DP780胶接点焊试件拉伸损伤过程的声发射特征分析

针对1.2 mm厚的DP780高强钢板,进行胶接点焊响应面实验.采集胶焊接头拉伸过程的声发射信号,拟合拉伸过程撞击计数的历程图,对信号进行小波包分解并分析归一化能量特征,对比分析胶焊接头界面撕裂与基板撕裂失效形式声发射信号时域及频域特征,并建立胶层失效时的累计撞击计数与焊接工艺参数之间的回归模型.结果表明:界面撕裂与基...     

A Study on Incipient Damage Monitoring in Rolling Contact Fatigue Process Using Acoustic Emission

Acoustic emissions (AE) technique was applied to rolling contact fatigue tests of two radially loaded rollers running under constant load and velocity to detect the incipient damage and damage location. Signals detected from contacts were processed using signal conditioning and enhancement techniques by an AE source locator to bring out the difference between the signals from the sound and damaged rollers. It was found that AE hit count pulse observations by the AE source locator can provide an indication of the damage at its initial stage. The conventional AE parameters and the AE signal features were studied and correlated with the AE source locator counts. The results demonstrated the successful use of the combination of the AE monitoring and the AE source locator as a new technique for detecting the incipient damage and forecasting the position of the damage in the roller, and this technique could allow the user to monitor the rate of deterioration of the rolling elements.     

结构疲劳损伤的声发射检测可靠性研究

针对声发射技术对金属结构损伤的检测可靠性问题,以金属疲劳裂纹检测试验为基础,利用声发射特征参数的趋势分析和关联分析法,首先根据贝叶斯理论,计算了声发射对一定长度疲劳裂纹的检测概率;其次,研究了检测结构起裂时对应声发射幅度参数的阈值及其对损伤判断的影响。该研究可为减少声发射检测中的金属疲劳损伤信号误判,提高检测效率,以及确定复杂航空结构疲劳寿命提供支持。     

Acoustic Emission Characteristics of Bond-Slip for BFRP Concrete at Different Loading Rates

Russian Journal of Nondestructive Testing - Strain rate effect as an important characteristic of concrete materials, the most research mainly focuses on mechanical properties but less for bond slip...     

Characterization of the Damage Process of Polypropylene Fiber Mortar at Medium Loading Rate by the Full Wave Acoustic Emission Technique

In order to obtains the damage characteristics of the polypropylene fiber mortar at medium loading rate (10^–3 s^–1). The damage evolution process (A, B and C stages) of mortar specimens with different polypropylene fiber content under uniaxial tension was studied by using the full waveform acoustic emission technology. The acoustic emission wavelet energy and spectrum characteristics of cd7 frequency band were analyzed. The results showed that with the increase of the polypropylene fiber content, the peak stress increases firstly and then decreases, the elastic modulus increases gradually, the peak frequency of cd7 frequency band decreases in the A and B stages but increases in the C stages. The peak frequency of cd7 frequency band down from 30–40 kHz to 20–30 kHz with the damage accumulation, the above characteristics can be used to identify the damage stages and damage mechanisms.     

Full Curve Damage Process of Polypropylene Fiber Reinforced Mortars under Dynamic Tensile Loading Based on Acoustic Emission Technique

The study of the full curve damage process of polypropylene fiber reinforced mortars under medium strain rate (10^–6 s^–1–10^–4 s^–1) could enrich the understanding of the dynamic damage characteristics of polypropylene fiber reinforced structures. In order to explore the physical mechanisms of polypropylene fiber in the dynamic damage process of the polypropylene fiber reinforced mortars. The real-time dynamic acoustic emission (AE) technology was applied to monitor the damage process of polypropylene fiber reinforced mortars at different strain rates. The analysis of characteristics of AE wavelet energy spectrum and the average AE peak frequency of polypropylene fiber reinforced mortars with different polypropylene fiber content at different strain rates were conducted. The results show that with the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increases first and then decreases and the average AE peak frequency increases gradually. The AE wavelet energy spectrum in ca8 frequency band and the average AE peak frequency decreases gradually with the increase of the strain rate, but them increases first and then decreases with the increase of polypropylene fiber content. The above AE characteristics could provide important information for the identification of dynamic damage mechanism of polypropylene reinforced fiber mortars.     

钽表面划痕过程声发射特性

以集成电路阻挡层材料钽为对象,研究其表面划痕过程中的声发射特性,初步探索材料去除机制,分析划痕参数对声发射特性的影响,为采用声发射技术监测材料去除过程提供依据。结果显示:在划痕过程中,钽交替经历犁沟和塑性流动,形成深浅起伏的沟槽,并产生连续型声发射信号;随着划痕速度增加,信号强度增高,包络波动更剧烈,冲击性更强,而中位频率先升高、后稳定甚至降低;随着划痕载荷增加,信号增强,冲击性呈正相关变化。钽的表面划痕过程可以用声发射表征。     

数控车床加工过程中的刀具声发射试验研究

利用SWAES声发射检测仪提取数控加工过程中金属切削声发射信号,对信号进行频谱分析,找出主要频段,并利用金属切削过程中的声发射模型及试验数据,对影响声发射信号的因素进行分析,指出进给速度和主轴转速对声发射信号影响较大.     

磨削加工过程声发射检测技术发展现状

针对声发射技术灵敏度高、响应速度快等优点,介绍了声发射检测技术的基本原理、特点和常用信号分析方法,综述了声发射检测技术的研究进展,揭示了声发射技术在磨削过程监测、磨削质量监测、智能磨削系统构建等领域的应用现状,并阐述了声发射技术在磨削状态监控存在的不足以及未来发展趋势。     

多重分形的耐火材料损伤声发射信号特征提取方法

为了对镁碳质耐火材料损伤声发射信号进行有效的特征提取,研究了利用非线性领域的分形方法进行特征提取的可行性。首先利用仿真声发射信号研究了多重分形谱参数(Δα、Δf、K),广义分形维数均值Mean Dq等参数表征信号频谱结构特征的能力,结果表明多重分形谱宽Δα能够有效的表征信号的频谱特征;然后对镁碳质耐火材料进行单轴压缩试验,采集损伤声发射信号,并计算出两种典型损伤声发射信号的多重分形谱宽Δα,通过多重分形谱宽的分布证实了利用其进行特征提取是可行的。     

FRP复合材料容器水压爆破声发射特性分析

通过FRP复合材料容器水压爆破过程的力学性能试验研究,结合声发射技术,研究FRP复合材料容器在受压损伤及爆破过程中的声发射信号变化规律。运用参数分析法,分析了FRP复合材料容器损伤过程的声发射特性,应用费利西蒂比评价其损伤程度。研究结果,为在用FRP复合材料容器的完整性评价提供试验依据。     

Investigation of Damage Processes of Mortar in Different Aggregate Size by Acoustic Emission Characteristics

In order to study acoustic emission (AE) characteristics of damage process of mortar in different aggregate size, mortar specimens were tested under axial compression in the experiment, the whole damage evolution processes were monitored by full-digital AE acquisition system. The effects of mortar in different aggregate size on damage processes and failure mode were conducted by cumulative AE energy, amplitude, peak frequency and the ratio N/E (hits/energy) respectively. The ratio of cumulative AE hits of each frequency band and amplitude band to the whole cumulative AE hits in different stress level were counted, and the difference and evolution process of microcracks of mortar in different aggregate size in the failure process were revealed. The results show that cumulative AE energy increase with the increase of aggregate size in mortar. Distribution of cumulative AE hits of each amplitude band versus the stress in different aggregate size are the same, and AE hits of each amplitude band increase sharply suggests that the specimen will be destroyed. Besides, AE hits focus on low-frequency band at low stress level, while all peak frequency bands are active at high stress level, and the aggregate size of mortar have significant influence on cumulative hits of each peak frequency band. The ratio N/E decreased with the increase of aggregate size, and which increased linearly with the increase of the stress.     

玻璃纤维/环氧树脂复合材料损伤与断裂过程的声发射特性

研究了几种不同的玻璃纤维增强的树脂基复合材料在承受拉伸栽荷时的损伤与断裂行为。结果表明：损伤与断裂的不同阶段，可用声发射信号的几种关联图进行区分。     

混凝土结构安全检测的声发射阵列传感器系统设计

设计8阵元声发射(acoustic emission,AE)均匀圆阵传感器系统,针对大型混凝土板内部缺陷(声发射源)进行检测,并在此传感器系统基础上,分别用常规波束形成法(conventional beam forming,CBF)和最小方差无畸变响应法(mini-mum variance distortionless response,MVDR)对混凝土板内部AE源进行测向仿真分析,MVDR算法比CBF算法有较高的角分辨率。在混凝土甲板上(3 m×3 m)进行实验,结果表明CBF算法测向出现混淆现象,不能确定AE信号的入射方向,而MVDR算法较好地辨别出AE信号的入射方向,但与模拟AE信号源方位相差2°左右。     

基于声发射技术的拉深过程中润滑状态分析

采用发射技术监测了拉深过程中的润滑状态.在干摩擦和润滑脂润滑下,进行了拉深成形实验,并分析了不同润滑状态下拉深过程中声发射信号的能量、振铃计数、信号幅度等参数的变化规律.结果表明,拉深中产生声发射信号对润滑状态非常灵敏,随着润滑状态改善,拉深过程中产生的声发射信号能量、振铃计数、信号幅度参数等均呈下降趋势;通过对声发射信号分析可以判断拉深件的摩擦状况,即将声发射技术引入金属板材拉深中的摩擦状态的监测是可行的.     

三维编织C/SiC复合材料拉伸损伤演化

利用声发射技术,对三维编织C/SiC复合材料在拉伸过程中损伤发展、演化进行了实验研究。实验采集了三维编织C/SiC复合材料拉伸过程的声发射信号。运用多参数分析法,分析了三维编织C/SiC复合材料拉伸损伤的声发射特性,宏观上揭示了材料拉伸损伤的发展、演化过程和规律。研究结果表明三维编织C/SiC复合材料拉伸损伤演化可被分为两个主要阶段,损伤初始阶段和损伤严重阶段。     

基于红外和声发射的复合材料疲劳损伤实时监测

采用红外热像和声发射技术,实时同步监测2D C/SiC复合材料带孔板的拉-拉疲劳损伤过程,并利用疲劳过程中模量的变化、声发射信号和试样表面温度变化,讨论了带孔板疲劳损伤演变情况.结果表明:当外加应力低于疲劳极限时,疲劳损伤在循环初始阶段产生,损伤随循环数增加逐渐增大,最后趋于稳定;当外加应力超过疲劳极限时,疲劳损伤在短...     

金属间化合物破断过程的声发射研究

用声发射技术监测金属间化合物的破断过程，并结合扫描电镜及金相分析研究了声发射特性与破断的相互关系，指出晶界强度不足是导致材料低应力破断的根源，并对破断过程进行了描述，从不同视角对此类材料的研究提供了具有参考价值的分析依据。     

Tribological Behavior of Sheet Metal Forming Process Using Acoustic Emission Characteristics

In this study, acoustic emissions (AE) signal processing using wavelet packet transform technique was used to identify damage mechanisms during sheet metal forming simulation experiments. Current investigation was carried out based on decomposing the recorded AE signals into different wavelet levels. Following decomposition process, the energy distribution criteria were used to characterize dominant components, which are considered to be related to dominant damage mechanisms. Results revealed that the energy of AE signals was distributed dominantly on four components, which can be correlated by 3 specific damage mechanisms occurred during simulation experiments. After comparison with previous works, results were validated by surface observations in order to establish a meaningful relation between dominant wavelet components and surface damage mechanisms.     

基于LabVIEW开发平台的磨削加工声发射监测系统研究

磨削加工在线监测可降低磨削过程中工件碰撞及工件、砂轮破碎、影响磨削质量等损失，避免各种安全事故的发生，也可确定砂轮修整与更换的最佳时机，从而提高砂轮使用寿命和磨削质量。传统方法是利用功率、力、扭矩、振动、加速度等技术来监测磨削过程，但它们在灵敏度、响应速度等方面都存在着一定的局限，而利用声发射（Acoustic Emission，简称AE）技术监测磨削过程能够较好地解决上述问题。本文对磨削加工过程中产生声发射现象的机理进行了分析，利用虚拟仪器技术与声发射技术构建了基于虚拟仪器的磨削加工过程声发射监测系统，并进行了试验。试验表明，不同工况下，声发射信号随着主轴转速的提高、AE传感器安装位置与磨削区距离的缩小、磨削深度的增大以及砂轮与工件之间距离缩小而变得更加剧烈。