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Subharmonic ultrasonic measurement and imaging for quantitative evaluation of stress corrosion and fatigue cracks

用于定量评估应力腐蚀和疲劳裂纹的次谐波超声测量和成像

基本信息

批准号：
16206071
负责人：
YAMANAKA Kazushi
金额：
$ 31.28万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

To establish the basis of subharmonic ultrasonic measurement and imaging of the fatigue and stress corrosion cracks, we first derived an analytical solution considering the adhesion force, and realized the relation between the threshold of subharmonic eave generation and the crack closure stress. Nest, we developed the elastc body-oscillator model since detailed information is needed to develop practical apparatus. Through numerical analysis of this model, we investigated the dependence of subharmonic wave upon the input wave amplitude and upon the closure stress, and comparison between measured and calculated waveform in experiments of fatigue cracks in an aluminum alloy (A7075).As the next step we developed nonlinear ultrasonic imaging system for detailed measurement of the depth of closed cracks in thickness direction. As a transmitter, we employed a LiNbO3 single crystal oscillator that has excellent durability for high voltage electric signal and employed an array sensor for producing image by the received signal focusing. Moreover, the delay law within the specimen was formulated and designed a IIR digital filter as a preprocess before imaging to construct a system that can be used to obtain linear and nonlinear images of cracks.In addition, we applied the developed system above described to open and closed cracks in aluminum alloy and showed that the subharmonic image is useful for imaging closed cracks. Moreover, we verified the system to closed crack in stainless steel (SUS316L) specimen with comparable thickness to that used in recirculator piping of atomic power plants. Then we proved that it has high accuracy in crack sizing. Finally, we applied this system to cracks in steel specimen generated under processing, and we showed that the system is useful for oblique and branched cracks.

为了建立疲劳和应力腐蚀裂纹的次谐波超声测量和成像的基础，我们首先推导了考虑粘附力的解析解，并实现了次谐波波峰产生阈值与裂纹闭合应力之间的关系。 Nest，我们开发了弹性体振荡器模型，因为开发实用设备需要详细信息。通过对该模型的数值分析，我们研究了次谐波对输入波幅和闭合应力的依赖性，以及铝合金 (A7075) 疲劳裂纹实验中测量波形和计算波形的比较。下一步，我们开发了非线性超声成像系统，用于详细测量厚度方向闭合裂纹的深度。作为发送器，我们采用了对高压电信号具有出色耐久性的 LiNbO3 单晶振荡器，并采用了阵列传感器，通过接收信号聚焦来产生图像。此外，制定了样本内的延迟定律，并设计了 IIR 数字滤波器作为成像前的预处理，以构建可用于获得裂纹的线性和非线性图像的系统。此外，我们将上述开发的系统应用于铝合金中的开放和闭合裂纹，并表明分谐波图像对于闭合裂纹成像非常有用。此外，我们还验证了该系统可闭合不锈钢 (SUS316L) 样本的裂纹，其厚度与原子能发电厂再循环器管道中使用的样本相当。然后我们证明了它在裂纹尺寸测量方面具有较高的准确性。最后，我们将该系统应用于钢试样加工过程中产生的裂纹，并表明该系统对于斜裂纹和分支裂纹很有用。