Detection of internal crack growth in polyethylene pipe using guided wave ultrasonic testing

Despite the success of guided wave ultrasonic inspection for internal defect detection in steel pipes,its application on polyethylene(PE)pipe remains relatively unexplored.The growth of internal cracks in PE pipe severely affects its pressure-holding capacity,hence the early detection of internal cracks is crucial for effective pipeline maintenance strategies.This study extends the scope of guided wave-based ultrasonic testing to detect the growth of internal cracks in a natural gas distribution PE pipe.Laboratory experiments and a finite element model were planned to study the wave-crack interaction at different stages of axially oriented internal crack growth with a piezoceramic transducer-based setup arranged in a pitch-catch configuration.Mode dispersion analysis supplemented with preliminary experiments was performed to isolate the optimal inspection frequency,leading to the selection of the T(0,1)mode at 50-kHz for the investigation.A transmission index based on the energy of the T(0,1)mode was developed to trace the extent of simulated crack growth.The findings revealed an inverse linear correlation between the transmission index and the crack depth for crack growth beyond 20%crack depth.

Propagation Characteristics of Ultrasonic Guided Waves in Grouted Rockbolt Systems with Bond Defects under Different Confining Conditions

A rockbolt acting in the rock mass is subjected to the combined action of the pull-out load and confining pressure, and the bond quality of the rockbolt directly affects the stability of the roadway and cavern. Therefore, in this study, confining pressure and pull-out load are applied to grouted rockbolt systems with bond defects by a numerical simulation method, and the rockbolt is detected by ultrasonic guided waves to study the propagation law of ultrasonic guided waves in defective rockbolt systems and the bond quality of rockbolts under the combined action of pull-out load and confining pressure. The numerical simulation results show that the length and location of bond defects can be detected by ultrasonic guided waves under the combined action of pull-out load and confining pressure. Under no pull-out load, with increasing confining pressure, the low-frequency part of the guided wave frequency in the rockbolt increases, the high-frequency part decreases, the weakening effect of the confining pressure on the guided wave propagation law increases, and the bond quality of the rockbolt increases. The existence of defects cannot change the strengthening effect of the confining pressure on the guided wave propagation law under the same pull-out load or the weakening effect of the pull-out load on the guided wave propagation law under the same confining pressure.

Temperature Dependence of Ultrasonic Longitudinal Guided Wave Propagation in Long Range Steel Strands

Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes due to temperature shift making the prestress measurement of steel strands inaccurate and even sometimes impossible.In the course of solving the problem,this paper reports on quantitative research on the temperature dependence of ultrasonic longitudinal guided wave propagation in long range steel strands.In order to achieve the generation and reception of a chosen longitudinal mode in a steel strand with a helical shaped surface,a new type of magnetostrictive transducer was developed,characterized by a group of thin clips and three identical permanent magnets.Excitation and reception of ultrasonic guided waves in a steel strand were performed experimentally.Experimental results shows that in the temperature range from-4 ℃ to 34 ℃,the propagation velocity of the L（0,1） mode at 160 kHz linearly decreased with increasing temperature and its temperature dependent coefficient was 0.90（m·s-1 ·（℃）-1） which is very close to the theoretical prediction.The effect of dimension deviation between the helical and center wires and the effect of the thermal expansion of the steel strand on ultrasonic longitudinal guided wave propagation were also analyzed.It was found that these effects could be ignored compared with the change in the material mechanical properties of the steel strands due to temperature shift.It was also observed that the longitudinal guided wave mode was somewhat more sensitive to temperature changes compared with conventional ultrasonic waves theoretically.Therefore,it is considered that the temperature effect on ultrasonic longitudinal guided wave propagation in order to improve the accuracy of stress measurement in prestressed steel strands.Quantitative research on the temperature dependence of ultrasonic guided wave propagation in steel strands provides an important basis for the compensation of temperature effects in stress measurement in steel strands by using ultrasonic guided wave inspection.

High Precision Ultrasonic Guided Wave Technique for Inspection of Power Transmission Line

Due to the merits of high inspection speed and long detecting distance, Ultrasonic Guided Wave（UGW） method has been commonly applied to the on-line maintenance of power transmission line. However, the guided wave propagation in this structure is very complicated, leading to the unfavorable defect localization accuracy. Aiming at this situation, a high precision UGW technique for inspection of local surface defect in power transmission line is proposed. The technique is realized by adopting a novel segmental piezoelectric ring transducer and transducer mounting scheme, combining with the comprehensive characterization of wave propagation and circumferential defect positioning with multiple piezoelectric elements. Firstly, the propagation path of guided waves in the multi-wires of transmission line under the proposed technique condition is investigated experimentally. Next, the wave velocities are calculated by dispersion curves and experiment test respectively, and from comparing of the two results, the guided wave mode propagated in transmission line is confirmed to be F（1,1） mode. Finally, the axial and circumferential positioning of local defective wires in transmission line are both achieved, by using multiple piezoelectric elements to surround the stands and send elastic waves into every single wire. The proposed research can play a role of guiding the development of highly effective UGW method and detecting system for multi-wire transmission line.

Defects detection in typical positions of bend pipes using low-frequency ultrasonic guided wave

In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE(finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution, mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.

Review on second-harmonic generation of ultrasonic guided waves in solid media(Ⅰ): Theoretical analyses

Considering the high sensitivity of the nonlinear ultrasonic measurement technique and great advantages of the guided wave testing method, the use of nonlinear ultrasonic guided waves provides a promising means for evaluating and characterizing the hidden and/or inaccessible damage/degradation in solid media. Increasing attention on the development of the testing method based on nonlinear ultrasonic guided waves is largely attributed to the theoretical advances of nonlinear guided waves propagation in solid media. One of the typical acoustic nonlinear responses is the generation of second harmonics that can be used to effectively evaluate damage/degradation in materials/structures. In this paper, the theoretical progress of second-harmonic generation（SHG） of ultrasonic guided wave propagation in solid media is reviewed. The advances and developments of theoretical investigations on the effect of SHG of ultrasonic guided wave propagation in different structures are addressed. Some obscure understandings and the ideas in dispute are also discussed.

Nonlinear inversion of ultrasonic guided waves for in vivo evaluation of cortical bone properties

Ultrasonic guided waves(UGWs),which propagate throughout the entire thickness of cortical bone,are attractive for the early diagnosis of osteoporosis.However,this is challenging due to the impact of soft tissue and the inherent difficulties related to multiparametric inversion of cortical bone quality factors,such as cortical thickness and bulk wave velocity.Therefore,in this research,a UGW-based multi-parameter inversion algorithm is developed to predict strength-related factors.In simulation,a free plate(cortical bone)and a bilayer plate(soft tissue and cortical bone)are used to validate the proposed method.The inversed cortical thickness(CTh),longitudinal velocity(V_(L))and transverse velocity(V_(T))are in accordance with the true values.Then four bovine cortical bone plates were used in in vitro experiments.Compared with the reference values,the relative errors for cortical thickness were 3.96%,0.83%,2.87%,and 4.25%,respectively.In the in vivo measurements,UGWs are collected from the tibias of 10 volunteers.The theoretical dispersion curves depicted by the estimated parameters(V_(T),V_(L),CTh)match well with the extracted experimental ones.In comparison with dual-energy x-ray absorptiometry,our results show that the estimated transverse velocity and cortical thickness are highly sensitive to osteoporosis.Therefore,these two parameters(CTh and V_(T))of long bones have potential to be used for diagnosis of bone status in clinical applications.

分离谱在L(0,2)模式管道检测中的应用研究

以现有技术为出发点,期望利用分离谱技术,增强L(0,2)管线检测方法的技术效果。基于L(0,2)超声导波测定方法,梳理了分离谱处理流程,阐述了分离谱技术的用法。采取技术对比形式,客观判断分离谱技术的优势。在实践管线检测对比中,分离谱采取信号重组形式,有效增强了L(0,2)模式的独立性,保持其导波的完整性。相比处理之前,分离谱技术使用效果较好,信号分辨率更高,信噪比平均增长了2.07倍,缺陷杂波比增加了至少4.09倍。

Flaw Detection Capability and Sensitivity in the Inspection of Nuclear Containment Liner and Shell Mock-Ups Utilizing a Magnetostrictive Sensor (MsS) Guided Wave UT Technique

This paper describes the results of a project on the inspection of visually inaccessible areas of nuclear containment liners and shells via the advanced Magnetostrictive sensor (MsS) Guided Wave (GW) nondestructive inspection technique. Full scale mockups that simulated shell and liner regions of interest in the containment of both a Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR) were constructed. Inspections were performed on the mock-ups in three stages to discern the signal attenuation caused by flaws and caused by concrete in the structures. The effect of concrete being in close proximity to the liner and shell was determined, and the capability to detect and size flaws via this GW technique was evaluated.

分离谱处理方法在L(0,2)模式超声导波管道检测中的应用

超声导波无损检测技术在管道检测过程中,由于超声导波存在频散和多模式特征,其遇到管道边界和不规则缺陷通常会发生模式转换,导致检测信号分辨率降低。为了将L(0,2)模式导波与其他模式导波分离,提升检测信号分辨率,提出使用分离谱处理方法处理L(0,2)模式超声导波检测信号。在分析该方法工作原理的基础上,优化了其滤波器参数,处理管道不同周向缺陷的检测信号,以信噪比和缺陷杂波比为标准,选择了具有最佳分离效果的SSP信号重组方法。研究结果表明:SSP可以将L(0,2)模式导波与其他模式导波分离,并只保留L(0,2)模式导波;与处理前信号相比,分离谱处理方法信号的分辨率得到了提升,信噪比和缺陷杂波比分别提高了约1.08倍和4.39倍。

Study of Intelligent Approaches to Identify Impact of Environmental Temperature on Ultrasonic GWs Based SHM:A Review

Structural health monitoring(SHM)is considered an effective approach to analyze the efficient working of several mechanical components.For this purpose,ultrasonic guided waves can cover long-distance and assess large infrastructures in just a single test using a small number of transducers.However,the working of the SHM mechanism can be affected by some sources of variations(i.e.,environmental).To improve the final results of ultrasonic guided wave inspections,it is necessary to highlight and attenuate these environmental variations.The loading parameters,temperature and humidity have been recognized as the core environmental sources of variations that affect the SHM sensing mechanism.Environmental temperature has the most significant influence on SHM results.There is still a need for extensive research to develop such a damage inspection approach that should be insensitive to environmental temperature variations.In this framework,the current research study will not only illuminate the effect of environmental temperature through different intelligent approaches but also suggest the standard mechanism to attenuate it in actual ultrasonic guided wave based SHM.Hence,the work presented in this article addresses one of the open research challenges that are the identification of the effect of environmental and operating conditions in practical applications of ultrasonic guided waves and impedance-based SHM.

改进型密集阵列全聚焦成像算法的碳纤维复合材料板损伤定位研究

本文针对各向异性碳纤维复合材料板的损伤定位问题,提出改进型密集阵列全聚焦成像方法。首先,考虑碳纤维复合材料板的各向异性,通过实验分析超声导波在板中的传播特性,得到沿不同传播方向的群速度值。其次,对密集型传感器阵列的参数进行分析和优化研究,分别对不同阵列参数即阵元间距和阵元数量进行指向性函数的数值分析,优化阵列的参数,以保证阵列主瓣较窄、旁瓣较低且无栅瓣。然后,提出了一种考虑碳纤维复合材料板各向异性的改进型密集传感器阵列板结构缺陷定位算法。使用超声导波在碳纤维复合材料板中沿不同传播方向的群速度值,对全聚焦算法进行修正,并利用虚拟聚焦原理对板结构进行全聚焦成像。最后,通过布置碳纤维复合材料孔洞损伤实验,对基于密集阵列全聚焦成像方法的定位精度进行分析。实验结果表明,改进型密集阵列全聚焦成像算法的定位精度为1.00 mm,相较于使用单一群速度值,该方法在定位孔洞损伤缺陷时具有更高的精度。

基于超声导波的车用氢瓶在线检验技术研究

在役车用氢瓶的安全性能直接影响到氢能产业交通应用场景的可行性。传统拆卸离线检验模式制约了产业发展,结合前期研究成果,创新车用气瓶定期检验策略,通过定位损伤引导判断是否应进行拆卸离线验证气瓶安全性能。本文开展超声导波技术对车用氢瓶缺陷的定位算法研究及装置开发,进而攻克金属基碳纤维复合材料制气瓶噪声干扰大、信噪比高等不利因素,有效提取损伤信号,实现高精度损伤定位,经对极端冲量损伤、表面裂纹损伤后的车用氢瓶进行试验,验证其损伤定位误差可达到5%以内,对在役车用氢瓶安全性能评估具有非常重要的应用前景。

空调冷凝器管道激光超声导波跨能量层级映射迁移检测方法

空调冷凝器是空调设备的关键部件,其弯管连接部位由于损伤类型多和几何形状复杂等原因造成传统接触式损伤检测手段难以应用,本文提出一种基于能量映射迁移网络的非接触式激光超声导波无损检测方法。首先,通过小波分解提取烧蚀信号和热弹信号的概貌波形,设计自编码能量映射函数将热弹信号特征空间映射到烧蚀信号特征空间,获得更接近烧蚀信号特征的映射热弹信号。其次,通过能量映射迁移网络对齐映射热弹信号和烧蚀信号特征空间,将网络模型中的域转换误差和样本标签误差之和用作特征空间对齐误差值。最后,对空调冷凝器泄漏、分层和裂纹等损伤进行检测实验验证所提新方法性能,结果表明其损伤识别精度为93.09%,比传统激光热弹激励检测方法提高了7.23%。

适用于声源定位的气体绝缘输电线路超声导波传播特性研究

基于到达时间差(TDOA)的声源定位方法是当前气体绝缘输电线路(GIL)故障定位的主要方式,声波在GIL结构上的传输特性深刻影响着定位结果的准确性。为进一步提升故障定位精度,该文提出了考虑导波频散与多模态特性的GIL壳体声传输分析模型,以典型220 kV GIL管段为研究对象,建立声波传输有限元模型,研究了导波特性对故障定位的影响,确定了适用于故障定位的超声导波模态以及GIL非直管结构对该模态导波的衰减与时延量,通过现场定位试验验证了分析模型的可行性,为GIL声源故障定位系统的传感器配置与定位阈值设置提供了计算依据。结果表明,在20~60 kHz频带内,F(1,1)模态导波具有能量高、波形形状稳定、抗干扰能力强等特点,使用该模态导波进行故障定位精度较高。GIL非直管结构会对F(1,1)模态导波造成较大的幅值衰减与一定程度的时延,在故障定位中考虑非直管结构衰减与时延影响可以使定位误差降低60%以上。

基于PZT/Terfenol-D双层复合结构的导波换能器研究

为了解决传统磁致伸缩换能器激励信号能量弱、检测效率低的问题,提出一种基于PZT/Terfenol-D双层复合结构的导波换能器以提高换能效率。首先,建立换能器的谐振磁电动力学模型,设计换能器结构;其次,对设计的换能器进行仿真,验证换能器模型的合理性及可行性,并对其进行结构优化;最后,制作样机进行试验,采集换能器的激励信号能量,与传统磁致伸缩换能器和PZT换能器进行对比,并对获取的各组超声导波信号进行滤波处理,计算各自信号的幅值平方和。试验结果表明:所设计的换能器激励信号幅值平方和为PZT换能器的1.49倍,大于传统磁致伸缩换能器与PZT换能器激励信号幅值平方的总和。

Effects of Ultrasound/Dilute H_2 SO_4 Pretreatment on Cellulase Activity of Corn Straw Liquid Fermentation

[ Objective] The aim was to study pretreatment of ultrasound enhancing dilute H2SO4 on cellulase activity of corn straw liquid fermentation and explore the pretretment＇ s optimal conditions. [ Method ] By using orthogonal test, the pretretment of ultrasound enhancing dilute H2SO4 on corn straw was studied, then straw was fermented as the sole carbon source. Finally, the cellulase activity in extracellular fermentation broth was determined. [Result] The results showed that cellulase activity in extracellular broth was greatest under the conditions of acid bath time 3 h, acid concentration 3.5%, ultrasonic power 150 W, and ultrasonic time 5 h. They were FPA 15.82 U/ml, Cx 39.9 U/ml, 13-Giu 55.94 U/ml respectively. [ Conclusion] Under the above conditions, extracellular cellulase production has a high stability.

基于频域合成孔径聚焦的输电线路钢管杆超声导波成像检测

输电线路钢管杆结构是一种带有拔梢斜度的大口径薄壁管,超声导波周向B扫描检测传感器激发的超声导波在钢管杆传播过程中存在波束扩散现象。为了解决钢管杆超声导波检测过程中波束扩散导致周向检测分辨率降低的问题,提出了一种钢管杆超声导波频域合成孔径聚焦方法(Synthetic Aperture Focusing Technique,SAFT)。采用文中构建的超声导波合成孔径成像检测装置对直径为608 mm的钢管杆进行超声导波扫查,可获得周向B扫描图像和频域合成孔径聚焦图像。对比钢管杆周向B扫描图像和频域合成孔径聚焦图像,频域合成孔径聚焦图像中散射体和通孔的周向检测分辨率明显优于B扫描图像,文章提出的钢管杆超声导波频域合成孔径聚焦方法能够显著改善超声导波周向检测分辨率。

超声剪切波弹性成像技术检测糖尿病患者不同功能状态下腓肠肌硬度及其临床意义

目的:应用超声剪切波弹性成像(SWE)技术检测2型糖尿病患者不同功能状态下腓肠肌的硬度,为临床早期发现骨骼肌损害提供客观化评价依据。方法:选取70例2型糖尿病患者作为糖尿病组,以70名健康体检者作为对照组。应用SWE技术分别测量2组研究对象腓肠肌在踝关节自然位松弛状态、踝关节跖屈位等张收缩状态和直立位等长收缩状态下的杨氏模量(E)值,并采用体质量指数(BMI)对E值进行标准化(E_(BMI)=E/BMI),比较2组研究对象腓肠肌不同状态下被动硬度和主动硬度的差异,采用Person相关性分析糖尿病患者E值与患者年龄、病程、糖化血红蛋白(HbA1c)水平和糖基化终产物(AGEs)水平的相关性。结果:2组研究对象腓肠肌在踝关节自然位被动硬度E值和E_(BMI)值比较差异无统计学意义(P>0.05);踝关节跖屈位主动硬度E值比较差异无统计学意义(P>0.05),糖尿病组患者E_(BMI)值组低于对照组(P<0.01);糖尿病组患者直立位主动硬度E值和E_(BMI)值均低于对照组(P<0.01)。糖尿病组患者腓肠肌主动硬度E值与患者病程、HbA1c水平和AGE水平呈负相关关系(r=-0.645,P<0.05;r=-0.741,P<0.05;r=-0.675,P<0.05),与患者年龄无相关性(r=-0.116,P>0.05)。结论:2型糖尿病患者存在腓肠肌主动硬度减低,被动硬度早期可能不受影响;采用超声SWE技术在直立位等长收缩状态下检测腓肠肌主动硬度有助于发现2型糖尿病患者亚临床阶段肌肉收缩功能减退。

L(0,2)模态导波检测弯管缺陷的数值模拟和实验研究

针对低频超声导波纵向模态L(0,2)在弯管中传播的复杂性和对弯头典型部位缺陷检测的难度,目前尚未深入研究该模态在弯管处传播的能量分布特性和弯头拱背处典型缺陷的检测。采用数值模拟法分析L(0,2)模态在5种不同曲率半径钢制弯管中的传播特性,从波场快照研究信号能量分布变化,从时域波形研究模态转换;采用实验研究8根不同弯管弯头拱背外侧和内侧环向缺陷、过弯头后直管段缺陷的检测,对比分析L(0,2)模态的缺陷检出能力和模态转换特性。研究结果表明:L(0,2)模态经过弯管时,在弯头拱背外侧发生能量聚焦,该部位缺陷容易检出;在弯头拱背内侧发生信号衰减,导致该部位缺陷易漏检;过弯头以及弯头后直管段缺陷后均发生明显波形转换。研究结论为管道超声导波检测工程应用提供理论指导。