RELIABLE NONDESTRUCTIVE EVALUATION OF DAMAGE IN INFRASTRUCTURE AND SOIL DYNAMIC CHARACTERIZATION USING NOVEL LASER TECHNOLOGY

如果我们要最大限度地延长民用基础设施(如学校、桥梁、输电线、管道)的使用寿命，就必须开发出更好、更具成本效益的方法来识别内部结构损伤和确定地基土的特性。我已经开发了一种基于激光技术的新型系统，这使得第一次有可能真正看到和量化换能器及其激发的材料中的超声波波场。这项创新技术有可能揭示超声波是如何产生、传播和衰减的基本知识，从而能够可靠地检测内部损伤并更好地表征地基土。我的研究计划的三个主要长期目标是：1)使用最先进的技术、实验室和现场测试以及数值模拟来促进对超声波产生、传播和衰减的基本了解；2)利用这种新的认识来开发可靠的无损评估方法(NDE)，以延长现有民用基础设施的使用寿命和安全性；以及3)将这些新的无损评估方法应用于地基土的动态表征，以提高新基础设施在地震、风力或机械振动作用下的安全性。因此，我的研究计划的短期目标是解决目前超声波检测缺乏可靠性的问题。我们将从问题的根源开始：正确描述超声波传感器。对于这项任务，我们将在我们的实验计划中使用两个新的协同开发：激光系统和透明颗粒材料。通过第一次看到样品内部的超声波波场，我们将能够测量真实的输入和输出超声波位移。从实际位移中，我们将对试件内部缺陷的产生、传播和相互作用有一个基本的了解。

If we are to maximize the service life of civil infrastructure (e.g. schools, bridges, power lines, pipelines), it is imperative to develop better and more cost effective methods to identify internal structural damage and characterize foundation soils. I have developed a novel system based on laser technology that makes it possible, for the first time, to actually see and quantify the ultrasonic wave field in the transducers and the materials they excite. This innovative technology has the potential to reveal fundamental understanding of how ultrasonic waves are generated, propagated, and attenuated so that internal damage can be reliably detected and foundation soils can be better characterized. The three main long-term goals of my research program are to 1) advance the fundamental understanding of ultrasonic wave generation, propagation, and attenuation using state-of-the art technology, laboratory and field testing, and numerical simulations; 2) use this new understanding to develop reliable nondestructive evaluation methods (NDE) to extend the service-life and safety of existing civil infrastructure; and 3) extend the application of these new NDE methods to the dynamic characterization of foundation soils to increase the safety of new infrastructure subjected to earthquake, wind, or machine vibrations. Consequently, the short-term goals of my research program are aimed at addressing the current lack of reliability of ultrasonic testing. We will start at the root of the problem: proper characterization of the ultrasonic sensors. For this task, we will use two new synergetic developments in our experimental program: the laser system and transparent particulate materials. By seeing for the first time the ultrasonic wave field inside the specimens, we will be able to measure the real input and output ultrasonic displacements. From the real displacements, we will gain fundamental understanding of the ultrasonic wave generation, propagation, and interaction of defects inside specimens.