Remote, 3D ultrasonic imaging in extreme environments using 2D laser induced phased arrays

相控阵超声的应用对科学和医学都产生了深远的影响。它是所有医用超声成像系统和声纳的核心技术。这一提议将相控阵技术等同于激光超声技术，用于远程、体积、三维超声成像。在激光超声技术中，由于入射激光辐射，被测材料通过快速加热和膨胀而产生声音。然而，这种技术存在严重的信噪比限制，可以使用阵列配置来解决这一问题，就像使用传统的基于换能器的阵列一样。到目前为止，利用激光进行相控阵超声一直是非常困难的，因为聚焦和引导超声体波以产生或检测的技术对硬件(用于产生超声的多个激光器或复杂的实验装置)和成本提出了严格的要求。拟议的工作将基于在后处理中合成激光诱导相控阵(LIPA)，首先获得完整的矩阵，然后应用合适的成像算法(例如，全聚焦方法-TFM)。在LIPAS中对基于光学的数据进行后处理，使实验装置简单且具有成本效益。这些远程、无偶联剂的超声波阵列由光制成，可应用于极端环境中，用于在线过程监控或在役体积检测。这项研究的目的是开发一种基于激光的超声测量能力，用于在安全关键应用的极端环境中进行远程、无损、定量评估和三维超声成像，在这些应用中，常规阵列无法应用。二维LIPA将能够从多个角度成像给定的缺陷，获得远远超过一维阵列的表征细节。该项目的核心研究目标是：*开发激光诱导相控阵，用于使用FMC和TFM进行三维超声成像。*优化激光超声的数据收集方法，以提高处理速度。*优化TFM成像算法，以实现高效的超声成像。*展示系统在极端环境中用于检测和过程监控的工业应用潜力。这项工作的成功将使无损检测领域受益，该项目将为激光超声波界提供技术支持，并将使工程师和材料科学家能够在制造过程中(例如添加剂制造)或在使用中(例如放射性废物容器的现场检查)测试其结构的性能，需要一种技术来应对极端环境和受限制的场所。潜在应用的例子包括：在焊接和添加剂制造等极端环境下的制造过程理解和控制，提高工艺可靠性，这对添加剂制造的未来至关重要；航空发动机或发电机中的现场超声波检测。在化学、生物和生物医学成像等需要在灭菌或腐蚀性环境中进行远程超声成像的领域，预计还会有其他应用。

The application of "phased array ultrasonics" has had a profound impact on science and medicine. It is the technology at the heart of all medical ultrasonic imaging systems and sonars. This proposal brings the equivalent of phased array technology to laser ultrasonics for remote, volumetric, 3D ultrasonic imaging.In laser ultrasonics the sound is generated through the rapid thermal heating and expansion of the material under test, due to the incident laser radiation. However, there are serious signal-to-noise limitations associated with this technique, which could be addressed using an array configuration just as it happens with conventional, transducer based arrays. Up to now it has been very difficult to perform phased array ultrasonics with lasers because the technology to focus and steer the ultrasonic bulk waves for generation or detection puts severe demands on hardware (multiple lasers for ultrasonic generation or complicated experimental setups) and cost. The proposed work will be based on synthesising the Laser Induced Phased Arrays (LIPAs) in post processing, by first acquiring the Full Matrix and then applying a suitable imaging algorithm (e.g. the Total Focusing Method - TFM). The post processing of the optical based data in LIPAs, keeps the experimental setup simple and cost effective. These remote, couplant-free ultrasonic arrays, made of light, can be applied in extreme environments, for in-line process monitoring or in-service volumetric inspection. The aim of the proposed research is to develop a laser based ultrasonic measurement capability for remote, nondestructive, quantitative evaluation and 3D ultrasonic imaging in extreme environments for safety critical applications, where conventional arrays cannot be applied. 2D LIPAs will be able to image a given defect from a range of angles, obtaining characterisation detail far beyond what is achievable with a 1D array.The core research objectives within this project are:* Development of laser induced phased arrays for 3D ultrasonic imaging using FMC and TFM.* Optimisation of the data collection method to laser ultrasonics to improve speed of process.* Optimisation of the TFM imaging algorithm to laser ultrasonics for efficient ultrasonic imaging.* Demonstration of system's industrial application potential for inspection and process monitoring in extreme environments.The success of this work will benefit the non-destructive testing community, the laser ultrasonics community and will enable engineers and material scientists in need of a technique to address extreme environments and places of restricted access, to test the performance of their structures, either during the manufacturing process (e.g. additive manufacturing) or in-service (e.g. in situ inspection of radioactive waste containers). Examples of potential applications include: process understanding and control for manufacturing in extreme environments such as welding and additive manufacturing, increasing process reliability which is crucial for the future of additive manufacturing; in situ ultrasonic inspection in aero-engines or power generators. Other applications are expected in fields such as chemistry, biology and biomedical imaging where remote ultrasonic imaging is needed in sterilised or corrosive environments.