Development of Nondestructive Evaluation System of Damage Process inside Materials by Ultrasonics-Wavelet Method

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For new materials such as fiber reinforced materials, polymer alloys, or functionally graded materials, macroscopic mechanical properties are often controlled by microscopic structures. In order to develop new materials having high stregth or high functions and to utilize such materials effectively, it is important to accurately understand the change in microscopic structures and associated damages inside materials under various loading conditions. Ultrasonic evaluation of materials seems an appropriate technique for such purposes. However, it has been difficult to effectively extract meaningful information from ultrasonic waveform.The final object of this study is to develop a system for nondestructive evaluation of the change in microscopic structures and damage inside materials by applying the wavelet transform to the time-frequency analysis of ultrasonic waveform. The results obtained during the project are as follows :(1) Some basic investigations were conducted about the time-frequency analysis of elastic waves by means of wavelet transform.(2) According to the results of (1), a new software was developed for extracting parameters related to microscopic structures of damage of materials by the time-frequency analysis of ultrasonic waveform.(3) Experimental equipment was developed for ultrasonic testing of materials.(4) Ultrasonic testing was performed for specimen partially damaged.(5) Data obtained in (4) were analyzed by the software developed in (3) to extract parameters related to microscopic structures or damage of materials.(6) Some papers were published in journals.