工程陶瓷磨削过程的声发射在线监测研究进展

工程陶瓷作为典型的硬脆性材料,其加工主要通过超硬精细磨料的精密磨削及研磨实现。在线监测磨削过程从而及时调整工艺参数是保证工件表面质量、提高磨削加工效率的重要途径,声发射凭借灵敏度高、实时响应的特性在磨削过程监测中得到了广泛的应用。本文阐述了声发射技术的基本原理,总结了磨削过程中声发射监测常用的信号分析方法,综述了声发射技术应用于工程陶瓷磨削过程中砂轮磨损与修整监测、磨削烧伤监测、工件表面质量预测及智能磨削智能监控系统构建等领域的国内外研究进展,并结合当前现状与不足对未来声发射技术在磨削加工监测中的应用前景进行了展望,以期推动声发射技术在工程陶瓷磨削监测领域的应用扩展。     

声发射技术监测疲劳损伤探讨

在实验室的高频疲劳试验机上,对紧凑拉伸试样进行疲劳损伤试验,用声发射技术记录声发射参数的变化.使用小波分析识别降噪方法和外触发采集卡(只在裂纹扩展时才采集数据,裂纹闭合时不采集数据)等措施,将各种噪音分离出去,最后只有试样的疲劳损伤裂纹起裂和扩展的声发射波形信号,经处理后获得的疲劳裂纹扩展长度与应力循环次数关系,接近于人工测得的疲劳裂纹扩展长度与应力循环次数关系曲线.     

基于DSP的声发射在线监测系统的研制

声发射信号频率范围宽,要求采样频率高,对其进行在线监测要处理的数据量相当大,对监测系统的信号处理速度和传输速度要求相当高.利用DSP的高速处理能力,把信号的声发射参数提取等初步处理都放在硬件内完成以减少向上位机传输的数据量,从而减少数据传输的时间.论文研究了整个系统的软、硬件设计中的关键问题,并给出了解决方案.     

储油罐声发射在线检测技术研究与应用

由于传统储罐检修中的定周期、盲目开罐可能造成巨大财力物力损失、“坏”罐漏检等问题,近年来国内外出现了睹罐在线检测技术。而声发射技术是目前国内外应用比较多的储油罐底板腐蚀在线检测定性评价技术。本文在声发射在线检测原理基础上,探索出一种实用的储罐声发射信号采集流程。在神经网络的声发射信号模式识别方法的基础上,提出了一种混合式的声发射信号处理方法。本文的研究成果成功应用于储油罐声发射在线检测的现场数据采集和分析处理,对储油罐在线检测技术研究具有一定的指导作用。     

基于空气传播声发射与深度迁移学习的激光粉末床熔融缺陷在线监测

目的 对激光粉末床熔融(LPBF)过程中的缺陷进行缺陷监测机理研究,并开发可靠的现场质量监测方法来指导零件生产过程。方法 使用空气传播声发射(ABAE)技术监测LPBF过程,获取多组变工况LPBF过程中的ABAE信号。通过对LPBF过程进行熔池动态分析及对比缺陷信号时频域特征,探究了LPBF缺陷声学监测机理。同时,提出了一种基于多源域知识融合的深度迁移学习(DTL-MDKF)方法以构建LPBF缺陷在线监测模型,并对模型的准确度和有效性进行了系统评估。结果 LPBF熔池状态与产生的缺陷密切相关,所对应的声源发生机理不同是导致其信号特征呈现差异性的主要原因。所提出的DTL-MDKF方法模型对5类LPBF缺陷的识别准确率可达98.2%,且t-SNE可视化分析结果证明了其良好的深度特征挖掘能力以及将模型中多源域自适应融合知识迁移用于目标域LPBF缺陷监测任务的有效性。结论 相比于传统单一源域迁移学习方法,所提出的方法模型具有更好的性能,能够实现对复杂多变工况的LPBF制造缺陷的精准实时监测,可为LPBF零件的生产提供一定的指导。     

岩体声发射与微震监测定位技术及其应用

岩体在破坏之前 ,都会出现声发射和微震现象。通过仪器监测声发射和微震 ,就可以判定岩体的失稳状态及其位置。文中论述了监测和定位原理 ,简介了专门开发的单通道监测仪和多通道监测定位系统的结构和功能。该系统的绝对定位误差为 8 6m ,相对误差小于 10 %。在 4个有色金属矿山的实际应用表明 ,利用该系统的监测结果 ,可对采场或空区的稳定性作出及时、准确的评价 ,对岩体的失稳状态作出预报     

岩体声发射与微震监测定位技术及其应用

岩体在破坏之前 ,都会出现声发射和微震现象。通过仪器监测声发射和微震 ,就可以判定岩体的失稳状态及其位置。文中论述了监测和定位原理 ,简介了专门开发的单通道监测仪和多通道监测定位系统的结构和功能。该系统的绝对定位误差为 8 6m ,相对误差小于 10 %。在 4个有色金属矿山的实际应用表明 ,利用该系统的监测结果 ,可对采场或空区的稳定性作出及时、准确的评价 ,对岩体的失稳状态作出预报     

应用声发射技术监测Q235钢的点蚀

声发射(AE)可灵敏地检测材料结构的变化及损伤,目前对该技术用于金属点蚀监测的研究不多。建立了有效的AE试验平台,提取了Q235钢点蚀过程中产生的AE信号样本。结果表明,该信号特征与理论分析相吻合,低碳钢点蚀过程确实会产生AE信号。该技术可用来研究腐蚀发展规律及监测和评估腐蚀损伤。     

铜表面划痕过程声发射特性

以半导体互连材料铜为对象,研究铜表面划痕过程声发射特征,探索划痕载荷及速度对划痕过程声发射特征影响及铜表面划痕损伤机制,为基于声发射技术表征铜表面微纳尺度材料去除过程提供理论依据。研究发现,铜划痕过程主要以塑性变形为主,呈现周期变化形貌,并产生连续型声发射信号;随划痕速度的增加,信号强度增加,而载荷变化对信号影响较小;信号强度与变形体积增加速率呈指数关系。声发射信号能较好表征划痕过程。     

声发射技术在工程结构疲劳损伤监测中的应用和展望

疲劳失效是工程结构和材料科学研究领域都十分关注的问题。研究疲劳损伤机制对于解决工程结构疲劳失效问题是很重要的。应用断裂力学理论研究工程结构的疲劳问题已取得了显著的成果，随着声发射技术研究的深入，将二者结合起来必将成为疲劳问题研究的更有效方法之一。阐述了国内外采用声发射技术对工程结构疲劳裂纹损伤监测中的声发射源机制状况的研究，展望了声发射技术结合断裂力学在该领域的应用前景。     

声发射测试系统的发展

综述了声发射测试系统的发展历程及现状。展望了其发展前景，给出了两种分类依据，重点介绍了几种目前先进的声发射仪．     

Monitoring of Impacted Aramid-Reinforced Composites by Embedded PVDF Acoustic Emission Sensors

Abstract:  An embedded piezoelectric [poly(vinylidene fluoride) (PVDF)] thin film sensors system for acoustic emission (AE) was realized to investigate the possibility of monitoring, in real time, the post-impact damage in aramid woven fabric-reinforced epoxy. The same sensors have been used in a previous work on similar specimens tested in flexure but not previously impacted, with the aim of verifying the suitability of these sensors to be embedded and their ability to detect AE signals under loading. This work is a continuation of the previous one aiming at evaluating the ability of these embedded PVDF sensors to point out the presence of impact damage, issue widely studied in literature. Aramid fibre/epoxy composite specimens with embedded PVDFs, previously impacted at different energies, namely 5, 10 and 15 J, were tested using three-point bending tests. It appeared from mechanical tests that the flexural strength decreased passing from non-impacted specimens to those impacted with the highest energy and that the embedment of PVDFs in the laminates did not markedly affect the structural integrity of the impacted composites. The degree of impact damage, represented by the decrease in mechanical properties, has been correlated with the AE activity by means of a parametric analysis of the AE signals detected during post-impact mechanical tests.     

On-line Condition Monitoring and Diagnostic Network System for Rotating Machine Set

1IntroductionThemachineryinfactoryisalwaysthekeyequipment,soOn-lineConditionMonitoringandDiagnosticSystemCMDS)isveryimportant.Usingthissy000000stem,engineerscanknowtherunningconditionclearlyandanalyzethepossiblefaultswhenthesemachinesetscannotrunnormally.Computerscience,numericsignalprocessing,sensorandnetworktechnologyarethekeytechnologiesofnetworkbaseddistributedon-lineCMDS,anddevelopmentofthesetechnologiesmakeCMDSplayamoreimportantroleinindustry.NetworkstructureandfunctionofCMDSare…     

316L奥氏体不锈钢点蚀的原位声发射监测

为了研究316L不锈钢自然点蚀的生长规律,发展基于声发射技术的小孔腐蚀监测方法,利用声发射技术原位研究了316L奥氏体不锈钢在pH=1.0和中性(pH=6.7)的3.5%NaCl溶液中的自然点蚀状况,同时监测了开路电位E_(OCP);通过扫描电镜对试验后样品的表面形貌进行表征,并通过Matlab平台对声发射信号进行聚类分析。结果表明:316L奥氏体不锈钢的自然点蚀具有不同的孕育周期,声发射信号的获取跟E_(OCP)的变化具有较好的对应关系。在点蚀快速发展阶段,声发射信号具有较高的绝对能量。在Matlab平台上建立了一套信号处理程序,并对声发射信号进行重新定义,对处理后的信号进行声发射信号参数分析,得到了3类较好的声发射信号聚类,来源于不同腐蚀现象或阶段。其中,在点蚀的快速发展阶段主要以高持续时间高计数和高持续时间低计数2类谐振信号为主。     

Acoustic Emission Monitoring and Microscopic Investigation of Cracks in ERCuNi Cladding

A corrosion resistant CuNi cladding was deposited on SM45C (equivalent to AISI1045) substrate by DC inverse arc welding. During the welding process, a three channel acoustic emission (AE) monitoring system was applied to detect the crack signals generating from both the cladding process and after cladding. Characteristics of the welding crack signal and noise signal had been analyzed systematically. Based on the record time of the signal, the solidification crack and delayed crack were distinguished. By two-dimensional AE source location, the crack position was located,and then investigated by scanning electron microscopy (SEM). Results showed that the AE system could detect the welding crack with high sensitivity and the two-dimensional source location could accurately determine the crack position. Microstructures of the cladding and heat affected zone (HAZ) were examined. Dendrites in the cladding and coarse grains in the HAZ were found.     

An On-line Ferrograph for Monitoring Machine Wear

In order to improve an on-line ferrograph , this paper simulates a three-dimensional magnetic field distribution of an electromagnet, builds a sinking motion model of a wear particle, and investigates the motion law of wear particles under two different conditions. Both numeric results and experimental results show that the on-line ferrograph is capable of monitoring machine wear conditions by measuring the concentration and size distribution of wear particles in lubricating oil.     

基于声发射和双谱分析的铝合金损伤原位监测研究

以列车车体材料7N01铝合金为研究对象,基于声发射和数字图像技术对7N01铝合金三点弯曲损伤过程进行了监测,采用传统的声发射参数与双谱法分析了7N01铝合金裂纹萌生及失稳扩展的声发射特征。结果表明:声发射能量和质心频率可有效预报7N01铝合金微裂纹的萌生。声发射信号的双谱等高线图显示两个频率成分之间的耦合关系,使得识别7N01铝合金三点弯曲过程中的不同阶段变得相对容易。7N01铝合金试样缺口尖端的损伤演变过程的数字图像监测结果,验证了声发射能量和质心频率对裂纹萌生的预测。实验结果显示声发射监测技术为裂纹演变行为的预测提供了依据。     

Application of Acoustic Emission for Masonry Arch Bridges

Abstract:  There are over 40 000 masonry arch bridges in the UK, 60% of which are over 100 years old. The ever increasing levels of loading and volumes of traffic make it imperative that the condition, life expectancy and load capacity of such bridges are accurately assessed. Assessment procedures, however, generally rely on visual methods without giving any information on the internal condition of the structure. The acoustic emission (AE) technique has the ability to record certain types of damages anywhere within the structure before their effect becomes visible on the surface. Although AE is increasingly widely used for monitoring concrete and metallic bridges, its application for masonry bridges is currently very limited. A series of multi-ring brickwork arches have been tested as part of an extended study on fatigue performance of masonry arch bridges at the University of Salford. The present study attempts to assess the applicability of the AE technique for masonry arch bridges under static and long-term cyclic loading, to study crack propagation and failure mechanisms.