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DEVELOPMENT OF LOW FREQUENCY ACOUSTIC MICROSCOPE

低频声学显微镜的研制

基本信息

批准号：
08555024
负责人：
KAWASHIMA Koichiro
金额：
$ 8.06万
依托单位：
NAGOYA INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

The purpose of this project is to develop a low frequency acoustic microscope which measures precisely the velocities and attenuation of the leaky surface waves and visualize small defects within solids, with lens-less focused ultrasonic transducers operated at frequency less than 5OMHz and digital signal processing. The main results are summarized in the following.1. A digital measurement system has established for precise velocity measurement of the leaky creeping, surface SY and Rayleigh waves as well as attenuation measurement of the leaky Rayleigh wave.2. The mass density within a surface layer has estimated with the measured velocities and 'attenuation mentioned above and equation of leaky surface waves. The measured density of aluminum alloy and fused quartz agrees with bulk density within 10%.3. With dynamic finite element method, the wave propagation in water and solid has analyzed for a model of line focused transducer and aluminum plate. The velocities of the leaky creeping and Rayleigh waves thus calculated agree with the measured within 2%.4. The change in Young's modulus in a functional gradient Al2O3/Ni ceramics has been estimated with the measured velocities of the leaky Rayleigh and longitudinal waves.5. A sizing method of minute defects far less than the focused beam diameter is proposed, where the reflection amplitude from defects is reduced by that of the wide plane at the same depth. The spherical voids of 50 mu m in ceramics is estimated within 20%.6. The growth or healing of spall damage within a target plate under repeated high velocity impacts is well visualized with a lens-less point focused PVDF transducer, from which we can monitor nondestructively the evolution process of internal voids or cracks.

该项目的目的是开发一种低频声学显微镜，通过以低于 5OMHz 的频率运行的无透镜聚焦超声换能器和数字信号处理，精确测量泄漏表面波的速度和衰减，并可视化固体内的小缺陷。主要结果如下： 1．建立了精确测量漏蠕动波、表面SY波和瑞利波速度以及漏瑞利波衰减的数字测量系统。 2．表层内的质量密度是用测量的速度和上述衰减以及泄漏表面波方程来估计的。铝合金和熔融石英的实测密度与堆积密度的吻合度在10%以内。3．采用动态有限元方法，对线聚焦换能器和铝板模型进行了波在水和固体中的传播分析。由此计算出的泄漏蠕变波和瑞利波的速度与实测值的吻合度在2%以内。4。利用漏瑞利波和纵波的测量速度估计了功能梯度Al2O3/Ni陶瓷杨氏模量的变化。 5．提出了一种远小于聚焦光束直径的微小缺陷的尺寸测量方法，其中来自缺陷的反射幅度被相同深度处的宽平面的反射幅度减小。陶瓷中50μm的球形空隙估计在20%以内。6。使用无透镜点聚焦 PVDF 传感器可以很好地可视化反复高速冲击下靶板内剥落损伤的生长或愈合情况，从中我们可以非破坏性地监测内部空隙或裂纹的演变过程。