超声导波损伤检测技术改进研究

发布时间：2018-04-05 19:01

本文选题：结构健康监测　切入点：Lamb波成像　出处：《中国科学技术大学》2017年硕士论文

【摘要】：在平板结构的健康监测领域,Lamb波由于具有传播范围广,对缺陷敏感等优点,被广泛使用。其中,Lamb波成像技术不仅能精确定位损伤位置,还能评估损伤程度,是Lamb波应用的研究热点。本文从Lamb波在应用中的局限性出发,提出了改进的模型和方法,旨在扩展Lamb波成像技术的应用范围,提高成像质量。本文首先对脉冲振声调制机理的做了初步研究,为后续的Lamb波振声调制效应提供理论指导。在此基础上,本文提出了基于双稳模型的Lamb波振声调制成像模型。该模型利用Lamb波的振声调制效应,可以实现Lamb波的无基准成像,同时利用双稳结构的振动特性,有效地提高板在非共振频率区的振幅,加强了调制现象。通过实验对比,发现该模型比传统模型在非共振频率区成像准确度更高,有效地扩展了 Lamb波振声调制成像方法的操作带宽。针对超声导波成像的频散补偿方法进行研究,本文提出了基于时频延时的频散补偿方法。传统频散补偿方法在结构材料属性未知下需要通过幅值计算和额外实验计算波数曲线,本文通过提出的新线性映射方法,利用窄带信号时延脊线估计映射参数,实现频散补偿。该方法相较于传统方法计算简单,适用性广。仿真和实验结果验证了该方法的有效性,并且展示了该方法可以有效地提高Lamb波成像的分辨率。通过以上研究,有效地改善了 Lamb波在振动系统和频散状态下的成像质量,扩展了 Lamb波在无基准监测、长距离监测和多故障检测中的应用。
[Abstract]:Lamb waves are widely used in the health monitoring field of flat structures because of their wide range of propagation and sensitivity to defects.Lamb wave imaging can not only accurately locate the location of damage, but also can evaluate the degree of damage. It is a research hotspot in the application of Lamb wave.Based on the limitation of Lamb wave in application, an improved model and method are proposed in this paper. The purpose of this paper is to extend the application of Lamb wave imaging technology and improve the imaging quality.In this paper, the mechanism of pulse vibration-acoustic modulation is studied in order to provide theoretical guidance for the subsequent Lamb wave vibration-acoustic modulation effect.On this basis, a bistable model of Lamb wave vibration-acoustic modulation image is presented in this paper.In this model, the vibration-acoustic modulation effect of Lamb wave can be used to realize the non-reference imaging of Lamb wave. At the same time, the vibration characteristics of bistable structure can be used to effectively increase the amplitude of plate in the non-resonance frequency region and strengthen the modulation phenomenon.The experimental results show that the proposed model is more accurate than the traditional model in the non-resonance frequency region and extends the bandwidth of the vibroacoustic modulation imaging method of Lamb wave effectively.In this paper, the dispersion compensation method based on time-frequency delay is proposed for ultrasonic guided wave imaging.The traditional dispersion compensation method needs to calculate the wavenumber curve through amplitude calculation and extra experiment when the properties of structural materials are unknown. In this paper, we use the new linear mapping method to estimate the mapping parameters of narrow band signal time-delay ridge line to realize dispersion compensation.Compared with the traditional method, this method is simpler and more applicable.The simulation and experimental results show that the proposed method is effective in improving the resolution of Lamb wave imaging.Through the above research, the imaging quality of Lamb wave in vibration system and dispersion state is improved effectively, and the application of Lamb wave in non-reference monitoring, long-distance monitoring and multi-fault detection is extended.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP391.41;TB559

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