Lockin-ESPI interferometric imaging for remote non-destructive testing

Electronic-speckle-pattern-interferometry (ESPI) is a sensitive interferometric imaging technique that responds to changes of surface topography caused, e.g., by pressure changes or by thermal expansion. Hidden defects are revealed by the inhomogeneity of such deformation fields. Unfortunately, field distortion may also be caused by, e.g., inhomogeneous excitation. Therefore the lockin technique has been transfered to ESPI in order to enhance its sensitivity by this kind of phase-sensitive narrow-band filtering where finally a self-normalised phase-angle image is obtained. Such an image displays features which are usually deeply hidden in noise, as will be shown on various examples.     

3-D movement simulation techniques using FE methods: Application to eddy current non-destructive testing

In this paper, sample calculations were performed with a three-dimensional (3-D) numerical method to describe the response of an eddy current (EC) probe to defects in a conducting plate. The governing field equations are given in terms of coupled magnetic vector and electrical scalar potentials and solved using a 3-D finite element method implemented in Matlab environment. The displacement of the sensor operating in absolute or differential mode is simulated using three methods: The first and second methods known, respectively, as the nodal interpolation technique (NIT) and the Lagrange multiplier technique (LMT) consist in ensuring the connection between fixed and moved 3-D independent meshes. The third method known as the properties assignment technique (PAT) is based on the geometrical band.In this work, these methods are used to compute the real and imaginary parts of the impedance correlation at every position of the coil(s). This allows the characterisation of the presence of a defect through the EC distribution.     

Ultrasonic arrays for non-destructive evaluation: A review

An ultrasonic array is a single transducer that contains a number of individually connected elements. Recent years have seen a dramatic increase in the use of ultrasonic arrays for non-destructive evaluation. Arrays offer great potential to increase inspection quality and reduce inspection time. Their main advantages are their increased flexibility over traditional single element transducer methods, meaning that one array can be used to perform a number of different inspections, and their ability to produce immediate images of the test structure. These advantages have led to the rapid uptake of arrays by the engineering industry. These industrial applications are underpinned by a wide range of published research which describes new piezoelectric materials, array geometries, modelling methods and inspection modalities. The aim of this paper is to bring together the most relevant published work on arrays for non-destructive evaluation applications, comment on the state-of the art and discuss future directions. There is also a significant body of published literature referring to use of arrays in the medical and sonar fields and the most relevant papers from these related areas are also reviewed. However, although there is much common ground, the use of arrays in non-destructive evaluation offers some distinctly different challenges to these other disciplines.     

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棒材表面的红外探伤是近年兴起的一项无损检测技术。介绍了红外探伤原理、技术方法、设备构成等。由于红外探伤是利用棒材辐射红外线的特点检测棒材表面质量,方法具有非接触、对材料弯曲度要求低、检测速度快、缺陷显示直观等特点,特别适合棒材表面质量在线检测。还概貌介绍了红外探伤设备的应用情况,并且证明了红外探伤的检测结果准确、探伤效率高。     

Expert system to automate the finite element analysis for non-destructive testing

This work describes an expert system that provides an intelligent interface between the non-destructive testing engineer and the finite element analysis (SDRC/I-DEAS) software. The system helps in efficiently evaluating the stress concentration resulting from the presence of volumetric discontinuities inside the body of the material.This expert system has a wide knowledge base and decision-making skills that are taken from the published documentation and the experience of human experts. In addition, it contains a large number of rules that determine the appropriate type of elements, meshing and solving techniques that should be used for different welded joints.The expert system asks the user questions about the shape and dimensions of the basic part that contains the discontinuities and the shape and dimensions of the embedded discontinuities. Then, it operates I-DEAS, creates the geometry of the basic part and the discontinuities, prepares surfaces for meshing, meshes according the appropriate set of rules, applies loads and boundary conditions and solves the model using the appropriate solving techniques. Finally, it produces a report describing the stress concentration around each discontinuity and checks whether it is harmful to the structure or not.The expert system has a modular structure that can be easily updated and applied for more sophisticated jobs.     

Lamb wave generation with an air-coupled piezoelectric concave array using square-wave burst excitation

In this paper, an improved pulse generator is proposed to emit a low-voltage square-wave burst. This generator will be used to excite a concave piezoelectric transducer array. Unlike classical single-pulse excitation circuits, this generator is also able to generate a square-wave burst signal. The Lamb waves generated in an aluminium plate with the square-wave burst generator are compared with those obtained using a classical single-pulse generator. Also, the signal conditioning system for all the transducer array elements has been implemented and tested.     

A comparative study of two non-destructive testing methods to assess near-surface mechanical damage in concrete structures

Concrete specimens displaying surface-breaking cracks are tested using two non-destructive testing techniques: the measurement of electrical resistivity and the transmission of ultrasonic surface waves. The capacity of each method to detect, localize and characterize the induced crack pattern—i.e. its width and depth—is investigated. The specimens are made of concrete with three different mixes. A major crack is induced in the middle of the specimen using a three point bending setup. As the bending strength is increased, three different loading levels are obtained. Both methods were able to correctly localize the main crack and follow its evolution. However, due to the complex crack pattern, the crack depth could not be estimated. Nevertheless, the ultrasonic technique was able to detect a change of state of the material before cracks became visible. As the crack intensity increases, variations of ultrasonic parameters in the apparently undamaged area surrounding the main crack were observed, thus highlighting the sensitivity of ultrasonic waves to distributed damage. The obtained results have also thrown bases for further research to couple resistivity and ultrasonic non-destructive methods.     

钢板超声波测厚仪测量误差及分析

使用超声波测厚仪检测钢板厚度时有时会存在较大的测量误差。分析了造成钢板测厚误差的原因。发现由于常用的超声波测厚仪的检测灵敏度非常高,会导致钢板内部存在的较小缺欠、分层、偏析、材质不均匀等材质缺陷影响了测厚精度和准确性。因此建议在使用超声波测厚仪出现异常读数时,需要使用超声波探伤仪对疑似异常位置进行探伤确认,排除材质缺陷,以免造成钢板测厚的误读和错误测量。     

浅谈复合材料超声手动扫描成像检测

针对复合材料超声成像检测,文章回顾和分析了超声手动扫描成像检测实现方法、超声换能器手动扫查定位方法以及超声信息处理与缺陷识别方法,对复合材料超声手动扫描成像检测技术发展有一定的指导意义。     

国外超声检测仿真软件的研究进展

对法国原子能委员会开发的CIVA,瑞典无损检测模拟中心开发的simSUNDT,加拿大的UTEX科学仪器公司开发的Imagine3D以及美国爱荷华州立大学无损评价中心开发的UTSim等超声检测仿真软件进行了介绍。重点介绍了CIVA中超声仿真单元的三个模块——计算探头超声场的Beam Computation模块和计算超声场与各类缺陷之间相互作用的Mephisto、DefectResponse模块,以及CIVA在数据分析、性能验证和检测方法的设计等方面的应用。     

塑料热熔焊接接头的超声波检测

采用对比试块对三种塑料的声学特性进行试验,测出各自的纵波声速和衰减值。采用研制的纵波斜角探头进行探头K值和前沿测定,取得较高精度。通过模拟试块检测试验,发现缺陷定位准确,测长精度较好。检测热熔焊接接头时,优先选用直射纵波法,当壁厚较薄受检测条件限制时,也可采用一次反射波进行检测。     

超声自动棒材检测系统的校准

介绍了ROB 250VIS超声波探伤仪的工作原理和设备结构,对影响样棒校准的关键因素进行了分析。结合实践操作,从技术上提出了有针对性的解决措施,取得了很好的效果。     

火车车轮轮辋超声相控阵检测

采用某超声相控阵检测设备对火车车轮轮辋做检测,检测结果表明相控阵设备具有灵敏度高、覆盖范围广、能多角度检测、曲线显示直观等优点。对超声相控阵检测同仁有一定借鉴意义。     

压力容器和管道早期氢腐蚀的超声波检测

高温氢损伤即氢腐蚀的早期检测,是石化企业实现设备长周期运行所急需解决的问题之一。针对压力容器和管道高温氢损伤的早期检测问题制作了带有氢腐蚀的标准试块;通过超声波检测技术,测量并分析了超声波声学参量与氢腐蚀程度的相关性;结合金相检验和硬度测试对氢腐蚀的程度进行表征和评价;为建立早期氢腐蚀的快速诊断检测方法积累数据。     

大直径空心轴类超声探伤系统

多数大型旋转装备的轴系采用大直径空心轴,必须定期进行在役无损检测。本文设计研制了用于直径30mm以上的空心轴类的超声探伤系统,由旋转式探头、超声检测系统、机械控制系统、机械推拔系统、油路耦合系统以及工业用计算机系统等子系统组成。本系统在国内某类大直径空心轴进行了检测实验,实验结果证明,本系统性能完全达到进口设备的水平。     

A new non-contacting non-destructive testing method for defect detection in concrete

A new non-destructive testing (NDT) method for defect detection in concrete structures is presented. The method is based on the dynamic response of flawed concrete structures subjected to impact loading. Conversely to similar NDT techniques, such as the impact-echo method, the present method uses non-contacting devices for both impact generation (a shock tube producing shock waves) and response monitoring (laser vibrometers measuring concrete surface velocity). Experimental and numerical (finite element) studies have been carried out for concrete specimens containing artificial defects (penny-shaped cracks parallel to the free surface) with varying length and depth. According to the experimental and numerical results, it appears that the present method enables an effective detection of defects, particularly in the range of shallow defects.     

压水堆承压容器厚大锻件超声检测标准的比较

分析比较了ASME，KTA，EJ／T1039相关标准规范中有关压水堆一回路主要承压容器低合金钢厚大锻件制造阶段超声检测方法、时机、记录和验收条件等内容。通过比较相关国内外标准，分析各自的特点和差异，结合使用性能要求、制造能力、工程反馈、超声检测的特点以及存在的主要问题，为合理确定制造阶段的超声检测技术指明方向，对压水堆一回路主要承压容器厚大锻件制造过程中的超声检测有一定借鉴意义。     

固体火箭发动机药柱超声检测技术

针对火箭发动机某型号药柱,利用超声反射法分别对人工标准缺陷和自然缺陷进行了试验检测,并根据超声缺陷特征和信号幅值信息进行了成像处理,通过X射线CT对自然缺陷的扫描结果对比表明,该检测方法能较好地实现该型号药柱的线性定量无损检测。     

管道对接焊缝的超声波检测

针对工艺管道对接焊缝的特点,对焊接方法、焊接位置及易产生的缺陷进行了分析。由于工艺管道对接焊缝壁厚范围大,多是直管与直管、直管与弯头、法兰、阀门等管件对接,采用单面焊接双面成型工艺,这种特殊结构型式和焊接工艺,使超声波检测只能进行单面双侧扫查或单面单侧扫查。为了提高缺陷的检出率,对不同规格、不同结构的焊缝在选择扫查面、探头数量、探头型号和探头尺寸时应有针对性。根部缺陷的判定对仪器扫描线调节精度提出了较高要求,对典型缺陷的回波特征进行了分析。通过以上分析和采取的措施,能有效提高工艺管道对接焊缝超声波检测的质量。     

汽轮机圆柱滑动轴承超声波检测

分析了西门子标准与国内常用标准的区别,介绍了按西门子标准方法与要求对汽轮机圆柱滑动轴承进行超声波检测的规程,并在实际检测中取得了较好的效果。