Nondestructive Testing and Characterization of Residual Stress Field Using an Ultrasonic Method

To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.

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.

Ultrasonic Nondestructive Testing of Superplastic Solid-State Welding Joint for Different Steels

Based on quantitative microscopic examinations of welds and welding rate for different steels(40Cr and T10A) joint,which possess the ultra-fine microstructure after high frequency hardening(HFH) and salt-bath cyclic quenching(SCQ),the suitable defect grey scale threshold value was determined,and the welding rate of superplastic solid-state welding of different steels(40Cr and T10 A steel) was systematically inspected and analyzed by means of self-made ultrasonic imaging inspection system.The experimental results showed that the superplastic solid-state weld of different steels can be inspected more accurately,reliably and quickly by this system,and the results were in good accordance with that of metallographic observation.The welding rate of superplastic welding is in linear relation with tensile strength of joint.

Monitoring of polymeric membrane fouling in hollow fiber module using ultrasonic nondestructive testing

This study describes the development of novel protocols extending the real-time ultrasonic reflectometry(UTDR) for the detection of membrane fouling in hollow fiber module during ultrafiltration(UF) of oily water treatment. A specially designed acoustic sensor with a frequency of 2.5 MHz was used. The hollow fiber membranes used were polysulphone(PSf) UF membranes with MWCO 40 kDa. The wastewaters with three different oily concentrations of 100, 500 and 1 000 mg/L were investigated. Diesel oil was utilized as the primary foulant. The results show that the permeate flux declines with operation time and its value becomes lower with the increase of the oily concentration in wastewater. It is found that ultrasonic measurement can detect the fouling and cleaning processes. A new signal analysis protocol-ultrasonic reflected energy was developed. Ultrasonic reflected energy obtained indicates the deposition of oily layer as a function of operation time and its removal after cleaning. The overall flux decline is reasonably correlated with the changes in ultrasonic reflected energy. This research provides the evidence that the ultrasonic reflectometry technique is capable of monitoring membrane fouling and cleaning in hollow fiber modules.

Determination of discontinuities in marble blocks via a nondestructive ultrasonic technique

Miners working in the marble industry have always been interested in identifying structural weaknesses in marble blocks before they are transported to marble processing plants. To achieve this difficult task, several simple methods have been developed among miners but observation-based methods do not consistently provide satisfactory results. A nondestructive method developed for testing concrete could be used for this purpose. In this study, this simple method based on differences in ultrasonic wave propagation in different materials was presented, and the test results performed both in the laboratory and a marble quarry were discussed.

Application of ultrasonic CT method in nondestructive detection of interior defects in large scale concrete structural member of bridge

The ultrasonic computed tomography(USCT)method is derived from the basic principles of X-ray section scanning.This method records the arriving times of ultrasonic wave between the probes and the sources to calculate the elastic wave velocity values in the section using the arrival times.Through analyzed the distribution of elastic wave velocity in aim area,the information of the strength and the homogeneity of the investigated zone could be got indirectly.The authors introduced the operational principle of USCT and a practical case of using this method to detect the interior defects in large scale concrete structural member.Compared with other exploration methods,this method is more efficient and accurate.

基于SoS核函数调制的超声图像伪影剔除方法

针对超声图像伪影严重的问题,提出了一种基于SoS核函数调制的超声图像伪影剔除方法,该方法能同时剔除由等声程线扩散、传感器拖尾现象和检测噪声产生的伪影.该方法利用SoS核函数对测得的超声回波信号进行调制,对调制后的信号等间隔低速率采样来获取离散序列值,再对离散序列进行离散傅里叶变换得到傅里叶系数序列,利用谱估计算法对回波信号参数进行估计,获取检测信号的特征参数,最后对回波信号进行自适应重构,计算声场得到超声图像.试验结果表明,聚焦和直探头对槽和通孔类缺陷的去伪影效果明显,与传统B扫图像相比,峰值信噪比分别达到了24.306、23.213、15.074和16.444 dB,结构相似度分别为0.931、0.932、0.746和0.773,表明该算法有效提高了缺陷图像的质量.

双探头梯形矩阵聚焦成像方法

R角是曲面变壁厚结构,传统超声检测方法难以对其轮廓和缺陷进行完整成像显示。针对此问题,首先,提出双探头全聚焦成像方法,实现R角区域的完整成像显示;其次,为了改善双探头全聚焦成像效率较低的问题,采用梯形矩阵聚焦成像算法,实现高效实时成像;最后,对典型变壁厚R角试件开展聚焦成像实验,验证了双探头梯形矩阵聚焦成像方法的有效性。结果表明,与传统单探头全聚焦成像方法相比,双探头梯形矩阵聚焦成像方法能够显示R角结构的完整内轮廓,并清楚显示和定位内部缺陷。

脉冲电磁式EMAT-涡流检测复合系统的研究

常规电磁超声换能器(EMAT)中永磁体难以应用于实际情况、产生的信号幅值较小,根据电磁超声检测和涡流检测在检测范围内的互补性,本文设计了脉冲电磁式EMAT—涡流检测复合传感器结构,采用多物理场耦合技术验证了复合检测方法的可行性,并讨论了影响传感器检测灵敏度的关键参数。结果表明:该复合传感器能够激发用于检测表面缺陷的涡流信号和检测深层缺陷的超声波信号,并且对不同宽度和深度缺陷具有良好的灵敏度;此外,对励磁线圈与涡流线圈进行参数优化设计,为电磁超声和涡流的复合检测应用提供思路。

基于激光超声的铝合金组织性能无损检测研究

目前对铝合金析出相和力学性能的检测主要采用扫描电镜(SEM)、透射电镜(TEM)、万能试验机等方式,费时费力且属于破坏性检测。采用激光超声无损检测技术对Al-Cu-Mg铝合金进行检测,通过变分模态分解法(Variational Modal Decomposition,VMD)对时域下的激光超声信号进行降噪处理,得到激光超声信号的衰减系数和声速等特征值,同时采用扫描电镜、电子背散射衍射(EBSD)、静拉伸实验获得Al-Cu-Mg铝合金的析出相和力学性能,将激光超声信号特征值与Al-Cu-Mg铝合金的析出相和力学性能进行耦合。结果发现:激光超声信号特征值与Al-Cu-Mg铝合金的析出相、晶粒尺寸、屈服强度以及显微硬度有较好的相关性。这为Al-Cu-Mg铝合金的微观组织和力学性能快速无损检测提供了一种新方法。

Enhanced air-coupled impact echo technique by phase analysis of signals from multiple sensors

This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave,but it is the 1st order symmetrical(S1)mode Lamb wave at zero group velocity(S1-ZGV).Therefore,it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference.As a result,the technique reduces the effect of propagating waves,including the direct acoustic wave and ambient noise.It is named the Constant Phase IE(CPIE).The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques.The CPIE shows a performance advantage,especially in a noisy environment.

基于超声辅助的汽车微小零部件内部缺陷无损检测方法

为了更准确、全面地分析汽车微小零部件缺陷,基于超声辅助的方式,设计了内部缺陷无损检测方法。根据超声波传播反射情况及声场变化,采集微小零部件图像;通过融合边缘信息消除图像中噪声,分割图像主体并完成边缘识别,确定存在内部缺陷的区域;利用核主成分分析技术,通过降维处理方式确定缺陷区域特征,进而完成无损检测。结果表明:利用所提方法获取的零部件图像清晰,缺陷检测准确率始终高于95%,对气泡和气孔缺陷的检测时间小于6 s,对裂纹缺陷的检测时间小于8 s,说明所提方法对内部缺陷的定位准确度和识别效率均较高。

焊缝质量离线检测技术的研究现状与发展前景

针对焊后焊缝成形缺陷存在的技术问题,对目前比较常用的几种无损检测技术,即结构光视觉检测、超声波检测、涡流检测、磁光成像检测和红外检测进行了深入研究。对上述检测方法的基本原理、系统结构、检测特点和各自的适用范围进行了讨论。研究结果表明:单种检测技术各有各的优势与短板,不能满足焊缝的全面检测要求,可以采用多种检测手段相结合的方法,实现优势互补。

在役管道应力无损检测方法试验研究

油气管道在长期运行时,会在各种地质灾害和其他异常荷载的影响下产生变形,进而引发管道安全事故。对在役管道进行定期的应力检测是一种行之有效的评估管道安全的手段。为探究更适用于在役管道的应力检测方法,选用主要材料为X70和X80钢板的在役管道进行拉伸试验,利用超声波法、磁各向异性法和矫顽力法检测不同荷载下钢板的应力,并对应力测试结果进行分析。在8组单向拉伸实验中,超声波法有5组试验数据拟合优度在0.99以上;在双向拉伸试验中,超声波法的拟合效果线性度最好,矫顽力法和磁各向异性法的数据拟合效果较为离散。随着提离值的增大,轴向矫顽力与环向矫顽力都呈下降趋势,磁各向异性法的检测信号也随着提离值的增大呈现降低趋势;超声检测的结果随着温度的升高而呈线性增加,矫顽力的测量结果随温度的升高而呈整体的下降趋势,磁各向异性技术的测量结果随温度的升高呈现先升高后降低的趋势。通过对3种方法试验结果对比分析,超声波法对在役管道应力检测精确度最高,为今后在役油气管道选择更高效的无损检测方法指明方向。

基于超声波信号的门式起重机无损快速探伤研究

目前常规的门式起重机无损快速探伤方法主要通过采用探测设备对检测区域进行扫描识别,从而获取损伤信息,由于存在扫描盲区,导致无损探伤精度较低。对此,本文提出基于超声波信号的门式起重机无损快速探伤方法。通过采用多个相互独立且角度不同的超声探头进行组合,缩小检测扫描盲区。并结合滤波算法对采集到的超声波信号数据进行去噪处理,同时提取超声信号的时域能量特征。最后通过计算超声波信号传输往返时间,获取起重机表面裂纹缺陷的具体位置,实现无损快速探伤检测。在实验中,对提出的方法进行了无损探伤性能的检验。经实验结果表明,采用提出的方法对不同类型的裂纹缺陷进行检测时,轴向定位误差值较低,具备较为理想的探伤检测精度。

OPCM阵列传感器及其在工程结构NDT中的应用

阵列换能器是在超声相控阵检测中实现电-声转换的传感器件,是影响无损检测(NDT)成像质量的关键因素。传统的超声相控阵换能器中存在力电参数不合理导致的结构不可设计性、驱动电压高等不足。为提高成像分辨率,设计了OPCM驱动/传感器相控阵列,并应用于铝板损伤检测。结果表明:OPCM驱动/传感器使相控阵超声损伤检测的成像分辨率优于常规的普通压电陶瓷阵列结果,研究拓展了复杂工程结构的无损检测技术(NDT)。

超声相控阵技术在轨道车辆转向架焊缝无损检测中的应用

转向架构架作为铁路客车的主承载部件,对焊接质量提出了十分严格的要求,其关键受力焊缝的无损检测技术也逐步提升。结合轨道车辆构架产品的结构特点,分析和破解轨道车辆构架关键焊缝内部检测工艺难点,对焊缝进行超声波相控阵检测并在实际检测中得到验证,超声相控阵技术可以准确检测出该类型焊缝中存在的未熔合、未焊透等内部缺陷,实现了轨道车辆转向架电机吊架、闸片托吊座、横梁管等关键焊缝检测的全覆盖,做到了缺陷焊缝的早发现、早消除,有效保障了轨道客车的行车安全。

应力波和超声波检测在木拱廊桥安全评估中的应用

木拱廊桥是木结构古建筑中重要的文化遗产,现存的部分木拱廊桥仍在使用中.为保护木拱廊桥,考虑各种复杂的环境因素和结构条件,将应力波和超声波检测技术应用于真实环境下的木拱廊桥检测中.挑选福州市闽侯县远济桥的承重木柱作为研究对象,针对木柱内部缺陷采用应力波检测与超声波检测.检测结果表明应力波和超声波检测木材缺陷时,超声波的检测精度更高,二者检测结果存在相似性;远济桥检测样本的承重木柱存在空洞、裂纹、虫蛀等缺陷,建议对远济桥的安全性进行优化和改进.基于木拱廊桥所处环境的实际情况,利用应力波和超声波检测相对照的检测方法,提出针对木拱廊桥的安全性等级进行划分,使应力波和超声波检测技术更好地应用于木拱廊桥的保护工程中.

超声检测在建筑钢结构焊缝无损检测中的应用

超声波检测技术基于超声波在材料中传播的原理,通过发射超声波脉冲并接收反射回来的信号来检测焊缝中的缺陷,这些反射信号可以提供有关焊缝内部结构和缺陷的信息,例如裂纹、气孔、夹渣等。基于此,文章阐述了超声波检测的原理,从缺陷特征、缺陷波形、底波3个方面分析了焊缝缺陷的性质,结合工程具体案例对超声检测在建筑钢结构焊缝检测中的应用进行了分析和探讨。

基于比分数和比率值的NDT实验室检测能力验证方法

无损检测(NDT)实验室或机构的检测能力直接影响检测的可靠性和一致性。将Z比分数和En比率值两种统计方法应用于无损检测实验室的检测能力比对,验证其检测能力。结合无损检测实验室的特点,以常用的焊缝超声检测为实例,设计了模拟比对试验。应用两种统计方法对比对的结果进行了分析,并对各模拟实验室的能力进行了评价。比对结果表明,Z比分数和En比率值两种不同的比对方法得出的评价结果相似,均可应用于无损检测实验室或机构的检测能力比对。