金属微裂纹的非线性超声检测系统研究

发布时间：2018-05-31 00:41

本文选题：非线性超声 + 信号调理　；参考：《电子科技大学》2017年硕士论文

【摘要】：在当今的工业生产中,金属构件在各类生产设备中被广泛地使用。而伴随着金属构件的制造、加工以及使用,会不可避免地在其表面或者内部形成微裂纹。同时,在长期载荷、温度变化和腐蚀介质的影响下,金属构件的微裂纹会增大,导致金属构件的断裂,给生产造成巨大的危害和损失。因此,检测金属构件的微裂纹已迫在眉睫。传统的超声波检测方法是利用声波的反射、散射等线性特征进行检测,故受限于其原理,对金属微裂纹的检测不敏感。而根据最新的材料力学和声学研究表明,材料内部性能变化(如应力、微裂纹等)与材料的超声非线性效应有着密切的关联。因此,非线性超声检测在材料的无损检测工作中得到了广泛的关注。但是对于非线性超声检测系统的开发还不尽完善,因此本文设计了一套完整的非线性超声检测系统,具体包括以下内容:1.首先是对非线性超声理论进行了相关研究,从非线性超声响应信号的分析出发,阐述了在非线性超声中高次谐波产生的原理。然后从理想情况下的一维非线性波动方程和连续性方程出发,推导出二阶相对非线性系数,并作为非线性超声检测的判断依据。2.接着介绍了现阶段非线性超声检测常用的检测方法,根据非线性超声的相关知识和自身条件选取有限振幅法作为本文金属微裂纹的非线性超声检测方法,并设计一套完整的非线性超声检测方案。3.设计合理的信号调理电路,对超声换能器接收端接收到的信号进行预处理。同时设计一套基于FPGA的非线性超声信号采集系统,包括其硬件电路设计和功能实现。4.利用上述设计的检测方案进行实验平台搭建,对铝制试件进行非线性超声实验检测,并对结果进行处理和分析,从而验证该非线性超声检测系统的实用性。
[Abstract]:In today's industrial production, metal components are widely used in all kinds of production equipment. With the manufacture, processing and use of metal components, microcracks will inevitably form on the surface or inside of metal components. At the same time, under the influence of long-term load, temperature change and corrosion medium, the micro-crack of metal member will increase, which will lead to the fracture of metal member and cause great harm and loss to production. Therefore, it is urgent to detect microcracks in metal components. The traditional ultrasonic detection method is based on the linear characteristics such as reflection and scattering of sound waves, so it is limited by its principle and is not sensitive to the detection of metal microcracks. According to the latest material mechanics and acoustics studies, it is shown that the change of internal properties (such as stress, microcracks, etc.) is closely related to the ultrasonic nonlinear effect of materials. Therefore, nonlinear ultrasonic testing has been widely concerned in the nondestructive testing of materials. However, the development of nonlinear ultrasonic detection system is not perfect, so this paper designs a complete nonlinear ultrasonic detection system, including the following contents: 1. Firstly, the theory of nonlinear ultrasound is studied. Based on the analysis of nonlinear ultrasonic response signal, the principle of high-order harmonic generation in nonlinear ultrasound is expounded. Then the second order relative nonlinear coefficient is derived from the one-dimensional nonlinear wave equation and continuity equation under ideal condition, which is used as the judgment basis of nonlinear ultrasonic detection. Then it introduces the commonly used detection methods of nonlinear ultrasonic detection at present. According to the relevant knowledge of nonlinear ultrasound and its own conditions, the finite amplitude method is selected as the nonlinear ultrasonic detection method for metal microcracks in this paper. And designed a complete set of nonlinear ultrasonic detection scheme. 3. A reasonable signal conditioning circuit is designed to preprocess the signal received at the receiving end of the ultrasonic transducer. At the same time, a nonlinear ultrasonic signal acquisition system based on FPGA is designed, including its hardware circuit design and function realization. The experimental platform is built with the above designed testing scheme, and the nonlinear ultrasonic testing of aluminum specimen is carried out, and the results are processed and analyzed to verify the practicability of the nonlinear ultrasonic testing system.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.285

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