Rapid Inspection of Complex Geometries Using Edge-Guided Ultrasonic Waves

薄板中的超声波具有许多有趣的特性，例如随频率变化的速度以及在给定频率下的多种可能的振动模式。该项目将使用一组特定的模式，这些模式遵循薄板的边缘，以创建一种监测碳纤维增强聚合物（CFRP）飞机部件边缘损坏的方法。结构健康监测，即工程结构不断测试的损害，允许显着改善的方式，工程结构的使用寿命的管理。以设计结构使其在超过计划使用寿命后仍能长期使用为基础的方法正在被依赖于监测第一个退化迹象然后进行适当修理或更换的方法所取代。这使得更轻的结构可以安全地使用，从而大大节省了建筑材料，并且对于飞机，船舶和汽车等结构，在其整个工作寿命中提高了效率。超声波已经成功地应用于板状结构和管道的结构健康监测，但是具有复杂几何形状和随方向变化的物理性质的结构（各向异性材料）对超声结构健康监测提出了特别的挑战。这项工作将产生理解的边缘导波在各向异性材料作为一种方法来测试的重要部分的复杂结构。超声波在薄，板状，结构有更复杂的行为比波通过散装材料，由于限制可能的形状（或模式）通过结构的厚度，随着波的传播表面的影响。这些导波可以传播很长的距离（高达几十米），并被缺陷散射，使其能够用于检测损坏。它们也可以在任何给定频率下具有多个模式，每个模式具有不同的频率依赖速度，这使它们的使用变得复杂。大量的工作已经完成，以寻找方法，将它们应用到损伤检测。薄结构边缘处的超声波行为由于边缘也充当波的引导而进一步复杂化。这导致模式沿板边缘沿着传播，但远离边缘迅速衰减。除了代表一个有趣的物理问题，这些模式，统称为边缘波，是一个候选解决方案的问题，检查复杂的几何结构的重要部分。特别是，它们非常适合于检查薄结构边缘的损伤，例如：机翼板或飞机控制面的加强件、涡轮机叶片或暴露的钢梁。机翼板加强件（垂直于板以防止其弯曲的小板）的检查非常重要，因为它们特别容易损坏并承受很大的载荷。要实现这一应用，需要实现以下目标：在各向异性材料中建立边缘波的数值模型，设计产生和测量边缘波的方法，并对受损结构进行实验，以确定缺陷对边缘波的影响。将创建一种检查特定结构（机翼壁板加强件）的方法，并生成技术，以允许应用于检查任何薄结构的边缘是否有损坏。一个演示系统将展示这种技术。

Ultrasonic waves in thin plates have a number of interesting properties, such as velocities that vary with frequency and multiple possible modes of vibration at a given frequency. This project will use one particular group of modes, which follow the edges of thin plates, to create a method of monitoring the edges of carbon fibre reinforced polymer (CFRP) aircraft components for damage. Structural health monitoring, whereby engineering structures are continually tested for damage, allows significant improvements in the way that the useful lifetime of engineering structures is managed. Methods based on designing structures to be viable long beyond their planned working life are being replaced by approaches that rely on monitoring for the first signs of deterioration and then repairing or replacing appropriately. This allows lighter structures to be used safely resulting in significant savings in construction materials and, for structures such as aircraft, ships and automobiles, improved efficiency throughout their working life. Ultrasonic waves have been successfully applied to structural health monitoring of plate-like structures and pipes, but structures with complicated geometries and physical properties that vary with direction (anisotropic materials) present particular challenges for ultrasonic structural health monitoring. This work will generate understanding of edge guided waves in anisotropic materials as a method of testing important sections of complicated structures.Ultrasonic waves in thin, plate-like, structures have more complicated behaviour than waves travelling through bulk materials due to the effect of the surfaces of the restricting the possible shapes (or modes) through the thickness of the structure as the wave propagates. These guided waves can travel large distances (up to tens of metres) and are scattered by defects, allowing them to be used to detect damage. They can also have multiple modes at any given frequency, each with a different frequency-dependent velocity and this complicates their use. Substantial work has been done to find methods of applying them to damage detection. The behaviour of ultrasonic waves at the edges of thin structures is further complicated by the edge also acting as a guide to the wave. This leads to modes that propagate along the plate edges, but decay rapidly away from the edge. In addition to representing an interesting physical problem, these modes, collectively referred to as edge waves, are a candidate solution to the problem of inspecting important parts of complicated geometry structures. In particularly they are ideally suited to inspecting for damage on the edges of thin structures such as: the stiffeners of wing panels or control surfaces of aircraft, turbine blades or exposed steel girders.The inspection of wing-panel stiffeners (small plates perpendicular to the panel to prevent it bending) is of interest as they are particularly susceptible to damage and carry significant loads. The following objectives will need to be achieved for this application to be realized: creating numerical models of edge waves in anisotropic materials, designing methods of generating and measuring edge waves, and performing experiments on damaged structures to determine the effect of defects on edge waves. A method of inspecting a specific structure (wing panel stiffeners) will be created and techniques generated to allow application to inspecting the edges of any thin structure for damage. A demonstrator system will be produced that showcases this technique.