Digital holographic inspection system for the inner surface of a straight pipe

A multicolor digital holographic inspection system achieving both automatic scanning sensing head and automatic correction of a distortion in the profile due to positional error of a sensing head has been applied to the inner surface of a straight brass pipe having artificial defects on its wall. To investigate the inner surface of the pipe, the sensing head consisting of a cone-shaped mirror (CSM) glued to an aluminum base in the pipe is illuminated by the collimated RGB laser beams from the outside of the pipe. In the system, by changing the wavelength of the illumination light and scanning the CSM in the pipe, data acquisitions and analysis are performed using a personal computer. It is shown that the pipe inspection, including a classification of defects, can be successfully conducted by comparing the multicolor intensity images and the height profile of inner surface of pipe.     

The Effect of Cooling Mode on Slow Crack Growth Resistance of Polyethylene Pipe

High-density polyethylene (HDPE) pipes have been widely used as gas or water transport pipes owing to their comprehensive advantages. One of the principal failure modes determining pipe service lifetime is slow crack growth (SCG) with the crack occurring first at the inner surface due to the slow cooling rate of the pipe's inner wall during polyethylene (PE) pipe extrusion. In order to change the conventional cooling mode and increase the cooling rate in the inner wall of PE pipe during extrusion, a novel extrusion equipment was designed and manufactured by our research team. For this paper, compressed air as a cooling medium was introduced through the interior of the hot extruded pipe during its extrusion to realize the quick inner wall cooling, and the effects of the inner wall's cooling rate on the microstructure and mechanical properties of the PE pipe were investigated. The experimental results showed that simultaneously cooling of both the outer and inner walls could decrease the difference in the solidification rate across the pipe and reduce the residual internal stresses in PE pipe. The quick cooling of the inner wall of the extruded pipe could also decrease the PE crystal thickness, and increase the number of tie molecules in the inner wall, which is a key parameter determining the resistance to SCG. As a result, compared to the PE pipe produced by the conventional extrusion, the crack initiation time of the PE pipe manufactured by the novel method increased from 27 h to 45 h and the crack growth rate was slower.     

Formation of nanostructured carbon on steel targets irradiated by a high-power ion beam

The effect of the preliminary high-power ion beam treatment of steel targets (12KhN3A, St3, St20, St45) on the morphology and structure of a carbon layer produced by DC discharge plasma enhanced chemical vapor deposition using a C₂H₂/H₂ gas mixture has been investigated. It has been found that carbon nanotubes are formed on the St3 and St20 surface irradiated by the high-power ion beam with the ion current densities 50 and 100 A/cm².     

Role of surface phenomena in the magnetoresistivity of polycrystalline manganites La1−x CaxMnO3

The dc electrical resistivity and magnetoresistivity of polycrystalline manganites La_1−x Ca_xMnO₃ (x=0–0.3) are investigated as functions of the temperature, magnetic field and electric field, along with the microwave surface resistance. The investigations show that the dc electrical resistivity and magnetoresistivity are governed by the surface properties of the intergranular boundaries. The dc electrical resistivity is observed to decrease substantially (tenfold) for a comparatively small electric field (E⋟100 V/cm). Estimates are obtained for the internal electrical resistivity of the granules, the thickness of the contact layer (which depends on the temperature and the magnetic field), and the height of the potential barrier between the interfaces separating the surface layer and inner layer of a granule. Fiz. Tverd. Tela (St. Petersburg) 40, 1881–1884 (October 1998)     

不锈钢管道低温溅射镀TiN薄膜技术

 设计了一套适用于加速器细长管道真空室的低温溅射镀TiN薄膜装置。利用该装置，对86 mm×2 000 mm的不锈钢管道真空室进行溅射镀TiN膜实验，并对镀膜实验结果进行分析，得到了适用于加速器管道真空室内壁溅射镀TiN膜的表面处理参数。样品测试结果表明：在压强为80～90 Pa、基体温度为160~180 ℃的镀膜参数下，不锈钢管道内壁获得的TiN薄膜最佳，薄膜沉积速率为0.145 nm/s。镀膜后真空室的二次电子产额明显降低。     

非接触光电窥测仪瞄准及定位方法研究

在非接触光电窥测仪的设计中需要解决两个基本问题：一是如何通过特殊的光学手段把在内孔狭小空间中的被测信息提取出来;二是如何进行测头定位来解决测量基准问题。本文报导了我们设计的非接触光电窥测装置的工作原理。通过方案比较,提出了以图像位置偏移作为瞄准判据及５ 步定位方法,分析了它们的精度及灵敏度     

圆结构光视觉三维点管道缺陷检测及重构

管道内表面的缺陷检测对于保证介质运输安全,避免泄漏和爆炸事故非常重要。在分析三维点分布几何特征的基础上,对基于视觉检测获得的管道内表面三维点,通过判断同一圆周上相邻点法线夹角变化检测管道内表面的凹凸缺陷,采用空间点相邻三角平面法线加权平均获取空间点的法线。依据三维点呈圆周分布的特点,采用相邻圆周上点顺次连接进行快速三角剖分。基于上述方法对实际测量的管道内表面三维点和仿真三维点分别进行了凹凸缺陷检测和三维重构。该方法能实现径向变化小于0.1 mm的管道凹凸缺陷的检测和识别,三维测量精度为0.081 mm。     

基于圆结构光照明和LED照明相结合的三维检测技术

针对孔内表面的检测问题,提出了一种新的基于结构光照明和LED照明相结合的三维检测技术。该方法主要包括三个步骤:首先通过圆结构光照明获取孔内表面的截面轮廓图像,并通过图像处理和系统标定得到当前截面上局部区域的深度值;然后通过平面光照明得到孔内表面的平面图像,并在分析成像关系的前提下,在对平面图像进行坐标变换后得到孔内表面的展开图像,结合图像处理算法,提取展开图像的局部区域的平面尺寸信息;最后将圆结构光数据和LED光源数据变换到同一全局坐标系下,得到内表面的三维信息。     

Attenuation and scattering of axisymmetrical modes in a fluid-filled round pipe with internally rough walls

The attenuation of axisymmetric eigenmodes in a cylindrical, elastic, fluid-filled waveguide with a statistically rough elastic wall is studied. It is shown that small perturbation theory can be used to relate explicitly the statistical characteristics of the internal wall surface roughness of an elastic pipe to the attenuation and scattering coefficients of the acoustic modes in the filling fluid. Analytical expressions for modal attenuation coefficients are obtained. The analysis of the frequency dependent attenuation coefficients and the ratio between the roughness correlation length and the inner radius of the pipe is made for different correlation functions of the roughness. It is shown that two scale parameters control the overall behavior of the modal attenuation coefficients. These are the ratios of the roughness correlation length and the inner pipe radius to the acoustic wavelength. The numerical results for sound propagation in a pipe and in a borehole with statistically rough, elastic walls are obtained and discussed.     

圆台形超声相控阵列在管材检测中的聚焦声场

针对一种新型的用于钢管横向缺陷检测的圆台形超声相控阵列,提出了计算管内一次波位移场的模型。设计了三维情况下,圆柱界面存在时的时间延迟法则,并在高频近似下,利用瑞利积分法结合稳相法,研究和计算了管材横截面以及纵剖面上的二维声场分布特性。最后详细讨论了圆台形相控阵列中心夹角、阵元宽度及动态阵元数等参数对管材中聚集声场的影响。结果表明,这种模型以及计算方法可以有效地分析圆台形阵列在钢管内的辐射位移场特性,为实际制作这种圆台形阵列提供理论指导。      

A waveguide reactor for IR multiphoton dissociation and its application to13C laser isotope separation

A waveguide reactor for infrared multiphoton dissociation reactions has been presented and applied to laser isotope separation of¹³C. The reactor is a sealed vessel containing a hollow waveguide for a CO₂ laser, and the laser beam is condensed in the waveguide. The waveguide is a pipe of total-reflection glass or metal-coated glass with a funnelled inlet; it is 50 cm long with a 3 mm inner diameter. The isotope separation of¹³C has been made by multiphoton dissociation of CHF₂Cl using a TEA CO₂ laser. The result has shown that the waveguide reactor increases the dissociation yield by four to ten times as much as that without the waveguide at the pulse rate of up to 150 Hz, while the separation factor remains on the same level. It is also found that an optical breakdown which is induced at the wall surface plays a significant role to reduce the isotope selectivity.This work is for a partial fulfilment of B.S. degree of Osaka Electric Communication University     

Fabrication and characterizations of a polymer hybrid OA/MA/St-TiO2

A nano-hybrid composite of octadecyl acrylate/maleic anhydride/styrene (OA/MA/St) encapsulating nano-TiO₂ with an average particle size of 30-60 nm was fabricated based on chemical modification of nanotitania. The polymer hybrid OA/MA/St-TiO₂ and nano-TiO₂ were characterized by infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), static contact angle (CA) as well as transmission electron microscopy (TEM). FT-IR spectra and TGA results suggest that the copolymer OA/MA/St adheres on the surface of nano-TiO₂ through physical adsorption and chemical bonding. The calculated reacted OH surface density is about 0.6 OH/nm², and the modification efficiency is approximately 27.28%. In addition, when the molar ratio of OA/MA/St is 7:2:1, the hybrid shows the strongest hydrophobicity, and its static contact angle reaches as high as 146°. TEM image of the hybrid OA/MA/St-TiO₂ reveals that the modified particles have good dispersibility and compatibility with n-hexane.     

Nitriding of steel and titanium surface layers under the action of compression plasma flows

The elemental and phase compositions of St3 steel and VT1-0 titanium surface layers nitrided by the action of compression plasma flows (CPFs) have been investigated. The plasma flow parameters are shown to be correlated with the modified-layer nitrogen content. The basic mechanism by which the steel and titanium surface layers are saturated with nitrogen has been revealed. The performed experiments indicate that an increase in the absorbed energy density leads to a decrease in the nitrogen concentration because a shock-compressed layer is formed in the near-surface region, impeding nitrogen diffusion into the sample. The higher nitrogen concentration of surface layers treated by CPFs is achieved by increasing the pressure of the residual nitrogen atmosphere. It has been established that γ_N-Fe nitrous austenite, α″-Fe(N) and α′-Ti(N) martensitic phases, and γ′-Fe₄N and δ-TiN _x nitrides can be produced by nitriding the surface layers of St3 steel and VT1-0 titanium.     

The Formation and Evolution of the Hierarchical Structure of Polyethylene Pipe During Extrusion Processing

The formation and evolution of the hierarchical structure of polyethylene (PE) pipe during extrusion processing were investigated and its structure-performance correlation is discussed. The experimental results showed that during the PE pipe processing the axial stress by the traction machine oriented the molecular chains along the axial direction, and gave rise to some shish-kebab structures in the external layer which were parallel to the axis, so that the PE pipe easily cracked along the axial direction. Moreover, the temperature gradient generated by different cooling rates across the pipe wall caused the kebab crystals and the spherulites nucleated further from the outer wall to only grow toward the inner wall. As a result, the lamellae were oriented along the radial direction of the PE pipe. On the other hand, owing to the slow cooling of the inner wall, its tie molecules were of lowest density and hence its resistance to slow crack growth was poor. Therefore, the inner layer, which also suffered the highest hoop stress, would become the weak point in PE pipe applications; that is, the cracks extended from the inner wall of the pipe, through the wall, and then in a longitudinal direction.     

无限液体介质内管道轴对称纵向导波激发与传播特性研究

利用声-结构耦合有限元法,分别对轴对称分布径的向及轴向外力作用在无限液体介质内未充液及充液管道内壁所激发导波进行了模拟,并进一步利用短时傅里叶变换技术对瞬态波形作时频分析,在此基础上,结合色散及衰减曲线,探讨了外力分布特征对导波激发的影响。研究表明,无限液体介质内未充液管中L(0,2)模式及充液管中L(0,3)~L(0,4)模式皆具有高群速度、弱色散且弱衰减频带,适宜用于缺陷探测,而通过控制轴对称分布外力的频率,并令其沿轴向作用于管内壁或外壁,可实现上述导波模式的高效激发。      

Electrostatic potential and field near the boundary between space charge and no charge regions within a cylindrical pipe

In electronic industries, a corona ionizer is widely used for the elimination of electrostatic charge on the material. Although the high frequency AC ionizer proved the effectiveness of its performance, the corona ions must be sent through a metal pipe to reach targeting area. In order to analyze the behavior of ions in elimination process, the potential and electric field within a pipe must be known. Since the potential and field distribution near the boundary between space charge and no charge regions are extremely important, the analytical solution for this problem was sought by using Bessel functions. Analytical solution showed that even in no charge region, there exists potential distribution within a pipe. Numerical calculation of electric field on the inner pipe surface indicated useful information to estimate the charge density in the pipe. Furthermore, some mathematical formulae were obtained by using Bessel functions.     

Effect of a bounding surface on the rotational viscosity of liquid crystals

The effect of a surface, bounding a nematic-liquid phase, on the rotational viscosity γ ₁ is investigated on the basis of a statistical approach employing direct correlation functions. Specific calculations are performed for a model system consisting of ellipsoidal molecules interacting via a Gay-Berne potential near the bounding surface. Fiz. Tverd. Tela (St. Petersburg) 40, 1945–1949 (October 1998)     

Experimental comparison of Triton X-100 and sodium dodecyl benzene sulfonate surfactants on thermal performance of TiO2–deionized water nanofluid in a thermosiphon

This study investigates how TiO₂/deionized water nanofluids affect the thermal performance of a two-phase closed thermosiphon (TPCT) at various states of operation, according to the surfactant types. A straight copper tube with an inner diameter of 13 mm, outer diameter of 15 mm, and length of 1 m was used as the TPCT, i.e., heat pipe. The nanofluid utilizing in experiments was prepared by mixing the TiO₂ nano-particles at the rate of 1.3% and a surfactant at the rate of 0.5% with deionized water. The surfactants used for lowering the surface tension give rise to prevent the flocculation in nanofluids. In order to see the influences of the surfactants on the nanofluid properties, two types surfactants, Triton X-100 and sodium dodecyl benzene sulfonate (SDBS), were selected as nonionic and ionic surfactants and used in this study. The nanofluid was charged with in the ratio of 33.3% (equals to 44.2 ml) of the volume of the TPCT. To be able to make experimental comparisons, three different working fluids prepared under the same conditions in the same heat pipe were tested at three different heating powers (200, 300, and 400W) and three different coolant water flow rates (5, 7.5, and 10 g/s). The experiments were conducted for both TiO₂ and Triton X 100–deionized water nanofluid and TiO₂ and SDBS–deionized water nanofluid. The findings obtained from the tests were also compared to each other for showing off to what extent a surfactant affects the nanofluid properties. The maximum improvement in the thermal resistance was achieved by 43.26% in the experiment realized at 200 W input power and 7.5 g/s cooling water mass flow rate, in which the working fluid is TiO₂ and SDBS–deionized water nanofluid.     

EFFECTS OF SURFACE ROUGHNESS ON FORCED CONVECTION AND FRICTION IN TRIANGULAR DUCTS

Experimental investigations had been conducted to study the forced convective heat transfer and pressure drop characteristics of the hydrodynamic fully developed turbulent flow in horizontal equilateral triangular ducts fabricated with Ike same length and hydraulic diameter but different surface roughness of 1.2, 3.0, and 11.5 μm. The experiments were performed with hydraulic diameter-based Reynolds number ranging from 7,000 to 20,000. The entire inner wall of the duct was heated uniformly, while the outer surface was thermally insulated. It was found that the variation of Stanton number (St) with friction factor (f) can be expressed by a relationship of St = C * f, where the constant (C) increases from 0.41 to 0.50 when the surface roughness is increased from 1,2 to 11.5 μm. It was also concluded that the duct with a higher surface roughness will have better heat transfer performance. Nondimensional expressions for the determination of the heat transfer coefficient and friction factor of the equilateral triangular ducts with different surface roughness were also developed.     

Effect of reactor surface modification on the neutral gas temperature in a transformer-coupled toroidal plasma

Transformer-coupled toroidal plasma (TCTP) has found applications in versatile fields as a high-power-density plasma source. However, most research on TCTP has focused on plasma states in the TCTP, without any change in reactor structures. Therefore, in this paper, we present a study on the effects of inner-surface modification of a TCTP reactor on plasma conditions. Using two types of reactors with different inner surfaces, the silicon-wafer etch rate by fluorine atoms from dissociated NF₃ gas molecules is compared. Then a computer simulation, which derives various plasma parameters, is carried out. As a result, the TCTP reactor with a grooved inner surface shows a higher etch rate than the reactor with a normal inner surface. The computer simulation suggests the reason for this etch rate difference is that the reactor with the grooved inner surface structure has a higher neutral gas temperature than the reactor with the normal inner surface so that more pyrolytic dissociation, resulting in a higher fluorine atom density, is achieved. Our results may be useful for those fields that require a higher neutral temperature or a higher degree of pyrolysis.