摘 要

渦流檢測是基于電磁感應(yīng)原理的一種常規(guī)無損檢測方法，具有檢測速度快，靈敏度高，非接觸測量等特點(diǎn)，已經(jīng)在航空、冶金、化工、機(jī)械等諸多工業(yè)領(lǐng)域得到了廣泛應(yīng)用。本文針對船舶焊縫裂紋進(jìn)行檢測，將渦流檢測技術(shù)、數(shù)據(jù)采集技術(shù)和數(shù)據(jù)分析處理技術(shù)有機(jī)結(jié)合起來，擬開發(fā)適合在線檢測的智能化渦流檢測系統(tǒng)。本文主要研究內(nèi)容包括：
1）在深入分析渦流檢測基本原理的基礎(chǔ)上，設(shè)計(jì)完成了一套以單片機(jī)和CPLD為控制核心的雙通道實(shí)時(shí)渦流檢測數(shù)據(jù)采集系統(tǒng)。該系統(tǒng)硬件電路包括信號放大、濾波、模數(shù)轉(zhuǎn)換、CPLD、單片機(jī)及其通信電路等，軟件設(shè)計(jì)主要涉及單片機(jī)C51程序、CPLD的VHDL程序、PC機(jī)VC程序等。該系統(tǒng)結(jié)構(gòu)簡單，性能穩(wěn)定，能較好地滿足實(shí)際需求。
2）對渦流傳感器的靜、動態(tài)特性進(jìn)行分析是評價(jià)該傳感器性能及實(shí)現(xiàn)在線補(bǔ)償?shù)闹匾h(huán)節(jié)之一。本文在了解傳感器靜態(tài)、動態(tài)性能指標(biāo)的基礎(chǔ)上，采用多種方法建立了渦流傳感器的靜、動態(tài)數(shù)學(xué)模型，并比較了相應(yīng)建模效果，為下一步傳感器特性進(jìn)行在線補(bǔ)償做了鋪墊。
3）為了減小檢測過程中的各種外界干擾和噪聲，準(zhǔn)確判斷數(shù)據(jù)，對渦流響應(yīng)信號進(jìn)行了預(yù)處理，剔除數(shù)據(jù)中的無意義壞點(diǎn)，對數(shù)據(jù)進(jìn)行平滑處理；應(yīng)用小波變換理論中小波的多尺度邊緣檢測原理對信號進(jìn)行除噪處理，極大的提高信號的信噪比，并提取了表征裂紋的特征量。
4）利用所建立的有限元模型對渦流傳感器參數(shù)進(jìn)行了仿真研究，分別討論了線圈內(nèi)徑、外徑、高度和放置方式對傳感器性能的影響，為渦流傳感器結(jié)構(gòu)參數(shù)的優(yōu)化提供了理論參考。采用優(yōu)化后的渦流傳感器，仿真分析了不同線圈位置，缺陷的長度、深度，埋藏深度和截面形狀對檢測線圈磁感應(yīng)強(qiáng)度分量的影響，為實(shí)際檢測過程中工件缺陷的定量分析奠定了基礎(chǔ)。

關(guān)鍵詞 渦流檢測；數(shù)據(jù)采集；數(shù)據(jù)處理；特性建模；有限元仿真
Abstract

Eddy current testing based on the electromagnetic induction principle is one of the regular nondestructive testing methods. Because it has the advantages of high speed, high sensitivity and non-contact measurement, it is widely applied to the manufacture field of aviation, metallurgy, chemical and mechanical industry. In order to test weld metal cracking in ship industry, a new eddy current testing system that suits for on-line detection is developed. The intelligence system is composed of eddy current inspection theory, data acquisition and processing technology and data analysis technology. The main contents are the following:
1) Based on the theory of eddy current testing technology, a data acquisition system based on MCU and CPLD (Complex Programmable Logic Device) as core control units has been designed. The hardware circuit includes signal amplification, filtering, A/D conversion, CPLD interface and MCU communication circuit. The software design includes the C51 program, VHDL program, VC program and so on. The system has simple structure and stable performance, which can meet the requirements of testing cracks.
2) Analysis on static property and dynamic property of eddy current sensor is the important point of eva luating sensor property and realizing on-line compensation. Based on the study of static and dynamic property, the mathematic models are built by various methods, and the results are compared. This work sets the stage for compensation.
3) In order to reduce the external interference and noise and judge the data accurately, the response signal of eddy current is preprocessed and the insignificant isolated points in the data are eliminated. Wavelet multi-scale edge detection technique is used to eliminate noise, improve the signal to noise and extract characteristic quantities.
4) Eddy current sensor is simulated by finite element model, and then the influences of coil’s diameter and placing mode are discussed. So this work provides the theoretic reference to the structure optimization of sensors. With the eddy current sensor optimized above, the variety disciplinarian of magnetic induction strength, which are affected by the length, depth, buried depth and shape of the different crack are simulated. It establishes basic to detect quantitatively the crack in the actual detecting process.

Keywords eddy current testing; data acquisition; data processing; property modeling;
finite element simulation
目 錄
摘 要 I
Abstract II
第1章 緒論 1
1.1 課題研究背景及意義 1
1.2 渦流檢測技術(shù) 1
1.2.1 渦流檢測技術(shù)特點(diǎn) 1
1.2.2 渦流檢測技術(shù)發(fā)展 3
1.3 渦流檢測國內(nèi)外研究現(xiàn)狀 5
1.3.1 信號處理技術(shù) 5
1.3.2 有限元分析技術(shù) 6
1.4 本課題的主要研究內(nèi)容 7
第2章 渦流檢測理論基礎(chǔ) 9
2.1 渦流檢測工作原理 9
2.1.1 渦流傳感器模型描述 9
2.1.2 渦流檢測等效電路 10
2.2 渦流檢測理論分析 11
2.2.1 電磁滲透方程 11
2.2.2 導(dǎo)體中的磁場傳播 12
2.2.3 導(dǎo)體中的渦流傳播 13
2.2.4 裂紋檢測 13
2.3 渦流檢測影響因素 14
2.4 本章小結(jié) 15
第3章 數(shù)據(jù)采集系統(tǒng)的設(shè)計(jì) 16
3.1 系統(tǒng)總體方案設(shè)計(jì) 16
3.2 調(diào)理電路模塊設(shè)計(jì) 16
3.2.1 前置放大電路設(shè)計(jì) 17
3.2.2 濾波電路設(shè)計(jì) 17
3.2.3 程控放大電路設(shè)計(jì) 18
3.3 A/D轉(zhuǎn)換模塊設(shè)計(jì) 19
3.4 控制模塊設(shè)計(jì) 19
3.4.1 CPLD模塊設(shè)計(jì) 20
3.4.2 單片機(jī)模塊設(shè)計(jì) 22
3.5 PC機(jī)程序設(shè)計(jì) 23
3.6 系統(tǒng)實(shí)現(xiàn) 24
3.6.1 系統(tǒng)實(shí)物 24
3.6.2 測試現(xiàn)場 25
3.7 本章小結(jié) 26
第4章 渦流傳感器靜/動態(tài)特性建模方法研究 27
4.1 靜/動態(tài)特性概..