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。     

仿生磷灰石涂层与钛基体结合强度的划痕法实验

本文采用碱热处理及SBF浸泡的方法在钛片上制备了仿生磷灰石涂层,并采用AES进行表面成分-深度分析,划痕法测定磷灰石涂层与基体的结合强度.结果显示,经碱热处理而制得的钛表面仿生磷灰石涂层与基体结合的界面为成分梯度界面,二者的结合要通过成分含量呈梯度变化的过渡层:Ca、P元素的含量从表面到基体逐渐下降,Ti元素的含量逐渐上升.热处理有利于提高涂层的基体结合强度,其原因是热处理使SBF中形成的磷灰石的晶核细小而均匀,使得表面涂层与基体之间的结合更为紧密.预钙化处理后形成的磷灰石涂层与金属之间仍为成分梯度界面,因此对涂层的基体结合强度影响不大.     

起重机钢梁疲劳特性声发射监测实验研究

起重机钢梁作为主要承力部位关系到起重机的安全运行,目前仍无有效手段对其疲劳特性进行在线实时监测。采用声发射技术对钢梁材料Q345疲劳特性进行实验研究,首先通过动态弯曲疲劳实验获得材料疲劳裂纹萌生、扩展和断裂全过程的声发射检测信号;然后提取和分析声发射信号中的特征参数,经过比较各参数历程图,发现在幅值和事件历程图中可以反映材料疲劳裂纹整体演变过程,而能量、计数、上升时间和持续时间这4个特征参数更能反映出裂纹变化的重要转折点。此外对各个阶段声发射信号产生的原因进行分析和总结,为下一步采用声发射技术对钢梁材料损伤定量及寿命预测的研究提供参考依据。     

试样参数对划痕试验临界载荷的影响

本文有摩擦力监测的划痕法研究了试样参数（基体硬度、膜厚、基体表面粗糙度等）对硬质摩膜（或软膜）的临界载荷Ｌｃ的影响．样品基材是Ｗ６Ｍｏ５Ｃｒ４Ｖ２、５ＣｒＭｎＭｏ、４５钢、Ａ３钢和不锈钢．膜层为磁控溅射离子镀ＴｉＮ膜和Ｔｉ膜、化学镀ＮｉＰＣＵ膜，以及在Ｓｉ３Ｎ４上溅射镀Ａｌ膜．结果发现离子度ＴｉＮ膜和Ｔｉ膜与ＮｉＰＣｕ膜规律不同，ＴｉＮ膜和Ｔｉ膜的临界载荷Ｌｃ随基体硬度的提高而提高，但当基体硬度接近和超过膜层硬度时，Ｌｃ变化不大；基体粗糙度增加时Ｌｃ下降；随膜厚的增加Ｌｃ提高．而化学镀ＮｉＰＣｕ膜的临界载荷Ｌｃ随基体硬度的提高而下降，随基体表面粗糙度的提高而增加．以Ｗ６Ｍｏ５Ｃｒ４Ｖ２为基体的ＮｉＰＣｕ膜，随膜厚的增加Ｌｃ变化不大．本文对上述规律的实质进行了初步探讨，并对目前生产中正在推广的工具钢磁控溅射离子镀ＴｉＮ膜的划痕法标准提出建议．     

基于划痕试验的超硬铝7A04微弧氧化膜基结合力的测试与评定

目前基于划痕试验法的金属防护层与基体结合力的研究大多是针对微弧氧化膜外的其他硬质膜层,且鲜有验证性试验.采用微弧氧化技术在7A04超硬铝合金表面成功制备出陶瓷膜层并观察了其微观形貌,利用WS-2005膜层附着力自动划痕仪在膜层上进行了划痕试验,采集了声发射信号,利用数显材料显微镜观察声发射图谱特征声信号峰对应划痕处的微观形貌,检测了划痕附近膜层显微硬度,判定了干扰信号,对膜基结合力进行了综合分析和评定.结果表明:7A04铝合金微弧氧化陶瓷膜层表面呈“火山喷射口”层叠状,划痕试验中膜层破坏仅发生在划痕内部,划痕周围没有发生大面积崩落,膜层与基体间结合力良好.     

声发射测量系统的研制

介绍一种干涉式光纤声发射传感器,其分辨率高达１０＾－１０ｍ量级,频率范围为１００ｋＨｚ至１．４ＭＨｚ,响应时间小于１μｓ,具有很高的测量稳定性,且可用于状态监测和故障诊断。     

基于DSP的声发射信号采集及分析系统的研究

本文主要阐述了利用DSP(数字信号处理器)技术的声发射检测系统的硬件构成和部分软件设计,并用所研究系统对在1.7MPa大气压力下的液化石油气储罐的声发射现象进行检测,检测得到声发射参数、声发射信号时域幅值图和声发射源大致定位.结果令人满意,说明利用DSP技术可以对声发射信号进行高频采样,并结合计算机做数字信号处理获得声发射信号的相关情况,从而判断物体内部的微小裂纹的产生和发展.这对于发展声发射无损检测技术有重要的意义.     

法向载荷对紫铜的微米划痕测试的影响

使用Rockwell C金刚石圆锥压头对紫铜进行微米划痕实验,研究了法向载荷对样品的微米划痕测试的影响。结果表明:随着法向载荷的增大,压入深度和残余深度均线性增加,弹性恢复率线性减小;划痕宽度随压入深度的增加先非线性地增大,之后趋于线性增加。当法向载荷在0.08～0.11 N的范围内时,摩擦力线性增大,摩擦系数趋于一个常数,摩擦机制为粘着摩擦;当法向载荷在0.11～17 N的范围内时,摩擦力和摩擦系数非线性地增大,摩擦机制为犁沟摩擦;当法向载荷在17～28 N的范围内时,摩擦系数趋于一个常数,摩擦力线性增大,摩擦机制为微切削。     

气体阀门内漏声发射评价参量研究及其应用

阀门是工业生产中必不可少的流体控制设备,阀门内漏往往不易发现和判定。近年来,声发射技术凭借其较高的灵敏度在阀门内漏检测中得到广泛应用。针对传统声发射参量——声发射均方根电压,在阀门内漏评价中表现出的抗干扰能力弱的特点,提出一个用于阀门内漏评价的新声发射参量——平均声发射能量。通过开展气体阀门内漏声发射检测实验,对新构建参量和传统评价参量评价效果进行对比,结果表明新参量评价精确度更高,阀门内漏率的估算误差低于10%,可满足工程应用的要求。     

压力容器声发射检测技术概述

阐述了声发射检测的基本原理,介绍了国内外压力容器声发射检测技术的发展历程和现状,给出了压力容器声发射检测方法的优点和压力容器用钢的声发射特性,最后指出了目前声发射检测需解决的问题和发展趋势。     

GCr15轴承钢表面PⅢD处理膜层膜基结合力的研究

采用等离子体浸没离子注入沉积(PIIID)技术在GCr15轴承钢表面形成TiN薄膜,并采用划痕法对不同参数条件下膜层的膜基结合力进行了测量.结果发现:适当的氩离子溅射清洗和加入合适的过渡层可以提高膜基结合力,而且膜基结合力也会随着注入电压和注入量与沉积量比例的变化而改变.     

Limitation of Acoustic Emission for Identifying Seeded Defects in Gearboxes

Acoustic Emissions (AE) is gaining ground as a Nonestructive Technique (NDT) for health diagnosis on rotating machinery. Vast opportunities exist for development of the AE technique on various forms of rotating machinery, including gearboxes. This paper reviews recent developments in application of AE to gear defect diagnosis. Furthermore, experimental results are presented that examine and explore the effectiveness of AE for gear defect diagnosis. It is concluded that application of AE to artificially seeded gear defect detection is fraught with difficulties, particularly for fault identification. In addition, the viability of the AE technique for gear defect detection by making observations from nonrotating components of a machine is called into question. Nevertheless, guidance is offered on applying the technique for monitoring the natural wear of gears.     

Acoustic Emission Study of Fatigue Cracks in Materials Used for AVLB

The Armored Vehicle Launch Bridge (AVLB) is subjected to cyclic loading during launching as well as during tank crossings. The cyclic loading causes cracks to initiate in critical bridge components, and then to propagate. Unless these cracks are detected and repaired before they rapidly grow to reach their critical stage of propagation, the failure of bridge components can occur. Three AVLB components, the splice doubler angle, the splice plate, and the bottom chord, are susceptible to fatigue damage. In the present study, laboratory fatigue tests on the materials used for the components, aluminum 2014-T6, aluminum 7050-T765, and ASTM A36 steel, were conducted using the acoustic emission (AE) fatigue crack monitoring technique. A total of fourteen compact-tension specimens were prepared in this study: six aluminum 2014-T6, four aluminum 7050-T76511, and four ASTM A36 steel specimens. The characteristics of AE signals associated with the stress intensity factor, K, were obtained to understand AE behavior corresponding to the fatigue crack growth in the materials. Several AE parameters, such as AE counts, energy, and hits, have been shown to be useful tools for detecting cracks, providing early warnings, and preventing failure of the AVLB structures. A major jump in AEcount rate as well as AE hit rate occurred when K_max reached a value of about 30~MPam (27 ksiin.) for aluminum 2014-T6 specimens and about 50 MPam (46 ksiin.) for aluminum 7050-T76511 specimens. Also, AE source location techniques were able to successfully locate the path ofcrack propagation.     

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．     

Optimization of Positioning of an Acoustic Emission Sensor for Monitoring Hot Forging

Optimization of a sensor location for effective characterization of a hot forging process using acoustic emission (AE) signals is discussed in this paper. Acoustic emission signals generated during forging operations on an aluminium alloy were recorded using three sensors simultaneously by mounting them on the top bolster, bottom bolster, and bottom die of the press. The AE signals with maximum sensitivity could be detected with a sensor attached to the bottom die in preference to the other positions. Using AE parameters, the forging process could be differentiated into three regions, i.e., 1) yielding of the workpiece material, 2) intermediate deformation region, and 3) filling of the die. The results show that the optimum position of the AE sensor for monitoring hot forging is found to be the bottom die of the forging press.     

The Use of Acoustic Emission for Estimation of Bearing Defect Size

Vibration monitoring of rolling element bearings is possibly the most established diagnostic technique for rotating machinery. The application of Acoustic Emission (AE) for bearing diagnosis is gaining ground as a complementary diagnostic tool, however, limitations in the successful application of the AE technique have been partly due to the difficulty in processing, interpreting and classifying the acquired data. Furthermore, the extent of bearing damage has eluded the AE diagnostician. The investigation reported in this paper was centered on the application of the Acoustic Emission technique for identifying the size of a defect on a radially loaded bearing. An experimental test-rig was designed such that defects of varying sizes could be seeded onto the outer race of a test bearing. It was concluded that AE can provide an indication of the defect size, thus allowing the user to monitor the rate of degradation on the bearing. This article was originally published as “The Use of Acoustic Emission for Estimation of Bearing Defect Size” in Essential Technologies for Successful Prognostics, Proceedings of the 59th Meeting of the Society for Machinery Failure Prevention Technology, Society for Machinery Failure Prevention Technology, 2005, pp. 583–591, and is reprinted with permission.     

压缩载荷下陶瓷材料声发射特性的实验研究

对陶瓷材料在两种压缩加载下破坏过程中的声发射特性进行实验研究.三点弯曲和巴西劈裂实验中,采用多通道声发射系统监测了陶瓷试件的破坏过程.对声发射信号进行分析,结果表明,声发射能量数、事件数、振铃数等参数都反映了材料内部损伤演化扩展直至试件宏观断裂的过程.利用声发射参数可以定位陶瓷试件的破坏位置;试件断面的宏细观分析表明,陶瓷的脆性破坏机制主要是颗粒附近的微裂纹开裂.     

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。