Guided Wave Tomography for Accurate Corrosion Mapping in Inaccessible Areas

在难以接近的区域进行准确的腐蚀深度测绘是广泛的行业中的一个重要问题。虽然有几种厚度测量技术可用，但它们仅适用于待检测区域可直接进入的情况。事实上，标准的测量方法需要一个探测传感器在预计会发生腐蚀损坏的区域进行扫描。然而，这并不总是可能的，因为由于其他结构构件的存在，访问可能受到限制。例如，确定管道支撑处的腐蚀深度是石化工业中的一个主要问题。目前，准确确定腐蚀深度的唯一可靠方法是从支架上提起管道并使用标准方法，因此导致非常昂贵且具有潜在危险的检查程序。在这里，我们提出了一种类似于X射线CT的断层扫描方法。然而，我们不使用电离辐射，而是采用可以从远程和可访问的换能器位置跨检查区域传输的引导超声波。虽然光子与物质的相互作用可以通过X射线CT中的简单射线模型来描述，但是散射、衍射和折射现象阻碍了导波信号中的机械特性信息的编码。这些现象增加了很多复杂性的问题，检索厚度图GWT和本建议的主要挑战。因此，在基本层面上，该方案旨在制定一个通用的方法来GWT，可以解决这个复杂性借用地球物理勘探和医疗诊断开发的想法。从一个更实用的角度来看，我们建议开发一个现场部署的原型映射腐蚀的支持，这将服务于双重目的，保持研究的重点放在实际问题和促进翻译的拟议技术的工业。此外，该原型将具有灵活的设计，允许其应用于管道支架以外无法进入的区域的腐蚀测绘问题，以确保拟议的技术将在广泛的行业中产生影响。该提案正在英国无损检测研究中心内提交给目标研究计划，EPSRC为工业驱动的无损检测研究指定了资金。它得到了壳牌和巴西国家石油公司的支持，他们为该项目提供了9万现金和实物捐助。

Accurate corrosion depth mapping in inaccessible areas is a problem of major importance across a wide spectrum of industries. While several thickness gauging techniques are available, they are only applicable when the area to be inspected is directly accessible. In fact, standard gauging methods require a probing sensor to be scanned over the area where corrosion damage is expected. However, this is not always possible as access can be limited due to the presence of other structural members. As an example, determination of the depth of corrosion at supports of pipelines is a major issue in the petrochemical industry. At present the only reliable way to determine the corrosion depth accurately is to lift the pipe from the support and to use standard methods, thus resulting in a very costly and potentially hazardous inspection procedure. Here, we propose a tomographic approach similar to X-ray CT. However, instead of using ionizing radiation we employ guided ultrasonic waves that can be transmitted across the inspection area from a remote and accessible transducer location. While the interaction of photons with matter can be described by simple ray models in X-ray CT, scattering, diffraction and refraction phenomena characterise the encoding of mechanical property information in guided wave signals. These phenomena add much complexity to the problem of retrieving thickness maps in GWT and represent the main challenge of this proposal. Therefore, at a fundamental level this programme aims at developing a general approach to GWT that can address this complexity borrowing ideas developed in geophysical exploration and medical diagnostics. From a more applied perspective, we propose to develop a field deployable prototype for mapping corrosion at supports which will serve the twofold purpose of maintaining the research focussed on practical problems and of facilitating the translation of the proposed technology to industry. Moreover, the prototype will have a flexible design that will allow its application to corrosion mapping problems in inaccessible areas other than pipe supports to ensure that the proposed technology will have an impact across a wide spectrum of industries. This proposal is being submitted within the UK Research Centre in NDE to the targeted research programme, the funding for which is earmarked by EPSRC for industrially driven NDE research. It is supported by Shell and Petrobras who are contributing 90k cash as well as in-kind contributions to the project.