Fracture toughness of multilayer pipes

Multilayer pipes composed of various materials improve partially the properties of a pipe system and are frequently used in service. To estimate the lifetime of these pipes the basic fracture parameters have to be measured. In the contribution a new approach to this estimation is presented. Special type of a C-shaped inhomogeneous fracture mechanics specimen machined directly from a pipe has been proposed, numerically analyzed and tested. The corresponding K values are calculated by finite-element method and fracture toughness values of polyethylene pipes material are obtained. __________ Translated from Problemy Prochnosti, No. 1, pp. 146–149, January–February, 2008.     

管道的断裂与落锤撕裂试验

介绍了避免油、气集输管道低应力断裂扩展的上裂原理与速度判据。管道裂纹的扩展速度主要取决于管道钢的转变温度ＦＡＴＴ。ＦＡＴＴ可由落锤撕裂试验测定。论述了落锤撕裂试验的特点、方法和标准，以及该试验在管道钢材、压力容器钢和船体结构钢薄板上的应用情况。     

Dynamic elastic-plastic behaviour of whipping pipes: experiments and theoretical model

This paper is concerned with the problem of pipe whip, the dynamic response of a high pressure piping system subjected to an end force as the result of a pipe break which releases a jet of fluid from the broken section. Both experimental and theoretical results are presented concerning the dynamic elastic-plastic behaviour of cantilever pipes subjected to a transverse force pulse at the free end. Comparisons between experimental data and theoretical predictions are made for mild-steel pipes with outer diameter-to-thickness ratios of 19.5, 28 and 32. It is demonstrated that, for these geometries, the whipping pipes display three characteristically different responses, viz. elastic, plastic hardening behaviour for thick pipes, elastic, plastic hardening-softening behaviour for moderately thick pipes and elastic, plastic hardening-softening-collapse behaviour for thinner pipes. The experimental data taken from a series of high-speed films are compared with the predictions of the instantaneous shapes of the whipping pipes derived from both a rigid, perfectly-plastic, large deflection, dynamic beam model and a more comprehensive model which incorporates the effects of elasticity and plastic hardening and softening, the details of which are presented in the paper.     

高性能复合材料管件制作工艺的比较及三维编织技术的应用

为了探索三维编织工艺用于高性能复合材料的低成本制造,首先对工程上常用的几种一维、二维复合材料管件的制作工艺进行了分析,指出了各自的优缺点,并进一步说明三维复合材料管件的性能优势。针对三维复合材料性能优越但成本昂贵的普遍认识,本工作指出三维编织工艺技术结合RTM成型工艺是实现高性能复合材料管件制造的低成本技术途径之一。最后通过实用的圆形管件型材的试制展示了整个三维编织工艺实现过程,并进而对各种类型管型制品的三维编织工艺的实现进行了展望。     

Determination of the dynamic characteristics of the strength of special steels from the results of tests on thick-walled pipes

To determine the dynamic characteristics of the strength of steels used in manufacture of thick-walled pipes used in the conditions of pulsed internal loading the authors determined experimental equipment and a method of determining the strength characteristics of the material. The results of tests on a number of structural steels are presented.Translated from Problemy Prochnosti, No. 2, pp. 46–51, February, 1993.     

Ductile failure analysis and crack behavior of X65 buried pipes using extended finite element method

This paper aims to study the ductile fracture mechanism of API X65 buried pipes including crack initiation and propagation using the extended finite element method (XFEM). First, the crack evolution histories of X65 specimens with initial crack-like flaws during tensile and three-point bending tests are illustrated, and the numerical results are compared with experimental data. In addition, effects of different crack configurations, damage initiation and evolution criteria are investigated. Second, the burst processes of straight pipes with initial gouge flaws are presented, and the FE results are compared with assessment in related standards and experiments. Finally, the crack onset and growth of buried pipes due to deflection arising from landslide movements are predicted, and the numerical results are compared with previous study. Particularly, the internal pressure, wall thickness, and soil properties on crack behavior and limit load-bearing ability are investigated. This paper provides a fundamental support for the integrity assessment and safety evaluation of buried pipes.     

Catastrophes of large diameter pipelines. The role of hydrogen fields

Fracture statistics on transmission pipelines is presented. Fractures of large-diameter pipelines are regarded as catastrophes. Fracture accidents of other pipes are less dangerous. Hydrogen makes outer layers of pipes brittle. Therefore, critical crack lengths for pipes have been calculated by a linear fracture mechanics technique. It was found that a crack of any length may be critical. The opposite opinion on reliable operation of large-diameter pipes (diameter 1420 mm) is discussed.Published inProblemy Prochnosti, Nos. 1–2, pp. 137–146, January–February, 1995.     

Nondestructive testing of composite and metallic pipes by the method of electronic shearography

A method for nondestructive testing of the quality of structures based on the application of electronic shearography is proposed. We present results of monitoring of the elements of pipes produced by welding and gluing. The presented results of investigations show that the developed technology can be applied under the conditions of manufacturing. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 4, pp. 66–70, July–August, 2007.     

不连续边界因素对周期管结构声传输特性的影响

为实现油气井测试的井下声遥测，提出纵波作为信息传输载体，应用有限单元法求解波动方程。研究钻杆等周期管结构信道的行波传输规律。由时域瞬态响应特性，探讨了通阻带交替、通带非平滑伴有谐振尖峰的梳状滤波器结构及产生机理。分析了端面、管箍截面积、杆长等边界对通阻带分布的影响，以及声换能器在钻杆信道的位置设计和泥浆介质的阻尼影响。力锤脉冲激励的实验结果表明：周期管结构信道存在多重回波、振铃衰落、通阻带交替和偏移等复杂特性，但利用扫频确定最佳载波频率或宽带通讯能够改善传输性能。     

Problems in building vertical high-temperature heat pipes

This paper examines problems arising in building vertical high-temperature heat pipes with simple and composite wicks. The author's test results with gas-free and gas-controlled sodium heat pipes are presented.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 3, pp. 389–395, March, 1980.     

充液管道开孔阻尼结构有限元分析

针对管道减振提出一种开孔阻尼结构,为分析此开孔阻尼结构的减振性能,采用模态应变能法,利用有限元软件ANSYS,并通过APDL语言编程,实现了弹性－粘弹性复合结构的近似动力学计算,为工程实际中粘弹阻尼结构的设计、分析提供一种简单可行的方法。采用此方法分析本文提出的开孔阻尼结构,得到一些有用的结论,可为类似充液管道的减振降噪提供有益借鉴。     

Zeitstandprüfung von Polypropylen bei 120 °C

Long Term Creep Tests of Polypropylene at 120 °C The mechanism of damage in the pipe wall during the internal pressure creep test of polypropylene-pipes at a test temperature of 120° is described. The resulting consequences from the investigations relating to the test method are shown and a test station with automatic recording of the time of damage is presented. Further on solutions are explained to eliminate the security risks during the tests of big pipes. A practical performance is described. On the basis of the time-temperature-correlation of the long term behavior of polypropylene the mathematical basis to interpolate minimum requirements for quality control are presented.     

Natural and accelerated weathering of PVC and polypropylene waste-water pipes

Plastic pipes and plumbing accessories for waste water are gaining popularity and replace the more conventional metal and asbestos-cement products. The main disadvantage of these pipes is their relative poor durability when exposed to external weathering conditions, particularly to the UV solar radiation. The work presented deals with the weathering behaviour of polyvinylchloride (PVC) and polypropylene (PP) pipes. Commerical pipes were exposed to natural and artificial-accelerated conditions and their mechanical properties tested after various periods of exposure. The results show that both the PVC and PP pipes are damaged by the accelerated and natural weathering within a short time, resulting in a rapid deterioration in the ultimate elongation. The drop in the extensibility of the PVC pipe is more gradual than that of the PP. The tensile strength, in both cases, is hardly affected—as expected—proving that the deterioration is mainly a surface phenomenon and depends on the cracking of the exposed surface.     

Heat transfer on the middle generatrix of a horizontal pipe in the turbulent flow of low-temperature helium

Results are presented from an experimental study of heat transfer in a turbulent helium flow under conditions of forced and mixed convection in horizontal pipes.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 3, pp. 357–362, March, 1984.     

STRESS INTENSITY FACTORS FOR CIRCUMFERENTIAL SURFACE CRACKS IN PIPES

Abstract Stress intensity factors for circumferential surface cracks in pipes have been derived using the finite element method. Both cracks located at the in- and outside of the pipes have been analysed. The derived solutions cover a wide range of geometry and load configurations and are presented in a tabular form that defines influence functions for the stress intensity factor along the whole crack front. The solutions show good agreements in comparisons to other published solutions.     

Application of volumetric method to the assessment of damage induced by action of foreign object on gas pipes

Gas pipes are submitted to three major types of damage: damages induced by impact of foreign objects, pits and craters produced by corrosion, weld defects produced during manufacturing. Damages induced by impact of foreign objects are considered as the most important problem for the gas pipes reliability and lead to dents, gouges or notches at the pipe failure. Geometrical effect of gauges or notches on brittle or elastoplastic failure of pipes submitted to internal pressure can be treated by the volumetric method. The volumetric method has been applied to a gas pipe submitted to internal pressure and exhibiting a longitudinal external and surface notch. We introduced a special procedure SINTAP, which allows one to compute the safety factor value. __________ Translated from Problemy Prochnosti, No. 4, pp. 109–117, July–August, 2006.     

Use of Acoustic Emission to Evaluate Residual Strength in FRP Pipes after Impact Damage

Acoustic Emission (AE) has proven to be a useful tool in the monitoring of fiberglass pressure vessels. The ASME Piping and Pressure Vessel Code (subsection X) implements AE as an approved method for quality control and in service testing of fiberglass pressure vessels, making it an accepted technique for the evaluation of fiber composite structures. This article presents the result of AE monitoring of fiber reinforced plastic (FRP) pipes after impact damage has incurred. The results from these tests indicate that AE can be used as a tool to predict the level of damage incurred in the pipes after impact and during pressurization. The use of the Felicity Ratio as the benchmark for evaluation is presented as the key evaluating value.     

Physical conditions of heat transfer and the design of heat pipes operating in the evaporation mode at moderate temperatures

Analyzed are the physical conditions of heat transfer in heat pipes operating in the evaporation mode at moderate temperatures. An engineering design method is proposed for heat pipes.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 4, pp. 597–605, October, 1972.     

Enhanced reference stress-based J and crack opening displacement estimation method for leak-before-break analysis and comparison with GE.EPRI method

Three-dimensional, elastic–plastic finite element analyses for circumferential through-wall cracked pipes are performed using actual tensile data of stainless steels, for two purposes. The first one is to validate the recently proposed enhanced reference stress (ERS) method to estimate the J -integral and rack-opening displacement (COD) for circumferential through-wall cracked pipes. The second one is to compare the J and COD results from the ERS method with those based on the GE/EPRI method, together with the finite element results. It is found that the GE/EPRI method generally provides poor estimations of J and COD, and such poor estimation results from the Ramberg–Osgood (R–O) fit. Moreover, the GE/EPRI results can be very sensitive to how the stress–strain data are fitted using the R–O relation. The most appropriate fitting range for the R–O fit depends on the material, and thus no specific guideline can be given. On the contrary, the J and COD estimations based on the ERS method give more accurate and robust results than the GE/EPRI estimation. The present results, together with the experimental validation presented in the previous paper, provide sufficient confidence in using the proposed method in the leak-before-break analysis.     

A method for the prediction of the service life of high-strength drill pipes based on the criteria of corrosion fatigue

We present the results of the investigation of the growth of corrosion fatigue cracks in TBVK 140×11L drill pipes, determine quantitative characteristics of fatigue cracks in the pipes under stresses of different types as functions of the elapsed part of the entire service life, perform their statistical analysis, and propose a method for the prediction of the residual service life of these pipes. Ivano-Frankivs'k State Technical University of Petroleum and Gas, Ivano-Frankivs'k; Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 1, pp. 103–106, January–February, 1997