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

对于纤维增强材料、聚合物合金或功能梯度材料等新材料，宏观力学性能往往由微观结构控制。为了开发具有高强度或高功能的新材料并有效地利用这些材料，重要的是要准确地了解在各种载荷条件下材料内部的微观结构变化和相关损伤。材料的超声波评价似乎是一个适当的技术，为这些目的。然而，从超声波波形中有效地提取有意义的信息一直是困难的，本研究的最终目的是将小波变换应用到超声波波形的时频分析中，开发一个无损评价系统，用于材料内部微观结构的变化和损伤。主要研究成果如下：（1）对小波变换在弹性波时频分析中的应用进行了初步研究。(2)在文献[1]的基础上，开发了一套基于超声波波形时频分析的材料损伤细观结构参数提取软件。(3)研制了材料超声检测实验装置。(4)对部分损坏的样本进行超声检测。(5)通过在（3）中开发的软件分析在（4）中获得的数据，以提取与材料的微观结构或损伤相关的参数。(6)一些论文发表在期刊上。

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.