【作者】 蒋志峰；

【导师】 周晓军；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2004， 硕士

【摘要】 超声波频域分析是把频域分析的理论和方法应用于超声检测的技术。一般来说，简单的超声波原始信号能够提供的信息是有限的，远不能满足声波分析和特征识别的需要，须对其进行一定的加工和处理。通过对域函数图谱的识别、特征提取和分析，能获得更多有用信息，以便更好地指导工程实践。 本文依托航空件超声扫描检测系统研制项目的工程背景，主要研究在超声自动检测、无损评价中超声信号处理、超声频域分析理论、方法及其对有关工件缺陷识别的应用。论文的主要章节内容安排如下： 第一章为绪论，介绍了课题研究背景和要求，阐述了传统超声波探伤技术的局限性，以及国内外检测中信号处理和频谱分析的现状和意义，并结合工程项目提出本文的研究内容，最后给出了论文的总体框架。 第二章在分析常规超声检测系统组成的基础上，建立超声波频谱分析系统理论模型，结合课题要求选择设计合理的超声波频谱分析实现系统。针对不同形状和大小的缺陷的幅频特性，以及超声场与缺陷相互作用机理进行理论研究，得出计算表达式。从声辐射场理论出发，证明利用各种缺陷在幅频特性上所显示的规律可确定它们的缺陷种类。 第三章针对超声波检测信号特点，给出超声频谱分析的基本原理与方法。根据超声检测机器人和系统频谱分析模型本身的特点，以及系统软件的要求，对频谱分析进程设计方法作了概括介绍。对频谱分析的总体要求、关键技术、主要算法及其相应软件数据结构的实现作了说明。 第四章介绍了在自行构建的超声频谱分析系统上，进行超声频域特征应用方法与技术的研究。利用超声频谱分析法对换能器进行频率特性分析，找出适合检测的最佳状态。研究典型金属工件缺陷或结构特性对声波调制的声学机理，给出了用超声频域分析法对工件缺陷特征进行分析的实例。 第五章探讨碳纤维复合材料孔隙率检测的频域分析理论和方法，对碳纤维复合材料孔隙率检测法进行频域实验分析和讨论，并分析了孔隙形态对超声衰减的影响。 第六章分析超声检测频域分析的误差来源和局限性，提出了减少误差可采取的相应方法。对自己的工作进行了回顾和总结，对下一步工作提出了一些初步的设想。更多还原

【Abstract】 Ultrasonic spectrum analysis is the ultrasonic testing technology which puts into use the spectrum analysis theory and approach. Generally speaking, simple and primitive ultrasonic signals can provide relatively limited information and therefore are far from being capable of satisfying the need of sonic analysis and feature recognition which the help of necessary processing and research. Through recognition of domain function chart as well as feature extraction and analysis, more useful information can be obtained to instruct the engineering application.This essay is to study under background of the project "ultrasonic scan testing system development for aircraft workpiece" ultrasonic automatic testing, ultrasonic signal processing in nondestructive evaluation, ultrasonic spectrum analysis theory, and approach as well as its application in relating workpiece-defection recognition. The six chapters of this essay are as follows:Chapter 1 is the preface which introduces the background and necessity of subject research, and thereafter describes the limitation of traditional ultrasonic flaw-detecting technique in addition to the current condition and significance of signal processing and spectrum analysis of testing technology in China and abroad. And along with the model engineering project the research target of this essay is then proposed to offer a general framework of the dissertation.Chapter 2 is to establish theoretical model of ultrasonic spectrum analysis system and to adopt in accordance with subject demands the reasonably designed practical system of ultrasonic spectrum analysis on the basis of regular ultrasonic testing system formation analysis. The calculation formula are attained aiming at the flaw spectrum features of different shapes and sizes as well as theoretical analysis of mutual function between ultrasonic field and flaws. Theory of sonic radiation field is adopted to define the flaw classification on the basis of confirmation of various flaws indicated on the frequency features.Chapter 3 provides primary principles and approaches of ultrasonic spectrum analysis in accordance with features of ultrasonic testing signals. With feature of ultrasonic testing robot, models of system spectrum analysis as well as demands of system software as the foundation, a general introduction of approaches of spectrum analytic processing designs is to offered. We also illustrate in this chapter the general demands, key techniques, chief calculation approaches and realization ofcorresponding software data structures.Chapter 4 introduces the research of application and techniques of ultrasonic spectrum features on the analytic system which has been constructed. Spectrum feature analysis of the transducer apparatus is also conducted with this approach and thus achieves the best testing status. Through the study of sonic adjustment of structure features, analytic examples of metal workpiece defect features are provided.Chapter 5 is to discuss spectrum analytic theory and application of void content measure testing of carbon fibre reinforced plastics in order to analyze and discuss spectrum experiment of it. The impact of void shape on ultrasonic attenuation is discussed as well.Chapter 6 is to analyze error sources and limitations of ultrasonic spectrum analysis and there by suggest the applicable approach to the research work, primary conception of the following research is being advanced.更多还原