Focusing behaviors of ultrasonic phased arrays in anisotropic and inhomogeneous weldments

It meets some difficulties in the case of ultrasonic phased arrays testing for the nickel-based alloy welded joint, since the ultrasound will propagate with curvilinear paths in this kind anisotropic joint. Thus, it is hard to calculate the phased array time delays properly according to the traditional focusing approach, which is based on the assumption that the sound beam will propagate in straight lines. In order to focus the phased arrays beam in this kind anisotropic joint, we provide a modified focusing approach by combining the ray tracing method and the bisectional searching optimization. With the help of this focusing approach, the curved ray path connecting each element position in phased arrays to the expected focus point in weldments can be determined, so that it can be used to calculate the proper time delay and control the beam focusing in the anisotropic weldment. Furthermore, some experimental examinations are carried out to compare the focusing behaviors between the traditional and the modified focusing approach. It shows that the provided focusing approach is more accurate than the traditional method in the case of inspection on the nickel-based alloy weldments.

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.

Simulation of acoustic fields emitted by ultrasonic phased array in austenitic steel weld

Ultrasonic inspection of austenitic steel weld is a great challenge due to skewed and distorted beam in such a highly anisotropic and inhomogeneous material. To improve the ultrasonic measurement in this situation, it is essential to have an in-depth understanding of ultrasound characteristics in austenitic steel weld. To meet such a need, in the present study we propose a method which combines the weld model, Dijkstra’s path-finding algorithm and Gaussian beam equivalent point source model to calculate the acoustic fields from ultrasonic phased array in such a weld. With this method, the acoustic field in a steel-austenitic weld-steel three-layered structure for a linear phase array transducer is calculated and the propagation characteristics of ultrasound in weld are studied. The research results show that the method proposed here is capable of calculating the acoustic field in austenitic weld. Additionally, beam steering and focusing can be still realized in the austenitic steel weld and the beam distortion is more severe in the middle of weld than at other positions.

Ultrasonic flaw detection of discontinuous defects in magnesium alloy materials

Phased array ultrasonic testing, an effective ultrasonic testing(UT) technology, has been widely used in steel inspection because of its high accuracy, sensitivity, and efficiency. However, as its application in as-cast magnesium alloys has just begun, more research is needed. Considering the important role of the gain compensation in quantifying defects in magnesium alloys by ultrasonic phased array technology, the effects of microstructure, the position, size, and overlap of defects, and boundary distance(distance from the defect position to the side surface of the test casting) on gain compensation of as-cast AZ80 and AZ31 magnesium alloys were studied. Results show the gain compensation increases with the increase of grain size. There is a strict linear positive correlation between gain compensation and defect depth, but such relationship no longer exists due to the defects overlap, orientation and boundary distance. In addition, there is a strict linear negative correlation between the gain compensation and defect size.

Ultrasonic Scattered Field Distribution of One and Two Cylindrical Solids with Phased Array Technique

The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field distributions of different incident waves created by elastic cylinders embedded in an elastic isotropic medium. Scattered waves, including longitudinal and transverse waves both inside and outside the cylinder, are described with specific modalities under an incident plane wave. A model with a scatterer embedded in a structural steel matrix and filled with aluminum is developed for comparison with the theoretical solution. The frequency of the plane wave ranged from 235 kHz to 2348 kHz, which corresponds to scaling factors from 0.5 to 5. Scattered field distributions in matrix materials blocked by an elastic cylindrical solid have been obtained by simulation or calculated using existing parameters. The simulation results are in good agreement with the theoretical solution, which supports the correctness of the simulation analysis. Furthermore, ultrasonic phased arrays are used to study scattered fields by changing the characteristics of the incident wave. On this foundation, a partial preliminary study of the scattered field distribution of double cylinders in a solid has been carried out, and the scattered field distribution at a given distance has been found to exhibit particular behaviors at different moments. Further studies on directivities and scattered fields are expected to improve the quantification of scattered images in isotropic solid materials by the phased array technique.

Ultrasonic focusing and scanning with multiple waves

This paper presents a new focusing and scanning method which focuses multiple waves on a target. The key of the method is to control excitation pulses for each element of the transducer array. The excitation pulse on each array element is obtained by time reversing the signal received by the same element, which is generated by an imaginary source at the target. The excitation pulses from all array elements are transmitted and arrive at the target simultaneously, and focusing is achieved. The performance of the two methods is compared in numerical examples, and it is demonstrated that the proposed method achieves a satisfactory focusing and a good signal-to-noise ratio no matter where the target location is.

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 easily.

Visualisation of air–water bubbly column flow using array Ultrasonic Velocity Profiler

In the present work, an experimental study of bubbly two-phase flow in a rectangular bubble column was performed using two ultrasonic array sensors, which can measure the instantaneous velocity of gas bubbles on multiple measurement lines. After the sound pressure distribution of sensors had been evaluated with a needle hydrophone technique, the array sensors were applied to two-phase bubble col- umn, To assess the accuracy of the measurement system with array sensors for one and two-dimensional velocity, a simultaneous measurement was performed with an optical measurement technique called particle image velocimetry （PIV）. Experimental results showed that accuracy of the measurement system with array sensors is under 10% for one-dimensional velocity profile measurement compared with PIV technique. The accuracy of the system was estimated to be under 20% along the mean flow direction in the case of two-dimensional vector mapping.

Industrialization of a Large Advanced Ultrasonic Flexible Probe for Non-destructive Testing of Austenitic Steel Pieces with Irregular Surface

Because the UT （ultrasonic testing） flexible probe technology may be an appropriate answer to examine components with uneven surface, AREVA has developed an industrial application of the CEA＇s （French Atomic Energy and Alternative Energies） flexible phased arrays sensors. As a ＂first of a kind＂ project, the challenges faced were significant, including developing a phased array smart probe suitable for industrial use on rather simple but large scale geometries, permitting UT propagation within a constraining media structure and then targeting a qualification according to ENIQ （European Network for Inspection Qualification） methodology. A prototype flexible probe, designed for UT validation, and final flexible linear array probes permitting the UT behavior （as, e.g., detection and sizing from diffraction type echoes） to be maintained on wavy coupling surfaces, have been manufactured. These probes include a profilemeter with optical sensors control and a specifically designed coupling circuit （avoiding probe housing tightness issues）. Qualification has been performed using open test blocks, （where known ＂defects＂ exist, for procedure qualification）, and blind test blocks, （where ＂defects＂ are unknown, for qualification of testing personnel）. One open test bloc was customized to represent a ＂real＂ surface condition, with gaps up to 2.5 mm under the regular rigid probes. AREVAI/BGSI in Germany was selected to lead the project, with assistance in development and manufacturing sub-contracted to ＂CEA/LIST＂ laboratory, and the companies ＂IMASONIC＂ and ＂M2M＂. This paper describes the development of these probes and explains a few features （ENIQ qualification objectives fulfilled, UT data acquired on actual perturbed surface） that made their industrial implementation successful.

Development of Measurement System for Flow and Shape Using Array Ultrasonic Sensors

In Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the fuel debris formed in the Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) at Unit 1 - 3. To accelerate and decide further decommissioning steps of the FDNPP, it is crucial to obtain realistic information of the debris and localize contaminated water leakage from PCV. Due to high radiation and dark environment inside the PCV, investigating instruments and techniques should necessarily to meet specification of radiation resistance, waterproofness, dust resistance and so on. This study focuses on development of ultrasonic measurement system using a couple of sectorial array sensors to localize contaminated water leakage and visualize shape of object that repre- senting fuel debris, simultaneously. In this study, Total Focusing Method (TFM) and Ultrasonic Velocity Profiler (UVP) methods are considered to visualize object shape and flow pattern around it, respectively. To demonstrate applicability and reliability of developed measurement system with sectorial array sensors, a mock-up experiment result of simulated water leakage and fuel debris shape were discussed in this paper.

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 2DOF 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 dejects of weld at tubular joint can be detected accurately with the presented inspection system.

Simulation as a Support for Ultrasonic Testing

Ultrasonic testing is a very important non-destructive method for testing components for safety of nuclear power plants and other security and delicate parts in other industries. Nowadays, thanks to the development of computer technology, it is possible to simulate processes which occur during ultrasonic testing. That is why numerical simulations are becoming an integral part of non-destructive testing. Simulations are used to determine parameters of ultrasonic examination, especially parameters of probes and scan plan and also in the analysis of results. They are used in such cases, when it is necessary to verify applicability of probes and methods. This verification could be provided on the weld and test block which are not manufactured. It could be also provided on defects, which are not manufactured in test block, but their presence is possible in given weld joint. Simulations are very useful for verifying the propagation of ultrasonic signal in given area (e.g. weld area). If movement of probe is limited, possibility of whole volume scan should be verified.

基于改进YOLOv8的地铁列车焊缝缺陷轻量化检测方法

针对现有的地铁列车车体焊接质量检测技术存在检测模型较大、检测精度和效率较低的问题,提出一种基于改进YOLOv8的焊缝缺陷轻量化检测方法。首先,利用相控阵超声波检测仪采集对接焊缝内部缺陷图像,通过图像预处理制作成焊缝缺陷数据集。然后,在YOLOv8模型基础上,利用Inner-SIoU优化原有损失函数、采用C2f-PConv替换C2f模块、引入大型可分离核注意力(LSKA)模块和挤压激励(SE)注意力机制,建立了基于改进YOLOv8的地铁列车车体焊缝缺陷质量检测模型,以提高焊缝缺陷特征提取和多尺度特征融合的能力。最后,利用改进的YOLOv8模型对焊缝缺陷数据集进行训练和测试。结果表明,改进的YOLOv8模型大小为7.91 M,对于焊缝缺陷的检测精度达到98.30%,检测速度达到138.9帧/s,与YOLOv8原始模型相比,模型更小,检测精度更高。

一种测量液膜厚度的超声相控阵实验装置

气液两相流存在于核反应堆蒸发、飞行器冷却、化工生产降膜蒸发等过程,界面波的动态测量对工业过程监控和生产优化具有重要意义。界面波的准确识别与特性参数测量是开展科学研究与工程实践的重要前提。基于超声相控阵测量系统,设计了扇扫的测量方式,可以用于气液界面清晰的流型中液膜厚度和界面波形态三维测量。通过静态标定和圆管验证,确定了像素点和液膜厚度之间的关系,在气相表观流速为0.0719~0.4316 m/s,液相表观流速为0.0567~1.4161 m/s的工况下进行实时动态实验,获得了实时流动过程中较高精度的截面气液相界面信息,并构建了管道内部界面波三维分布形态,为界面波特性研究提供了一种实验参考方法。

在役螺栓超声三维成像监测数据的智能化分析方法

螺栓是一种常见的机械连接件,一旦失效,可能会导致设备损坏、结构崩塌,甚至危及人身安全。因此,在役螺栓的监测一直受到广泛关注。将相控阵超声全聚焦技术应用于螺栓在役监测,开发了专用系统和阵列探头,实现了三维成像可视化监测,改变了螺栓监测数据单一的现状。针对大量三维图像化数据处理的关键问题,提出了智能化分析方法,对比分析了决策树、支持向量机和神经网络算法的适用性,最终开发了基于决策树算法的智能分析评价软件模块并取得了较好的检测效果。

航空铝合金薄板搅拌摩擦焊内部缺陷的超声相控阵检测

针对3 mm厚度下航空铝合金薄板搅拌摩擦焊焊缝的检测需求,基于典型缺陷特征以及缺陷对焊接接头性能的影响规律分析,明确了搅拌摩擦焊无损检测应重点关注的缺陷类型;设计了不同深度和尺寸的隧道以及未焊透缺陷模拟样件,利用模拟缺陷样件验证了超声相控阵检测技术对铝合金搅拌摩擦焊中1 mm埋深0.2 mm孔径的隧道缺陷以及1.6 mm埋深2 mm长、0.2 mm深未焊透缺陷的检测能力,对3 mm厚度下搅拌摩擦焊实际样件的检测结果与X射线检测结果及断口观察结果吻合,超声相控阵检测技术可以用于3 mm以下航空铝合金薄板搅拌摩擦焊焊缝的检测。

管道超声相控阵全聚焦成像仿真及算法优化

针对厚壁管道内部缺陷识别困难、可视化差等问题,提出基于超声相控阵理论和全聚焦算法对厚壁管道内部缺陷进行图像重构。并针对全聚焦成像效率低的缺点,采用有限元法对外径为550 mm,壁厚为65 mm的厚壁管道超声相控阵全聚焦成像进行仿真,模拟缺陷检测过程和成像结果,并使用稀疏矩阵对算法进行优化。结果表明:在基本满足成像质量要求的情况下,采用激发中心频率为5 MHz,阵元宽度为0.5 mm,阵元间距为1 mm,阵元数量为32时,稀疏激发矩阵比全矩阵全聚焦成像效率提高了74.81%,有效提高了成像速度,满足全聚焦快速成像的需求。

焊缝缺陷三维成像及亚像素定量方法研究

为实现工业设备中焊缝结构内部缺陷准确地定量分析,针对构造缺陷三维重构模型时缺陷图谱的过分割和欠分割导致定量分析不够精确的问题,提出了一种基于图谱颜色分割的新算法。利用该算法处理缺陷切片并进行三维重构获取其长度,应用Canny算子与三次样条插值法结合获取缺陷亚像素边缘,基于缺陷区域连通标记算法和累加法可获取缺陷面积和体积的方法。研究结果表明:与实际数据对比,未焊透、未熔合、夹渣缺陷重构的长度误差分别为8.18%、5%、9.62%,基于此对分割缺陷的亚像素边缘内连通域进行标记以准确地获取其面积及体积。该方法能够在不破坏焊缝结构的情况下即时获取焊缝内部缺陷的形貌并对其进行精准且全面的定量分析。

楔块耦合的碳纤维增强复合材料褶皱缺陷全聚焦成像

褶皱是碳纤维增强复合材料中最主要的缺陷类型之一,当使用超声相控阵对复合材料薄板进行检测时,由于采集系统非线性效应和电子串扰等干扰会引发盲区现象,掩盖了薄板内的褶皱信息。为削弱盲区影响,考虑在相控阵与复合材料薄板(小于10 mm)之间增加楔块,提出楔块耦合的最短路径射线追踪全聚焦方法。基于费马原理与斯涅耳定律,建立楔块耦合的多层介质超声波传播模型;制备含褶皱缺陷的碳纤维增强复合材料试样,搭建超声相控阵数据采集系统,采集全矩阵数据;将楔块耦合的最短路径射线追踪全聚焦方法和传统全聚焦方法的成像效果进行对比。结果表明,基于楔块耦合的最短路径射线追踪全聚焦方法能减小试样表面盲区深度,修正声时偏差,削弱盲区影响,恢复出试样内的褶皱缺陷。相比传统全聚焦方法,纤维褶皱长度、褶皱顶部高度、褶皱角度这3个参数表征的精准程度分别提高了5.9%、4.1%、4.2%。该文为碳纤维增强复合材料薄板褶皱缺陷的检测提供了新思路。