97,648 research outputs found

    Modeling and analysis of water-hammer in coaxial pipes

    Full text link
    The fluid-structure interaction is studied for a system composed of two coaxial pipes in an annular geometry, for both homogeneous isotropic metal pipes and fiber-reinforced (anisotropic) pipes. Multiple waves, traveling at different speeds and amplitudes, result when a projectile impacts on the water filling the annular space between the pipes. In the case of carbon fiber-reinforced plastic thin pipes we compute the wavespeeds, the fluid pressure and mechanical strains as functions of the fiber winding angle. This generalizes the single-pipe analysis of J. H. You, and K. Inaba, Fluid-structure interaction in water-filled pipes of anisotropic composite materials, J. Fl. Str. 36 (2013). Comparison with a set of experimental measurements seems to validate our models and predictions

    Plastic collapse of pipe bends under combined internal pressure and in-plane bending

    Get PDF
    Plastic collapse of pipe bends with attached straight pipes under combined internal pressure and in-plane closing moment is investigated by elasticā€“plastic finite element analysis. Three load histories are investigated, proportional loading, sequential pressureā€“moment loading and sequential momentā€“pressure loading. Three categories of ductile failure load are defined: limit load, plastic load (with associated criteria of collapse) and instability loads. The results show that theoretical limit analysis is not conservative for all the load combinations considered. The calculated plastic load is dependent on the plastic collapse criteria used. The plastic instability load gives an objective measure of failure and accounts for the effects of large deformations. The proportional and pressureā€“moment load cases exhibit significant geometric strengthening, whereas the momentā€“pressure load case exhibits significant geometric weakening

    Laboratory and Field Performance of Buried Steel-Reinforced High Density Polyethylene (SRHDPE) Pipes in a Ditch Condition under a Shallow Cover

    Get PDF
    Metal and plastic pipes have been used extensively as storm sewers and buried drainage structures in transportation projects. Metal pipes have high strength and stiffness but are susceptible to corrosion from wastewaters containing acid, and from aggressive soils. Plastic pipes are resistant to corrosion, erosion, and biological attack but have certain disadvantages including lower long-term strength and stiffness (dimensional reliability), buckling, and tearing of pipe wall. To address the disadvantages of metal and plastic pipes, a new product, steel-reinforced high-density polyethylene (SRHDPE) pipe, has been developed and introduced to the market, which has high-strength steel reinforcing ribs wound helically and covered by corrosion-resistant high density polyethylene (HDPE) resin inside and outside. The steel reinforcement adds ring stiffness to the pipe to maintain the cross-section shape during installation and to support overburden stresses and traffic loading. The HDPE resin protects the steel against corrosion and provides a smooth inner wall. The combination of steel and plastic materials results in a strong and durable material with a smooth inner wall. Different methods are available for the design of metal and plastic pipes. The American Water Works Association (AWWA) Manual M11 (2004) provided the design procedure for metal pipes and the 2007 ASSHTO LRFD Bridge Design Specifications had separate design procedures for metal and plastic pipes. However, it is not clear whether any of these procedures for metal and plastic pipes can be used to design an SRHDPE pipe. Moreover, no approved installation or design specification is available SPECIFICALLY for the SRHDPE pipes. Some research has been conducted on SRHDPE pipes to understand the performance of SRHDPE pipes in the laboratory including the laboratory tests conducted by Khatri (2012). To investigate the performance of the pipe with various backfills, in addition to the laboratory tests conducted by Khatri (2012) with the sand backfill, a laboratory test with the crushed stone backfill was conducted in a ditch condition under 2 feet of shallow cover. This was performed in a large geotechnical testing box 10 feet long x 6.6 feet wide x 6.6 feet high. Based on the laboratory testing and analysis on the SRHDPE pipes, it can be concluded that (1) the pipe wall-soil interface should be designed as a fully bonded interface to be conservative, (2) the Giroud and Han (2004) method and the simplified distribution method in the 2007 AASHTO LRFD Bridge Design Specifications reasonably predicted the pressures on the top of the SRHDPE pipes induced by static and cyclic loadings, (3) the modified Iowa formula (1958) under predicted the deflections of the SRHDPE pipes during the installation and over-predicted the deflections during static and cyclic loadings, (4) the formula provided by Masada (2000) can be comfortably used to determine the ratio of the vertical to horizontal deflection of the SRHDPE pipe, (5) the pipe wall area was enough to resist the wall thrust during installation and loadings, and (6) the highest measured strains recorded in steel and plastic during the installation and loadings in all the tests were within the permissible values. The laboratory tests however have some limitations. For example, the installation procedure of the pipe in the test box may be different from the field installation due to the limited space and construction equipment in the laboratory. The laboratory box tests may have a boundary effect. Therefore, a field test was conducted to verify the lab test results The results obtained in the field test were found in agreement with the results obtained for the laboratory test during the installation and the traffic loading

    The research system for vibration analysis in domestic installation pipes

    Get PDF
    A measurement and data processing system was developed for investigation of processes that influence sound propagation in pipes, which are commonly used in residence building industry. An impact-type excitation was mainly used for a controlled wide-band frequency mechanical vibrations excitation. Pipe surface vibrations were measured by means of accelerometers and microphones. Scanning device was used for positioning transducers over a tested pipe. The wave propagation and vibration analysis in pipeline segments of several types of pipes (plastic and metallic) was carried out. Because of various pipes working conditions, empty and filled pipes were tested as well. The experimental data indicates that both in metal and plastic pipes vibrations up to several kilohertz may propagate with low attenuation facto

    A project and competition to design and build a simple heat exchanger

    Get PDF
    To address a declining interest in process engineering, a project to design and build a compact heat exchanger was initiated in the second year of a four-year, multidisciplinary degree programme in biotechnology. The heat exchangers had a double-pipe configuration and employed plastic outer pipes and copper inner pipes of various diameters. Designs produced ranged from coiled inner pipes to various multi-pass arrangements and were assessed on the basis of heat transfer achieved per unit mean temperature difference per unit cost. The project, which also formed the basis of a competition, was very well received by students and gave them hands-on experience of engineering design and construction, as well as team work, problem solving, engineering drawing and the use of simple tools. Based on the success of this project, a similar problem based learning approach will be initiated in the third year of the same degree programme and will focus on bioethanol production

    Effect Of The Internal Fluid Flow In The Glass Fibre Reinforced Plastic (GFRP) Pipe Dynamic

    Get PDF
    The petroleum produced by the offshore platforms is transported to processing plant through carbon steel pipelines. Usually, expectancy of maximum production capacity of pipelines is never meeting the prediction made in the early stage. Among the main reason for the declining of production capacity of pipelines over time is corrosion. This project aims to prove the dynamic of glass fibre reinforced plastic ( GFRP) pipe dynamic is better than steel pipes dynamic in oil pipelines. Whilst it is more common to see in Oil and Gas industry to utilize steel pipes in their pipelines, GFRP pipes show a promising future to reduce corrosion problems. When it comes to pipeline, corrosion had caused severe to production capacity of a line to replace the corroded pipelines will cost a lot of money. The industries are desperate to alternative for the steel pipes. With that in mind, this Final Year Project will be focused more on study of the dynamic behavior of glass fibre reinforced plastic (GFRP) pipe fluid flow properties. A pipe modeling will be created to study the effect of the internal fluid flow in the GFRP pipe and compare it with the steel pipes dynamic. This project may lead to explore a better option than steel pipes to use in the oil and gas industry

    Network modelling of the influence of swelling on the transport behaviour of bentonite

    Get PDF
    Wetting of bentonite is a complex hydro-mechanical process that involves swelling and, if confined, significant structural changes in its void structure. A coupled structural transport network model is proposed to investigate the effect of wetting of bentonite on retention conductivity and swelling pressure response. The transport network of spheres and pipes, representing voids and throats, respectively, relies on Laplaceā€“Youngā€™s equation to model the wetting process. The structural network uses a simple elasto-plastic approach without hardening to model the rearrangement of the fabric. Swelling is introduced in the form of an eigenstrain in the structural elements, which are adjacent to water filled spheres. For a constrained cell, swelling is shown to produce plastic strains, which result in a reduction of pipe and sphere spaces and, therefore, influence the conductivity and retention behaviour

    Characterisation and analysis of polyethylene pipes and polymers in water pressure pipe applications

    Get PDF
    Lifetime prediction of plastic pipelines is a critical aspect of any long term asset management programme. From the existing literature, material degradation, mechanical damage, fatigue, inherent flaws, operational pressure changes or welding defects are the most common reasons for failure in plastic water mains pressure pipes. Thanks to project sponsors, the UK Water Industry Research (UKWIR) and the Engineering and Physical Science Research Council (EPSRC), this thesis will deliver some early stage research work needed to support any later development of a non-destructive or accelerated method to assist in predicting the lifetime expectancy and condition of polyethylene pipes used in the water pressure-pipe sector. [Continues.

    Influence of notch orientation on ductile tearing in SENT specimens

    Get PDF
    There is a growing interest for the use of spiral welded pipes in strain based design related applications. Since the influence of the spiral weld on the plastic behaviour of the pipe is not yet fully understood, further research on this topic is required. An important aspect of this plastic behaviour is the effect of mixed mode loading on weld defects located in the helical weld. This paper elaborates on the first experimental trials to evaluate ductile tearing by means of single edge notched tensile specimen (SENT) testing with slanted notches. Tests were performed on two SENT specimens, one with a slanted notch and another with a straight notch in order to investigate the influence of mixed mode loading. The crack mouth opening displacement and crack extension were determined experimentally by means of digital image correlation and potential drop measurements respectively. The crack extension and the potential drop measurements were related by means of finite element simulations
    • ā€¦