【作者】 张俊；

【导师】 丁辉；

【作者基本信息】 武汉大学 ， 材料学， 2010， 博士

【摘要】 超声波检测在保障设备运行安全及产品品质方面扮演着重要角色,如何提高和评定超声检测可靠性已经成为我国由工业大国向工业强国转变中所亟待解决的关键问题之一。本文主要从声场计算和检测可靠性研究两个方面开展工作：首先通过建立超声声场计算模型,研究了超声声场传播及其与缺陷相互作用机理,实现了检测工艺辅助设计、能力验证、回波辅助分析等功能,提高了超声检测的可靠性；然后基于检测可靠性分析方法,设计并进行了超声检测实验,研究了不同检测因素对检出率及定量准确率的影响；最后提出了基于随机参数生成模型、声场计算模型和可靠性概率统计模型的检测工艺可靠性评定方法。在超声声场计算方面,基于瑞利积分和Pencil法建立了适用于各类探头及传播介质的超声传播模型,得到声场分布与工件、探头及检测参数之间的定量关系。考虑了超声检测常用探头(如接触式探头、水浸聚焦式探头、双晶探头、相控阵探头等)发射声场；声场在各向同性和各向异性介质,多层介质中的传播和衰减；声场在工件表面和底面的反射,折射及波型转换。利用MATLAB编程实现了各类声场分布的计算及数字化显示,并将计算结果与商用软件进行比较,验证模型精度。结果表明所建超声传播模型精度达到超声检测实际应用的要求,可以应用于各类探头及介质声场的计算,从而辅助探头及检测工艺设计。为了提高计算精度和速度,基于基尔霍夫近似和波恩近似理论,分别建立了适用于裂纹类缺陷和体积类(不含夹渣)缺陷的缺陷散射声场计算模型和适用于夹渣类缺陷的夹渣缺陷散射计算模型。利用MATLAB编程实现了单层各向同性介质中各类缺陷回波的计算,并以A扫描、B扫描、C扫描和回波动态曲线的方式显示计算结果,并将计算结果与商用软件及实验结果进行比较,验证模型精度。结果表明自建模型计算精度达到商用软件精度,满足现场应用的要求。同时,结合已建立的超声传播声场模型和缺陷散射声场模型,基于奥尔特互易原则建立了适用于复杂介质的UT-CAS系统,并将其应用于复杂工件超声检测的工艺设计、能力验证和回波分析。在超声检测可靠性分析方面,基于检测可靠性分析方法,设计并进行了碳钢及不锈钢板焊缝的自动及手动超声检测实验。在自动超声检测实验中,基于Bootstrap重抽样技术和对数正态分布模型,计算并比较了不同探头类型、缺陷类型、扫查位置等检测条件下的缺陷检出率和定量准确率,定量评定不同参数对检测可靠性的影响。在手工超声实验中,基于Log-odds模型和对数正态分布模型,计算并比较了较高水平、低水平检测人员及自动化设备检测结果的缺陷检出率和定量准确率,研究人员因素对检测可靠性的影响。结果表明超声检测结果存在较大的随机性,各种因素对检测可靠性都存在较大的影响,特别是人员因素,不同检测人员对同一缺陷进行检测时得到的结果相差较大,必须进行有效的可靠性评定。为解决现场数据小子样、实验试块制作困难且成本高的问题,提出了基于声场计算的检测工艺可靠性分析方法,通过随机参数生成模型和声场计算模型计算缺陷回波信号,获得可靠性分析所需要的数据源,然后以回波信号响应数据作为输入,基于可靠性概率统计模型,计算得到检出率随着缺陷参数(尺寸、角度和位置等)的变化曲线。并将其应用于核电站在役检查工艺的可靠性定量评定和优化,分析复杂工件结构、缺陷尺寸和偏转角度、探头参数及组合方式等因素对检测可靠性的影响。更多还原

【Abstract】 Ultrasonic test plays an important role in guaranteeing the operational safety and product quality, and how to improve and evaluate the reliability of ultrasonic testing has become one of the key issues that need be solved for our country’s industrial transformation. The main works included in this article focus on the acoustic field calculation and inspection reliability. Firstly, the ultrasonic acoustic field calculation model is established and the mechanism of the propagation of ultrasonic acoustic field and its interaction with the defect is studied, and the application of our model on the aided design of inspection procedure, performance demonstration and echo analysis could improve the reliability of ultrasonic testing; Secondly, based on reliability analysis method of detection, ultrasonic detection experiments are designed to study the influence of different factors on reliability of the detection(POD) and reliability of the sizing (POS); Finally, a reliability assessment method for procedure evaluation and optimum is proposed based on the random parameters generation model, acoustic field calculation model and POD probability model.The acoustic propagation model for calculation of the acoustic field of all types of probe and transmission medium is established based on the Raleigh integral and Pencil method, and so as the quantitative relationship between acoustic field distribution and the parameters of specimen, probe and inspection. The model considered the sound field emission of the common ultrasound probe, such as the contact probe, flooding focused probe, double crystal probe, phased array probes, etc; the transmission and attenuation of acoustic field in the isotropic and anisotropic media, multi-media and the reflection, refraction and wave mode conversion on the surface and bottom of specimen. The MATLAB programs are developed for calculation and digital display of the distribution of acoustic field, and the calculation results are compared with the commercial software for validation of our model. The result indicates that the ultrasound propagation model is suitable for the practical application of ultrasonic testing, and could be applied to probe and testing procedure design.In order to improve the accuracy and speed of calculation, the defect scattering model for crack-like and volume defects (excluding slag), and slags are established based on the Kirchhoff approximation and the Born approximation theory. The MATLAB programs are developed for calculation various types of defect echo in one-layer isotropic media, and the results could be displayed in terms of A scan, B scan, C scan and echo dynamic curves. The numerical results are compared with experimental results and commercial software for validation of our model. The results show that the self-built model is suitable for the on-site applications. At the same time, the Ultrasonic Testing Calculation and analysis system (UT-CAS) is established based on the propagation model, defect scattering model and Auld’s reciprocity principle, and its application of aided design of inspection procedure, performance demonstration and echo analysis for ultrasonic testing of complex medium is given.Based on reliability analysis method of inspection, the experiments of automatic and manual ultrasonic testing of carbon steel and stainless steel weld are designed. In automatic ultrasonic testing experiments, the POD and POS of different probe types, defect types, scanning locations are calculated and compared based on Bootstrap re-sampling technique and log-normal distribution model, and the influence of different inspection parameters on reliability of detection is quantitatively assessed. In the manual ultrasonic test, the POD and POS of the high level, low-level people and the automation equipment are calculated and compared based on Log-odds model and the log-normal distribution model. The results show that the ultrasonic test results is a random process, the inspection parameters have a great impact on the reliability of detection, especially for human factors, different inspectors in the same conditions obtained much different results form echo other. So the effective reliability assessment is extremely needed.The reliability analysis method based on acoustic field calculation is proposed to solve the small sample problem of field data, and avoid high cost and difficulty of block manufacture. The defect echo signal which is used as an input for the probability model to calculate the POD and parameter (size, angle and location) curves is calculated based on randomly generated model and acoustic field calculation model. This method could be applied to the assessment and optimum of the nuclear power plant in-service inspection process through quantitative analysis of the influence of complex component structures, defect size and orientation, probe and array parameters on the reliability of detection.更多还原