Visible and infrared deflectometry for contactless and full-field vibration measurements

机械、声学或空气动力激励可以引起结构振动，而后者在噪声和振动监测与控制、材料测试和结构动力学方面具有重要意义。一个多世纪以来，人们一直使用加速度计来测量振动。激光多普勒振动测量仪引入了非接触式振动测量，可以对结构进行二维和三维振动测量。与此同时，随着高速数码相机的普及，非接触式和全场振动测量也迅速发展起来。通过一次成像整个表面，他们可以提供时间和空间分辨的测量，非常适合于研究非平稳或瞬态现象。在数字图像相关等成熟的测量技术中，偏转测量是一种备受关注的测量方法。偏转计提供可靠的测量，具有良好的灵敏度，所有这些都是通过简单的设置和单个相机实现的。最近的一项进展是成功地将偏转法应用于红外光谱的动态振动测量。与可见域相比，移动到红外域和更长的波长放宽了对被测样品表面粗糙度的限制，并允许在普通和未准备的表面上进行测量。该项目的两个主要目标是提高技术准备水平和扩大偏转测量方法的应用范围。在实验室和研究环境中使用的综合测量系统的发展将发挥集中作用，正在与几个合作者进行的项目中发展和使用。涵盖的主题将从平面和弯曲各向同性面板和生态材料的特性，到有关载荷或材料特性的识别方法。在中等帧率（< 1000-2000图像每秒）下，还将考虑两种新的偏转测量实现。第一个将基于使用工业级相机的多摄像头设置的开发，第二个将基于便携式设备（手机，平板电脑）的开发，以评估使用此类设备执行动态偏转测量的可能性。红外偏转计用于动态振动测量的有效性仅在2021年建立，这项工作预计将产生后续的科学发展和出版物流。该工具的可用性将扩大偏转测量技术的潜在应用范围，并将为加拿大的工业和研究提供战略优势。可靠的全场非接触式测量的可用性可以为“材料和结构测试2.0”范式铺平道路。通过在多学科背景下提供实用的现代工业鼓励的研究和教育课题，这项工作将最终为培养学生提供一个完美的环境。

Mechanical, acoustical or aerodynamic excitations can induce structural vibrations, and the latter are of interest in noise and vibration monitoring and control, material testing and structural dynamics. Vibrations have been measured for more than a century using accelerometers. Contactless vibration measurements were introduced with the laser Doppler vibrometry that allows 2D and 3D vibration measurement on structures. In parallel, contactless and full-field vibration measurements have burgeoned with the availability of high-speed digital cameras. By imaging an entire surface at once, they can provide time- and space-resolved measurements that are well-suited for the study of non-stationary or transient phenomena. Among well-established techniques like digital image correlation, deflectometry is a measurement method gaining interest. Deflectometry provides reliable measurements with good sensitivity, all with a simple setup and a single camera. A recent progress is the successful application of deflectometry in the infrared spectrum for dynamic vibration measurements. Moving to the infrared domain and longer wavelengths compared to the visible domain relaxes the constraints on the surface roughness of a tested specimen, and allows measurements to be performed on common and unprepared surfaces. The two main objectives of the program are to increase the technology readiness level and to extend the application range of the deflectometry method. The development of an integrated measurement system to be used in laboratory and research contexts will play a centralizing role, being developed and used in projects conducted with several collaborators. Covered topics will range from the characterization of plane and curved isotropic panels and eco-materials, to identification methods concerning loadings or materials properties. Two novel implementations of deflectometry will also be considered at moderate frame rates (< 1000-2000 images per second). The first will be based on the development of a multi-camera setup using industrial grade cameras, and the second will be based on the development of a portable device (cellular phone, tablet) to evaluate the possibility of performing dynamic deflectometry measurements using such devices. The effectiveness of infrared deflectometry for dynamic vibration measurements was only established in 2021, and this work is expected to generate a subsequent stream of scientific developments and publications. The availability of a tool will broaden the range of potential applications for the deflectometry technique, and will provide a strategic advantage for industries and research in Canada. The availability of reliable full-field contactless measurements can pave the way towards a « materials and structures testing 2.0 » paradigm. This work will finally provide a perfect setting for training students by providing practical and modern industry-encouraged research and education topics in a multidisciplinary context.