空间曲线型微细管道局部几何性质检测

开发了适于测量空间微细管道局部几何性质的传感器及其检测系统。在管道机器人潜入式检测过程中曲率传感器可适应管道的几何形状发生弯曲,同时内部的光路也将发生变化。根据激光束在PSD光敏面上的照射位置和传感器结构参数,确定管道曲率传感器上设立的活动标架沿轴线的转动速率,得到两个相邻活动标架之间的位置关系。结合初始活动标架方位、传感器结构,运用递推算法计算管道中心线局部几何性质参数。实验结果表明,测量相对误差小于4%,适合测量f10～f13mm、曲率半径大于100mm的管道几何性质。     

一维PSD定位精度的实验研究

本文根据实验研究测试了一维(二象限)PSD的线性特性,光斑大小和光束倾斜对PSD定位精度的影响,同时分析了其它一些因素的影响。实验表明,1mm直径的He—Ne激光束定位精度2.5μm,光斑越大,倾斜角越大,PSD的定位精度越低。PSD的线性性除与入射光能量有关外,还与后续处理电路有关。     

Optical grating diffraction method: from strain microscope to strain gauge

The grating diffraction method for direct strain measurement is reviewed. Two systems which use this method are presented. The first system is a compact strain microscope. A Leitz optical transmitting microscope with white light source is reconstructed by developing a loading and recording system. Gratings with median density of between 40 and 200 lines/mm are used. With the help of a Bertrand lens, the Fourier spectrum of the grating is formed with high image quality on the CCD sensor plane. Software is developed to precisely, quickly and automatically determine the diffraction spot centroids. The second system is a new strain sensor based on a high-frequency grating and two Position Sensor Detectors (PSDs). The grating, attached to the surface of the specimen, is illuminated by a focused laser beam, generally with a frequency of 1,200 lines/mm. The centroids of diffracted beam spots from the grating are automatically determined using two PSD sensors connected to a personal computer. The shift of diffracted beam spots due to specimen deformation is detected. Strain sensitivity of one micro-strain can be obtained, as can a 0.4 mm spatial resolution for strain measurement. The system can be used for both static and dynamic tests.     

基于环形激光的深孔内膛形貌检测系统研究

提出了一种基于环形激光的深孔内膛检测系统,该系统主要由环形激光发生器、反射锥镜、CCD相机以及驱动装置等组成。通过对环形激光器投射在被测身管内膛上的环形光斑进行成像和分析计算,可对身管内膛的一个截面形廓进行检测,并在驱动装置的驱动下,实现对深孔内膛形貌的三维检测。     

Hydraulic transport of solids in pipes: a simple method for the prediction of pressure drop

Suspensions such as grouting slurries, concrete and dredge muds exhibit a complex flow behaviour in pipes which is not fully understood. This flow in cement systems is often complicated by the time-dependent behaviour of the material and the apparent slippage at the wall of the pipe. Most of the methods which have been developed to predict the flow behaviour of thick suspensions are very complex and are frequently inaccurate. In this paper a simple method is discussed which can be used to predict the pressure drop in pipes for time-dependent or time-independent materials with a yield stress. The method is based on the assumption that the sheared layer in the pipe can be simulated by a similar layer in the coasial cylinder viscometer, and the properties of the layer are only dependent on plug speed in both systems. The implication of this assumption is that the shear stresses at the surface of the pipe and at the surface of the inner cylinder of the coaxial viscometer are independent of the pipe diameter and the diameter of the cylinders. The method was tested against the authors’ own data and by other data from the literature.     

双四象限光电探测器在线测试虚拟仪器

通过监测与所接收的激光弥散斑相对应的输出信号的变化率可以对探测器进行实时非接触测量,从而实现以双四象限探测器为接收器件的产品的在线检测和质量控制。介绍了以Labwindows/CVI为开发平台的双四象限探测器的测试、分析系统。建立了探测器接收弥散斑与输出信号变化率的关系模型,采用三次样条插值函数提高欠采样时ns级极窄光电脉冲信号峰值的求取精度。通过实验得到了探测器接收弥散斑与光敏面直径的最佳比值为0.5。研究结果表明,弥散斑直径测量的分辨力为0.0096mm,峰值电压测量幅值分辨力0.1mV。     

Failure Analysis of Cracks Formed at Extrados of Bend Pipe of API 5L X65M Grade

A metallurgical and root cause analysis was performed on hot induction bent pipes that exhibited cracking at the extrados. The bent pipe of 1016 mm (40 in.) diameter by 18.5 mm wall thickness was API 5L X65 PSL2 line pipe containing a longitudinal submerged arc weld. A metallurgical cross section was removed at a crack on the bent pipe extrados to document the crack morphology using optical microscopy. In addition to the cracking, golden-yellow streaks were visible at the extrados of the bent pipe. The composition of the streaks was examined using scanning electron microscopy with energy dispersive spectroscopy.     

Structural integrity analysis of HDPE pipes for water supplying network

A problem of reliability of polymer pipes manufactured with the high‐density polyethylene (HDPE) for drinking water supply was considered. The safety of the pipelines network was analyzed with taking into account two main factors: arising of sudden overpressure (water hammer phenomenon) and presence of defects on pipe surface. Based on elastoplastic fracture mechanics and using of J‐integral approach, the numerical model of cracked pipe was developed and verified by direct experimental test. The formula for calculation of crack initiation pressure, which is the function of pipe size and size of external surface defect, was derived. The validity of this relation was proved for pipes of diameter 450 to 800 mm. It was also shown that the pressure peaks of the water hammer phenomenon are quickly damped because of the high deformability of the polyethylene pipes and the defect depth that is equivalent to 40% of pipe wall thickness can be considered as acceptable. The applicability of developed tools was demonstrated under analysis in the real state of South Tunisian water supply network.     

建筑隔震橡胶柔性管道抗震性能试验研究

橡胶柔性管道在隔震建筑中逐渐得到应用,其震后能否正常工作会直接影响建筑的使用功能。该文选取竖向安装的橡胶柔性管道作为研究对象,变形位移需求为400 mm,考虑2种公称内径和4种管道设计长度影响,进行了抗震性能试验,对比分析了该类管道的地震损伤演化模式、变形和承载能力特征。试验结果表明:设计长度较小的管道均无法满足预期变形目标,经历管道绷直以及单侧断裂破坏两个关键状态,震后必须更换;对于设计长度符合规范建议的管道,则可以满足变形需求;回归分析获得了管道公称内径和设计长度与其水平变形能力之间的量化关系;管道设计长度相同时,管道公称内径与其破坏时的水平极限荷载呈正相关关系,但大公称内径和小公称内径管道的极限水平荷载之比小于公称内径比。     

基于激光跟踪仪的超声流量计几何参数实测方法

针对需要现场安装的大口径超声流量计的几何参数外部测量问题,建立了基于激光跟踪仪的大口径超声流量计几何参数测量方法。利用跟踪仪在管道外部测量管段壁面和超声探头的三维特征,并通过三维建模工具获得管段和探头的相对位置关系,进而计算得到流量计几何参数。结合现场测量案例,评估了内径、声道长度、声道角、声道高度等参数对流量不确定度的贡献。该方法不仅解决了管道外部几何参数实测问题,而且能将不确定度水平控制在0.2%左右。与跟踪仪实测值相比,几何参数厂家设置值存在一定的差异,建议厂家和用户给予几何参数实测更多的关注。     

Quantitative Evaluation of Corrosion in a Thin Small-Bore Piping System Using Bobbin-Type Magnetic Camera

Nondestructive testing (NDT) methods have been developed to ensure the integrity of heat exchanger pipes. NDT systems can be used to not only locate cracks on the pipes but also evaluate the size and position of the cracks. A bobbin-type magnetic camera (BMC), an electromagnetic NDT system, was developed to inspect both the inner and outer diameters (ID and OD, respectively) for stress corrosion cracking on a small-bore piping system with a high spatial resolution at high speeds. In this paper, an algorithm that discriminates the ID cracks from the OD cracks and estimates the crack volume is proposed. Artificial ID and OD hole-type cracks which have diameter of 1–4.5 mm and depth of 0.3–27 mm were used to imitate the corrosions on a 1.27 mm thickness and 16.56 mm inner diameter copper alloy pipe to verify the proposed algorithm. The inspection results of the BMC with respect to excited frequencies from 1–9 kHz are presented. 100 % of the ID and OD cracks were discriminated, and their volumes were estimated with a standard deviation of 1.132 mm³ for volume from 1.00–9.01 mm³.     

Experimental method for determining through thickness residual hoop stresses in thin walled pipes and tubes without inside access

The determination of through thickness residual stresses in pipes and pressure vessels is of growing interest because of emphasis placed on life prediction, design, and failure analysis of piping systems. Most of the through thickness residual stress measurement techniques require the placement of gauges on the outside and inside of the pipe. These methods are severely hampered when gauges cannot be placed on the inside of the pipe. This constraint could arise for small diameter pipes, long pipes or for pipes that have been used in a service condition causing corrosion or fouling of the inner surface.
This paper focuses on the first step of a three step procedure for determining residual hoop stresses in thin walled pipes and tubes. The method described is designed for cases where it is impossible to place gauges on the inside of the pipe. The method yses biaxial strain gauges on the outside of the pipe and involves a through thickness axial cut of the pipe. Based on the change in strain on the outside of the pipe, changes in the hoop residual stress distribution due to the axial cut are obtained with the method presented here. The method provides a means to evaluate changes in stresses on both the outside surface and the inside surface of the pipe as well as an evaluation of the change in through thickness hoop stress distribution at any location in the pipe cross section. This paper further demonstrates that the problem of shortening long pipes to enable placement of gauges on the inside of the pipe can result in the loss of significant residual stress information.     

利用测头等效法确定激光单点测头的方向

提出了一种利用测头等效法和迭代标定法确定激光单点测头方向的方法。该方法通过求解从激光测头的一维坐标向三维坐标转换的变换矩阵确定激光测头在测量机直角坐标系中的方向。利用测头等效法将激光测头等效为接触式测头,保证它在标定过程中的测量值不变,使其能测量空间的一个固定点,从而确定了求解变换矩阵的“共轭对”;利用迭代标定法保证了“共轭对”的确定满足测头等效条件,使变换矩阵的解(激光束的方向)逐步趋近于理想值。实验表明,当测头的一维测量精度为0.0128mm时,利用变换矩阵转换得到的三维数据的精度为0.0173mm,这证明利用该方法所确定的激光单点测头的方向具有较高的精度。     

Digital holographic profilometry of the inner surface of a pipe using a current-induced wavelength change of a laser diode

Phase-shifting digital holography is applied to the measurement of the surface profile of the inner surface of a pipe for the detection of a hole in its wall. For surface contouring of the inner wall, a two-wavelength method involving an injection-current-induced wavelength change of a laser diode is used. To illuminate and obtain information on the inner surface, a cone-shaped mirror is set inside the pipe and moved along in a longitudinal direction. The distribution of a calculated optical path length in an experimental alignment is used to compensate for the distortion due to the misalignment of the mirror in the pipe. Using the proposed method, two pieces of metal sheet pasted on the inner wall of the pipe and a hole in the wall are detected. This shows that the three-dimensional profile of a metal plate on the inner wall of a pipe can be measured using simple image processing.     

建筑隔震金属柔性管道抗震性能试验研究

隔震层中具有大变形需求的柔性管道显著影响隔震建筑的震后功能可恢复能力,然而目前对于柔性管道抗震性能的研究还相对较少。该文以量大面广且承载重要功能的竖向安装金属柔性管道为研究对象,考虑实际工程应用现状和相关规范建议,以400 mm变形为目标,以公称内径、管道安装长度、管道设计长度为研究变量,共设计了9组27个试件,进行了抗震性能试验,研究了金属柔性管道的损伤演化模式、关键损伤状态及其变形和承载能力。结果表明:目前工程上采用的柔性管道设计方案无法满足大变形需求或存在安全隐患,规范建议的方案则可很好地满足目标;对于破坏的柔性管道主要经历两个关键状态,即外金属套网绷直和单侧完全拔出破坏,破坏后无法承受工作压强需要更换;水平变形能力主要取决于管道安装长度和管道设计长度,随两者的增大而增大;破坏主要取决于管道受拉竖向荷载分量,该分量近似正比于公称内径,破坏水平荷载随着公称内径和极限水平位移的增大而增大。该文的研究成果可为建筑隔震金属柔性管道的抗震设计和易损性研究提供重要参考。     

光斑直径对含能材料激光点火性能的影响

用光电探测法研究了激光光斑直径对含能材料激光点火特性的影响.试验结果表明,在相同的激光能量下,光斑直径大,能量密度小;光斑直径小,能量密度高.过小的激光束会引起样品表面产生烧蚀和气化,带走部分激光能量,对点火过程不利,体现在点火延迟期变长了.同样,过大的激光束能量密度太小,不足以点燃含能材料.因此,选择合适的激光束直径对研究含能材料的激光点火特性很重要.     

Stress Intensity Factors of partly circumferential surface cracks at the outer wall of a pipe

By means of the finite element method stress intensity factors were calculated for partly circumferential surface cracks at the outer wall of a pipe. The crack shape considered can be described as curved rectangular shape. The cracks considered have crack depths between 20 and 80 percent of the wall thickness of the pipe and crack lengths (defined by the angle of circumference φ) between φ = 10° and φ = 60°. The pipe is loaded by a constant axial tensile stress σ₀ (equal to 136 Nmm^?2 in the numerial calculations), and the wall thickness to inner radius ratio of the pipe was chosen to 0.1. A wall thickness of 20 mm was used for the numerical calculations.     

激光测速仪定焦系统设计

为满足激光测速仪在米级距离的测速需要,设计了一种激光测速仪定焦系统.通过光束分析仪测量距离激光出射口不同位置处的光斑半径,利用函数拟合的方法得到激光束腰斑半径与腰斑位置.采用望远镜系统作为定焦系统的基本结构,通过MATLAB软件穷举定焦系统的各项参数,记录满足条件的参数.根据操作过程中的实际条件选择其中一种数据搭建定焦...     

Dynamic optical limiting experiments on vanadium dioxide and vanadium pentoxide thin films irradiated by a laser beam

Vanadium dioxide (VO2) and vanadium pentoxide (V2O5) thin films are irradiated by a near-infrared continuous-wave laser beam and the dynamic optical limiting performance is measured. The temperature varying with time of the films induced by a laser beam is also recorded by an IR thermal sensor. Under the irradiation of a laser beam with an intensity of 255 W/cm2 and a spot diameter of 2 mm, the laser beam transmittance of the VO2 film decreases from 47% before phase transition to 28% after phase transition, and the response time is approximately 200 ms; the laser beam transmittance of the V2O5 film decreases from 51% before phase transition to 24% after phase transition, and the response time is approximately 40 ms. The optical limiting is realized by this laser heating-induced phase transition.     

基于环形光切图像法的管内壁激光测量系统

研制了基于环形光切图像法的管内壁测量系统。测量系统主要由半导体激光器、环形光发生器以及CCD摄像机组成。来自光环发生器的环形光带投射于被测管内壁上并成像于CCD摄像机。根据光散射和反射的理论,测量系统参数被选择以优化系统。实验结果显示原理正确、技术可行。