SUB-MHZ ULTRASONIC INSPECTION

该建议与EPSRC支持的研究中心英国NDE研究中心（RCNDE）的目标研究计划有关。从与RCNDE内的学术界和工业界成员的讨论中可以清楚地看出，高散射/衰减材料的超声检测仍然是一个需要解决的大问题。所涉及的特殊材料--如隔热材料、耐火衬里、橡胶和玻璃纤维增强聚合物复合材料的厚段--在工业上非常重要。在许多情况下，可供选择的检查方法并不多，特别是在需要便携性和非放射性方法的情况下。该研究将探讨低于1 MHz的超声波频率可以应用于这个问题的新方法。这将需要对计量的各个方面进行研究。首先，将需要新的换能器设计，其可以产生具有所需带宽的信号。计划为此尝试微纤维复合材料（MFC）设备，与更传统的PZT元件合作。然后，这些将与各种形式的编码波形一起使用，使得互相关可以在可检测性和降低的信噪比水平方面增强测量。此外，来自界面和非缺陷对象的散射导致信号中的杂波。计划研究减少这些影响的方法，通过使用其他的想法，如（a）使用准直系统，和（B）使用偏振剪切波。最后，将设计一个系统，该系统将使用部分或全部这些元件，并可根据应用调整到不同的频率范围。这项工作将与三个工业部门合作进行：海洋船舶制造，石油和天然气工业以及金属成型。所有这些都在检查声衰减和散射材料的方法方面存在特殊问题。这些包括涂层和厚复合材料;热绝缘层，绝缘下的腐蚀，以及耐火材料等。作为这项工作的一部分，这项研究将用于设计一个可用于这些行业的便携式系统。在每种情况下进行实地测试之前，将在实验室进行测试。

This proposal is associated with the targeted research programme of the UK Research Centre for NDE (RCNDE), an EPSRC-supported research centre. It is clear from discussions held with both academics and industrial members within RCNDE that the ultrasonic inspection of highly scattering/attenuating materials is still a large problem that needs to be addressed. The particular materials in question - such as thermal insulation materials, refractory linings, rubbers and thick sections of glass fibre reinforced polymer composites - are industrially very important. In many cases, there are not many alternatives for inspection, in particular if portability and non-radiological methods are required. The research will investigate new ways in which ultrasonic frequencies below 1 MHz can be applied to this problem. This will require research into various aspects of the measurement. Firstly, new transducer designs will be needed, that can generate signals with the required bandwidth. It is planned to try micro fibre composite (MFC) devices for this, teamed up with more conventional PZT elements. These will then be used with various forms of coded waveform, so that cross-correlation can enhance the measurement in terms of detectability and reduced signal to noise levels. In addition, scattering from interfaces and non-defect objects casue clutter in the signal. It is planned to investigate ways of reducing these effects, byusing other ideas such as (a) using a collimation system, and (b) using polarised shear waves. Finally, a system will be dseigned which uses some or all of these elements, and which can tuned to operate at different frequency ranges, depending on the application.The work will be performed in collaboration with three industrial sectors: marine vessel manufacture, the oil and gas industries, and metal forming. All have particular problems with methods of inspecting acoustically attenuating and scattering material. These include coatings and thick composites; thermal insulation layers, corrosion under insulation, and risers; refractory materials, and others. As part of the work, the research will be used to design a portable system that can be used in these industries. This will be tested in the laboratory, before field tests are performed in each case.