Nonlinear ultrasonic imaging for material and defect characterisation

对工程结构中的材料和缺陷进行更准确的表征，可以改善对剩余寿命的预测，从而提高安全性和可靠性。最近的研究表明，非线性超声提供了关于材料和缺陷性质的高度敏感的信息。该项目旨在使用这种非线性信息，以及其他传统技术，以提供更准确的表征。特别是，非线性成像技术有可能精确定位的功能，如封闭的裂纹尖端和区域的塑性，迄今为止，已被证明是不可能检测到的。该项目将调查，理解和量化的新信息提供的非线性成像技术从一系列材料退化和缺陷形态。所采取的核心方法将是数字建模。目标是了解a）非线性信号是如何产生的，B）它们如何传播并与测试结构相互作用，以及c）如何优化测量以最好地消除损坏。除了这种建模之外，还需要确保模型得到适当实验的验证。该项目还将探索如何将这种非线性信息与传统的相控阵成像最佳结合，以提供最准确、最全面的表征结果。

More accurate characterisation of materials and defects in engineering structures leads to improved predictions of remaining life and hence increased safety and reliability. Recent research suggests that nonlinear ultrasonics provides highly sensitive information on the nature of materials and defects. This project aims to use this nonlinear information, alongside other traditional techniques, to provide more accurate characterisation. In particular, nonlinear imaging techniques have the potential to pinpoint features such as closed crack tips and regions of plasticity that have, to date, proved impossible to detect. This project will investigate, understand and quantify the new information provided by nonlinear imaging techniques from a range of material degradation and defect morphologies. The core approach taken will be numerical modelling. The objectives will be to understand a) how the nonlinear signals are created, b) how they spread out and interact with the test structure and c) how measurements can be optimised to best characterise the damage. Alongside this modelling will be the requirement to ensure that the models are validated with suitable experiments. This project will also explore how this nonlinear information can be best combined with traditional phased array imaging, to provide the most accurate and comprehensive characterisation results.