复合材料手动扫描超声特征成像检测

研究了复合材料手动扫描超声特征成像检测，通过对超声检测信号的全波列采集与处理，实现了A，B，C扫描成像；相位特征成像；当量特征成像；超声层析技术和超声频谱分析技术。该系统已经在复合材料的检测上得到了良好的应用。     

基于空耦换能器的碳纤维增强环氧树脂编织复合材料激光超声检测技术

激光超声技术具有无需耦合剂、快速及高分辨等特点,适用于各向异性碳纤维增强树脂编织复合材料的缺陷检测。运用有限元法分析了激励位置和编织结构对激光点源激发超声波信号的影响,获得了弹性波在材料内部的传播规律以及能量分布特征,并采用1 MHz空气耦合换能器搭建了一套小型化、低成本的非接触激光超声C扫描成像系统,开展了斜纹和缎纹碳纤维增强树脂编织复合材料的近表微结构和内部缺陷检测实验。结果表明,基于空气耦合换能器的激光超声成像可以高精度地再现碳纤维增强树脂编织复合材料的近表树脂囊、碳纤维束形状、取向、尺寸及其内部缺陷等空间分布特征,有望为航空复合材料提供一种原位的微结构表征和缺陷检测方法。      

炭纤维复合材料超声多维扫描成像检测技术

针对各种形状炭纤维复合材料构件，本文介绍了一种实时超声多维扫描成像检测技术。     

超声C扫描设备定量评价方法研究

超声C扫描系统在超声成像检测、缺陷识别等无损检测领域获得了广泛应用。但是,对C扫描图像的缺陷进行精确分析和表征一直是超声领域的难点之一。基于超声C扫描缺陷图像,给出了一种结合K-means聚类与Graham算法的图像特征参数定量估计方法,通过定量估计的参数能够有效地评价超声C扫描系统的检测质量。实验结果表明该方法能够有效描述标准圆形人工缺陷区域特征,有利于进一步评价超声C扫描设备。     

超声C扫描成像系统在SiC_p/Al复合材料无损检测中的应用

应用超声C扫描系统对SiCp Al复合材料进行无损检测 ,提供了一种能够直观显示复合材料内部缺陷截面图的检测方法。可以根据所得到的图形确定材料中缺陷的尺寸和形状 ,并根据缺陷形状和分布判定缺陷的性质。     

基于概率损伤算法的复合材料板空气耦合Lamb波扫描成像

采用非接触空耦传感器在准各向同性复合材料板中激励出单一的Lamb波模态,用于分层缺陷的扫描检测。扫描时,激励和接收传感器置于复合材料板同侧并相对倾斜布置,传感器沿2个正交方向同步线性扫描,得到不同位置的检测信号。对不同扫描路径下的检测信号进行连续小波变换,提取激励频率下的小波系数包络信号,对分层缺陷进行成像。在此基础上,利用概率损伤算法定义损伤指数,结合不同方向的损伤指数实现分层缺陷成像。采用全加法和全乘法对2个正交扫描方向得到的成像结果进行数据融合,实现了分层缺陷的定位和重构。并在成像算法中引入阈值,进一步提高了分层缺陷的定位精度以及重构质量。     

薄壁金属与非金属环形粘接件粘接质量超声检测方法研究

为了解决薄壁金属与非金属环形粘接件粘接质量的常规无损检测方法缺陷定位、定量准确性不高的问题,本文采用超声C扫描成像检测和接触式超声脉冲回波法,通过对环形粘接件人工缺陷对比试块、粘接产品件的检测,以及人工缺陷对比试块的解剖,对薄壁金属与非金属环形粘接件的粘接质量进行了研究.结果表明采用超声C扫描成像检测方法能检出大面积的脱粘缺陷和气孔缺陷,而接触式超声脉冲回波法无法区分粘接界面的缺陷信号,粘接缺陷无法被检出.因此超声C扫描成像检测方法对环形粘接件粘接质量具有良好的检测适用性和可靠性,是评价薄壁金属与非金属环形粘接件粘接质量有效的无损检测方法.     

SiC/Al层状梯度复合材料的制备与抗毁伤特性

用真空热压法制备了SiC/Al层状梯度复合材料;采用热压扩散工艺,实现了不同SiC含量的复合材料间的有效连接.实验表明SiC/Al层状梯度复合材料制备时,添加纯铝过渡层有助于提高层间结合强度.通过穿甲试验对SiC/Al层状复合材料的抗毁伤性能进行了分析,结果表明所制备的SiC/Al层状复合材料具有比纯铝材料更为良好的抗毁伤性能.     

超声波技术在现代战机复合材料结构损伤缺陷检测中的应用

文章论述了现代战机机体上复合材料胶接结构的超声检测技术.该技术以声阻法为原理,对相应的超声检测系统进行了设计.据此系统可以检测复合材料脱粘伤等缺陷形式,并且可以定性评估缺陷损伤程度.在实际应用中,已经验证了该方法的可行性、可靠性和准确性.     

Al2O3/Al2O3-ZrO2（3Y）层状纳米复合材料的制备与性能优化

为优化Al2O3层状复合材料的制备工艺及力学性能,选用不同初始粉体为原料制备了系列Al2O3/Al2O3-ZrO2(3Y)层状复合材料。借助X射线衍射、冷场发射扫描电镜和万能试验机等手段,系统考察了粉体结构和形貌对层状复合材料显微结构和性能的影响。结果表明:初始粉体的颗粒尺寸及尺寸分布会显著影响层状复合材料的显微结构及力学性能,以球磨微-纳米复合粉体为原料制备的层状复合材料具有最佳的力学性能,其抗弯强度和断裂功分别可达740MPa及3892J.m-2。同时,材料具有较高的层间结合强度,平行于层方向的抗弯强度高达436MPa。     

Impact damage growth in composites under fatigue conditions monitored by acoustography

The real-time monitoring of damage in composite materials during fatigue loading has been made possible by an emerging new ultrasonic imaging technology, acoustography. The successful integration of acoustographic technology and a servo-hydraulic test machine has resulted in a new measurement system which can be used for the in-situ imaging of impact damage in composite specimens during long-term fatigue tests. Results show that damage area growth during constant load fatigue occurs in three stages. After an initial small enlargement, damage grows at a constant rate until the last stage is reached when damage grows with an increasing rate to final failure.     

Using a Single Transducer Ultrasonic Imaging Method to Eliminate the Effect of Thickness Variation in the Images of Ceramic and Composite Plates

This article describes a single transducer ultrasonic imaging method based on ultrasonic velocity measurement that eliminates the effect of thickness variation in the images of ceramic and composite plate samples. The method is based on using a reflector located behind the sample and acquiring echoes off the sample and reflector surfaces in two scans. As a result of being thickness-independent, the method isolates ultrasonic variations due to material microstructure. Its use can result in significant cost savings because the ultrasonic image can be interpreted correctly without the need for precision thickness machining during nondestructive evaluation stages of material development. Velocity images obtained using the thickness-independent methodology are compared with apparent velocity maps and c-scan echo peak amplitude images for monolithic ceramic (silicon nitride), metal matrix composite and polymer matrix composite materials having thickness and microstructural variations. It was found that the thickness-independent ultrasonic images reveal and quantify correctly areas of global microstructural (pore and fiber volume fraction) variation due to the elimination of thickness effects. A major goal achieved in this study was to move the thickness-independent imaging technology out of the lab prototype environment and into the commercial arena so that it would be available to users worldwide. The method has been implemented on commercially-available ultra-sonic can systems manufactured by Sonix, Inc. via a formal technology transfer agreement between NASA and Sonix.     

Radome health management based on synthesized impact detection,laser ultrasonic spectral imaging,and wavelet-transformed ultrasonic propagation imaging methods

A radome must not only withstand various forces during operation, but also provide a window for electromagnetic signals. A radome is generally a composite sandwich structure. Much of the damage to radomes is barely visible to the naked eye on the outer surface, but is severe internally. In this study, a radome health management strategy consisting of in-flight damage event detection and ground damage evaluation processes is proposed. A radome health management system, composed of an on-board subsystem and a ground subsystem, was developed to realize the strategy. An in-flight event detection system was developed based on acoustic emission (AE) technology. A built-in amplifier-integrated PZT sensor was used, and the minimum impact energy that the on-board subsystem can detect was determined. The AE sensor was then switched to an ultrasonic receiver. A scanning laser ultrasonic technology was combined with the ultrasonic receiver to develop a ground nondestructive evaluation subsystem. For in situ damage visualization, laser ultrasonic frequency tomography and wavelet-transformed ultrasonic propagation imaging algorithms were developed in this study. To demonstrate the robustness of the ground subsystem, a damage was generated by 5.42 J impact in a glass/epoxy radome with honeycomb core, and the impact image of 25 mm in diameter invisible outside could be visualized with the combination of ultrasonic spectral imaging (USI) and wavelet-transformed ultrasonic propagation imaging (WUPI), which made the propagation of only the damage-related ultrasonic modes visible.     

Radome health management based on synthesized impact detection,laser ultrasonic spectral imaging,and wavelet-transformed ultrasonic propagation imaging methods

A radome must not only withstand various forces during operation, but also provide a window for electromagnetic signals. A radome is generally a composite sandwich structure. Much of the damage to radomes is barely visible to the naked eye on the outer surface, but is severe internally. In this study, a radome health management strategy consisting of in-flight damage event detection and ground damage evaluation processes is proposed. A radome health management system, composed of an on-board subsystem and a ground subsystem, was developed to realize the strategy. An in-flight event detection system was developed based on acoustic emission (AE) technology. A built-in amplifier-integrated PZT sensor was used, and the minimum impact energy that the on-board subsystem can detect was determined. The AE sensor was then switched to an ultrasonic receiver. A scanning laser ultrasonic technology was combined with the ultrasonic receiver to develop a ground nondestructive evaluation subsystem. For in situ damage visualization, laser ultrasonic frequency tomography and wavelet-transformed ultrasonic propagation imaging algorithms were developed in this study. To demonstrate the robustness of the ground subsystem, a damage was generated by 5.42 J impact in a glass/epoxy radome with honeycomb core, and the impact image of 25 mm in diameter invisible outside could be visualized with the combination of ultrasonic spectral imaging (USI) and wavelet-transformed ultrasonic propagation imaging (WUPI), which made the propagation of only the damage-related ultrasonic modes visible.     

单激励纵扭复合超声铣削系统研究

针对切削、焊接过程中超声复合振动能获得较高加工质量、效率及有助于延长刀具使用寿命,研究分析纵扭复合超声铣削系统运动特性及切削轨迹特征;基于斜梁振动原理,提出加工工艺简单、制造成本低的斜梁式超声变幅杆,并利用有限元软件ANSYS进行结构动力学分析, 证实通过单向激励可产生纵扭复合振动;应用研制的纵扭复合超声振动铣削系统对碳纤维复合材料进行切削试验,获得较好加工效果,从而验证理论分析与数值模拟结果的正确性。     

纵-扭复合超声振动加工系统设计及频率简并研究

纵-扭复合超声振动加工技术在硬脆性材料的加工中受到越来越多的重视,针对该种需求,设计了一种纵-扭复合超声振动加工系统,基于有限元方法对该类系统普遍存在的频率简并问题进行了研究。利用数值解析方法设计出超声换能器和超声变幅杆,之后在变幅杆上做出螺旋槽,一部分纵向振动转换为扭转振动;以目标频率附近的纵、扭谐振频率尽量接近为原则,利用有限元软件分析系统的结构参数对纵、扭谐振频率的影响规律,实现频率简并;在此基础上对系统进行模态分析和瞬态动力学分析,结果表明系统可以实现纵-扭复合超声振动,验证了此种频率简并方法的有效性和实用性。     

Non-destructive evaluation of composite materials using a capacitive imaging technique

This paper describes the application of the capacitive imaging technique to the inspection of composite materials. The fundamental theory of the capacitive imaging technique was briefly described. Experiments using prototype capacitive imaging probes were also carried out. The proof-of-concept results indicated that the capacitive imaging technique could be used to detect cracks and delaminations in the glass fibre composite, defects in the aluminium core through the glass fibre face as well as surface features on the carbon fibre specimens.     

An investigation of the effects of material anisotropy and heterogeneity on pulsed, laser-generated acoustic signals

Point-source and line-source models for the laser ultrasonic source in materials exhibiting transverse isotropy are applied to the specific problem of laser generation and ultrasonic propagation in unidirectional, polymer matrix composite materials. Comparing experiment and theory, it is shown that these composite materials exhibit homogeneous behavior, at the frequencies investigated, for ultrasonic wave propagation perpendicular to the fiber direction. For ultrasonic propagation in the fiber direction, ultrasonic dispersion, resulting from the inhomogeneous nature of the composite, affects the laser ultrasonic signal.