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Chen Y.,China University of Petroleum - Beijing | Zhang J.,PowerChina Beijing Engineering Corporation Ltd | Zhang H.,China University of Petroleum - Beijing | Li X.,Dalian University of Technology | Zhou J.,Dalian University of Technology
International Journal of Structural Stability and Dynamics | Year: 2016

Flapwise flexural vibration of rotating beams has been extensively studied since the 1970s. Existing methods for solving the aforementioned vibration problem range from the conventional finite element method to variable-order finite element method, Frobenius method, differential transformation method and dynamic stiffness method (DSM). Although various approximation methods are available, most of these methods are based on perturbation or discretization of the governing equation, often leading to tedious calculations. This paper re-examines flapwise flexural vibration of rotating beams using the method of variational iteration, which is relatively new and capable of providing accurate solutions for eigenvalue problems. The extracted natural frequencies and mode shapes for sample rotating beams with various rotational speeds and hub radii are compared with existing results that were published in the open literature. © 2016 World Scientific Publishing Company. Source


Wan Y.,CAS Wuhan Institute of Rock and Soil Mechanics | Xue Q.,CAS Wuhan Institute of Rock and Soil Mechanics | Wu Y.,PowerChina Beijing Engineering Corporation Ltd | Zhao L.-Y.,CAS Wuhan Institute of Rock and Soil Mechanics
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

To investigate the problems such as the failure of compacted clay liners as the anti-seepage structure in the landfills cover system under the action of drying-wetting cycles, experiments under the simulated climatic environment of landfills have been conducted to determine the mechanical properties of compacted clay and its microstructure characteristics during the drying-wetting cycles and hence to reveals the intrinsic nature of the damage of compacted clay from the micro level. The experimental results show that as the number of drying-wetting cycle increases, all the secant moduli of low-, medium- and high-compacted clays increase at initial stage, while they decrease significantly at later stage, and the magnitude of secant modulus variation increases with the increase of initial compactness. Meanwhile, the shear strengths of above-mentioned three compacted clays decrease, and the magnitude of variation decreases with the increase of initial compactness or confining pressure. After three drying-wetting cycles, the total pore volume of compacted clay shows irreversible shrinkage, resulting in the increase of initial tangent modulus and shear strength. The shrinkage ratio decreases with the increase of compactness, and the shrinkage ratios of low- and high-compacted clays are 20.5% and 11.5%, respectively. The large pore volumes of low- and high-compacted clays increase 25.7% and 53.9% and the microcrack volumes increase 3.1% and 41.7%, respectively, resulting in a decrease in the shear strength and tangent modulus at later stage. The effect of drying-wetting cycles on the mechanical property of compacted clay with different compactness is controlled by two factors, i.e. the decrease of total pore volume and the increase of big-pore and microcracks. ©, 2015, Science Press. All right reserved. Source


Chen Y.,China University of Petroleum - Beijing | Zhang H.,China University of Petroleum - Beijing | Zhang J.,PowerChina Beijing Engineering Corporation Ltd | Liu X.,China University of Petroleum - Beijing | And 2 more authors.
Engineering Failure Analysis | Year: 2015

Corrosion defects may compromise the safety of oil and gas pipelines. This paper investigates the failure behavior and failure pressure of X80 pipelines with longitudinally and circumferentially aligned interacting corrosion defects based on nonlinear finite element method, X80 pipeline with single corrosion defect is studied as well. On the basis of proposed failure pressure regression equations for X80 pipeline with single corrosion defect, this paper develops an assessment procedure for predicting failure pressure of pipeline with interacting corrosion defects. Through comparing predicted failure pressures using proposed solutions and assessment methods as well as experimental results available in previous literature, the accuracy of proposed solutions is demonstrated consequently. © 2014 Elsevier Ltd. Source


Zhang L.,Hohai University | Zhang L.,PowerChina Beijing Engineering Corporation Ltd | Zhou D.,Hohai University | Chen H.,Hohai University
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2015

Three-dimensional unsteady numerical simulations, combined with the normal single-phase model and the VOF model, were executed on the geometrical model of the whole flow system of a pumped storage power station. Through numerical calculation, the changeable flow configuration and variation law of some parameters, such as unit rotating speed, flux, runner moment and pressure of measurement points were obtained and compared with the experimental data. Results show that the extreme value of unit rotating speed and measurement points pressure agree fairly well with the experimental data. In the shutdown transient process, pressure variation at spiral casing inlet and draft tube inlet is influenced by the closure law of guide vanes, while that between runner and guide vanes is mainly affected by runner rotation. As guide vanes close and flux decreases, water flows upstream through the inner side of the draft tube and rotates with the runner. After guide vanes close completely, vortex inside the draft tube is the key factor of its hydraulic energy loss. ©, 2015, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved. Source


Chen Y.,China University of Petroleum - Beijing | Zhang H.,China University of Petroleum - Beijing | Zhang J.,PowerChina Beijing Engineering Corporation Ltd | Li X.,Dalian University of Technology | Zhou J.,Dalian University of Technology
Materials and Design | Year: 2015

Corrosion will compromise safety operation of oil and gas pipelines, accurate determination of failure pressure finds importance in residual strength assessment and corrosion allowance design of onshore and offshore pipelines. This paper investigates failure pressure of high strength pipeline with single and multiple corrosions using nonlinear finite element analysis. On the basis of developed regression equations for failure pressure prediction of high strength pipeline with single corrosion, the paper proposes an assessment procedure for predicting failure pressure of high strength pipeline with multiple corrosions. Furthermore, failure pressures predicted by proposed solutions are compared with experimental results and various assessment methods available in literature, where accuracy and versatility are demonstrated. © 2014 Elsevier Ltd. Source

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