Research On New Technology Measuring In-plane Displacement Of A Rigid Body Using Ultrasonic Speckle Correlation Method

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.