromising operational efficiency. Additionally, the development of acoustic monitoring systems can aid in assessing noise levels in the ocean and identifying areas of concern.Education and public awareness are also vital components of mitigating oceanic noise pollution. By raising awareness about the impacts of noise pollution on marine life and ecosystems, individuals can make informed choices and advocate for policy changes. Engaging stakeholders through outreach programs, educationalcampaigns, and citizen science initiatives can foster a sense of stewardship for the ocean and promote collective action towards conservation efforts.In conclusion, noise pollution poses a significant threat to the health and integrity of the ocean ecosystem. Its detrimental effects on marine life, ecological processes, and human well-being underscore the urgent need for concerted action. By implementing regulatory measures, fostering technological innovation, and raising public awareness, we can work towards mitigating the impacts of noise pollution and preserving the acoustic sanctity of the ocean for future generations.。

基于声发射技术的裂缝检测与监测应用综述发布时间：2022-11-07T06:53:48.648Z 来源：《科学与技术》2022年7月第13期作者：郑永来文源潘坦博[导读] 随着基础设施大规模建设高峰期逐渐远去，对于结构安全的关注重点逐渐由建设向运营与养护转移。

在评估构件与结构的健康状况时，采用无损检测技术对裂缝的进行正确检测与监测至关重要。

郑永来文源潘坦博同济大学摘要：随着基础设施大规模建设高峰期逐渐远去，对于结构安全的关注重点逐渐由建设向运营与养护转移。

在评估构件与结构的健康状况时，采用无损检测技术对裂缝的进行正确检测与监测至关重要。

本文将简要介绍无损检测技术中最为常用的技术——声发射技术，其可以应用于混凝土、复合材料、金属、木材与岩石等不同材料，是一项面向未来的、科学可靠的、市场广阔的技术。

关键词：声发射；监测；裂缝1 声发射技术的介绍1.1 声发射现象当固体材料受到超过其机械阻力承受能力的荷载作用时，其内部结构会发生错位与断裂，这个过程伴随着能量的释放，这种能量在介质中以机械波的形式，从损伤部位向周围环境传播，被称为声发射(Acoustic Emissions)。

声发射本质上是指在介质中产生非永久变形的高频应力波的传播，由于其振幅会迅速衰减，因此他们具有瞬态特性。

摩擦接触、冲击、热变形、以及裂缝的形成与扩展都会导致声发射的产生。

1.2声发射监测原理及其系统组成典型的声发射监测布置采用传感元件表面接触的布置方法。

大多数的声发射传感器基于压电效应原理研发，利用某些材料在收到机械应力时会产生电压的原理制作而成。

一般有两类AE传感器，即用于测量所有类型AE波的体声波传感器，及用于测量瑞丽波的表面声波传感器，后者应用较为广泛。

传感器接收到AE信号后通常被预放大，然后使用高速A/D转换器进行采样（理想情况下采样频率应高于1MHZ）。

通过这种方式会记录到两种类型的声发射信号，一种是连续型信号，另一种为突发型信号。

Designation:F1797–98(Reapproved2003)An American National Standard Standard Test Method forAcoustic Emission Testing of Insulated Digger Derricks1This standard is issued under thefixed designation F1797;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1This test method covers a procedure for acoustic emis-sion(AE)testing of insulated digger derricks.1.1.1Equipment Covered—This test method applies to special multipurpose vehicle-mounted machines,commonly known as digger derricks.These machines are primarily designed to dig holes,set poles,and position materials and apparatus.1.1.1.1Insulated type digger derricks may be evaluated with this test method.1.1.1.2Digger derricks,if so equipped to position personnel or equipment,or both,may also be evaluated with this test method in conjunction with Test Method F914.1.1.2Equipment Not Covered—Excluded from this test method are general-purpose cranes designed only for lifting service and machines primarily designed only for digging holes.1.2The AE test method is used to detect and area-locate emission sources.Verification of emission sources may require the use of other nondestructive test(NDT)methods,such as radiography,ultrasonic,magnetic particle,liquid penetrant,and visual inspection.1.3Precaution—This test method requires that external loads be applied to the superstructure of the vehicle under test. During the test,caution must be taken to safeguard personnel and equipment against unexpected failure or instability of the vehicle or components.1.4This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1ASTM Standards:E569Practice for Acoustic Emission Monitoring of Struc-tures During Controlled Stimulation2E610Definitions of Terms Relating to Acoustic Emission2 E650Guide for Mounting Piezoelectric Acoustic Emission Contact Sensors2E750Practice for Characterizing Acoustic Emission Instru-mentation2E976Guide for Determining the Reproducibility of Acous-tic Emission Sensor Response2E1067Practice for Acoustic Emission Examination of Fiberglass Reinforced Plastic Resin(FRP)Tanks/Vessels2 F914Test Method for Acoustic Emission for Insulated Aerial Personnel Devices32.2Other Standards:ASNT Recommended Practice SNT-TC-1A—Personnel Qualification and Certification in Nondestructive Testing4 ANSI A10.31Digger Derricks—Safety Requirements, Definitions,and Specifications5EMI Nomenclature and Specifications for Truck-Mounted Extensible Aerial Devices,Articulating Aerial Devices, Digger-Derricks63.Terminology3.1Definitions:3.1.1acoustic emission,AE—the class of phenomena whereby elastic waves are generated by the rapid release of energy from a localized source or sources within a material,or the transient elastic wave(s)so generated.3.1.1.1Discussion—acoustic emission is the recommended term for general use.Other terms that have been used in AE literature include(1)stress wave emission,(2)microseismic activity,and(3)emission or acoustic emission with other qualifying modifiers.3.1.2amplitude(acoustic emission signal amplitude)—the peak voltage of the largest excursion attained by the signal waveform from an emission event.3.1.3amplitude distribution—a display of the number of acoustic emission events with signals that exceed an arbitrary amplitude as a function of amplitude.1This test method is under the jurisdiction of ASTM Committee F18on Electrical Protective Equipment for Workers and is the direct responsibility of Subcommittee F18.55on Acoustic Emission.Current edition approved Nov.10,1998.Published February1999.Originally published as F1797–st previous edition F1797–97.2Annual Book of ASTM Standards,V ol03.03.3Annual Book of ASTM Standards,V ol10.03.4Available from American Society of Nondestructive Testing,4153Arlingate Plaza,Caller#28518,Columbus,OH43228.5Available from the American National Standards Institute,1430Broadway, New York,NY10018.6Available from the Equipment Manufacturer’s Institute,410N.Michigan Ave., Chicago,IL60611.1Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States. 电子发烧友 电子技术论坛3.1.4attenuation —loss of energy per unit distance,typi-cally measured as loss of signal peak amplitude with unit distance from the source of emission.3.1.5channel —an input to the main AE instrument that accepts a preamplifier output.3.1.6commoned —two or more sensors interconnected such that the sensor outputs are electronically processed by a single channel without differentiation of sensor origin.(syn.teed)3.1.7count ,n —(acoustic emission count)the number of times the acoustic emission signal amplitude exceeds a preset threshold during any selected portion of a test.3.1.8decibel,dB —a reference scale that expresses the logarithmic ratio of a signal peak amplitude to a fixed reference amplitude.Signal peak amplitude ~dB !520log 10A 1A(1)where:A 0=1µV at the sensor output (before amplification),and A 1=peak voltage of the measured acoustic emissionsignal.Acoustic Emission Reference ScaledB Value Voltage At Sensor Output Voltage at Integral Preamp Sensor Output (40dB Gain)01µV 100µV 2010µV 1mV 40100µV 10mV 601mV 100mV8010mV 1V 100100mV10V3.1.9event (acoustic emission event)—a local material change giving rise to acoustic emission.3.1.10event count,N —the number obtained by counting each discerned acoustic emission event once.3.1.11first-hit —a mode of operation of AE monitoring equipment in which an event occurring on one channel willprevent all other channels from processing data for a specified period of time.The channel with a sensor closest to the physical location of the emission source will then be the only channel processing data from that source.3.1.12insulator —any part of the digger derrick such as,but not limited to,any of the extensible boom sections or support-ing structure,made of a material having a high dielectric strength,usually FRP or the equivalent.3.1.13noise —any undesired signal that tends to interfere with the normal reception or processing of the desired signal.3.1.14qualified personnel —personnel who,by possession of a recognized degree,certificate,professional standing,or skill,and who,by knowledge,training,and experience,have demonstrated the ability to deal with problems relating to the subject matter,the work,or the project.3.1.15signal (emission signal)—a signal obtained by detec-tion of one or more acoustic emission events.3.1.16For definitions of other terms in this test method,refer to Definitions E 610and the EMI Nomenclature and Specifications.3.2Definitions of Terms Specific to the Standard:3.2.1auger —the hole-boring tool of the digger.3.2.2authorized person —a qualified person approved and assigned by the user to perform a specific type of duty or duties or to be at a specific location or locations at the job site.3.2.3boom angle indicator —a device that indicates the angle between the boom and a horizontal plane.3.2.4boom pin —the horizontal shaft about which the boom pivots as it is raised or lowered relative to the turntable.3.2.5boom tip sheave —the sheave,located at the tip of a boom,that carries the winch line.3.2.6capacity chart —a chart that indicates the load capac-ity or rated capacity of the digger derrick,and by the choice of the user reflects either the load capacity or the ratedcapacity.FIG.1Insulated Digger DerrickNomenclature3.2.7centerline of rotation—the vertical axis about which the digger derrick rotates.3.2.8critical members—those components,members,or structures in a digger derrick whose failure would cause catastrophic failure of the digger derrick system.3.2.9design stress—the maximum stress at which the com-ponent is designed to operate under conditions of rated capacity.3.2.10digger—the mechanism that drives the auger.3.2.11extension cylinder—the hydraulic cylinder or cylin-ders that extend the boom.3.2.12instability—a condition of a mobile unit in which the sum of the moments tending to overturn the unit is equal to or exceeds the sum of the moments tending to resist overturning.3.2.13intermediate boom(C)7—structural member or members that extend and are located between the upper and lower booms.3.2.14jib—an auxiliary boom that attaches to the upper boom tip to extend the reach of the boom.3.2.15lift cylinder—a hydraulic cylinder that lifts the boom.3.2.16load block—a component consisting of a sheave or sheaves and a hook that is used for multiple parting of the load line.3.2.17load capacity—the maximum load,specified by the manufacturer,that can be lifted by the mobile unit at regular intervals of load radius and boom angle,through the specified ranges of boom elevation,extension,and rotation,with options installed and inclusive of stability requirements.3.2.18load line—the load hoisting line.3.2.19lower boom(D)—the structural member,attached to the turntable,that supports the extensible boom or booms. 3.2.20manufacturer—one who originally constructs the digger derrick.3.2.21model—manufacturer’s designation for digger der-rick specified.3.2.22operator—the person actually engaged in the opera-tion of the digger derrick.3.2.23outrigger cylinder—the hydraulic cylinder that ex-tends the outrigger.3.2.24outriggers(L)—the structural members that are ex-tended or deployed to assist in stabilizing the mobile unit. 3.2.25pedestal(G)—the stationary base of the digger derrick that supports the turntable.3.2.26platform(H)—the optional personnel-carrying com-ponent of a digger derrick,such as a bucket,basket,stand,or equivalent.3.2.27platform pin—the horizontal pin about which the optional platform rotates relative to the boom.3.2.28structural components—those elements of a digger derrick that are subjected to stress during operation.3.2.29turntable(F)—the structure above the rotation bear-ing that supports the booms.3.2.30ultimate strength—for materials that do not have a clearly defined yield strength,the stress level at which failure of a material will occur.3.2.31upper boom(B)—the structural member that extends the farthest,and that supports the boom tip sheave,or the optional platform,or both.3.2.32upper boom tip(A)—the end of the boom farthest from the turntable.4.Summary of Test Method4.1This test method consists of applying a predetermined load to an insulated digger derrick while it is being monitored by sensors that are sensitive to acoustic emissions(AE)caused by active defects.These acoustic emissions can be generated by,but are not limited to,the following:crack nucleation, movement,or propagation in the metal components;or matrix crazing,delamination orfiber breakage of thefiber reinforced plastic(FRP)material,or both.4.2The insulated digger derrick is loaded at a uniform rate until a predetermined load is reached,which is held for a period of time.The load is removed and the cycle is repeated. Acoustic emissions are monitored for the components being evaluated during both cycles,and the data is reviewed.5.Significance and Use5.1This test method permits testing of the major compo-nents of an insulated digger derrick shown in Table1.The test method provides a means of detecting acoustic emissions generated by the rapid release of energy from localized sources within the digger derrick under controlled loading.The energy releases occur during intentional application of a predeter-mined load.These energy releases can be monitored and interpreted by qualified individuals.Acceptance/rejection cri-teria are beyond the scope of this test method.The test may be discontinued at any time to investigate a particular area of concern,or to avoid imminent damage to the digger derrick resulting from the application of the test load.5.2Significant sources of acoustic emission found with this test method shall be evaluated by either more refined acoustic emission test techniques or by other nondestructive methods (visual,liquid penetrant,radiography,ultrasonic,magnetic particle,etc.).Other nondestructive methods may be required in order to precisely locate defects in the digger derrick,and to estimate their size.Additional tests are outside the scope of this test method.7Letters in parentheses refer to the corresponding letters in Table1and Fig.1.TABLE1Insulated Digger Derrick Components That May be Monitored with Acoustic EmissionComponentCorresponding Letter inFig.1Upper Boom Tip A AUpper Boom B A Intermediate Boom(s),if equipped CLower Boom DLower Boom Lift Cylinder Attach Bracket ETurntable FPedestal GOptional Components—if equippedPlatform HPlatform Attachment IJib J AJib Bracket/Cylinder Attach Bracket K A Outriggers LA These components must bemonitored.5.3Defective areas found in digger derricks by this test method should be repaired and retested as appropriate.Repair procedure recommendations are outside the scope of this test method.6.Personnel Qualifications6.1The test method shall be performed by qualified person-nel.Qualification shall be in accordance with an established written program prepared by a person familiar with design, manufacture,and operation of insulated digger derricks.The program shall include an established format of ASNT SNT-TC-1A for training,qualification,and certification of personnel for conducting AE testing.N OTE1—Personnel performing subsequent nondestructive evaluation (visual,liquid penetrant,radiography,ultrasonic,magnetic particle,etc.) on digger derricks should be certified in accordance with ASNT SNT-TC-1A guidelines.6.2Acoustic emission test personnel shall be familiar with the design,manufacture,and operation of insulated digger derricks.Relevant information is contained in ANSI A10.31 and manufacturers’operating and service manuals.7.Acoustic Emission Instrumentation7.1The AE instrument shall be capable of data acquisition from discrete channels using60kHz and150kHz sensors.The number of AE instrument channels shall be determined by the attenuation characteristics of the digger derrick in order to provide coverage of those components identified in Table1. Refer to the description of mandatory instrumentation charac-teristics in Annex A1.N OTE2—Annex A1requires the use of a minimum of eight channels. N OTE3—The sensors used by most testing agencies are resonant at60 kHz for FRP components and150kHz for metal components.Selection of sensors other than these may significantly affect test results.8.Test Preparation8.1Prior to the AE test,a visual evaluation of the digger derrick shall be performed to determine,as far as practical,that the derrick is free from any condition that may prohibit the test or adversely affect the test results.8.2The components to be monitored in an insulated digger derrick shall include,but not be limited to,those specified in Table 1.Additional channels and sensors may be used to supplement the minimum test requirements and improve loca-tion resolution.8.3Position the sensors on the FRP and metal portions of the components to be monitored.The extent of the coverage is determined by the number of sensors used and the attenuation characteristics of the individual components,and can be verified by a simulated AE technique as indicated in Guide E976.Record the amplitude of the simulated AE source at a distance of12in.(304mm)from the sensor as a reference. Continue to move the simulated AE source away from the sensor until the amplitude is no more than15dB less than the reference amplitude.This will establish the maximum effective coverage of the sensor.8.4The mounting of sensors shall be in accordance with Practice E569and E650.The couplant used shall not affect the integrity of the digger derrick.N OTE4—The couplant should be compatible with the digger derrick; not a possible cause of contamination.The couplant should be completely removable from the surface after testing,leaving the original surface intact.9.AE Instrumentation System Performance Check9.1Performance verification shall be made with an AE simulator immediately prior to application of test load.This simulator should be capable of producing a transient elastic wave having an amplitude representative of the AE signals to be recorded.9.2The AE simulator may be gas jet,pencil lead break technique or an electronically induced event or equivalent. 9.3The detected peak amplitude of the simulated event at a fixed distance,typically6to9in.(152to228mm),from each sensor shall not vary more than6dB from the average of all the sensors on the same type material.The detected peak ampli-tude of any sensor shall not exceed90dB to avoid saturation of amplifier(s).10.System Calibration10.1Subject the AE system to a thorough calibration and functional check to verify accurate performance in accordance with the manufacturer’s specification,in conjunction with Practice E750.Perform calibration annually as a minimum in accordance with a written calibration procedure.Include in the calibration,as a minimum:calibration of threshold levels, amplitude measurement circuits,count measurement circuits, AE sensors and load measuring devices.10.2Subject the AE system to a routine performance check, which shall include as a minimum,verification of threshold levels and amplitude measurements.Performance checks should be conducted monthly or after40h of operation, whichever is more frequent.11.Procedure11.1Test the digger derrick in a position such that the components indicated in Table1can be monitored.Ideally,this would be with the insulated boom only extended at an angle of zero degrees(horizontal).Fig.2shows the recommended test positions.The insulated boom test load shall be150%of its maximum rated capacity.11.2Attach the load measuring device to the load applica-tion system,which in turn shall attach to an adequate dead weight or anchor.11.3Loads should be applied to the actual load line used for material handling.The line may run just over the outer sheave and a loading mechanism or stiffer line attached to minimize line stretch.11.4All components of the load application system shall be capable of supporting the test load.11.5Perform the loading sequence as shown in Fig.3. 11.6Platforms should be tested separately in accordance with Test Method F914.11.7If the unit is equipped with a jib,it should be tested separately with booms retracted so as not to require the monitoring of the digger derrick during the jib tests,except for the interface between the jib and derrick.The jib shall be tested in its fully extended position at an angle of0-degrees.Thetestload shall be 150%of its rated capacity.Where applicable the actual loadline shall be used.11.8If the digger derrick is rated with other load ratings or other loading positions that would cause significantlydifferentNotes (Apply To All Tests):(1)Position truck in most favorable stable position,on firm,level ground.(2)Extend outriggers.(3)Refer to manufacturers load charts,operational manuals,and decals before testing.(4)Maintain weights (test loads)within 2ft of the ground at all times.FIG.2Insulated Digger Derrick Recommended Test Positions and TestLoadsFIG.3Acoustic Emission Test Sequence for Insulated DiggerDerrickstresses or potential for defect initiation,then it shall be tested in those positions in addition to the standard position described previously.11.9Pass/Fail Criteria for Acoustic Emission Testing of FRP Components:11.9.1The following acceptance criteria are valid only when using this test method and applied loads remain constant during hold cycles.The following AE responses from moni-toring FRP components constitute acceptance:11.9.1.1Zero events or counts,or both,during the last3min of the second hold,at test load,or11.9.1.2Fewer total events or counts,or both,recorded during the second hold period at test load than the total events or counts,or both,recorded during thefirst hold period(Kaiser effect).A clear reduction in the rate of acoustic activity over both hold periods should also be observed(that is,the slope of events/time or counts/time decreases over the hold periods).11.9.2Acoustic responses outside the previously described parameters are unacceptable to this test method.Suitability for service of FRP components that do not meet this test method must be carefully evaluated.12.Report12.1The report shall be signed and dated by the responsible qualified personnel performing the tests.The information recorded shall be sufficient to permit complete analysis of the results.12.2Test Equipment—Instrument settings shall be included in all reports submitted for the examination.The report shall include,but is not limited to:12.2.1Sensor manufacturer,model number,serial numbers, nominal peak frequency response,methods of sensor attach-ment,and type of couplant.12.2.2Diagram or sketch of sensor locations including a description indicating areas of coverage.12.2.3Description of load application and measured test load sequence.12.2.3.1Identify the type of load application,that is,con-stant load versus time or constant displacement versus time.12.2.3.2Report the variation of load versus time during each of the load hold periods in pounds or percent of full load.12.2.4Permanent data record in the form of charts,graphs or tabulations,or combination thereof.12.2.5Ambient conditions during test,such as wind,tem-perature,rain,etc.12.3Digger Derrick—All submitted reports of the exami-nation shall include,but not be limited to,the following information:12.3.1The digger derrick manufacturer,model,serial num-ber,and year of manufacture.12.3.2General description including rated capacities of the boom,jibs,platforms and other attachments in the positions tested.12.3.3Modifications,changes,repairs and damage or sus-pected damage to the digger derrick.12.4Other Test Information:12.4.1The method used for determination of the test load.12.4.2A description of the test position(s)used,and12.4.3Any additional pertinent information.12.5Any departure from the procedures specified in this test method shall be adequately justified and documented in the test record.13.Precision and Bias13.1Each testing agency has the responsibility of judging the acceptability of its own results.The precision of the results is a function of the procedures,facilities utilized,as well as compliance to the recommended industry state-of-the-art prac-tices.Reproducible analysis determinations by different users can be achieved only with identical facilities and trained conscientious personnel.ANNEX(Mandatory Information)A1.INSTRUMENT PERFORMANCE REQUIREMENTSA1.1Sensors—AE sensors shall be stable over the tem-perature range of use,and shall not exhibit sensitivity changes greater than3dB over this range.Sensors shall be shielded against radio frequency and electromagnetic noise interference through proper shielding practice or differential(anticoinci-dent)element design,or both.Sensors shall have omnidirec-tional response,with variations not exceeding4dB from the peak response.A1.1.1High frequency sensors,used on metal components of the digger derrick,should have the primary resonant frequency at150kHz610kHz.Minimum sensitivity shall be−80dB referred to1V per microbar,or−40dB for integral preamp sensors as determined by face-to-face ultrasonic swept-frequency calibration.AE sensors should not vary in sensitivity more than3dB from the average.A1.1.2Low frequency sensors,used onfiberglass compo-nents of the digger derrick,should have the primary resonant frequency at60kHz610kHz.Minimum sensitivity shall be equivalent or greater than high sensitivity accelerometers designed for use at60kHz.A1.1.3Up to two sensors may be commoned into a single channel.A1.2Signal Cable—The signal cable from sensor to preamplifier shall not exceed6ft(1.8m)in length and shallbeshielded against electromagnetic interference.This require-ment is omitted where the preamplifier is mounted in the sensor housing,or a line-driving(matched impedance)sensor is used. A1.3Preamplifier—The preamplifier may be separate or may be mounted in the sensor housing.For sensors with integral preamplifiers,frequency response characteristics may be confined to a range consistent with the operational fre-quency of the sensor.If the preamplifier is of differential design,a minimum of40dB of common-mode noise rejection shall be provided.Unfiltered frequency response shall not vary more than3dB over the frequency range of20to400kHz,and over the temperature range of use.A1.4Filters—Filters shall be of the band pass or high pass type,and shall provide a minimum of−24dB/octave signal attenuation.Filters may be located in preamplifier or post-preamplifier circuits,or may be integrated into the component design of the sensor,preamplifier,or processor to limit fre-quency response.Filters or integral design characteristics,or both,shall ensure that the principal processing frequency for high frequency sensors is not less than100kHz,and for low frequency sensors,not less than25kHz.A1.5Power-Signal Cable—The cable providing power to the preamplifier and conducting the amplified signal to the main processor shall be shielded against electromagnetic noise. Signal loss shall be no more than1dB per100ft(30.4m)of cable length.Five hundred feet(152m)is the recommended maximum cable length to avoid excessive signal attenuation. Digital or radio transmission of signals is allowed consistent with standard practice in transmitting those signal forms.A1.6Main Amplifiers—The main amplifier,if used,shall have signal response with variations not exceeding3dB over the frequency range of20to400kHz,and temperature range of use.The main amplifier shall have adjustable gain,or an adjustable threshold for event detection and counting.A1.7Main Processor:A1.7.1General—The main processors shall have a mini-mum of eight independent channel inputs for signal processing of events.If mixer(s)are used,first-hit event processing for each channel must be provided.A1.7.1.1Independent processing of counts,events,and amplitude(per event)for each channel is preferred;but as a minimum,two active processing circuits shall process counts and amplitude information from metal andfiberglass channels independently.A1.7.1.2The system shall be capable of processing and storing at least100events/s for limited periods of time.A1.7.2Peak Amplitude Detection—Usable dynamic range shall be a minimum of60dB with5dB resolution over the frequency band of20to400kHz,and the temperature range of use.Not more than2dB variation in peak detection accuracy shall be allowed over the stated temperature range.Amplitude values may be stated in volts or dB,but must be referenced to afixed gain output of the system(sensor or preamp).A1.7.3Source Location—Source location using time differ-ence processing between channels is optional,and may be used where it improves source identification on the structure. However,use of the source location algorithms shall not prohibit processing of individual orfirst-hit sensor information. A1.7.4Signal Outputs and Recording—The processor shall provide as a minimum outputs for permanent recording of: A1.7.4.1Events by channel(events versus time).A1.7.4.2Counts versus time or load for metal channels,A1.7.4.3Counts versus time or load forfiberglass channels, A1.7.4.4Amplitude distribution for metal channels,A1.7.4.5Amplitude distribution forfiberglass channels,and A1.7.4.6Load versus time.N OTE A1.1—The required outputs should be based onfirst hit infor-mation.A1.7.5Load Measuring Device—The load cell or other load measuring device shall be capable of registering the loads applied during testing within its calibration range.The device shall be calibrated in a manner and at intervals recommended by the manufacturer’s specifications.The percent error for loads within the loading range of the load cell and readout shall not exceed61.0%of reading.In load readouts that possess multiple-capacity ranges,the verified loading of each range shall not exceed61.0%of reading.An electronic output of the load measuring device,proportional to applied load,shall be properly conditioned and amplified to match the requirements of the recording device used.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this ers of this standard are expressly advised that determination of the validity of any such patent rights,and the risk of infringement of such rights,are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed everyfive years and if not revised,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards,at the address shown below.This standard is copyrighted by ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959, United States.Individual reprints(single or multiple copies)of this standard may be obtained by contacting ASTM at the above address or at610-832-9585(phone),610-832-9555(fax),or service@(e-mail);or through the ASTM website().。

声学气体探测英语English:Acoustic gas detection is a technique used to identify and quantify gases in a given environment by analyzing the sound waves they produce. This method relies on the unique acoustic signatures generated when gases interact with sound waves. When sound waves pass through a gas, variations in density, temperature, and composition cause changes in the speed and amplitude of the waves. By measuring these changes, it becomes possible to infer the presence and concentration of specific gases. Acoustic gas detectors typically consist of a microphone or sensor to capture sound waves, signal processing hardware to analyze the captured signals, and algorithms to interpret the data and identify the gases present. This approach offers several advantages, including the ability to detect gases over a wide area, even in harsh environments where traditional detection methods may be impractical or unsafe. Additionally, acoustic gas detection is non-intrusive, meaning it does not require physical contact with the gas source, making it suitable for monitoring applications where contamination or interference is a concern.中文翻译:声学气体探测是一种通过分析气体产生的声波来识别和量化给定环境中的气体的技术。

COGas Monitor for one detection point 2Operations Manual1194 Oak Valley Dr, Ste 20, Ann Arbor MI 48108 USAGfG Products for Increased Safety Congratulations on your purchase of a high technology product from GfG – you have made an excellent choice!Our detectors are characterized by reliability, safety, peak performance and economic efficiency. They comply with national and international directives. This manual will help you operate the detector quickly and safely.Please take note of these instructions before putting the device into operation!If you have any questions, please feel free to contact us.GfG Instrumentation, Inc.1194 Oak Valley Drive, Ste 20Ann Arbor, MI 48108 USAPhone: (800) 959-0329 or (734) 769-0573Fax: (734) 769-1888E-mail: ****************Website: Table of Contents Introduction 1 Safety 1 YourFor1PurposeApplicationand2Infra-redPrinciple-DetectionNotes 3 OperationTurning On 3 Function Test 3 Mode 3 DetectionElements 3OperationDisplayandAlarm for Gas Hazards 4 Remote Reset 4 Quick Adjustment - Yellow LED 4 Fault - Red and Yellow LED’s 4 Service 5 Checking and Adjusting Alarm Thresholds 5 Maintenance and Inspection 6 Mounting 6 Accessories 6 Notes for Technical Safety 7 Protection 7 ContactTechnical Data 7313 8GMADiagramConnectionIntroductionForYourSafetyLike any piece of complex equipment, the GMA 313 will do the job itis designed to do only if it is used and serviced in accordance with the manufacturer’s instructions.CAUTION: For safety reasons, this equipment must be operated and serviced by qualified personnel only. Read and understandthe instruction manual completely before operating orservicing this device.The warranties made by GfG with respect to the product are voided if the product is not used and serviced in accordance with the instructions in this manual. Please protect yourself and your employees by following them. The above does not alter statements regarding GfG’s warranties and conditions of sale and delivery.ApplicationandPurposeThe GMA 313 is a compact gas monitor for continuous monitoring ofambient air against carbon dioxide (CO2) hazards. Sensor and controller areintegrated in one casing. Should the CO2 concentration exceed a threshold,the GMA 313 gives an audible and visual warning. In addition to this, a relay is activated.Detectionprinciple-Infra-redThe GMA 313 uses the infra-red detection principle (NDIR) for accurate andreliable measurement of carbon dioxide (CO2). Infra-red light is lead throughthe sensor chamber. The gas from the ambient air enters the sensor chamber by means of diffusion. Carbon dioxide absorbs a part of the light in a narrow spectral region. The light remaining in this spectrum is measured by the detector. The difference between the light emitted and received is proportional to the gas concentration. Water vapor and other gases, which might be in the sensor chamber, do not affect the absorption of light in this spectral region. A special thermostat control eliminates temperature effects.Diffusion inlet IR - SourceSensor chamber Sensor signalIR - LightOptical filterOperational Notes Turning ON Once you have connected the GMA 313 to 110 V main voltage, the detector is turned on. Allow 30 minutes warm-up time. During this time, the yellow LED “F” and the red LED “A” are lit. During the warm-up period the GMA 313 cannot detect an increased CO 2 concentration. Once the warm-up time is completed, the GMA 313 turns to the detection and warning mode automatically.Function test Press button “T” for a short self-test of the gas monitor. Operational andfault LED as well as the buzzer and the alarm relay are shortly activated and checked for their function.Detection mode After the warm-up time the yellow and the red LED (“F” and “A”) go out. The GMA 313 turns to the detection mode automatically. The green LED “ON” lights and indicates, that the GMA 313 now monitors the ambient air continuously for hazards caused by carbon dioxide (CO 2).Display and operation elements“Reset” buttonSensor inlet“Test” button LED “Fault” - yellowLED “Alarm” - redAcoustic alarmAlarm for gas hazards The GMA 313 provides two alarm thresholds: Alarm 1 (low alarm) and Alarm 2 (high alarm). These thresholds are set to standard values. Should the carbon dioxide (CO 2) concentration exceed a threshold, the GMA 313 gives a warning by means of the red alarm-LED and the buzzer. In addition to this, a relay is activated. The difference between alarm 1 and alarm 2 is indicated by pulsed or permanent alarm signals.Alarm 1 is non-latching and goes out automatically, when the gasconcentration has fallen below the threshold, i.e. if there are less than 1.5% Vol. CO 2. Alarm 2 is latching. Once it is triggered, it remains stored, even if the gas concentration has fallen below the setpoint. Alarm 2 must be reset by pressing the reset button “Q”.The buzzer in the GMA 313 can be reset at any time by pressing the reset button “Q”.The alarm relay is activated according to alarm 1 and alarm 2.Remote Reset with GMA 313 EQ (optional)The GMA 313 EQ is a remote alarm and reset unit. For connection of the remote reset GMA 313 EQ the gas monitor must include the component “External Reset”.Quick adjustment - when the yellow LED is lit If the yellow LED is lit, press the button “Q” for approx. 10 seconds to re-adjust the GMA 313. In case the yellow LED should not go out during this time, call for GfG service.Fault - when the red and yellow LEDs are lit In case of a fault, the yellow LED “F” and the red LED “A” at the GMA 313 and the alarm lamp at the remote reset GMA 313 EQ will be lit. A fault message is indicated:• During the warm-up period. If the yellow LED “F” does not go out after this period,the microprocessor or the memory module may be faulty.• In case of overrange.• If the IR source is faulty.In case of a fault, disconnect the GMA 313 from the main voltage for a few seconds. Then re-connect and allow another warm-up period of approx. 30 minutes. Should the unit still indicate a fault, call for GfG service.Alarm Threshold Signal Alarm Storing 1 1.5% Vol. CO2Pulsed alarm Non-latchingl 2 3.0% Vol. CO2Permanent alarm LatchingServiceChecking and adjusting the alarm thresholdsFor checking or adjusting the alarm thresholds, use the calibration adapter tosupply a test gas concentration (1.5 Vol. or 3% Vol.) of carbon dioxide (CO2)to the sensor. Adjustment is done by means of the buttons “T” and “Q”. Before you do any adjustment, make sure that the GMA 313 has been turned onfor at least 4 hours and is operating in the detection mode without any fault indications. Adhere to the following procedure to adjust the alarm thresholds:1. Fix the calibration adapter into the sensor inlet.2. Press button “Q” and keep it pressed, then press button “T” and keep both buttons pressed for approx. 3 seconds. Now the GMA 313 turns to service mode. The yellow LED “F” blinks in short intervals. In this mode the alarm signal from the relay is blocked. The GMA 313 returns automatically to detection mode after approx. 30 minutes, even if you do not do any adjustment.3. Use the calibration adapter to supply a carbon dioxide (CO2) concentration of 3% Vol.for adjustment of alarm threshold 2. Make sure that the flow rate is approx. 0.6 l/minute.4. Purge the sensor with the gas for at least 2 minutes. A permanent acoustic sound indicates that the sensor has adapted to the gas concentration.5. Once the sensor has adapted to the gas concentration, press button “Q” to acceptthe supplied concentration for alarm 2. Should the GMA 313 note a calibration error, the yellow “F” will light for approx. 5 seconds. In this case you should repeat the calibration from point 3. If you do not want to accept the supplied gas concentration, press button “T”.6. The yellow LED “F” blinks slowly, and you may - for a very accurate adjustment - set the alarm 1 threshold (points 7 to 9). Pressing button “T” again overrides the second adjustment, and the GMA 313 returns to detection mode.7. For adjusting the alarm 1 threshold use the calibration adapter and supply aconcentration of 1.5% Vol. carbon dioxide (CO2) to the sensor. Make sure that the flowrate is approx. 0.6 l/minute.8. Purge the sensor with the gas for approx. 2 minutes. A permanent acoustic sound indicates that the sensor has adapted to the gas concentration.9. Once the sensor has adapted to the gas concentration, press button “Q” to acceptthe supplied concentration for alarm 1. Should the GMA 313 note a calibration error, the yellow “F” will light for approx. 5 seconds. In this case you should repeat the calibration from point 7. If you do not want to accept the supplied gas concentration, press button “T”. The GMA 313 returns to detection mode.Maintenance and inspection are measures, which maintain the nominalstatus of the gas monitor and include regular checks and adjustments of the alarm setpoints. In addition to this, the functions of the gas monitor must be checked. Both maintenance and inspection may be done by an expert. The maintenance interval should not exceed 1 year according to BGI 836. In case of repair make sure that only the manufacturer’s genuine spare parts are being used.For deciding on the mounting position you have to know and to consider the ambient conditions, e.g. ventilation, exactly. Do not forget, furthermore, that carbon dioxide is heavier than air. Mount the GMA 313, therefore, approx. 12 inches from the floor. Make sure that the gases reach the sensor even in case of bad ventilation. The sensor inlet must be accessible and free from any obstacles after the installation. The GMA 313 is protected against water and dust (IP54). Additional safety against mechanical damage is provided by the impact protection (optional). The mounting lugs (optional) allow quick and easy wall mounting without having to open the top of the GMA 313.Accessories Part Number GMA 313 EQ External additl’ alarm/reset for complete sets 2313201-1GMA 313 Calibration adapter with tubing 2313203-1Mounting brackets for wall mounting 2313207-1Protective housing includes installation material 2313206-1Maintenance and inspection MountingContact protection The main supply and relay contacts of the GMA 313 provide insulation distances of 3 mm, i.e. they are designed for 110V operational insulation. In case a contact is operated on a contact-critical potential, the contacts closest to it are also considered as contact-critical. According to contact protection the contacts are not considered to be separated safely. The insulation of the secondary circuit from the primary circuit and the relay contacts complies to the requirements for contact protection. Distances of6.5 mm ensure a safe separation. The secondary circuit operates on extra-low safety voltage.Notes for technical safetyTechnical Data8Connection Diagram GMA 313 One detection point, main connection by plug, connection of GMA 313 EQ optional.Cable of 0.5 to 1.5 mm 2, cable gland (PG11) may be adapted to cablediameter by means of a reducer.GfG Instrumentation, Inc.1194 Oak Valley Dr.Suite 20Ann Arbor, MI 48108USAUS/Canada: (800) 959-0329US/Canada Fax: (734) 769-1888International: +1 734 769 0573International Fax: +1 734 769 1888Website: Worldwide Manufacturer of Gas Detection Solutions2013 Rev 2 (06/06/13)。