Nonlinear Inspection Using Phased Arrays

日益老化的基础设施和向更先进材料的转变带来了新的、目前尚未解决的检查挑战。疲劳和蠕变损伤是工程结构中最常见的两种失效模式，但这两种损伤都很难在发展的早期阶段被发现。同样，人们越来越需要检查粘接接头，无论是主要工程部件的粘接复合材料，还是扩散连接的金属部件，如超塑性变形的风扇叶片。这种检测技术的缺乏人为地限制了工程部件的寿命和使用，最近被一组工业终端用户强调为非破坏性评估(NDE)的一项关键要求。他们特别强调需要“为裂纹前体、困难的和新的工程材料确定技术”，这一奖学金将使申请人能够利用超声设备的最新发展，特别是高度灵活的相控阵系统和新的实验技术，开发实用和可部署的非线性超声检测技术，以监测每一种损害情况。使用专门为无损检测量身定做的相控阵是关键。它们允许多次测量，而无需重新定位传感器，从而消除了高度耦合和对准变异性，而这种高度耦合和对准变异性很容易掩盖极小的非线性信号。更重要的是，这项研究的方法将能够在样本中定位非线性。目前，这在任何程度的可靠性下都是不可能的，这是更广泛地采用这一令人兴奋的检查方法的关键障碍。

Ageing infrastructure and the move towards more advanced materials raises new, currently unsolved, inspection challenges. Fatigue and creep damage are two of the most common modes of failure in engineering structures, yet both are extremely difficult to detect in early stages of development. Similarly, there is a growing need to inspect bonded joints, be it adhesively bonded composites for major engineering components, or diffusion bonded metal components such as super-plastically deformed fan blades. This lack of inspection technique is artificially limiting the lifetimes and use of engineering components and was recently highlighted as a key requirement on the 5-10 year horizon by a group of industrial end-users of Non-Destructive Evaluation (NDE). They specifically highlighted the need for ``techniques identified for crack precursors, difficult and new engineering materials''.This fellowship will enable the applicant to develop practical and deployable nonlinear ultrasonic inspection techniques for monitoring of each of these damage scenarios, making use of recent developments in ultrasonic equipment, specifically highly flexible phased array systems and novel experimental techniques. The use of phased arrays, which are specifically tailored for NDE, is key. They allow multiple measurements without sensor repositioning, eliminating the high coupling and alignment variability that can readily mask the extremely small nonlinear signals. Even more importantly, the approach in this fellowship will enable localisation of nonlinearity within a specimen. This is currently not possible with any degree of reliability and represents a key barrier to wider adoption of this exciting inspection approach.