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ULTRASOUND DETECTION AND EMISSION TECHNIQUES: APPLICATION TO THE STUDY OF FIRST-ORDER PHASE TRANSITIONS

超声检测和发射技术：在一阶相变研究中的应用

基本信息

批准号：
EP/H024247/1
负责人：
Steven Dixon
金额：
$ 6.02万
依托单位：
University of Warwick
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH024247%2F1
关键词：
ULTRASOUND DETECTION EMISSION TECHNIQUES APPLICATION

项目摘要

The technique of Acoustic Emission has been used widely in non-destructive testing, but also has applications in measurements of first order phase transitions in single crystals. When a material is subjected to an external stimulus, such as the application of stress or changing the temperature, energy can be released in the form of elastic waves, measurable as acoustic emission. This can be due to, for example, a structural phase transition, or the formation or motion of defects (as used in non-destructive testing). These elastic waves will travel through the sample, reflecting off its sides, and can be detected at the surface. Most workers in non-destructive testing are interested mainly in the detection of sufficient events to be of significance to indicate formation of a defect. However, an understanding of the statistics of the events can have many benefits.The group at the University of Barcelona are pioneers in studying acoustic emission in martensitic-type structural phase transitions, where a crystal will change its structure as the stress and/or temperature is changed, and in understanding the characteristic avalanche phenomena observed in such transitions. We will improve on the experimental understanding and the techniques required to detect the acoustic emission. Modelling will be performed of the wave propagation within the complex sample geometries required for use in the stress rig, to develop an algorithm for locating the sources of acoustic emission, and to identify optimal transducer positions for detection of AE events. Non-contact techniques will be investigated for improving measurements, for example electromagnetic acoustic transducers and also laser based detection. Laser detection will allow smaller measurement spot-size and greater spatial resolution, and confirmation of modelling results. Laser generation of ultrasound will also be investigated; a recent study has shown that the application of ultrasonic pulses can reduce the energy barriers to hysteresis in some structural transitions in NiMnGa single crystals. We will look at generating the ultrasound pulses using non-contact methods, such as laser generation, to increase spatial resolution and simplify measurements.Samples studied will include CuZnAl and FePd, which are known to have a martensitic phase transition and will be provided by the group of Prof. Vives, and magnetic systems such as NiMnGa will be investigated to study magnetic phase transitions. This proposal covers research which is highly beneficial to both groups and which will lead to much further collaboration, as well as being of interest to other researchers. This research is not possible without a combination of expertise in theoretical models of acoustic emission, modelling of ultrasound and non-contact ultrasonics.

声发射技术不仅在无损检测中得到了广泛的应用，而且在单晶一级相变的测量中也得到了应用。当材料受到外部刺激时，例如施加应力或改变温度，能量可以以弹性波的形式释放，可以作为声发射测量。这可能是由于，例如，结构相变，或缺陷的形成或运动（如在无损检测中使用的）。这些弹性波将穿过样品，从其侧面反射，并可以在表面检测到。大多数从事无损检测的工作人员主要对检测到足以表明缺陷形成的重要事件感兴趣。然而，了解这些事件的统计数据可以带来很多好处。巴塞罗那大学的研究小组是研究马氏体型结构相变中声发射的先驱，在这种相变中，晶体会随着应力和/或温度的变化而改变其结构，并了解在这种转变中观察到的特征雪崩现象。我们将提高对实验的理解和检测声发射所需的技术。将对应力试验台所需的复杂样品几何形状内的波传播进行建模，以开发定位声发射源的算法，并确定检测AE事件的最佳换能器位置。将研究非接触技术以改进测量，例如电磁声换能器和基于激光的检测。激光探测将允许更小的测量点尺寸和更大的空间分辨率，并确认建模结果。激光产生的超声波也将进行研究;最近的一项研究表明，应用超声波脉冲可以减少在NiMnGa单晶的一些结构转变的滞后的能量障碍。我们将研究使用非接触方法（如激光产生）产生超声脉冲，以提高空间分辨率并简化测量。研究的样品将包括CuZnAl和FePd，已知它们具有马氏体相变，将由Vives教授的小组提供，并将研究NiMnGa等磁性系统以研究磁性相变。这项建议涵盖了对两个群体都非常有益的研究，这将导致进一步的合作，以及其他研究人员的兴趣。这项研究是不可能的，如果没有在声发射的理论模型，超声波和非接触式超声波建模的专业知识相结合。