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.     

传热管道设备的内壁状态监测方法

在特定边界条件下对热传导方程进行求解,优化所得温度分布方程的系数,并利用分段积分法对系数进行化简,建立了传热管道设备表面温度、材料特性与内壁状态3者间的关联模型,并将其应用在传热管道设备的内壁状态监测上。结合导热反问题,利用所建立的关联模型分析传热管道设备外表面的温度数据,得到内壁几何形状。通过仿真实验验证了该方法的可行性,从而为传热管道设备内壁状态的实时监测提供依据。     

Experimental study on cooling enhancement of crushed rock layer with perforated ventilation pipe under air-tight top surface

Under the warm and ice-rich nature of permafrost and the scenarios of climate warming on the Qinghai-Tibet Plateau, it will be necessary to use combinatorial techniques of cooling the ground temperature in the proposed Qinghai-Tibet Express Highway of construction. For the crushed rock highway embankment embedded a perforated ventilation pipe in permafrost regions of the Qinghai-Tibet Plateau, the mechanism of impact on the cooling capability enhanced by a perforated ventilation pipe in the air-tight crushed rock layer was studied using laboratory experiment. All boundary conditions at each edge of the crushed rock sample with dimensions of 100 × 60 × 100 cm except the inlet and outlet of the perforated pipe are air-tight. A ventilation steel pipe with an inner diameter of 8 cm was drilled with many small holes with a diameter of 1 cm and horizontally embedded in the length direction of the crushed rock sample with a depth of 53 cm. The laboratory experiments with a periodically fluctuating air temperature in the inner test tank regulated by program control were performed. The perforated pipe is only ventilated during the negative temperature fluctuation period in the inner test tank. The results show that the heat transfer processes in the crushed rock layer embedded a perforated ventilation pipe with an air-tight surface include pure heat conduction, forced convection that occurs in the crushed rock layer forming directly a pore air circulation in conjunction with the in-duct air by the small holes of perforated pipe wall absorbed from the inner test tank, and convective heat transport between the in-duct air and the inner surface of ventilation pipe wall. When air temperatures in the inner test tank are colder than the pore air temperatures in the crushed rock region around the perforated ventilation pipe, the perforated ventilation pipe can produce a significantly enhanced cooling of the crushed rock layer base due to the direct formation of a complete pore air circulation in the crushed rock layer in conjunction with the in-duct air via the small holes of the perforated pipe wall. When the fluctuating air temperature in the inner test tank rises from a minimum value to a warmer one than the pore air temperature in the crushed rock region around the perforated pipe during the negative temperature ventilating period, a warming process begins to occur in the crushed rock layer due to a warmer in-duct air absorbed from the inner test tank. This stronger warming process in the crushed rock region around the perforated pipe may decrease the cooling capability of the air-tight crushed rock layer. Thus, in order to avoid this warming process at this stage before ventilating end, the ventilating end time of ventilation pipe ought to be brought forward.     

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。     

Noncontact Laser Inspection Based on a PSD for the Inner Surface of Minidiameter Pipes

A new noncontact laser-inspection technique based on a position-sensitive detector (PSD) to inspect the inner surface of minidiameter pipes is proposed, and the corresponding sensor is developed. A light spot is projected onto the pipe inner wall after the laser beam is reflected by two mirrors. At the same time, four current signals are produced when the light spot is read by the 2-D PSD. According to the magnitude of the current signals and the structure parameters of the sensor, the spot position on the inner wall can be calculated in a local 3-D coordinate system. With a micromotor, the surface of the whole inner wall can be scanned by the laser beam. This way, the coordinates of all the sample points in the section are obtained. After that, several reasonable data-processing methods are used, such as data segmentation and least squares fitting. Finally, the section curve can be reconstructed. The radius and defects of the section can also be obtained. Driven by a micropipe robot, the sensor can inspect a long curved pipe. The inspection system based on this technique can detect the inner surface of minidiameter pipes, which has an inner diameter of 9.5–10.5 mm and a curvature radius of more than 100 mm. The measurement accuracy of this inspection system for the inner diameter and surface defect reaches $pm$0.1 mm.      

The transmittance by a hollow specularly reflecting cylindrical light pipe of isotropically incident radiation

A simple expression for the transmittance of a hollow cylindrical light pipe irradiated by isotropic incident radiation as a function of pipe size and inner wall reflectance is derived using a method based on the geometrical factor of particle telescopes. The predictions are confirmed by both a Monte Carlo calculation and experimental measurements.     

组合圆筒管的优化设计

用外缠绕玻璃纤维增强复壁钢管来代替油气田内部承高压的高强度钢管,既可节省大量的优质钢材,又能对场内集输管道起到良好的外防腐效果。本文着重研究由玻璃钢/钢组合而成的厚壁圆筒管在管内高压作用下的优化设计问题。首先利用组合管的边界条件,由弹性理论导出了平面应变状态下组合管壁内三个主应力的计算公式;然后建立了以组合管总壁厚、玻璃钢外套管壁厚和玻璃纤维缠绕角为设计变量,单位长度组合管的材料成本为目标函数以及钢管的强度约束和玻璃钢的变形限制为约束条件的优化设计数学模型,采用复形法对本问题求得了最优解。作者还用所编的电算程序计算了各种管内径,各种内压及各种钢管强度等级所对应的设计变量最佳取值,从而讨论了管内径、内压及钢管强度等级变化对优化设计变量的影响,计算实例表明,在承受相同内压作用的情况下,组合管的材料成本较单纯钢管低,组合管的重量减轻尤为明显。主题词:组合圆筒管;内压;平面应变状态;优化设计;复形法。     

管内机器人研究中的几项新技术

介绍了我们研制的管内机器人中应用的具有创新性的三项技术：１．轮式全主动新型行走机构；２．内壁环带视觉装置；３．新型离心喷涂器。     

基于密度聚类和圆外切线斜率拟合的埋地排水管道声呐点云去噪技术

针对环扫声呐扫描结果受到排水管道内混合水声的影响问题,提出一种声呐扫描点云数据去噪的方法:在环扫声呐扫描得到的三维点云数据基础上,通过密度聚类优化算法,去除点云数据中的噪声,然后采用类圆外切线斜率拟合的方式,识别出管道内壁界限和淤泥淤积线,最终得出包含排水管道内壁界限和淤积线特征的模型。为验证有效性,以武汉市某排水管道为例进行分析,基于现场采集的98万个点云坐标进行数据去噪和特征提取,结果表明:采用密度聚类优化算法进行点云数据初筛后,通过圆外切线斜率拟合算法能有效识别出排水管道内壁界限和淤积线,拟合半径均方误差0.0071m,相较于单一密度聚类算法拟合精度更高,去噪效果更好。     

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.     

管道修复用涤纶-苎麻复合机织物性能试验

针对传统管道内衬修复材料施工中易出现内壁塌陷等问题,结合目前快速发展的绿色纤维复合材料,提出在涤纶机织物内衬材料中加入苎麻纱线,制作涤纶-苎麻复合机织物材料来提高树脂对管道修复用内衬机织物的浸透性能,增强内衬材料和管壁的粘结性能。以纤维外观、抽拔实验后纤维断面形貌的电镜观察,并通过树脂与织物接触角的测试、粘结实验,综合分析了涤-麻复合机织物的树脂浸透性,同时对涤纶-苎麻复合机织物力学性能进行测试来保障内衬复合材料满足强度的要求。实验结果表明,采用上述涤-麻复合织造的方法,可以显著提高树脂的浸透性能,有利于携带更多的树脂粘结剂提高树脂与管壁的粘结性,减少塌陷发生的可能性。同时加入麻复合的机织物,拉伸顶破性能都满足高压燃气管道的修复要求。     

螺旋结构冷却塔的塔板设计方法

针对冷却塔中螺旋结构类型的气液交换塔,提出其内部螺旋塔板形状的设计方法,包括塔壁上外螺旋线和塔中心轴管上内螺旋线的位置确定,以及两线之间螺旋曲面板在平面上的拓扑尺寸。通过塔的几何参数确定螺旋曲面板设计的关键参数,可实现扭曲状塔板与塔壁及内轴的准确配合。     

Characterization of corrosion products formed on mild steel in deoxygenated water by Raman spectroscopy and energy dispersive X-ray spectrometry

The corrosion of steel parts of heating systems is nowadays not commonly observed failure because of the lack of oxygen in circulated media. In rare cases corrosion rapidly initiates and propagates due to various, mostly unexplained mechanisms. A voluminous corrosion product that was found in the vicinity of a perforation to a pipe wall was investigated in order to understand the reasons for the observed rapid corrosion processes. Raman spectroscopy and energy dispersive X-ray microanalysis were used to examine this corrosion product across the whole cross-section of the pipe. It was observed that the inner part of the corrosion product at the contact with the pipe's inner surface mostly consisted of magnetite. The outer part of the corrosion product, which was in contact with the water in the pipe, was mostly goethite. These findings confirmed the hypothesis that the magnetite sediments on the surface of the new pipe caused oxygen concentration cell formation, which triggered corrosion dissolution of the pipe wall and led to a rapid perforation.     

On the admissibility of replacing the heat conduction equation of a pipe wall by the heat balance equation in investigating transients in heat exchangers

An expression is obtained to determine the fraction of the thermal resistance of a pipe wall which must be referred to the inner boundary when using the heat balance equation for the wall instead of the heat conduction equation (for a heat exchanger with independent heating). Limits of applicability of the model with temperature concentrated along the pipe radius are given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 6, pp. 1079–1087, December, 1970.     

Failure analysis of nozzle zone before valve of negative pressure chamber from main pipe coolant system in nuclear power plant

Nozzle zone before valve of negative pressure chamber from main pipe coolant system in the secondary circuit of reactor is made of F316 stainless as usual. The butt weld between nozzle and socket in main pipe is the weakest part. If the rupture occurs, it will directly lead to the leakage of main system. One nuclear power plant finds a local penetration crack in the weld of nozzle zone, and it leads to leakage in the inspection. The length of crack is 23.6 mm, nearly 41.7% of the perimeter. In this work, crack morphology observation, composition analysis, metallographic structure observation and hardness measurement are done for the leak part. Analysing with the service environment and force condition, the inner wall of nozzle has a greater stress concentration. It easily leads to fatigue cracking near the fusion line area with poor welding, and the crack extends from inner wall to outer wall. The fatigue crack evolves to corrosion fatigue crack during the crack propagation, and the further advices for use are provided.     

X70钢螺旋焊缝冷弯管的质量评价

对φ1219mm的X70钢螺旋焊缝冷弯管的性能进行了试验研究。结果表明：冷弯管管端椭圆度变化比较明显,外弧处的壁厚减薄率较大。钢管弯制过程未对焊缝结构及性能产生明显的影响。相比弯管直管段,弯管外弧处母材的强度及硬度在时效处理后增大比较明显;弯管伸长率及冲击韧度略有减小。     

充粘性液体管材中超声导波的应力分析

对超声纵向导波在充粘液管材中的应力分布进行了分析,并讨论了用各模式检测充粘液管材的最佳频厚积范围和检测位置。分析表明,随频厚积的增加,L(0,1)和L(0,3)模式的平面内应力在管外壁上的值由负向变为正向,而L(0,2)和L(0,4)模式面内应力的值则相反,变换方向的点恰好在各模式的下一高阶模式群速度最大时的频厚积点附近;而在管内壁上,法向应力分布曲线达到零点的位置恰好在各模式群速度最大时的频厚积点附近。在各模式群速度较大的频厚积区域内,该模式在管内外表面上的平面内应力较大,而法向应力较小,因此能量泄漏较小。故在各模式群速度较大的频厚积区域内,用该模式来检测充粘液管材较合适。     

管道内旋转细长梁的固液耦合方法研究

管道内旋转细长梁是石油钻采工程中的特有结构,旋转细长梁不仅与管道内壁产生随机多向碰撞,还与细长梁内外管道和环空流体耦合,是一个复杂的非线性固液耦合系统,迄今还未见该方面的研究文献.该文考虑管道内旋转细长梁的结构和工作状态,将结构动力学方程、流体连续方程和动量方程耦合,推导了界面力和界面位移的计算公式、迭代格式及收敛准则...     

Stress intensity factors for circumferential semielliptical surface cracks in a pipe under thermal loading

Stress intensity factors are calculated at the deepest point and at the surface points of circumferential semielliptical surface cracks in a thermally shocked pipe. The method of calculation is based on weight functions following a proposal by Munz et al. Numerical values of the stress intensity factors are given for a wide range of crack depths and crack lengths considering a pipe with a wall thickness to inner radius ratio of $\text{1}\text{10}$.     

Analysis of the Stressed State of a Pipe of Gas Pipeline with Hydrogen-Induced Macrodefect

Materials Science - The long-term operation of gas mains may lead to the appearance of large-scale delamination inside the pipe wall under the conditions of its hydrogenation from the inner...