Abstract
Based on the conventional digital photoelastic method, this dissertation developed a digital dynamic photoelastic system to record the dynamic photoelastic fringe patterns. First, the system can be used to observe the stress distributions of standing wave and thermal stress generated by the ultrasonic wave. In the field of industrial production, the application of the ultrasonic wave can be found frequently. Only after sufficient understanding and proper practice of the ultrasonic wave, the efficiency and quality of the production can be improved. Next, the states of stresses in several photoelastic strips with different sizes of V-notches under the incidence of the ultrasonic wave were investigated. The obtained results are useful when applying the ultrasonic wave in the optoelectronic semiconductor industry. Finally, the dynamic photoelastic system was used to investigate the stress wave of T-shape structural components under impact. The dynamic loading usually causes critical damage of the structures during impact or earthquake. To ensure safety, it is necessary to analyze the stress concentration effect of structures under impact. When the object is affected by the ultrasonic wave or impact, the generated stress wave is different from the conventional static stress distribution. For whole field and real time observation, the dynamic photoelastic method is the best method to investigate this problem. With the aid of finite element method, complete understanding can be obtained and further research can be performed. In addition, the efficiency of the ultrasonic machining can be improved, new fields of the ultrasonic machining technology can be developed, and evaluation of the safety of the structures under dynamic load can be facilitated. In this dissertation, the time-averaged photoelastic method was proposed. By comparing the gray level distributions of the proposed theory and experimentally obtained photoelastic fringe pattern generated by standing wave only, the correctness of the time-averaged photoelastic method was verified. By using this new method, stress characteristics of a harmonic wave motion can be readily obtained and the experimental procedures are much simplified.