Compact thermosonic NDE system

热声技术是一种新型的无损检测技术，它采用红外摄像机来检测被检测部件振动时缺陷表面摩擦产生的热量，从而对缺陷（通常是裂纹或分层）进行成像。通常，在试件的一点上施加20-100 kHz范围内的高功率超声脉冲，以在结构中产生高频振动场。这种方法比需要逐点扫描的传统超声波或涡流检测技术要快得多。该方法还特别适合于检测可能导致其他技术问题的封闭裂缝。虽然世界上许多实验室已经取得了令人印象深刻的结果，但该系统，特别是激励，还需要工程设计。系统的可靠性需要改进——有人担心某些地方的缺陷会被遗漏；这几乎肯定是激振器产生的振动场的函数。需要确定所需的振动幅度，并保证这不会传播缺陷。迄今为止，商业上生产的用于焊接塑料的高功率超声波喇叭已用于激发振动。高功率喇叭的主要缺点是体积大，很难与结构重复耦合。该提案遵循早期的研究计划，其中申请人已经建立了对成功的热超声检查的激励要求的定量理解。该计划表明，对于许多工业上重要的应用，成功的热超声检查可以使用比高功率超声波焊接喇叭更低的振幅振动来完成。本提案的目标是设计和生产为特定演示应用而设计的超声波激励器。在与支持该项目的工业合作伙伴协商后，将从特别适合（即需要低激励功率）进行热超声检查的应用中选择这些演示器。较低的功率要求和量身定制的设计应该使励磁器比目前使用的笨重的超声波焊接喇叭更小、更轻。热超声系统的另一部分是红外摄像机，直到最近，它也是一个笨重的部件。然而，非常小的微bolomer阵列红外摄像机现在可用于无损检测系统。其目的是生产一种紧凑的便携式，可能是手持的热超声检测系统，该系统包含一个小型微辐射热计阵列摄像机和一个定制工程振动激励器。将完成演示部件的全振动分析，以确定最佳激励模式，以确保检测的可靠性。该系统还将包括一种监测振动的手段，使用户能够检查零件是否产生了足够的振动幅度，以可靠地完成测试。该检测系统将在选定的演示部件上进行现场测试。该项目的总体目标是将热声波技术——一种非常有前途的新濒死技术——从实验室中带出来，并成功地引入工业。除了生产原型测试系统外，该项目还将促进对超声波激振器性能的科学理解，特别是激振器与结构之间耦合的影响。对激振器产生的振动场进行非接触测量的新方法将被研究，这些方法可能具有其他科学和工业应用。

Thermosonics is a novel non-destructive evaluation (NDE) technique that employs an infrared camera to image defects, typically cracks or delaminations, by detecting the heating caused by friction at the surfaces of defects when a part under inspection is vibrated. Typically, a pulse of high power ultrasound in the 20-100 kHz range is applied at one point on the test-piece to generate a high frequency vibration field in the structure. The method is considerably quicker than conventional ultrasonic or eddy current inspection techniques that require point by point scanning. The method is also particularly well suited to the detection of closed cracks that can cause problems with other techniques. Whilst impressive results have been achieved in a number of laboratories worldwide, the system, particularly the excitation, needs engineering. The reliability of the system needs to be improved - there is concern that defects in some locations are missed; this is almost certainly a function of the vibration field that is generated by the exciter. The amplitude of vibration required needs to be defined and assurance that this will not propagate the defects is required. To date a high power ultrasound horn, of the type produced commercially to weld plastics has been used to excite vibrations. The high power horn has the major disadvantage that it is bulky and is very difficult to couple reproducibly to the structure. This proposal follows an earlier research programme in which the applicants have established a quantitative understanding of the excitation requirements for a successful thermosonic inspection. This programme has shown that for a number of industrially important applications, successful thermosonic inspections can be completed using significantly lower amplitude vibrations than those associated with high power ultrasonic welding horns. An objective of this proposal is to design and produce ultrasonic exciters that are engineered for specific demonstrator applications. These demonstrators will be selected from applications that have been found to be particularly suitable (ie requiring low excitation power) for thermosonic inspection in consultation with the industrial partners who are supporting the project. The lower power requirement and tailored design should make the exciter significantly smaller and lighter than the bulky ultrasonic welding horns in current use. The other part of a thermosonic system is an infrared camera that was, until recently, also a bulky heavy component. However, very small microbolomer array infrared cameras are now available for use in NDE systems. The intention is to produce a compact portable, possibly hand held, thermosonic inspection system incorporating a small microbolometer array camera and a custom engineered vibration exciter. A full vibration analysis of the demonstrator parts will be completed to determine the optimum mode to excitation to ensure the reliability of the inspection. The system will also include a means of monitoring the vibrations to enable the user to check that adequate vibration amplitude is produced in a part to reliably complete a test. The inspection system will be field tested on a selection of demonstrator parts. The overall aim of the project is to take thermosonics, a very promising new NDE technique, out of the laboratory and to introduce it successfully into industry.In addition to producing a prototype testing system, the project will advance scientific understanding of the performance of ultrasonic exciters, and in particular the influence of the coupling between the exciter and the structure. Novel means of non-contacting measurement of the vibration field produced by the exciter will be investigated and these are likely to have other scientific and industrial applications.