兆赫兹磁致伸缩超声导波管道检测系统的研制

研制的扭转模态磁致伸缩管道检测系统采用排线式磁致伸缩传感器时,可在管道中激励出低频T（0,1）模态超声导波,并有效检测出管道中截面缺失率为3％的通孔缺陷。为拓展检测系统的工作频率范围,设计出一款柔性印刷感应线圈,对其进行的实验验证结果表明,柔性线圈式磁致伸缩传感器可在管道中激励出兆赫兹T（0,1）模态超声导波,传感器的中心频率达1．30MHz,有望进一步提高磁致伸缩传感器的缺陷检测灵敏度。柔性印刷线圈无需使用适配器,可直接卷曲贴覆在管道表面,易于拆装。由此,研制的磁致伸缩管道检测系统的频率范围可覆盖几十千赫兹到兆赫兹,适合应用于实际工程检测。     

超声导波模态识别方法比较

模态转化是超声导波缺陷检测的重要表征之一,因而确定超声导波的模态在超声导波检测中有重要意义。采用数值模拟方法,得到利用窄带信号激励梳状换能器,在铝管中产生轴对称纵向导波时,铝管表面的面内位移和离面位移值。对采集到的位移信号分别使用时域法、二维傅里叶变换法以及矩阵束方法进行处理,从中提取存在的导波模态。由处理结果可知,三种方法均能判断导波模态,但其又具有各自的特点和局限性。     

管中导波的频散计算和缺陷检测

航空结构中不易拆卸的小口径管路和石油输油管道都需要一种高效快捷的损伤检测手段,研究了基于压电传感器的导波技术对中小口径管结构损伤的检测方法。借助Matlab软件求解频散方程,绘制频散曲线,根据频散曲线分析最佳激励频率及最佳导波模态,进一步得到检测信号的激励方法。结合数据处理及损伤定位方法,给出一套管路损伤的导波检测方法。试验结果表明:使用L(0,2)模态导波有效检测出φ25 mm不锈钢管上φ2 mm通孔,检测距离达70 m,使用T(0,1)模态导波有效检测出石油管道上的腐蚀缺陷。     

小径不锈钢管超声导波检测

介绍了超声导波检测的基本理论,利用不同数量的压电陶瓷换能器,选用70kHz、10个周期经汉宁窗调制的正弦波信号,对无缺陷和带有裂纹缺陷的8mm×1.5mm的小径不锈钢管进行了超声导波检测,讨论了超声导波的频散和多模态现象。试验成功激发出L(0,1)模态导波,结果表明对于此种小径管,采用两发两收的方式得到的波形会更好,并能有效地检测出一定尺寸的裂纹缺陷。     

不锈钢管材中弯曲模态导波试验

使用单探头激励法在管壁中激励弯曲模态的导波,以频散曲线为切入点,研究了弯曲模态导波在不锈钢管材中的传播规律以及对缺陷检测的可行性。根据频散曲线选定F(n,3)及L(0,2)模态,进而确定激励频率和入射角。得到弯曲模态导波可对φ1 mm(含φ1 mm)的通孔进行有效检测的结论。     

弯折小径管中槽型缺陷的L(0,1)模态导波检测

利用L(0,1)模态超声导波对直径为10 mm,壁厚为2 mm的不锈钢小径弯折管中的槽型缺陷进行检测.首先,建立有限元仿真模型,分析L(0,1)模态在具有不同弯折角度弯头处的模态转换和反射特性,观察到不同模态的反射回波信号能量与弯折角度间存在非单调关系;其次,利用磁致伸缩传感器在小径管中激励中心频率为90 kHz的L(...     

PVDF梳状传感器及在超声导波检测中的应用

为了减少多模态现象对超声导波检测的影响，设计制作了偏聚氟乙烯（PVDF）梳状传感器，在薄钢板中进行超声导波检测试验研究。结果表明，这种传感器可以实现单一模态超声导波的激励与接收，并可实现薄钢板表面污物的检测。     

超声导波管道表面激励接收的仿真分析

目前已有的超声导波激励模型均是在管道端部截面处施加瞬时载荷。然而,实际检测中,导波探头一般安装在管道外表面。为此,本文使用Ansys LS-DYNA显性动力学模块建立管道3-D模型,分别在管道表面施加汉宁窗调制的位移荷载和力载荷,可以成功地激励出轴对称纵向模态导波。仿真信号的波速接近理论值,缺陷定位准确。该方法很好地从声场角度对压电导波和电磁超声导波进行仿真分析,也为非轴对称局部加载激励导波的数值模拟提供了方法。     

海洋石油静电脱水压力容器的超声导波检测

针对海洋石油静电脱水压力容器的在役检验,采用超声导波方法进行了检测应用探索。对于此规格容器的内外壁腐蚀类缺陷,研制单斜超声导波换能器,并进行了试验研究和工业现场测试。检测结果为利用自行研制的导波换能器可以清晰检出1 400mm×600mm×5mm试样中6mm×1.25mm的平底孔,一次检测距离可达1 000mm。可以检出海洋石油静电脱水压力容器内外壁腐蚀类缺陷。由于表面漆层、内部液体介质对声波衰减较大,一次探测距离长度不大于500mm效果较理想。检测结果表明超声导波检测方法可实现对在役压力容器腐蚀类缺陷的快速检测。     

管道中激励和接收扭转模态导波专用探头的研制与应用

超声导波检测技术是一种新兴的无损检测方法。扭转模态是管道中超声导波的模态之一,可以检测各类缺陷。采用厚度切变型压电陶瓷作为敏感元件的探头,其外形尺寸为20 mm×10 mm×20 mm,在4 m长的钢管中进行了扭转模态的激励与接收试验。结果表明,该探头能够有效地激励和接收扭转模态,抑制了其它模态导波的干扰。     

在役石油平台用压力容器超声导波检测

超声换能器发射波在容器壁形成的超声导波可在涂层或其他覆盖物下沿容器壁传播,可以检测出容器腐蚀形成的缺陷及其内部缺陷,实现在役容器的快速检测。采用ISONIC2005超声检测系统,针对海洋石油钻井平台压力容器,利用模拟仿真和试验测试相结合方法,采用自行研制的超声导波换能器,制定相应的导波检测规范进行检测。检测结果表明,导波频率1.5 MHz,压电陶瓷晶片尺寸23 mm×28 mm,入射角为53°时,有效检测距探头1 000 mm处的6 mm×1.25 mm的平底孔信号,在实际在役石油平台容器检测中,探测距离长度不大于500 mm时,可以有效检测出带表面漆层和内部液体压力容器内外壁腐蚀类缺陷,超声导波检测结果与实际腐蚀减薄量相一致。     

空心抽油杆镦锻工艺的实验研究

通过对空心抽油杆镦锻工艺中金属流动特征的分析和实验研究 ,解决了空心抽油杆中部压方成形等无规则可循的难题。提出了避免空心抽油杆在镦锻过程中产生内壁凹陷、折叠、难充满的有效措施。在制订镦锻工艺时 ,采用倒装结构的凹模 ,减小了金属在模腔中的流动阻力 ,制订了36mm空心抽油杆镦锻成形工艺。     

Circumferential guided wave EMAT system for pipeline screening using shear horizontal ultrasound

The use of guided waves is now widespread in industrial NDT for locating metal loss in pipelines, that manifests as pitting, corrosion and general wall thinning. In this paper, a screening technique is assessed in terms of defect detection and defect sizing capability. Shear Horizontal (SH) guided waves propagate circumferentially around the pipe whilst the scanner is moved axially along the length. This type of tool is preferable to other methods, being applied to the exterior of the pipe, without requiring full circumferential access, and is able to operate through thin coatings (up to 1 mm thick). It is designed to provide a pipe screening tool for petrochemical pipelines both topside and subsea, particularly for detecting defects at pipe support areas. The system's efficacy in terms of detection and sizing of defects is considered via experimental measurements on artificially induced defects and in service corrosion patches, with results compared to finite element modelling of the interaction of the guided waves with artificial defects. Finite element modelling has been used to better understand the behaviour of different wave modes when they interact with defects, focusing on the mode conversions and reflections that occur.     

Circumferential higher order guided wave modes for the detection and sizing of cracks and pinholes in pipe support regions

The non-dispersive propagation of ultrasonic guided wave higher order modes cluster (HOMC) traveling along the circumferential direction in a hollow cylinder and its interaction with defects in pipe support regions is reported. These circumferential guided waves were generated in mild steel (MS) pipe specimens containing artificially created axial notches (simulating axial cracks) and pinholes (simulating pinhole-like defects) of different sizes in order to simulate conditions such as cracking and corrosion under pipe supports. The characteristics of these guided waves were also studied as a function of parameters related to how they were generated; namely, using: (a) 2.25 MHz linear phased array transducer, (b) 2.25 MHz conventional circular transducer and (c) 1 MHz conventional circular transducer. These higher frequency modes were explored for their ability to detect and size defects. Because of access limitations to the pipe support region in actual field testing, the transducer was always placed at a fixed circumferential position and moved axially along the length of the pipe. The defect position along the circumference was ascertained from the time of flight while the defect size was estimated using the amplitude data. The signals obtained for all three transducer configurations are compared for their ability to locate, detect and size the above-mentioned defects. It was shown that at these relatively higher frequencies, the guided wave modes exhibit small dispersion and have the ability to provide improved imaging of small size defects throughout the cross-section of the pipe.     

一种用于焊接结构多帧满秩成像检测的超声SH导波换能器

超声水平剪切(shear horizontal, SH)导波换能器在对焊接板结构进行缺陷检测时具有重要的应用价值. 为了研制换能器以对焊接结构进行多帧满秩成像检测, 运用导波半波长理论对超声SH导波的激发和换能器内部多重散射回波进行了分析.根据多重散射理论推导了匹配层介质颗粒密度与衰减的关系, 确定匹配层的组分. 提出3种V型斜楔结构, 对平面型前楔结构换能器和非平面型前楔结构换能器内部的多重散射回波进行对比试验. 结果表明,正交前楔结构换能器内部二重以上散射回波幅值减小了45%以上. 对正交前楔结构换能器进行性能测试, 其所激发的SH导波对焊接结构板中尺寸当量为?12 mm的缺陷回波信号信噪比达到了14.5 dB,具有较为优异的检测能力. 试验验证了理论分析的有效性, 所研制的正交前楔结构超声SH导波换能器可对焊接结构板中与波长尺寸当量的缺陷进行多帧满秩成像检测.     

抽油杆交流漏磁检测方法与装置研究

基于交流漏磁检测原理,采用穿过式线圈对抽油杆进行交变励磁,实现对其表面上多种类型缺陷的无损检测。实验结果表明,缺陷深度、激励磁场强度和提离值等参数对检测信号幅值产生较大的影响,并对各种参数产生的影响进行了分析。穿过式线圈磁化实现抽油杆全周向交流漏磁检测,其检测的灵敏度较高,可以对腐蚀产生的微小麻点进行评价,能实施对含腐蚀性环境下的抽油杆探伤。     

一种基于导波技术检测锚杆长度及缺陷的新方法

分析了自由钢杆与置于土壤中钢杆的频散曲线,并利用所建立的试验系统,采用导波技术,对上述两种锚杆的长度进行了检测。结果表明,频散曲线可以作为导波检测的理论指导,利用频散曲线选择合适的频率范围,通过激励纵向轴对称L(0,1)模态的导波可有效地检测锚杆长度;与置于空气中锚杆相比,置于土壤中锚杆的端面回波的信号幅度有所衰减,并且利用L(0,1)模态实现了对埋于土壤中锚杆缺陷的检测。     

管道导波检测中激发频率的选择及灵敏度分析

采用超声纵向导波对热交换管进行检测。首先利用导波的频散曲线，选定了检测的最佳导波模式L(0，2)，然后用位移分布、应力分布及总能量密度分布等选取了用该模式检测特定管道的频厚积，最后通过试验分析了管道导波检测的灵敏度。试验结果表明，L(0，2)模式的波长比缺陷尺寸大10倍时，也能非常清楚地检测到缺陷。     

Detectability of corrosion damage with circumferential guided waves in reflection and transmission

There is an increasing interest in high frequency short range guided waves to screen or monitor for corrosion. This contrasts with long range guided waves (LRGWs) which screen pipes for large patches of corrosion and have been successfully used in corrosion management for the past twenty years. The fundamental setup described in this paper uses circumferential guided waves, which are excited at a single location on a pipe and travel around the pipe wall and are detected at the same location. The study uses a finite element model assisted method to evaluate the detection capability of two short range circumferential guided wave setups which use both the reflected and transmitted signals. The setups themselves consist of either an axial array of transducers, for monitoring, or a single transducer which axially scans a pipe. Both setups have an array or scan pitch between either adjacent transducers or measurements. The detection capability of the fundamental Lamb wave modes (A0 and S0) in both reflection and transmission have been compared, as well as a hybrid shear horizontal wave setup, which uses the SH0 mode in reflection and the SH1 mode in transmission. A sensitivity analysis was conducted using two separate methods to determine the probability of detection (POD) for either the reflection or transmission signals. Both methods determine a POD for a specific defect, noise level, and array or scan pitch. Probability images are produced which map the POD for a range of defect sizes. For the parameters investigated in this study, it was found that in transmission large diameter defects have a higher detectability, whereas deep, narrow diameter defects are more detectable in reflection. A generalised overview of the sensitivity of short range guided waves is presented by combining both the reflection and transmission PODs. The data fused sensitivity of the S0 and SH hybrid modes are given as 0.6% and 0.75% cross sectional area (CSA) respectively, allowing for the comparison with LRGWs. The A0 mode was excluded from the POD analysis because it was much less sensitive than the other two modes.