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Photoelasticity for opaque objects

不透明物体的光弹性

基本信息

批准号：
EP/L022249/1
负责人：
Andrew Moore
金额：
$ 23.97万
依托单位：
Heriot-Watt University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FL022249%2F1
关键词：
Photoelasticity opaque objects

项目摘要

Birefringence is a difference in refractive index that occurs along different axes in a material. In some materials this effect is intrinsic due to the atomic structure. In other materials, artificial birefringence can be induced by a mechanical stress that produces anisotropies in the material. Polarized waves travel at different velocities through the stressed regions depending on their polarization direction. This phenomenon is exploited in the well-established technique of photoelasticity, in which a model of the component of interest is made in an optically transparent plastic material and placed between polarizing optics. The induced birefringence is directly proportional to the stress experienced at a given point: contours of constant difference in the principal stresses and contours of the principal stress direction appear as fringe patterns. The technique has played a fundamental role in experimental mechanics, design and manufacturing.This project is concerned with measuring the stress-induced birefringence in materials that are opaque at visible wavelengths. We will use THz illumination between 0.3 and 1.5 THz where some fraction is transmitted through a range of non-polar materials including ceramics, plastics and composites. Measuring the stress-induced birefringence will provide information on the internal stress distribution in real components that are opaque at visible wavelengths, removing the need to model it in transparent plastic. This new unique stress visualisation technique might be considered as 'photoelesticity for opaque objects', although more accurate techniques will be used to measure the phase difference that arises between the polarized components of the illumination. Measurement from the real components also enables direct validation of numerical models. These new techniques will enable in-process control during manufacturing applications and in-service quality assurance, for a range of materials where this is not currently available, enabling step changes in the manufacturing processes used and the components that can be produced.This project will provide the underpinning research to determine if measuring stress-induced birefringence at THz frequencies is feasible. The phenomenon has not been reported in the literature. Based on the fundamental measurements of the stress-optic coefficients, THz systems will be built to measure residual stress distributions and stresses produced by direct loading in ceramic and polymer materials. Non-spectroscopic imaging at THz frequencies is not well developed, enabling novel phase measurement techniques to be implemented with single point detectors and start-of-the-art line detectors. The project brings together research expertise in optical instrumentation for industrially relevant metrology and industrial collaborators with strong track records in innovation for high value manufacturing applications.

双折射是指在材料中沿不同轴方向发生的折射率差异。在某些材料中，由于原子结构，这种效应是固有的。在其他材料中，人工双折射可以由产生材料各向异性的机械应力引起。极化波以不同的速度通过应力区，这取决于它们的极化方向。这种现象在成熟的光弹性技术中得到了利用，在这种技术中，感兴趣的组件的模型被制作在光学透明的塑料材料中，并放置在偏振光学器件之间。诱导双折射与在某一点所受的应力成正比：主应力和主应力方向的等高线呈条纹状。该技术在实验力学、设计和制造中发挥了基础性作用。这个项目是关于测量在可见光波段不透明的材料的应力诱导双折射。我们将使用0.3和1.5太赫兹之间的太赫兹照明，其中一些部分通过一系列非极性材料（包括陶瓷，塑料和复合材料）传输。测量应力诱导的双折射将提供在可见光波段不透明的真实组件内部应力分布的信息，从而消除了在透明塑料中建模的需要。这种新的独特的应力可视化技术可以被认为是“不透明物体的光弹性”，尽管更精确的技术将用于测量照明偏振分量之间产生的相位差。来自真实组件的测量也可以直接验证数值模型。这些新技术将使制造应用过程中的过程控制和服务质量保证成为可能，对于目前无法获得的一系列材料，使所使用的制造工艺和可生产的组件能够进行步骤更改。该项目将提供基础研究，以确定在太赫兹频率下测量应力诱导双折射是否可行。这一现象在文献中未见报道。基于应力光学系数的基本测量，太赫兹系统将用于测量陶瓷和聚合物材料中的残余应力分布和直接加载产生的应力。太赫兹频率下的非光谱成像还没有得到很好的发展，这使得新的相位测量技术可以通过单点探测器和最先进的线探测器来实现。该项目汇集了工业相关计量光学仪器的研究专业知识，以及在高价值制造应用创新方面具有良好记录的工业合作者。