Guided Wave Tomography for Accurate Corrosion Mapping in Inaccessible Areas

在难以到达的区域进行准确的腐蚀深度测绘是一个非常重要的问题。虽然有几种厚度测量技术可用，但它们仅适用于被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腐蚀损坏的区域进行扫描。然而，这并不总是可能的，因为访问可能由于其他结构成员的存在而受到限制。例如，确定管道支架处的腐蚀深度是石油化工行业的一个主要问题。目前，准确确定腐蚀深度的唯一可靠方法是将管道从支架上抬起并使用标准方法，从而导致非常昂贵且具有潜在危险的检查程序。在这里，我们提出一种类似x线CT的断层扫描方法。然而，我们使用的不是电离辐射，而是引导超声波，它可以从远程和可访问的换能器位置传输到整个检测区域。虽然光子与物质的相互作用可以用x射线CT中的简单射线模型来描述，但散射、衍射和折射现象表征了导波信号中力学性质信息的编码。这些现象增加了在GWT中检索厚度图问题的复杂性，并代表了本建议的主要挑战。因此，在基本层面上，本方案的目的是制定一种通用的GWT方法，以借鉴地球物理勘探和医学诊断方面发展起来的思想，解决这种复杂性问题。从更实用的角度来看，我们建议开发一种现场可部署的原型，用于绘制支架腐蚀图，这将达到双重目的，即保持研究集中在实际问题上，并促进拟议技术向工业的转化。此外，该原型具有灵活的设计，可以应用于除管道支撑之外的难以进入区域的腐蚀测绘问题，以确保所提出的技术将在广泛的行业中产生影响。该提案正在英国濒死体验研究中心提交给目标研究计划，该计划的资金由EPSRC指定用于工业驱动的濒死体验研究。它得到了壳牌和巴西石油公司的支持，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.