超声波法测定不同材料的杨氏模量

弹性模量是一个关键的机械性能，用来弹性变形下的应力和应变之间的关系。超声波测量是检测弹性模量的一个高效的方法。这种方法是一种非破坏性的测量，不会打破或损坏材料，具有较高的精度。这份报告介绍了超声波检测的背景和理论;解释了超声波探测量的两种模式;描述了几种声速测量方法;设计了一个超声波测量系统。报告所涉及的实验包括样品准备，超声波检测和数据同步到电脑进行分析。通过超声波在材料中通过速度和材料密度获得材料的杨氏模量。实验结果显示金属样品测量精度优于塑料样品。实验的未来工作包括提高测量精度和扩大样品范围。
关键词：杨氏模量， 超声波测量，超声波速度，非破坏性测量
Abstract
Elastic Modulus is a critical mechanical property describing the relationship between stress and strain under elastic deformation. One effective and efficient method to detect elastic modulus is by ultrasonic measurement. This method is one kind of Non-destructive Measurement which will not break or damage the material while measuring it, and has a high accuracy compared with other methods. In this report, background and theory of ultrasonic testing are introduced; two modes of ultrasonic testing and measurement are explained; a series of ultrasonic velocity measuring methods are reviewed; and an ultrasonic measuring system is designed, followed by selecting appropriate equipment. Samples for measurements are first prepared according to the requirement. After that, several experiments are conducted to measure the ultrasonic velocity in these samples of different materials. The results are loaded to a PC for better calibration. The obtained experimental velocity is then used to determine the elastic modulus of these materials. Testing results of metals are better than results of polymers. Because ultrasonic waves penetrate much faster in polymers, makes it difficult to figure out round trip times. Further efforts have to be made to improve the accuracy of testing results. This includes a better design of ultrasonic wave measurement method and a better set up of experimental equipment. Lastly, testing range could be widened to ceramics and fibre-reinforced composite, which are difficult to measure the elastic modulus by traditional methods.

Keywords: Young’s Modulus, Ultrasonic Measurement, Ultrasonic Velocity, non-destructive measurement
Chapter One: Introductio

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