Year

2018

Degree Name

Master of Philosophy

Department

School of Electrical, Computer and Telecommunications Engineering

Abstract

Material related parameters such as Young’s modulus and internal friction are important for mechanical and material engineering. These parameters play key roles in the material performances. It has been a great interest to measure the value of these parameters. Traditional methods including tensile test, flexure test, and others are destructive methods often cause damages to specimen and have low accuracy. In recent years, the impulse excitation technique (IET), a non-destructive technique to determine Young’s modulus and internal friction of the material has attracted great attention. The detection system used for IET is normally microphone, accelerometer and so on. Selfmixing interferometry (SMI), an emerging sensing technique, which is non-destructive, non-contact, compact structure, and low-cost has been developed for high accuracy sensing applications, such as displacement, velocity and distance measurement and so on is suitable for the material related parameters measurement. A normal SMI system consists of a laser diode (LD) and a target to form the external cavity of the LD. When a portion of the light is reflected or backscattered to the laser cavity, leading to a modulated laser power of LD. This modulated laser power is referred as SMI signal, which carries the information of vibration of the target.

In this thesis, a measurement method combining IET with SMI for material related parameters measurement is proposed. By applying wavelet transform onto the SMI signal, both resonant frequency and damping factor of the specimen vibration can be retrieved at the same time. Therefore, both Young’s modulus and internal friction of the specimen can be calculated simultaneously. The optical fibre is introduced to the system. With the installation of the optical fibre, the flexibility of the measurement is greatly improved. The measurement results show the feasibility for simultaneous measurement of material related parameters. A graphical user interface is designed to improve the user experience for the measurement.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.