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，宏观力学性能往往受微观结构的控制。为了开发高强度或高功能的新材料并有效地利用这些材料，准确地了解不同加载条件下材料内部微观结构的变化及其相关的损伤是非常重要的。材料的超声波评估似乎是一种适合于这一目的的技术。本研究的最终目的是将小波变换应用到超声波形的时频分析中，开发一种对材料内部微观结构变化和损伤进行无损评价的系统。本课题取得的成果如下：(1)利用小波变换对弹性波时频分析进行了一些基础性研究。(2)根据(1)的结果，(3)研制了材料超声检测的实验装置。(4)对部分损伤的试件进行了超声检测。(5)利用(3)中开发的软件对(4)中的数据进行了分析，以提取与材料微观结构或损伤相关的参数。(6)在期刊上发表了一些论文。

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.