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High Frequency Flexural Ultrasonic Transducers (HiFFUT) - a new class of transducer

高频弯曲超声波换能器 (HiFFUT) - 一种新型换能器

基本信息

批准号：
EP/N025393/1
负责人：
Steven Dixon
金额：
$ 152.15万
依托单位：
University of Warwick
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FN025393%2F1
关键词：
Frequency Flexural Ultrasonic Transducers HiFFUT

项目摘要

Flexural transducer currently are only designed for operation in ambient atmospheric conditions, at frequencies of up to approximately 50 kHz, with a long wavelengths in fluids and therefore reduced measurement resolution in many cases. If we could find a way to increase the frequency range of operation of these devices, whilst at the same time creating new designs that could withstand high pressures and temperatures, a plethora of new applications will open up, in some cases enabling measurements to be made that could not otherwise be taken - that is what this project will do, establishing a world lead in this field of research of High Frequency Flexural Transducers. Techniques will be created that used the HiFFUTs for the non-destructive testing of low acoustic impedance materials such as aerospace composites, flow measurements and metrology in hostile environments.Flexural ultrasonic transducers (sometimes referred to as uni-morphs) operate through the action of the bending / flexing of a piezoelectric material that is attached to a passive material. This is exactly how an ultrasonic car parking sensor operates, and these devices operating at twice the maximum audible frequency of humans, of around 40kHz, have had a tremendous impact, particularly on the automotive sector. The key to the success of flexural transducers used in parking sensors lies in the fact that they are extremely sensitive and efficient, whilst at the same time they are relatively simple to construct and are extremely robust. Imagine the typical environment that these sensors have to survive in; high vibration, large fluctuations in operating temperature, corrosive, dirty and wet conditions - whilst operating at a low power with a high sensitivity. So what makes these flexural transducers attractive to the automotive sector, where there is high pressure to keep sensor costs low at the same time as the sensors being very reliable? The two key factors are that (1) the piezoelectric element is bonded to the inside of a metal cap and the rear of the cap is hermetically sealed, and (2) the flexing of the metal cap and thin piezoelectric element, either from piezoelectric excitation or the arrival of a pressure wave requires relatively little energy. There is currently a surprising lack of any published, rigorous scientific study on these types of small flexural transducers, even at low frequencies and nothing appears to have been attempted using these types of transducers in liquids or for non-destructive evaluation. The vibration characteristics of a HiFFUT are dependent on the combined response and interaction of all the sensor's components with the medium it operates within or upon. Usually the mechanical response of these transducers is dominated by the vibration behaviour of the passive flexing membrane of the transducer housing to which the piezoelectric is attached, rather than the thickness or diameter of the piezoelectric element bonded to the housing. There are related examples of MEMs based transducers that operate by a flexural membrane at higher frequencies such as Capacitive Micro-machined Ultrasonic Transducers and Piezoelectric Micro-machined Ultrasonic Transducers and whilst these are clearly elegant devices, there are clearly a number of significant advantages to the use of HiFFUTs in many industrial applications. The most useful modes of operation are probably the axisymmetric modes, which will generate axisymmetric wave fields and work will mainly focus on these, but there may be instances where an anisotropic wave field provides an advantage. Flexural transducers or HiFFUTs can also be driven at a number of axisymmetric harmonic modes or frequencies - using one transducer to cover a wide bandwidth, with each mode having a different directivity pattern will dramatically increase the depth and breadth of information that can be obtained. These transducers are going to find applications in a wide range of industrial application

目前，弯曲换能器仅设计用于在大气环境条件下工作，频率高达约50 kHz，在流体中具有长波长，因此在许多情况下降低了测量分辨率。如果我们能找到一种方法来增加这些设备的工作频率范围，同时创造出能够承受高压和高温的新设计，那么大量的新应用将会打开，在某些情况下，可以进行无法进行的测量-这就是这个项目将要做的，在高频弯曲换能器的研究领域建立世界领先地位。将创建使用hiffut的技术，用于低声阻抗材料的无损检测，如航空航天复合材料，恶劣环境下的流量测量和计量。弯曲超声换能器（有时被称为单变形换能器）通过附着在被动材料上的压电材料的弯曲/弯曲作用来工作。这正是超声波停车传感器的工作原理，这些设备的工作频率是人类最大可听频率的两倍，约为40kHz，已经产生了巨大的影响，特别是在汽车领域。用于驻车传感器的弯曲换能器成功的关键在于它们非常敏感和高效，同时它们构造相对简单并且非常坚固。想象一下这些传感器必须生存的典型环境；高振动，工作温度大波动，腐蚀性，肮脏和潮湿的条件-同时在高灵敏度的低功率下工作。那么，是什么让这些弯曲传感器对汽车行业有吸引力呢？在汽车行业，要保持传感器的低成本，同时又要保证传感器的可靠性，这是一个很高的压力。两个关键因素是：(1)压电元件粘接在金属帽的内部和帽的后部是密封的；(2)金属帽和薄压电元件的弯曲，无论是压电激励还是压力波的到来，都需要相对较少的能量。目前令人惊讶的是，即使在低频率下，对这些类型的小型弯曲换能器也缺乏任何已发表的严格的科学研究，并且似乎没有尝试在液体中使用这些类型的换能器或进行无损评估。HiFFUT的振动特性取决于所有传感器组件与介质的综合响应和相互作用。通常，这些换能器的机械响应是由压电元件所附着的换能器外壳的被动弯曲膜的振动行为所决定的，而不是与外壳结合的压电元件的厚度或直径。基于MEMs的换能器在更高频率下通过弯曲膜工作，例如电容式微机械超声换能器和压电式微机械超声换能器，虽然这些显然是优雅的设备，但在许多工业应用中使用hiffut显然有许多显着的优势。最有用的工作模式可能是轴对称模式，它将产生轴对称波场，工作将主要集中在这些模式上，但也可能存在各向异性波场提供优势的情况。弯曲换能器或hifft也可以在多个轴对称谐波模式或频率下驱动-使用一个换能器覆盖很宽的带宽，每个模式具有不同的指向性模式，将大大增加可以获得的信息的深度和广度。这些传感器将在广泛的工业应用中得到应用