基于背散射信号时频分析的碳纤维复合材料微缺陷研究
发布时间：2019-05-18 12:57
【摘要】：碳纤维复合材料广泛应用于各个领域,随着材料结构和工艺的不断发展,传统的超声检测技术在复合材料无损检测中遇到了很多问题。本文针对碳纤维复合材料在使用超声波脉冲反射法检测时,传统的底波衰减法难以对材料缺陷进行定位以及由于材料形状复杂及超声波衰减严重导致没有底波的情况,结合复合材料微缺陷超声背散射检测相关自然科学基金项目,通过理论分析背散射信号的机理和特点并结合具体实验研究,为复合材料的超声波检测技术提供了新的思路。第一章阐述了论文的研究背景和意义,介绍了碳纤维复合材料主要的微缺陷类型,对微缺陷的无损检测技术以及与复合材料超声检测相关的信号处理技术进行分析,并给出论文研究的主要内容和章节安排。第二章研究了超声波在层状复合材料中的传播特性,分析了层状复合材料结构噪声的原理,给出了结构噪声一阶谐振频率的计算公式。研究了缺陷的低通滤波特性,分析了背散射信号的组成成分及其特点。第三章介绍了常用的超声检测信号频谱分析方法及其不足之处,分析了选取小波时频分析方法处理背散射信号的优点,深入分析了CMOR基小波的特性,选择了较佳的CMOR小波参数,介绍了背散射信号时频图像的意义。第四章介绍了本论文实验所采用的五自由度水浸式超声检测系统,提出了用区域划分的方法对碳纤维复合材料超声检测背散射信号进行时频分析,采用三维时频图像和纹理子图对背散射信号频率轮廓与系统噪声频率的变化趋势进行了分析。第五章选择了小波阈值去噪方法对远表面背散射信号去噪处理,针对背散射信号不同区域内缺陷的特征建立了不同的缺陷识别定位算法,通过实验验证了采用时频分析和缺陷定位方法对碳纤维复合材料微缺陷评估的可行性。第六章总结了全文的主要内容和研究成果,并对接下来的研究内容作了展望。
[Abstract]:Carbon fiber composites are widely used in various fields. With the continuous development of material structure and technology, the traditional ultrasonic testing technology has encountered many problems in the nondestructive testing of composite materials. In this paper, when carbon fiber composites are detected by ultrasonic pulse reflection method, the traditional bottom wave attenuation method is difficult to locate the material defects and there is no bottom wave due to the complex shape of the material and the serious ultrasonic attenuation. Combined with the related natural science fund projects of ultrasonic backscattering detection of composite microdefects, the mechanism and characteristics of backscattering signal are analyzed theoretically and combined with specific experimental research, which provides a new idea for ultrasonic testing technology of composite materials. In the first chapter, the research background and significance of the paper are described, the main types of micro-defects of carbon fiber composites are introduced, and the nondestructive testing technology of micro-defects and the signal processing technology related to ultrasonic testing of composite materials are analyzed. The main contents and chapter arrangements of the paper are given. In chapter 2, the propagation characteristics of ultrasonic wave in layered composites are studied, the principle of structural noise of layered composites is analyzed, and the formula for calculating the first order resonance frequency of structural noise is given. The low pass filtering characteristics of defects are studied, and the composition and characteristics of backscattering signals are analyzed. In the third chapter, the common spectrum analysis methods of ultrasonic detection signals and their shortcomings are introduced, the advantages of selecting wavelet time-frequency analysis method to deal with backscattering signals are analyzed, the characteristics of CMOR based wavelet are deeply analyzed, and the better CMOR wavelet parameters are selected. The significance of time-frequency image of backscattering signal is introduced. In the fourth chapter, the five-degree-of-freedom water immersion ultrasonic testing system used in this paper is introduced, and the time-frequency analysis of the backscattering signal of carbon fiber composite ultrasonic testing is carried out by using the method of region division. The frequency profile of backscattering signal and the changing trend of system noise frequency are analyzed by using three-dimensional time-frequency image and texture subgraph. In chapter 5, wavelet threshold denoising method is selected to Denoise the far surface backscattering signal, and different defect recognition and location algorithms are established according to the characteristics of defects in different regions of backscattering signal. The feasibility of using time-frequency analysis and defect location method to evaluate the micro-defects of carbon fiber composites is verified by experiments. The sixth chapter summarizes the main content and research results of the full text, and looks forward to the next research content.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332
本文编号：2480026
[Abstract]:Carbon fiber composites are widely used in various fields. With the continuous development of material structure and technology, the traditional ultrasonic testing technology has encountered many problems in the nondestructive testing of composite materials. In this paper, when carbon fiber composites are detected by ultrasonic pulse reflection method, the traditional bottom wave attenuation method is difficult to locate the material defects and there is no bottom wave due to the complex shape of the material and the serious ultrasonic attenuation. Combined with the related natural science fund projects of ultrasonic backscattering detection of composite microdefects, the mechanism and characteristics of backscattering signal are analyzed theoretically and combined with specific experimental research, which provides a new idea for ultrasonic testing technology of composite materials. In the first chapter, the research background and significance of the paper are described, the main types of micro-defects of carbon fiber composites are introduced, and the nondestructive testing technology of micro-defects and the signal processing technology related to ultrasonic testing of composite materials are analyzed. The main contents and chapter arrangements of the paper are given. In chapter 2, the propagation characteristics of ultrasonic wave in layered composites are studied, the principle of structural noise of layered composites is analyzed, and the formula for calculating the first order resonance frequency of structural noise is given. The low pass filtering characteristics of defects are studied, and the composition and characteristics of backscattering signals are analyzed. In the third chapter, the common spectrum analysis methods of ultrasonic detection signals and their shortcomings are introduced, the advantages of selecting wavelet time-frequency analysis method to deal with backscattering signals are analyzed, the characteristics of CMOR based wavelet are deeply analyzed, and the better CMOR wavelet parameters are selected. The significance of time-frequency image of backscattering signal is introduced. In the fourth chapter, the five-degree-of-freedom water immersion ultrasonic testing system used in this paper is introduced, and the time-frequency analysis of the backscattering signal of carbon fiber composite ultrasonic testing is carried out by using the method of region division. The frequency profile of backscattering signal and the changing trend of system noise frequency are analyzed by using three-dimensional time-frequency image and texture subgraph. In chapter 5, wavelet threshold denoising method is selected to Denoise the far surface backscattering signal, and different defect recognition and location algorithms are established according to the characteristics of defects in different regions of backscattering signal. The feasibility of using time-frequency analysis and defect location method to evaluate the micro-defects of carbon fiber composites is verified by experiments. The sixth chapter summarizes the main content and research results of the full text, and looks forward to the next research content.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332
【参考文献】
相关期刊论文 前4条
1 牟云飞;林莉;郭广平;李喜孟;;CFRP随机孔隙模型及孔隙率超声检测数值模拟[J];材料工程;2010年01期
2 刘玲,路明坤,张博明,王殿富,郑岩,张春清;孔隙率对碳纤维复合材料超声衰减系数和力学性能的影响[J];复合材料学报;2004年05期
3 周晓军,游红武,程耀东;含孔隙碳纤维复合材料的超声衰减模型[J];复合材料学报;1997年03期
4 刘继忠;蒋志峰;华志恒;;含孔隙形态分布特征的孔隙率超声衰减测试建模[J];航空材料学报;2006年02期
相关硕士学位论文 前1条
1 罗明;碳纤维增强树脂基复合材料孔隙率超声无损检测[D];大连理工大学;2007年
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