Study of ultrasonic phased array inspection imaging technology for NDT

A research about the ultrasonic phased array imaging principle from A-scan signal to B-scan image for non-destructive testing （NDT） was conducted in this paper, the ultrasonic phased array inspection imaging system used in industrial field was developed and the experiment was performed on the steel testing block by the system with 64 elements, 5 MHz phased array transducer. Experimental results show that the flaws could be accurately detected and the flaws size could be estimated from the B-scan images, and the B-scan images could clearly show the location of the flaws, but the quality of B-scan images needs to be enhanced by digital signal processing and controlling dynamic focusing for improving the image resolution.     

管道内检测的环形相控阵超声聚焦方法

针对管道内检测中相控阵超声聚焦的问题,分析了管道中环形相控阵超声辐射的超声波传播原理,建立了聚焦数学模型,计算了阵元间激励信号的延时;采用128阵元的换能器对直径为168 mm的管道进行试验,结果表明,环形相控阵超声的延时法则实现了不同工作阵元数量以及不同焦距条件时,声束在管壁中的聚焦.在工作区间内,一定数量的阵元可获...     

超声相控阵二维面阵实现三维成像研究进展

实现基于二维阵列的三维成像会遇到阵元多、通道数多、系统复杂、回波信号弱等困难。从阵元排列的设计着手,分析了时间-空间信号在离散有限长窗函数下的特征,推导出阵列设计的一般准则;依据此准则,根据脉冲回波场理论,在计算机模拟的基础上设计了8×8二维阵列;并利用该阵列实现了相控阵三维体数据的扫描和显示。扫描试验所得人工缺陷的三维图像呈现出良好的轮廓和走向等信息。     

基于阵列超声成像法的混凝土裂缝深度检测

针对传统超声法检测混凝土裂缝深度时人为影响因素较多,检测效率十分低下的问题,引入了阵列超声成像法,研究了阵列超声成像法检测裂缝深度的原理及其计算方法,并在实验室设计制作了一块预设7条不同深度裂缝的素混凝土试件,进行了跨单裂缝和试件整体成像检测试验。试验结果表明:阵列超声成像法根据缝底反射超声波的传播时间来检测裂缝深度,生成的二维图像可以显示缝底位置,但无法显示缝身;该检测法的检测精度较高,并且随着裂缝深度的加深逐渐提高;检测时应考虑边界效应,否则无法准确检测裂缝深度;检测时存在盲区,当缝底位于盲区内时会出现漏检。     

相控阵超声检测曲面阵列与平面阵列的对比

在小径管相控阵超声检测中,平面阵列与曲面阵列的耦合效果与聚焦效应是影响检测效果的关键因素。分析了两种换能器的缺陷成像特点,进行了两种换能器对相同缺陷的成像效果对比试验,结果表明曲面阵列在小径管检测应用中具有更高的信噪比和更好的成像效果,而平面阵列需增加补偿来达到曲面阵列的检测效果。     

核电站小径薄壁管插接焊缝的相控阵超声检测

小径薄壁管是核电站运行中最容易生成缺陷和发生泄漏的部件和位置。小径薄壁管插接焊缝一般采用射线法进行检测,但是射线检测存在辐射风险,检测区域需要隔离且检测工期较长,并不适于核电站大修期间的大范围应用。通过自然缺陷试块进行小径薄壁管插接焊缝相控阵超声波检测工艺分析及检测能力验证研究。在此基础上,成功将相控阵超声检测技术应用于核电大修现场并发现缺陷。     

Development of a segmented annular array transducer for acoustic imaging

A 1.6 MHz segmented annular array transducer of 64 elements made from a piezoelectric composite as a monolithic support has been manufactured and characterised. Input electrical impedance and pulse response of each array element was in good agreement with the results calculated by using the KLM model. Cross-coupling between nearest neighbours was −45 dB at the resonance frequency assuring the good array performance in terms of cross-coupling and elements isolation. Vibration surface measurement of a sector of elements excited simultaneously was made. The transducer was designed for the inspection of solid materials in non-destructive testing (NDT).     

奥氏体不锈钢小径管焊接接头的相控阵超声检测

针对奥氏体不锈钢小径管焊接接头的检测难点,开展了专用试块设计、检测参数优化、检测能力验证、缺陷分析评定等相关技术的研究,总结形成了一套相控阵超声检测工艺和评定方法.检测工艺适用于外径为32～100 mm,壁厚为4～20 mm的奥氏体不锈钢小径管焊接接头的质量评定,通过在火力发电机组安装和检修工程中的成功应用,验证了该工...     

An application of ultrasonic phased array imaging in electron beam welding inspection

The basic principle and features of ultrasonic phased array imaging are discussed in this paper,Through the ultrasonic phased array technology,the electron beam welding defects and frozen keyholes characterization and imaging were realized.The ultrasonic phased array technology can detect kinds of defects in electron beam welding (EBW) quickly and realized.The ultrasonic phased array technology can detect kinds of defects in electron beam welding (EBW) quickly and easily.     

An ultrasonic array-based system for real-time inspection of carbon-epoxy composite plates

A real-time ultrasonic imager operating at a frequency of 3.5 MHz to test composites in immersion has been developed. It is based on linear array transducers and provides either B-scan or transmission images of composite plates of a few centimeters thickness. The electronic scanning has a pitch of 1.25 mm and an amplitude of 80 mm, and the electronic focusing as well as the acoustic lens on the arrays are set to work at a depth of 40 mm in water. Tests made on composite and plastic plates of 5 to 17 mm thickness show that the system allows the detection of different types of defects and that the interpretation of the ultrasonic signals can be performed on line.     

A numerical database for ultrasonic defect characterisation using array data: Robustness and accuracy

Elastodynamic scattering matrices are known to contain geometrical information about a given scatterer, such as its size and shape. Here, the extent to which this scattered information can be retrieved using an ultrasonic array and used to characterise defects for Non-Destructive Evaluation is explored. Experimentally measured defect scattering matrices are compared to a database of possible scatterers and the nearest neighbour used to characterise the defect's geometry in terms of crack length and orientation. As an example, a database of scattering matrices for small (lengths 0.2–2.0 mm) cracks at a range of frequencies (2–20 MHz) is formed. The short range similarity (i.e. that between close neighbours) and the long range similarity (i.e. uniqueness) are used to understand the uncertainties inherent in this approach. In addition, the effect of spatially coherent noise, such as grain scattering in a polycrystalline metal, on the scattered information content is quantified. It is shown that as the noise level or frequency increases, so the information retrievable from a given crack is reduced, setting bounds on the accuracy of characterisation possible from a given ultrasonic dataset.     

Inspection system for welded tubular joint based on ultrasonic phased array

A manual inspection of large-diameter tubular joints is difficult. As a result a scanner with three degrees of freedom (DOFs) was developed based on the scanning principle of ultrasonic phased array. The weld tracing is realized by a 2D0F motion of scanner. The pose of ultrasonic probe is controlled by the third one. The control strategy is put forward based on a programmable multi-axis controller. Four kinds of scanning modes can be implemented simultaneously employing this ultrasonic inspection system. Experiments on reference blocks of tubular joints reveal that the automatic ultrasonic phased array inspection system has the same inspection accuracy as a manual ultrasonic inspection. This system is superior to the manual ultrasonic system in terms of reliability and repeatability. The artificial defects of weld at tubular joint can be detected accurately with the presented inspection system.     

圆钢相控阵超声漏检因素分析

介绍了圆钢全自动相控阵超声的设备结构及其主要技术参数,结合具体的相控阵探头参数,主要从聚焦法则、周向覆盖率、轴向覆盖率3个方面,对影响相控阵超声检测漏检的关键因素进行了分析,并且从聚焦法则、轴向分辨率、检测速度等参数的设置方面给出了具体解决措施,为相关人员理解相控阵、操作类似相控阵设备提供了经验参考,同时为产品实现无缺陷交货提供了理论依据。     

A focused two-dimensional air-coupled ultrasonic array for non-contact generation

Air-coupled ultrasonic sources are relatively inefficient because the high impedance mismatch at the air/solid boundary means that most of the input energy (in air) is reflected at this boundary. The objective of this research is to increase efficiency—specifically an increase in ultrasonic signal amplitude—by designing and building a focused, 2D-array of electrostatic transducers (individual diameters of 38 mm). The operating frequency of this array is in the range of 50–100 kHz; this range is selected for civil infrastructure applications. Numerical simulations are used to design an array by modeling the pressure field in air, and then optimizing an array consisting of 20 transducers to create a line-source. An array is then built (following this design) and the emitted pressure field (in air) of the as built array is measured with a microphone and compared to the pressure field predicted by the numerical model. Finally, the as built focused array is used as an ultrasonic source, and its robustness is verified by comparing the numerical simulation of a transient line-load on an elastic half-space with (completely non-contact) experimentally measured values. There is excellent agreement between these two representations, which confirms the possibility of developing a completely non-contact, scanning ultrasonic system in the 50–100 kHz range.     

声波散射在焊接板结构超声导波合成孔径阵列成像中的作用

为揭示声波散射在焊接板结构超声导波合成孔径阵列成像中的作用机制,将散射回波矩阵和散射渡越时间矩阵用于分析描述超声水平剪切（shear horizontal,SH）导波声波散射,探讨了焊缝散射和边界散射在导波成像中的作用关系.结果表明,散射矩阵是揭示声波散射在超声导波阵列成像作用机制的有效工具,散射回波矩阵与散射渡越时间矩阵具有相同的散射矩阵因子,导波图像出现与散射矩阵因子成倍数关系的“条带”伪像,图像椭圆簇轨迹特征复杂化,图像背景噪声增强,图像信噪比减小.研究工作可为深入开展焊接板结构超声导波非直线阵列成像算法研究提供基础.     

超声沉淀法制备纳米Al2O3粉体

将超声辐射应用于以硫酸铝铵 (NH4Al(SO4) 2 ·12H2 O )和碳酸氢铵 (NH4HCO3 )为原料的沉淀法制备Al2 O3 纳米粉体的化学反应工艺过程 ,制备了粒径为 12nm的α Al2 O3 纳米粉体。通过SEM、TEM等分析手段研究了超声辐射对前驱体NH4Al(OH) 2 CO3 沉淀物及最终粉体尺寸、形貌及其团聚行为的影响 ,并探讨了其作用机理。结果表明 :超声辐射由于其自身的空化作用不仅细化了前驱体颗粒、抑制了其间的团聚 ,而且延缓了其向凝胶的转变过程 ,从而有效地细化α Al2 O3 颗粒 ,但过高的频率却易导致颗粒间的进一步聚合     

UPA based 3D visualization of discontinuities in great thickness EBW seam 1

Electron beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined.It is a complex high-temperature metallurgical process,and the quality of welding may deteriorate because of defects caused by improper welding parameters,especially in the EBW of thickened aluminum alloy plate.Ultrasonic phased array(UPA) technology has been applied more widely in the field of nondestructive testing because of its ability of effectively controlling the shape and direction of the emitted ultrasonic beam.In present research,a specimen with EBW seam on thickened aluminum plate was tested with a linear array ultrasonic phased array probe,and a large number of B-scan images of the weld were acquired by electronic scanning in probe combined with the mechanical scanning of the probe along the weld direction.This large number of B-scan images were stacked to construct the volume data,with which the 3D image of the weld discontinuities were reconstructed,and the 3D visualization was realized.More details about weld discontinuities' spatial distribution and orientation were revealed,and this approach also made the results of non-destructive ultrasonic testing more easily to understand.     

A 2D model of ultrasonic wave propagation in an anisotropic weld

In order to enable ultrasonic measurement of anisotropy and the directivity of dendrites in a weld, a forward formulation is presented in this paper. It describes a model of an anisotropic weld, a probe model defined by consistent boundary conditions, together with a 2D ray tracing algorithm. The capability of this developed model is illustrated in numerical examples. This hybrid model of the forward formulation will later be applied to solve the inverse problem.     

超声相控阵检测焊缝三维可视化

介绍超声相控阵扇形（S型）扫查法对焊缝实施全体积检测的优势：信号（色码幅度）实时显示,自动存储,特别是检测数据可三维（3D）显示,又可多视角观测,缺陷四定（定位、定性、定量、定级）更方便,符合国际权威法规ASME最新版（2011a）的有关要求。期盼UT人员能在日常焊缝检测中熟练运用相控阵三维可视化技术。