An ultrasonic multi-wave focusing and imaging method for linear phased arrays

To overcome the inherent limits of traditional single wave imaging for nondestructive testing,the multi-wave focusing and imaging method is thoroughly studied.This method makes the compressional waves and shear waves focused in both emission and reception processes,which strengthens the focusing energy and improves the signal-to-noise ratio of received signals.A numerical model is developed to study the characteristics of a multi-wave focusing field.It is shown that the element width approaching 0.8 wavelengths of shear waves can keep a balance between the radiation energy of two waves,which can achieve a desirable multi-wave focusing performance.And an experiment using different imaging methods for a linear phased array is performed.It can be concluded that due to the combination of the propagation and reflection characteristics of two waves,the multi-wave focusing and imaging method can significantly improve the imaging distinguishability of defects and expand the available sweeping range to a sector of-650 to 65°.

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.

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.

Model and optimization of ultrasonic phased array parameters

Beam focusing is one of the unique characteristics of ultrasonic phased array compared with conventional ultrasound.On the basis of two-dimensional radiated sound field of phased array,the three-dimensional radiated sound field was simulated in the paper,and then the effect of different frequencies,different number of array elements and different element spacings on focal spot,the depth of focus and the effect on horizontal and vertical resolution were analyzed.The optimal results of transducer parameters have certain reference value for the design of phased array probe.

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.

Simplified Matrix Focusing Imaging Algorithm for Ultrasonic Nondestructive Testing

Full matrix focusing method of ultrasonic phased array has been proved with advantages of good signal-to-noise ratio and imaging resolution in the field of Ultrasonic NDT.However,it is still suffering from the time-consuming data acquisition and processing.In order to solve the problem,two simplified matrix focusing methods are provided in the paper.One provided method is a triangular matrix focusing algorithm based on the principle of reciprocity for the multi-channel ultrasonic system.The other provided method is a trapezoidal matrix focusing algorithm based on the energy weight of the different channel to the focusing area.Time of data acquisition and computational is decreased with the provided simplified matrix focusing methods.In order to prove the validity of two provided algorithms,both side-drilled holes and oblique cracks are used for imaging experiments.The experimental results show that the imaging quality of the triangular matrix focusing algorithm is basically consistent to that of the full matrix focusing method.And imaging quality of the trapezoidal matrix focusing algorithm is slightly reduced with the amount of multi-channel data decreasing.Both data acquisition and computational efficiency using the triangular matrix focusing algorithm and the trapezoidal matrix focusing algorithm have been improved significantly compared with original full matrix focusing method.

Ultrasound Imaging of Spinal Vertebrae to Study Scoliosis

Scoliosis is a musculoskeletal disorder manifested as a three-dimensional spinal deformity. It affects 2% - 3% of the adolescent population. The conventional method to diagnose scoliosis is to measure the Cobb angle from posteroante-rior radiograph. Since radiation exposure is not desirable for patients, other non-ionizing methods have been explored. Among all the non-ionization methods, ultrasound (US) is a potential cost-effective method. However, our understand-ing of US interaction with the vertebrae or the spine is limited. The purpose of this study was to demonstrate the ability of US to identify bony landmarks for measuring spinal deformity. This study used a phased array US system with a 5 MHz transducer and a position encoder. In-vitro experiment on a cadaver vertebra and a pilot clinical study were carried out. The in-vitro experimental results showed that the lamina and spinous process were strong reflectors from the single vertebra. Less than 4% of error occurred on the dimension measurements. The pilot study was performed on a healthy subject and a scoliotic patient. The results indicated the lamina and spinous process could be identified and the curvature of the spine could be estimated using the reflectors. The difference of the curvature angle of the spine measured from the radiograph and the US images was 2?. These results have illustrated that US is a promising tool to measure curvature of spinal deformity and study scoliosis.

相控阵超声平面波全聚焦成像算法及其应用

介绍了相控阵超声平面波全聚焦成像算法。首先描述了平面波全聚焦成像技术的数据采集方法,推导了不含楔块和含楔块情况下的声时计算公式,在此基础上阐述了平面波全聚焦成像的原理和步骤,并描述了算法在不同模态下的声时计算方法和算法有效区域的处理方法。然后通过试验展示了平面波全聚焦成像结果。接着,将平面波全聚焦成像分别和相控阵聚焦成像以及基于FMC(全矩阵捕获)的全聚焦成像检测结果进行比较,总结平面波全聚焦成像算法的优点和不足。最后结合平面波成像算法优点对平面波成像的应用进行分析。试验结果表明,PWI-TFM(平面波全聚焦)成像算法和现有成像算法相比,具有多方面的优势,是具有较高实用价值的成像算法。

相控阵超声后处理成像技术研究、应用和发展

相控阵超声后处理成像技术采用离线计算的方式对超声回波数据进行分析,实现缺陷的成像及评价,与基于实时成像的常规相控阵超声检测技术相比,成像更清晰,缺陷表征能力更强。近年来,相控阵超声后处理成像技术逐渐成为研究热点,国内外相关学者相继建立全聚焦成像、向量全聚焦成像、波数域成像和时间反转成像等一系列基于全矩阵数据的后处理成像算法,检测精度及缺陷表征尺寸极限取得了很大突破。为此,从全矩阵数据的基础理论出发,介绍基于虚拟聚焦思想和频域反演思想的相控阵超声后处理典型成像算法的基本原理、技术特点、研究进展及应用现状,总结当前发展存在的问题和不足,预测相控阵后处理成像技术的未来发展。

基于脉冲压缩技术的相邻缺陷识别方法研究

超声成像技术可以为探伤人员提供更可靠、直观的检测结果,在超声无损检测中的应用越来越普遍。然而,超声检测信号的时间宽度较宽,时间分辨率较低,在两缺陷相距较近的情况下,缺陷的反射回波往往叠加在一起,使得超声成像时难以实现相邻缺陷的辨识。为提高超声波检测信号时间分辨率,实现相邻缺陷的识别,将维纳滤波和自回归谱技术相结合,发展了一种超声脉冲压缩技术,并将其应用于超声阵列成像处理。研究了自回归谱分析中回归阶数和衰减窗宽度对缺陷识别效果的影响,并优化出最佳的处理参数。仿真和检测实验结果表明,通过对超声检测信号进行维纳滤波和自回归谱分析,可以大大提高超声检测信号的时间分辨率,从而实现相邻缺陷的识别。

埋地聚乙烯管道安全检验关键技术及工程应用

PE管道具有优良的性价比,广泛应用在能源、燃气等工程中,但因其焊接接头质量难以检测、探查难度大,使PE管道的安全状况难以控制,并导致泄漏等事故。结合国内出台的PE管道规范、标准及钢质管道检验的经验,提出了PE管道的安全检验关键技术,并介绍了部分科研成果,如PE管焊接质量超声相控阵动态聚焦和B扫查成像技术、探地雷达、泄漏检测等。文中提出的检验关键技术在某市PE燃气管网中得到了有效应用,检验出多项安全隐患,为城市燃气的安全提供了保障。

预应力管道压浆质量的超声波相控阵检测方法

为提高预应力管道压浆缺陷的检测效果,利用相控阵进行超声波检测数值模拟研究。通过与单震源对比,定量计算相控震源对信噪比的提升能力。在压浆缺陷的定量计算方面,利用虚拟动态聚焦成像法进行缺陷可视化研究。研究结果表明:根据相控阵和波纹管的特征,利用相控震源发射定向超声波,使超声波能量集中在预应力管道附近,可以大大提高有效信号的信噪比,突出空洞等异常体的反射信号;利用本文提出的超声波相控阵法可以解决预应力管道压浆质量的无损检测难题,检测方法易实现,效率较高,检测分辨率可以达到10mm。

超声相控阵矩阵阵列三维合成聚焦成像方法

掌握缺陷的三维形态信息,会更利于无损评估,因此将合成聚焦二维成像方法扩展,初步探索了三维合成聚焦成像方法,以直观得到缺陷的超声三维成像.将该方法在MATLAB平台编程实现,然后通过超声相控阵矩阵探头采集到的完备集数据后处理进行了验证.结果表明,通过三维合成聚焦处理后,得到探头下方空间的超声成像的三维图像数据,然后在此基础上使用等值面法将缺陷的三维图像分割出来.该图像能够清晰反映出反射体的真实位置及空间分布;在超声探头没有机械移动扫描的前提下能够得到缺陷三维图像.对于探头移动空间受限的检测位置获取缺陷三维图像有一定的理论意义及实用价值.

超声波相控阵技术原理及特点

介绍超声波相控阵技术的原理,分析该技术的独特优势,即:对工件的检测更具针对性,可以明显提高缺陷检出率及检测速度。同时展望了该技术在无损检测领域广阔的应用前景。

超声相控阵全聚焦法成像检测

超声相控阵全聚焦法(TFM)是用全矩阵捕获模式(FMC)获取的数据来进行信号处理的,所有计算均以30帧/s的刷新率完成。与标准相控阵法相比,全聚焦法成像分辨力甚高,能优化缺陷的定位、定量、表征等,并可对形状复杂试件进行检测。综述了超声相控阵全聚焦法成像检测的典型工业应用,并作了相关讨论,以供国内同行借鉴。

航空铝试块疲劳裂纹相控阵超声成像检测

表面疲劳裂纹扩展可导致结构失效,利用相控阵超声成像技术监测疲劳裂纹,获取结构完整性评价所需裂纹信息,可及时对结构失效提出安全预警。采用三点弯曲疲劳试验法在航空铝试块上生长疲劳裂纹,对裂纹开口面材料进行逐步切削来获得不同长度的疲劳裂纹,利用相控阵超声全矩阵采集(FMC)和全聚焦方法(TFM)获得的裂纹尖端和开口图像信息来监测裂纹扩展和测量裂纹长度,并测试了相控阵超声探头放置位置、裂纹张开/闭合、裂纹表面粗糙度对超声成像检测效果的影响。研究结果表明:相控阵超声探头从裂纹侧面入射检测能更好地对裂纹进行超声成像,并真实反映材料内部裂纹扩展前缘形貌。当疲劳裂纹长度大于3倍超声波长时,裂纹尖端和开口图像完全分离,相控阵超声全矩阵采集和全聚焦成像技术可有效测量裂纹长度,测量误差小于0.2 mm。相比裂纹张开时,疲劳裂纹闭合效应会使裂纹尖端超声图像信号减弱4.5 dB,长度测量值小0.6 mm。

TFM实时成像技术在缺陷检测中的应用

在压力容器的超声检测中,为解决传统相控阵(PA)二维成像存在缺陷图像畸变,难以准确定性等问题,采用1种基于全聚焦法(TFM)的实时超声成像技术,使用一维线阵和二维面阵分别对孔等典型实际缺陷进行扫查,获得缺陷的二维和三维图像,从定量角度对比分析2者的准确度。结果表明:该方法获得的三维图像测量误差在8%以内,具有更高的精确度和检出率,对于孔类缺陷的还原度更高,这对于缺陷检测与评估以及和特种设备的安全生产具有重要意义。

超声横波反射三维成像技术及在水工混凝土缺陷诊断中的应用

水利工程在长期运行的过程中,其混凝土构件会出现磨蚀、裂缝等损伤,如不及时进行处理,将会严重影响水利工程的安全运行。本文以混凝土内部缺陷所导致的波阻抗差异为基础,采用超声横波反射三维成像法探测。该方法具有横波探测、阵列式耦合、相控阵成像、合成孔径聚焦等特点,在多发多收的配置下,可实现对地下目标高信噪比、强分辨力、强穿透力、高工作效率的探测。通过将超声横波反射三维成像法应用于水工混凝土地面和蜗壳内部侧墙的混凝土裂缝精细化检测,为后续维护、维修提供有效的数据服务和决策支持。实践证明,超声横波反射三维成像技术在裂缝、脱空等水工混凝土缺陷诊断中具有良好的应用效果,值得在同类案例中进行应用和推广。

钢轨缺陷的超声相控阵波数成像算法

该文应用超声相控阵全矩阵捕获的波数成像算法,检测带有通孔缺陷的钢轨和B型相控阵试块。以实验获取的全矩阵数据为基础,研究了自发自收模式和全矩阵模式的波数成像算法,理论上分析了全聚焦方法和波数算法的计算性能,取得波数成像的结果并与全聚焦方法的成像结果做了对比。实验结果表明:波数成像算法具有更快的计算速度和更高的横向分辨率,且能够更加精准地还原钢轨中缺陷大小和形状,而传统的全聚焦方法计算耗时长,聚焦点分布不均匀,重建较大的缺陷出现了纵向拉长的现象,不能够较好地反映钢轨中的大缺陷。波数成像算法在各向同性材料实时检测中有很大的应用潜能。

缺陷的多模式全聚焦三维重构

分别采用超声相控阵扇扫、多模式全聚焦、多模式融合等3种成像方法,对焊缝夹渣缺陷进行了三维重构,并通过刻槽试块验证了多模式融合图像的真实性。结果表明,多模式融合成像法能够整合不同模式的有效信息,显示缺陷相对完整的立体轮廓,对焊缝缺陷的走向分析与类型识别有重要意义。