【作者】 邓玲惠；

【导师】 朱鸿茂；

【作者基本信息】 华中科技大学 ， 固体力学， 2007， 硕士

【摘要】 相干波入射到介质粗糙界面时,其折射波和背向散射波都会在空间相互干涉,形成振幅和相位随机分布的散斑场。散斑从一方面来讲是一种噪声,它会影响波的成像质量、引起信号失真等,但是另一方面来看它却是一类反映事物性质及其变化规律的信息载体。超声散射与激光、微波、应力波散射具有相似之处,对超声散射场的特性进行研究不仅有助于探索各种物质波散射场的共同特性,而且通过对超声散射场的基本特性的认识有助于创建性能优越的超声散斑干涉计量术,它将比激光散斑干涉计量的应用更为广泛和深入。对位移和应变的测量是力学测量中的重要任务。数字散斑相关法(DSCM)是一种能精确测量物体位移场的计算机辅助计量方法,其基本思想是计算物体变形前后所采集物体表面的两幅散斑图像间的互相关系数或互相关函数值随着位移及应变的变化,找出互相关系数或互相关函数值的最大值所在的点,在一定条件下,该点对应的位移与应变即为物体表面测点的实际位移和应变。本文基于激光数字散斑相关法和数字随机信号互相关及数字信号处理的理论,首先对超声散斑数字相关法测量粗糙界面的一维和二维面内位移的方法进行了理论研究,然后通过实验验证了超声散斑数字相关法测量物体面内平动位移的可行性。其次对超声散斑数字相关法测量刚体面内转动的方法进行了比较深入的研究,通过实验分析及计算,验证了算法的可行性。更多还原

【Abstract】 When a rough interface is insonified by coherent waves, there will be a speckle field in the space because of the interference between the refraction waves and the back-scattered waves. Speckles can be viewed as a kind of noise, which affects the quality of image and leads to signal distortion, whereas it can also be viewed as an information carrier of the characteristics of the interface. Ultrasound scattering is similar to laser, mircrowave and stress wave scattering. Not only the research on the properties of ultrasound scattering field will be helpful to search for the common properties of the scattering fields of various kinds of material waves, but also the analyzing of the basic properties of ultrasonic scattering field will lead to found the ultrasonic speckle interferometry, which will be used more widely than laser speckle interferometry.It is an important task to measure the displacement and strain in the mechanical testing. The digital speckle correlation method (DSCM) is a kind of computer aid test methods, which can accurately measure displacement field of an object. The basic theories of digital speckle correlation method is as follows: after the correlation coefficients or function between the speckle field images, which are changed with the displacement and strain of the object, are calculated, the point at which the correlation coefficient reaches the maximum can be found out. As a result, the displacement and strain of this maximum point are equal to that of the object under some conditions.My study is based on the theories of laser digital speckle correlation method, random digital signal correlation and digital signal process. Firstly, the theorem of ultrasonic speckle digital correlation method for measuring one and two dimensional in-plane displacement of a rough interface was studied. Then the experiments were performed and the experimental results show that the practicability of the method was viable. Lastly, the ultrasonic speckle digital correlation method for measuring in-plane rotation displacement of a rigid body was deeply explored, and it was revealed that the theoretical analysis and the experiment results were reasonable.更多还原