Combined remote thermography and non-contact ultrasonic inspection techniques using pulsed laser excitation

2005年5月，这项新提案的研究人员开始了一项为期一年的可行性研究（EP/C517695/1和EP/C517709/1），这项新的无损检测技术表明，金属部件中的裂纹可以通过连续波和脉冲激光束加热的热成像法检测出来。该研究是由EPSRC和三个RCNDE工业合作伙伴（Rolls-Royce，BNFL和RWE Npower）通过英国无损评估研究中心（RCNDE）资助的有针对性的研究项目。RCNDE一开始就要求进行一次简短的可行性研究，因为拟议的技术未经试验，并被认为具有重大的技术风险，但RCNDE董事会同意，如果可行性研究取得的结果令人鼓舞，将随后申请进行全面的研究方案，这就是目前的研究提案。RCNDE董事会同意，应在上述工业伙伴的支持下，作为一个有针对性的研究项目，进行更广泛的调查。EPSRC对可行性研究最后报告的审查将结果评为优秀。激光束加热用于热成像的新方法具有传统闪光灯热成像无损检测的所有优点：它是一种非接触技术;它提供了一个非常清晰和简单的解释缺陷指示;可以快速检测大面积（使用扫描脉冲激光束），并且它需要很少的样品表面准备。此外，在使用脉冲激光器的情况下，同时产生超声波，并且超声波可以被监测以确认裂纹的存在并进一步消除裂纹。目前，大多数复杂部件，例如燃气涡轮机叶片，采用荧光染料渗透法检查裂纹，这种方法需要仔细和耗时的部件清洗和表面处理，由表面划痕产生的裂纹引起的呼叫。我们的新技术提供了一个有吸引力的替代方案，具有更快，更可靠的潜力，并提供有关检测到的缺陷的更多定量信息。此外，由于激光束可以沿沿着光纤传输，并且现在可以使用非常小的红外摄像机，因此该技术提供了一种检查严格限制进入的部件（例如管内）的方法。虽然为期一年的可行性研究表明，新的无损检测技术具有上述令人兴奋的优点，但它们还没有准备好在工业中实施，因为它们的缺陷检测灵敏度尚未确定，它们在真实的部件检测中的可靠性尚未得到测试。这个后续项目的任务是完成所需的调查，这是必要的，使一个新的无损检测技术的点，它可以被引入到工业中。

In May 2005, the investigators of this new proposal started a one-year feasibility study (EP/C517695/1 & EP/C517709/1) of a novel NDE technique that showed cracks in metal components can be detected by thermography using cw and pulse laser beam heating. The study was a targeted research project funded by EPSRC and three RCNDE industrial partners (Rolls-Royce, BNFL & RWE Npower) through the UK Research Centre in Non Destructive Evaluation (RCNDE). A short feasibility study was requested by RCNDE at the outset because the proposed techniques were untried and judged to have significant technical risk, but there was agreement from the RCNDE Board that if the results obtained in the feasibility study were encouraging, an application would follow for a full research programme which is the current research proposal. The RCNDE Board have agreed that a more extensive investigation should proceed as a targeted research project supported by the same industrial partners, listed above. The EPSRC Review of the Final Report on the feasibility study ranked the outcome as tending to outstanding . The new method of laser beam heating for thermography has all the advantages of conventional flash lamp thermography NDE: it is a non-contact technique; it provides a very clear and simple to interpret defect indication; large areas can be inspected rapidly (using a scanned pulse laser beam) and it requires little sample surface preparation. In addition, where a pulsed laser is used, ultrasonic waves are generated simultaneously and can be monitored to confirm the presence of a crack and to further characterise it. Currently, most complex components, eg gas turbine blades, are inspected for cracks by the fluorescent dye penetrant method which relies on careful and time-consuming component cleaning and surface preparation and is prone to false-calls caused by surface scratches producing indications of cracks. Our new techniques provide an attractive alternative that has the potential of being quicker, more reliable and of providing more quantitative information about a detected defect. In addition, because laser beams can be delivered along optical fibres and very small infrared cameras are now available, the techniques offer a means of inspecting parts where access is severely restricted / eg inside tubes. Whilst the one year feasibility study has shown the new NDE techniques to have the exciting advantages summarised above, they are not ready for implementation in industry because their defect detection sensitivities have not been determined and their reliability in the inspection of real components has not been tested. The tasks of this follow on project are to complete the required investigations that are necessary to bring a new NDE technique to the point at which it can be introduced into industry.