Elastic-plastic fracture mechanics assessment of test data for circumferential cracked pipes

This paper presents experimental validation of two reference stress based methods for circumferential cracked pipes. One is the R6 method where the reference stress is defined by the plastic limit load. The other is the enhanced reference stress method, recently proposed by the authors, where the reference stress is defined by the optimised reference load. Using 38 published pipe test data, the predicted maximum instability loads according to both methods are compared with the experimental ones for pipes with circumferential through-thickness cracks and with part circumferential surface cracks. It is found that the R6 method gives conservative estimates of the maximum loads for all cases. Ratios of the experimental maximum load to the predicted load range from 0.54 to 0.98. On the other hand, the proposed method gives overall closer maximum loads than R6, compared to the experimental data. However, for part through-thickness surface cracks, the estimated loads were slightly non-conservative for four cases, and possible reasons are fully discussed.     

BFe30-1-1白铜管早期腐蚀失效原因分析

某电厂凝汽器BFe30-1-1白铜管投运后几年内出现较为严重的局部腐蚀和点腐蚀，为此，对材质、水质等诸多因素进行了分析研究，通过宏观、微观检查和电化学试验，认为是微生物及生物粘泥的附着引起了铜管的早期腐蚀失效。     

Efficient Approximation of Unsteady Friction Weighting Functions

A simple method is presented for evaluating wall shear stresses from known flow histories in unsteady pipe flows. The method builds on previous work by Trikha, but has two important differences. One of these enables the method to be used with much larger integration time steps than are acceptable with Trikha’s method. The other, a general procedure for determining approximations to weighting functions, enables it to be used at indefinitely small times (high frequencies). The method is applicable to both laminar and turbulent flows.     

基于MEMS技术的新型微冷却方式

针对高功率电子器件散热问题,介绍了国际前沿领域电子设备热控制的技术动态．讨论了基于MEMS技术的微冷却器有体积小,散热面积大,消耗功率低,批量制作经济性好等优点。分析了微通道、微喷流和微热管3种基于MEMS技术的新型微冷却方式的传热原理、目前的技术状况及应用前景微通道的采用增加了对流换热面积,提高了对流换热系数;微喷流冷却器中由于高速冷却液的形成,显著提高了换热系数;微热管均热效果极佳。     

高密度电法在顶管施工选址勘探中的应用

对施工区钻孔勘探发现该区域地层复杂,存在大量卵石及其它坚硬岩石,这对顶管掘进会造成很大影响,需要为顶管施工选择合适、有效的施工场址,降低卡钻概率。采用高密度电法技术勘探设备对施工区地层进行详细的勘测,首先对施工区域附近断崖层进行测量,对比剖面反演图分析,证明了高密度电法技术在对地层分布、岩层产状勘探解释上的可靠性,最后采用温纳装置和斯伦贝格装置分别对拟施工区域进行勘测并取得了较好的效果,初步为顶管施工拟定了一条卵石分布较少、卡钻概率较低的地下埋深走向,也减少了钻孔勘探量。     

Current deflection NDE for the inspection and monitoring of pipes

Routine inspection of oil and gas pipes for time dependent degradation is essential. Pipelines are most commonly inspected using In-Line Inspection (ILI), however restrictions from pipe geometry, features or flow rate can prevent its use. Facility pipework rarely facilitates ILI, and external inspection often warrants the undesirable removal of the pipe insulation and cladding. This work investigates the applicability of a current deflection non-destructive evaluation technique for both the detection and growth monitoring of defects, particularly focusing on corrosion. Magnetic sensors are used to monitor variations in the spatial distribution of the induced magnetic flux density outside a pipe that arise from deflection of an injected electric current around inner or outer wall defects. An array of orthogonal magnetoresistive sensors has been used to measure the magnetic flux density surrounding six-inch schedule 40 seamless and welded carbon steel and austenitic steel pipes. The measurements were stable and repeatable to the order of 100 pT which suggests that the defect detection or growth monitoring of corrosion-type defects may be possible with a few amps of injected current when measurements are taken at around 50 mm lift-off. The sensitivity of the technique is dependent on factors including defect geometry, sensor lift-off, bends, variations in nominal pipe geometry or material properties, and the presence of ferromagnetic objects, each of which were investigated using either experiment or a validated finite element model.     

浅淡50kt/a三聚磷酸钠装置设计

从工艺流程、设备布置、材料和标准的选择、管架的选用等方面对三聚磷酸钠装置设计的特点进行了总结。对本装置设计的不足之处也进行了探讨。     

Utility detection and positioning on the urban site Sense-City using Ground-Penetrating Radar systems

This paper presents the design of a novel Ground-Penetrating Radar (GPR) test site that has been integrated into the mini-city demonstrator Sense-City located at University Paris-Est (France). This test site provides several sources of measurement interest expressed by the presence of a multilayered soil with significant dielectric contrasts, and various dielectric pipes and blades buried at various depths in trenches filled with a backfill soil different from the natural soil. This paper presents experimental Bscans associated with the pipe zone acquired by three different GPR systems at frequencies ranging from 300 MHz to 1.5 GHz. The interpretation and comparison of the raw Bscans have allowed to characterize the dielectric properties of the soil layers, and to detect the hyperbola signatures of the buried pipes. The results of this study will help to guide future developments on polarization, operating frequency and signal processing to extract parameters (orientation, dielectric characteristics, position and size) associated with pipes.     

Measurement method and pipe wall misalignment adjustment algorithm of the pipe butting machine

This paper presents a runout measurement method and a novel finite grouping method to predict and optimize the rotational angle and translational displacement of butting pipes to minimize pipe wall misalignment (PWM). This study develops a method to minimize the PWM of the pipes excluding the positions of welding seams. In this method, the measurement data are divided into finite groups and the criteria are created to identify the positions of welding seams and eliminate the effect of the welding seams. Finally, the rotational angle and translational displacement of the butting pipes are optimized to minimize the PWM. A butting machine is designed to implement this method. The machine is benchmarked by a standard smooth pipe to minimize system errors. Three butting experiments have been performed with welded pipes of diameter 406 mm. The comparison shows that the computation results agree with the experimental results very well. The maximum PWMs in three experiments are less than 1.87 mm, which satisfies the butting requirements, that is, a PWM of less than 2.0 mm. Then, the uncertainties of the measurement results are discussed.     

The inhibitory effect of carbon monoxide contained in hydrogen gas environment on hydrogen-accelerated fatigue crack growth and its loading frequency dependency

The effect of carbon monoxide (CO) contained in H₂ gas as an impurity on the hydrogen-accelerated fatigue crack growth of A333 pipe steel was studied in association with loading frequency dependency. The addition of CO to H₂ gas inhibited the accelerated fatigue crack growth due to the hydrogen. The inhibitory effect was affected by the CO content in the H₂ gas, loading frequency, and crack growth rate. Based on these results, it was revealed that the inhibitory effect of CO was governed by both competition between the rate of fresh surface creation by the crack growth and the rate of coverage of the surface by CO and time for hydrogen diffusion in the material to the crack tip with reduced hydrogen entry by CO.