电子剪切散斑技术在木材无损检测中的应用

复合板材及木制品等表面或内部的缺陷对材料性能有很大影响,如何快速准确地对其进行无损检测,并判断缺陷的位置大小是很有意义的.针对松木板试件,通过预置表面和内部隐藏缺陷来近似模拟实际缺陷情况,提出一种基于剪切散斑干涉技术的木材无损检测技术新方法,实现了对松木试件的无损检测.在表面缺陷的检测中讨论了剪切量对结果的影响,利用像素标定的方法,得到直径为6、5、3mm的缺陷信息;在内部隐藏缺陷检测中,借助热加载技术同时引入相移技术使剪切散斑检测技术不仅具有非接触、全场实时检测等特点,而且完成对内部隐藏近表面缺陷的定量无损检测.整个检测过程光路简单,实时快速,实验结果与实际情况符合较好.     

激光剪切散斑检测技术在飞机复合材料检测中的应用

针对目前采用敲击法检测飞机复合材料存在可靠性差,检测灵敏度低等缺陷,本文采用激光剪切散斑检测系统对飞机复合材料进行检测,并应用该系统对含损伤的多层粘接复合材料及双层蜂窝粘接复合材料试件进行了检测试验。试验结果表明,激光剪切散斑检测灵敏度高,结果直观,不漏检,可以定量测量缺陷的尺寸,精度达0．1mm,可以测量纵向变形,精度达0．1μm,还可以测量缺陷之间的距离。该系统无需专门隔振,具有计算机实时图像记录等特点,对飞机复合材料的检测具有较好的效果。     

基于真空加载的激光错位散斑干涉自动化检测系统

为满足某橡胶/金属粘接结构产品的批量化检测需求,提升检测效率和自动化水平,设计开发了一套基于真空加载的激光错位散斑自动化检测系统。该系统集成了轻量化框架和紧凑型光路,并通过检测软件和检测流程优化,得到了较为理想的散斑检测图像;同时结合产品结构特点和检测灵敏度要求,设计了基于PLC控制的真空舱和运动控制装置,实现了产品粘接质量的自动化检测应用。结果表明,该系统可检测出检测试块上预置的人工缺陷,与原有手动检测模式相比,在保证检测产品检测灵敏度要求的前提下,极大地提升了检测效率,降低了检测人员的劳动强度,具有良好的工程应用价值。     

物体变形测量的相移数字散斑剪切干涉术

相移数字散斑剪切干涉技术可以提高检测精度,利用该方法对圆形铝板试件进行测量。为了实现全场相位的精确求解,运用等四步相移Carré算法定量计算相位。将该非接触测量技术与弹性力学理论分析相结合,对四周固支,中心受集中载荷试件的离面位移导数进行测量与分析,另外采用有限元方法进行模拟。最后将实验结果分别和理论结果、有限元结果进...     

Slope of the Out‐of‐Plane Deflection Measurement of Composite Sandwich Plate With a Fully Potted Insert by Using Digital Phase‐Shifting Shearography

Abstract: A digital shearographic (DS) technique is a tool well‐suited for precision strain measurement and is a non‐destructive testing technology. But the fringe patterns of DS have not so high sensitivity due to the limitation of CCD camera resolution. Therefore a phase‐shifting technique is incorporated into DS and demonstrated to yield fringe patterns with good quality. The main purpose of this study is to set‐up a measuring system of digital phase‐shifting shearography (DPSS) to measure slope of the out‐of‐plane deflection of sandwich plate with a fully potted insert. The present system includes piezoelectric transducer, servo controller, Michelson shearing mechanism, image processing system and loading system. The four‐step phase shifting method is used to obtain phase map and then the phase expansion is proceeded by Macy algorithm to obtain the slope of the out‐of‐plane deflection of honeycomb sandwich plate with insert/potting material. Finally, comparing the slope of the out‐of‐plane deflection of DPSS with that of DS shows 2 to 7% difference of slope of deflection exhibiting.     

轮胎气泡边缘检测算法的研究

针对轮胎激光剪切散斑干涉图像背景中存在大量条纹的特点,为避免其对气泡边缘检测产生妨碍,主要对其边缘检测算法进行了研究.给出了对常用的几种算子进行边缘检测后的轮胎激光剪切散斑干涉图像,并分析了其在处理图像时的不适用性,设计出基于模糊理论的小波多尺度边缘检测算法.在多尺度边缘检测过程中,设计了适合的模糊算子,改善了轮胎气泡边缘检测的效果.由仿真结果可知:本文设计的算法与常用边缘检测算法相比,更好地标记出了轮胎气泡的边缘图像,滤除图像中的伪边缘.     

Analysis of thermal strains and stresses in heated fibre metal laminates

Current trends in aircraft design are to increase the economic efficiency by integrating different features in multifunctional materials. One strategy is to embed resistance heater elements between glass‐fibre epoxy layers in (heated) fibre metal laminates and to use them as anti or de‐icing devices in leading edges of wings. Heated glass fibre reinforced aluminium (GLARE) is an example of such a multifunctional material where heating functionality was added to the (certified) structural feature of GLARE. As heated fibre metal laminates are an innovative and rather new material, the possible (local) effects of embedded heating on the stress–strain state have not yet been investigated. This research couples experimental characterisation of heated GLARE surface behaviour and numerical modelling analysis to investigate the surface and the through‐the‐thickness strain‐stress state and temperature distributions due to the embedded heating. For the experimental part, the surface strains and the temperatures of a developed specimen were measured in a slow heating regime (temperature increase from 22.7 to 39.4 °C within 120 s) using, respectively, a developed shearography instrument and thermocouples with an infrared camera. Then a numerical model of heated GLARE was developed and verified with experimental results. Further, the numerical model was used to predict strains, stresses, and temperatures during a temperature increase similar to that used for de‐icing in a real operation (temperature increase from −25 to 86.7 °C within 4.8 s).     

水轮机转轮叶片表面缺陷的检测方法

为实现对水轮机转轮叶片修补时的自动焊接和打磨,检测出叶片的局部表面缺陷和整体型面曲线,提出了利用计算机图像处理技术、光切法和计算机立体视觉原理进行叶片型面及表面缺陷的捡测方案．实践表明,本方案的实施可极大地提高检测系统的准确度．     

基于激光剪切散斑技术分辨铝蜂窝缺陷类型

运用激光剪切散斑技术结合负气压加载,实现了蜂窝夹层结构内部缺陷类型的分辨,并使用数值计算方法分析不同类型缺陷在负压加载下的力学变形差异。文章首先制备了一块预置不同类型缺陷的卫星用铝蒙皮铝蜂窝夹层结构,缺陷类型分别为:上胶层垫膜、下胶层垫膜、去胶层、去胶层垫膜、去胶层油膜以及铣去蜂窝芯,尺寸依此为:10 mm、20 mm、30 mm和40 mm;接着简单介绍了剪切散斑干涉的基本原理,运用自行研制的激光剪切散斑系统结合负气压加载对蜂窝夹层试块加载;然后通过数值计算方法对比分析不同类型缺陷在负气压加载下的力学变形机理;最后使用热辐射加载进一步对样品进行探伤测试,分析两种加载方式的优劣。实验结果表明,激光剪切散斑干涉技术结合负气压加载可有效分辨铝蜂窝夹层结构内部的脱粘和夹杂等类型缺陷,数值计算方法可进一步佐证了实验结果。本文的研究可为蜂窝夹层结构的缺陷检测、缺陷类型分辨以及缺陷的力学变形机理分析提供技术支撑。     

激光技术在无损检测领域中的应用

激光具有单色性好、方向性好、强度高的特点,使其在无损检测领域的应用不断扩大,并逐渐形成了激光全息、激光散斑、激光超声、激光轮廓测量、激光瞬时热成像等无损检测新技术。随着成本低、性能高、安全性好的激光器的出现,将进一步降低检测成本,推动无损检测技术的发展。本文综述了几种激光无损检测技术的原理及应用、发展情况。