声发射技术在球罐检测中的应用

球罐的定期检验中,无损检测是其最重要的部分。本文系统分析了球罐的破裂形式,介绍了利用声发射检测的原理、仪器以及应用,详细讨论了利用声发射检测,再用磁粉检测和超声波检测进行复验的方法,对在用球罐进行无损检测的特点,说明了该方法的科学性和有效性。     

声发射技术在压力容器检测中的应用

介绍了声发射技术的原理、历史与发展情况、与其它无损检测手段相比的优点,并在此基础上对声发射技术具体应用作了简单说明。     

声发射技术在压力容器无损检测中的应用

压力容器大量应用在工业部门的生产及人民的生活。文章概述了压力容器的定义及分类,对压力容器的安全和检测做了简单说明。通过对声发射检测技术的说明,结合压力容器提出了压力容器声发射检测技术的程序。并重点介绍了声发技术及其在压力容器检测中的国内外应用进展。     

声发射技术在复合材料中的应用及研究进展

本文介绍了声发射的发展史和当前国内外声发射技术在复合材料方面的应用及发展现状，最后介绍了声发射技术应用于检测复合材料飞轮的损伤与断裂的研究情况。     

声发射技术在石油设备检测中的应用

声发射技术作为一种动态无损检测技术,以其动态特性、整体性、实时性、高效性和经济性等特点,在压力容器的制造质量验证、在线监测上被广泛应用。我国已制定并发布了与此相配套的检测评定标准。应用声发射检测技术与应力测定两种方法对加氢精制预反应器进行检验与评定,结果表明采用新检测及评价技术与常规检验技术相结合的方法,对容器进行全面安全评定,特别是超期服役的容器,是一种安全、可行的方法。     

声发射技术在化工过程中的应用

在简要介绍声发射技术原理、测量手段与分析分析方法的基础上,系统回顾了被动声发射技术在化工过程中对于物理化学变化以及设备状态监控的广泛应用,对声发射技术在流程工业中各个单元操作以及设备监控等各个方面的应用进行了综述。总结表明,声发射技术适用于各种恶劣的工业环境,能够实时在线、准确地实现流程工业中关键过程参数的检测,具有广阔的工业应用前景;相比于传统的检测手段,声发射技术具有更为广阔的工业应用前景。     

声发射检测技术在球罐检验中的应用

运用声发射检测技术对某空气球罐进行整体检测,在不开罐的情况下判断球罐的安全状况。     

声发射技术在液化气储罐检测中的应用

简单介绍了声发射检测技术的基本原理和特点,通过100m^3LPG储罐声发射检测的应用实例,说明了声发射检测的实施过程和结论分析,因其具有简捷、经济、灵敏度高,又能检测“动态”缺陷等特点,已发展成为金属压力容器检测和安全评定的主要无损检测方法之一。     

基于声发射技术的垂直管气液两相流动检测方法

声发射（AE）作为一种无损检测手段,用于气液两相流的测量具有非侵入式、测量不破坏被测管道及流场分布,信号强、灵敏度高等优点。利用声发射技术在河北大学垂直管气液两相流管道上进行了大量实验,运用现代信息数据处理方法对气液两相流垂直管道流型特征参数进行了提取。分析结果表明利用声发射手段提取出的流型特征参数可以反映出典型流型下的动力学特征。垂直管道中,泡状流、弹状流、环状流以及过渡状态下的乳沫状流在时域和频域信号中有着明显区别,小波能量和小波包分解后的信息熵的值也存在较大的差异性,从另一角度验证了在不同流型下两相流体在管道内部不同的运动状态,利用模式识别的思想,对垂直管4种典型流型进行了流型识别,取得了较好的效果,研究结果表明声发射技术可以作为一种技术手段用于气液两相流流动的检测。     

Mechanical characterization and damage assessment of thick adhesives for wind turbine blades using acoustic emission and digital image correlation techniques

Adhesives play a key role in the structural integrity of the Wind Turbine Blades as they are one of the main load carrying materials. A deep knowledge of the adhesives' mechanical behaviour in terms of failure mechanisms and damage processes enhances the attempt to optimize the blade design. Therefore, a comprehensive experimental programme was performed in order to determine the static mechanical properties of the adhesives. Ultimate tensile strength, ultimate compression strength, ultimate shear strength and the elastic properties of the adhesive specimens were determined through tensile and compression tests on dogbone specimens and single-lap bonded joints. The Acoustic Emission (AE) technique was used to relate the acoustic activity in the specimens to their damage state. More specifically, a frequency-based methodology, analysing the AE data, was used for the identification of the different damage mechanisms into the material during the loading. In addition, Digital Image Correlation technique, as a full-field technique, was used to measure displacements and deformations.     

Radial variations in fracture and acoustic emission of a thermic graphite electrode

For an extruded electrode graphite, grain orientation increases and porosity decreases with increasing radial distance from the centre of the log. Radial variation in grain orientation is produced during the extrusion stage of manufacture. The radial porosity gradient may be influenced partly by orientation of grains and also by the impregnation and baking stages of manufacture. Dynamic elastic modulus, flexural strength and critical stress intensity factor increase with distance from the centre of the log; these trends are related to the radial porosity gradient. Fracture toughness and the total number of acoustic emissions at fracture, σ_AE, are insensitive to graphite microstructure. Fracture of the graphite is non-linear and deviations from linear elastic fracture mechanics increase with distance from the centre of the log, a trend which is related to the radial porosity gradient. An empirical correlation between a non-ideal fracture parameter and σ_AE is demonstrated for the electrode graphite and three nuclear graphites.     

用声发射监测陶瓷材料的热震损伤

介绍了声发射技术的基本原理,用声发射技术监测了莫来石－钛酸铝陶瓷材料急冷时热震损伤强度衰减及裂纹的扩展过程,结果表明：由热应力引起的微裂纹稳态扩展和失稳扩展的声发射特性与该试样热震损伤后的残余强度变化趋势是一致的。     

Use of acoustic emission in the analysis of polypropylene failure caused by photodegradation

Photodegradation is among the most frequent causes for the low performance of polypropylene (PP) products during service. This type of failure has been investigated extensively throughout the years using conventional methods including infrared spectroscopy and molar mass measurements. The use of acoustic emission, conversely, is not a common technique to evaluate polymer behavior, even though showed to be very useful to detect and locate damage during loading, contributing to the understanding and, hence, to the prevention of failure. In this investigation, injection molded tensile bars were exposed to the ultraviolet radiation in the laboratory for periods of up to 35 weeks and then characterized by Fourier transform infrared spectroscopy, X-ray diffraction, tensile properties, and scanning electron microscopy. During tensile testing, the acoustic emission technique was applied to monitor parameters like intensity of hits, events, and energy released during deformation. The results confirmed the high efficiency of hindered amines light stabilizers to inhibit chemical degradation of PP and the high sensitivity of the neat polymer toward UV exposure. The several steps of polymer failure were detected by acoustic emission, being a very important tool to understand the differences in mechanical behavior of the types of samples under investigation. It showed the beginning of the failure process as well as significant events that occurred during the test, such as the formation of shear bands, cracking, and material fracture. These observations, combined with the traditional degradation monitoring procedures, allowed a good understanding of the effect of UV radiation on PP failure mechanism. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46943.     

Presentation of a novel sensor based on acoustic emission in injection molding

Injection molding is the most important process to produce plastic parts. Because of increasing complexity of the plastic parts and the aim to reach zero‐defect production it is a must to control the dynamic injection molding process. Therefore information from the inside of the mold, measured with sensors, is necessary. State of the art is to implement wired mold cavity pressure sensors as well as wired cavity temperature sensors. This article presents a novel wireless measurement setup which uses structure borne sound as transport medium. The sound is generated by an acoustic actor which is activated by the passing flow front at certain predetermined positions in the cavity (or cavities). Beside the mechanical setup of the sensor proof of concept measurements with a prototype setup are shown in this article. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

池内水沸腾状态的声发射测量

采用声发射技术,结合频域和时域分析手段,研究了池内水沸腾过程中声信号变化与沸腾状态转变的对应关系。结果表明,当过热度为5℃时,沸腾由自然对流状态转变为核态沸腾状态,此时声信号能量、标准偏差和平均绝对偏差值均达到极值点;当过热度为30℃时,沸腾由核态沸腾状态转变为过渡沸腾状态,此时声信号能量、标准偏差和平均绝对偏差值开始出现剧烈的波动。与此同时,随过热度的增加,沸腾过程中声信号主频出现两次明显的阶跃性下降,分别对应于沸腾状态转变为核态沸腾和过渡沸腾。因此,声信号主频的阶跃性变化可作为沸腾状态转变的判据。与该领域的其他工作相比,不仅考察了自然对流状态和核态沸腾状态,还考察了核态沸腾向过渡沸腾的转变过程,同时提出了沸腾状态转变的判据。与传统方法相比,该法相对简单准确,具有灵敏度高、非侵入式、实时在线的优点。     

气固流化床中声发生机理及在工业装置中的应用

利用声测量技术,结合频谱分析,建立了颗粒碰撞的声波频率模型,可定量描述声波主频随颗粒粒径、弹性模量和密度的变化规律.通过改变流化颗粒的粒径、弹性模量参数和密度,发现声波主频与频率模型计算值之间的最大偏差为8.3%,说明声波主频可以代表颗粒在壁面的碰撞频率.讨论了热态和冷态条件下声波主频之间变化规律,通过对弹性模量参数的校正,声测量技术可以用于预测工业装置中物料的平均粒径变化,并将该模型应用于线性低密度聚乙烯、高密度聚乙烯和双峰聚乙烯工业生产装置中的平均粒径测量,发现与传统的取样筛分方法所得测量结果十分接近.同时,发现当系统产生聚合物颗粒结块时,声波主频将急剧降低,声波频谱的能量分布将明显集中增大,这可作为判断流化床稳定运行的一个判据.     

Chemical degradation and failure analyses by acoustic emission of PP/EOC blends exposed to ultraviolet radiation

In this work, acoustic emission was used to investigate the effects of ultraviolet radiation on the mechanical behavior of blends of polypropylene (PP) with ethylene-octene copolymer (EOC) containing photo stabilizers. Together with traditional techniques, like infrared spectroscopy and microscopy, the data obtained from acoustic emission helped the understanding of the failure caused by photodegradation and the influence of the stabilizing additives. Parameters like number and intensity of hits, released energy and acoustic events were recorded and related to the estate of the degradation and to the stress-strain behavior. The results confirmed the high sensitivity of PP/EOC blends to ultraviolet and the better performance of stabilized compounds, especially when hindered amine light stabilizers (HALS) were present. Acoustic emission experiments showed that in stabilized samples the crack propagation took place over a larger time interval, releasing more energy during failure and, hence, postponing the final fracture, from a few seconds for the neat blend to more than 500 seconds for the samples with 0.5% HALS.     

Monitoring by acoustic emission the mechanical behavior of polystyrene submitted to stress cracking at different temperatures

Environmental stress cracking (ESC) is one of the main phenomena that limit the use of polymers, being responsible for an expressive number of premature failures in service. This occurs when mechanical loading is combined with a certain kind of chemical agent, causing surface cracks and, eventually, catastrophic failure. This issue is not widely reported in the literature, and the usual procedures for investigation involve conventional mechanical testing. Alternative tools, such as, the technique of acoustic emission (AE) to monitor the stages of fracture, are rarely used. In this work, injection molded polystyrene were submitted to stress cracking conditions, using two types of active fluids and different exposure temperatures (25, 40, and 55°C). The AE technique was applied simultaneously with the mechanical testing to monitor parameters like intensity of the hits and energy released during the deformation and fracture. The results showed that the failure by ESC was related to the fluid interaction with the polymer and was very dependent on the exposure temperature. The use of acoustic emission technique was very useful to differentiate the effects of the various exposure conditions and to explain certain fracture characteristics observed by visual inspection and by scanning electron microscopy.