焊接结构水下无损检测技术及其进展

介绍了水下无损检测技术基本问题与常规水下无损检测方法的特点,着重论述了水下无损检测新方法与遥控潜水器无损检测的新进展及其在焊缝检测中的应用,最后对水下无损检测技术的发展作了展望。     

水下无损检测的质量保证

根据中国船级社《水下无损检测的质量保证体系要求》及其ＩＳＯ９０００族标准的基本原理，对水下无损检测（ＵＷＮＤＴ）质量保证的有关要求与内容进行了分析和讨论，包括建立质量保证体系的目的与原则，质量保证体系要素的要求，体系文件的组成及验船师的现场监督等。     

第一专题 水下无损检测技术综述：（一）对象,目的与方法

介绍水下无损检测服务对象的类型及其工作环境特点，分析损伤缺陷的种类，形式及其对构件失效速率和可靠性的影响。简要阐述了水下无损检测的目的和技术方法。     

第一专题 水下无损检测技术综述：（二） 水下环境因素对检测作业的影响

分析了水下光学、水下声学特点以及水下环境因素对潜水员生理与心理的影响,深入探讨了水下环境对水下无损检测工作的实施及其结果可靠性的影响。     

第一专题 水下无损检测技术综述：（三）过程,程序与基本特征

介绍水下无损检测(UWNDT)的基本工艺过程与检测程序,包括检测计划、检测准备、操作方法、原始记录及检测报告等内容。同时还提出并阐述了UWNDT的技术特征。     

第七专题 水下无损检测的质量保证

根据中国船级社《水下无损检测的质量保证体系要求》及其ISO9000族标准的基本原理,对水下无损检测(UWNDT)质量保证的有关要求与内容进行了分析和讨论,包括建立质量保证体系的目的与原则、质量保证体系要素的要求、体系文件的组成及验船师的现场监督等.     

第八专题 水下无损检测技术的发展

对水下无损检测(UWNDT)技术的研究与发展状况进行了简要介绍与分析,内容包括Magfoil磁膜检测法、管道超声波检测工具、水下电磁检测、交流电位降法及水下交流磁场测量等新的技术方法和英美等国资助的一系列研究工作与计划。     

建筑结构无损检测方法简介

在建筑结构检测中 ,采用的无损检测技术越来越多。如超声法检测[1,2 ] 、高应变动力[3 ] 和低应变动力检测[4 ] 、探地雷达检测[5] 及ＦＣＴ10 1测试仪检测[6 ] 等。超声波无损检测技术多年来在非金属材料的力学性能测试、混凝土结构物建筑质量的检验以及岩土工程勘测方面获得了广泛应用。1　混凝土结构缺陷检测超声法是国内目前普遍采用的现场混凝土结构质量检测方法 ,并已制订了相应的技术规程[1] ,包括对裂缝深度、灌注桩和钢管混凝土缺陷、混凝土密实情况及空洞以及混凝土表面损伤层的检测[711] 。浅裂缝检测方法是指适用于结构混凝土开…     

混凝土结构中的光纤传感无损检测

近年来,混凝土结构建筑物的完整性得到越来越多的关注,花费在保证其安全性上的时间与精力显著增加。尽管已有各种高性能的材料以及先进的结构分析和设计,但对混凝土结构建筑物在使用与运行的动态过程中结构的强度变化与整体完整性的评估技术还相对缺乏,且已有的方法也都具有破坏性。虽然开发出一些基于x射线和γ射线技术的无损检测手段,然而它们并不总是非常可靠,且费用高、费时间。较为先进的方法是:在混凝土建筑物建造过程中,在其内部关键部位埋置入光纤传感器或阵列,利用光纤周围混凝土的力及热分布状态的变化对光纤光强、相位、波长或偏振态的影响,实时地传感在使用的动态环境中结构内部温度和应力的变化,探测裂缝的发生和增长及检测混凝土的蠕变、热应力。而各种测量及损伤的定位则可利用光时域反射计(OTDR)和光频域反射计(OFDR)技术来完成。     

管道腐蚀检测中新型脉冲涡流传感器的设计

提出了一种新型脉冲涡流传感器设计思路。它将脉冲涡流激励场从空间上转化为匀强涡流场,从而等效为一种自差分式的涡流检测技术,因此无需进行差分处理,可避免差分信号的不同步导致的检测精度和灵敏度不高。采用该新型脉冲涡流传感器对钢管腐蚀缺陷进行了检测,试验结果表明设计的传感器具有较高的灵敏度和检测精度。     

Optoelectronic nondestructive testing techniques of cocoon properties and applications

In this paper, cocoon properties are examined, spectral characteristics and mathematical expressions that define cocoon shell's absorption and reflection of light in various wavelengths are obtained and given in graphical form. Finally, optoelectronic methods and systems that determine cocoon properties are designed and explained.     

Utilization of two-directional AC current distribution for enhancing sizing ability of electromagnetic nondestructive testing methods

This paper proposes a novel method for accurately evaluating the depth of a defect using electromagnetic phenomena. The novel method induces AC currents inside a conductive medium and detects the disturbance of the currents. Whereas the principle itself has been utilized in conventional methods, the uniqueness of this new method lies in realizing a current distribution in which there is a region where currents near the surface and those deeply inside the specimen flow opposite to each other. The novel method provides a clear indication corresponding to the depth of the inspected defect. In addition, it enables one to evaluate the depth of a defect that is much deeper than the depth of penetration. After the physical background of this new method is explained, the results of experimental verifications and subsequent numerical simulations are presented.     

Application of neuro-fuzzy techniques in oil pipeline ultrasonic nondestructive testing

This paper presents a novel approach to the problem of nondestructive pipeline testing using ultrasonic imaging. The identification of the flaw type and its dimensions are the most important problems in the pipeline inspection. Unlike typical methods, a decision based neural network is used for the detection of flaws. We train a generalized regression neural network to determine the dimensions of the corrosions and generate the whole image of both the internal and external walls of the oil pipeline. As an improvement to the detection algorithm, we introduce fuzzy decision-based neural network algorithms for the detection and classification of the corrosions. The simulation and experimental systems results show that these new methods outperform the existing methods.     

交变磁场测量数学模型及类匀强场的建立

在介绍了交变磁场测量原理的基础上，分析并给出了交变磁场测量法的数学和理论模型，对缺陷模型进行了详尽的分析。为了实现交变磁场测量法，提出了类匀强场的概念并对其进行了论证。分析了用复合矩形激励线圈产生类匀强场的方法和理论基础。最后通过ANSYS有限元仿真技术对在该复合线圈激励下，工件表层感应电场及其相位，以及工件周围感应磁场进行了分析，验证了试验模型的正确性。     

Computed tomography with image intensifier: potential use for nondestructive testing and imaging of small objects

An image intensifier based computed tomography scanner and a tube source of X-rays are used for nondestructive evaluation, imaging of small objects for archaeological studies and conservation of works of art and micro analysis of soft materials. It consists of a charge coupled device (CCD) camera and an acquisition board. The CCD camera and the acquisition board allow image processing, filtration and restoration. The object is irradiated by an X-ray tube with a conical collimator and rotated on 180°. Projections are obtained at various angles as cross sectional image slices. A reconstruction program written in pascal is able to give the reconstruction matrix of the linear attenuation coefficients, simulates the matrix and related tomography. The flux emitted by the tube is filtered using the appropriate filters at the chosen optimum energy and reasonable monochromacy is achieved for all the images. Although X-ray imaging is a potential tool for strongly attenuating materials, the images of weakly attenuating materials provide new information to know about their structure and also the foreign body for the image reconstruction at an optimum value. The image of the plastic material which contains the internal defect is studied thoroughly at the optimum value in order to image the small objects for nondestructive testing, archaeological studies and conservation of works of art. The images are analysed using the profile data showing the internal defect of the object to obtain information at the optimum value. At the optimum value and with the aid of the tomographic image, the size and location of the defect could be ascertained.     

Online nondestructive testing for fine steel wire rope in electromagnetic interference environment

The diameter of fine steel wire rope (FSWR) is generally a few millimeters. Its magnetic flux leakage (MFL) signal is weak, and the number of magnetic sensors installed for defect detection is limited because of the small diameter. In FSWR production workshops, different kinds of machinery work together, deteriorating the power quality and making the spatial electromagnetic environment complex; the weak MFL is thus interfered with further. It is difficult to carry out online nondestructive testing (NDT) of FSWR in the process of manufacturing. In this paper we present a novel MFL method for FSWR NDT in a strong electromagnetic interference environment. We use a three-dimensional finite element method (FEM) to analyze the MFL signals. A simplified magnetic circuit is presented to excite the FSWR; the circuit comprises two half-sized radial magnetizing ring NdFeB magnets, and because there is no need for a magnetic yoke, the device is simple and light. A single Hall sensor is used to measure the flux leakage field. A stable performance power system is designed for the NDT power supply, which is not only resistant to voltage sags, but also has very low output noise. To enhance the signal-to-noise ratio (SNR) of the MFL defects signal, a signal conditioning and processing circuit are designed to enhance the detectability of signals in MFL data. The novel and small FSWR NDT system realizes on-line testing in an environment of strong electromagnetic interference, and for the experiment with a 1.5-mm-diameter wire rope twisted by 19 wires, the minimum damage of a pit on half of a wire can be identified.     

无损检测交变磁场测量法

准确测定缺陷的尺寸,对带缺陷结构的寿命评估具有十分重要的意义。交流磁场测量法是近年来兴起的一种评价表面缺陷的无损检测方法,它通过测量工件表面感应磁场的变化来进行材料中缺陷的定性定量,具有非接触的优点,广泛应用于结构的在役检测。