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Littérature scientifique sur le sujet « Non-uniform tension field »
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Articles de revues sur le sujet "Non-uniform tension field"
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Khine, Yu Yu, et John S. Walker. « Thermocapillary convection in a cylinder with a strong non-uniform axisymmetric magnetic field ». Journal of Fluid Mechanics 276 (10 octobre 1994) : 369–88. http://dx.doi.org/10.1017/s0022112094002600.
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This paper treats a surface-tension-driven liquid-metal flow in a cylinder with a steady externally applied non-uniform axisymmetric magnetic field. The top boundary consists of an annular free surface around a solid disk, modelling the Czochralski growth of silicon crystals. A radial temperature gradient produces a decrease of the surface tension from the disk edge to the vertical cylinder wall. The magnetic flux density is sufficiently large that inertial effects and convective heat transfer are negligible. First we present large-Hartmann-number asymptotic solutions for magnetic fields with either a non-zero or a zero axial component at the free surface. The asymptotic solutions indicate that a purely radial magnetic field at the free surface represents a singular limit of more general magnetic fields. Secondly we present numerical solutions for arbitrary values of the Hartmann number, and we treat the evolution of the thermocapillary convection as the axial magnetic field at the free surface is changed continuously from the full field strength to zero.
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Mironov, Boris, et Yuriy Mironov. « Torsion of anisotropic and non-uniform cylindrical rods with elliptical section ». MATEC Web of Conferences 251 (2018) : 04037. http://dx.doi.org/10.1051/matecconf/201825104037.
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In work the limit state of cylindrical and prismatic rods from anisotropic ideal rigid-plastic material is investigated under torsion for arbitrary condition of plasticity, and the torsion of anisotropic and non-uniform rods with elliptic section under the condition of Mises-Hill plasticity is considered. The integrals determining the stressed state of an anisotropic rod under arbitrary condition of plasticity are obtained, the field of characteristics of the basic ratios for anisotropic and composite rods under the condition of Mises-Hill plasticity is constructed, the ratios along characteristics are obtained, the envelopes of the family of characteristics and lines of tension rupture are found.
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Shao, Mingyue, Miao Zhang, Jimei Wu, Xuxia Guo, Qiumin Wu et Jiajuan Qing. « Vibration and stability analysis of tensioned moving printed electronic laminated membrane under multiple working conditions ». AIP Advances 12, no 10 (1 octobre 2022) : 105017. http://dx.doi.org/10.1063/5.0110799.
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In this paper, the thermoelastic coupled vibration of roll-to-roll printed electronic laminated membrane under multiple working conditions, such as in a thermal environment, air resistance, and non-uniform tension are investigated. First, a mathematical model of a moving electronic laminated membrane was established, which takes into account the non-uniform tension at each end of the membrane and the non-uniform temperature field. The vibration differential equation of the moving electronic laminated membrane is derived considering the air resistance based on Hamilton’s principle; the differential quadrature method is used to calculate and analyze the effect of the moving electronic laminated membrane aspect ratio, thermoelastic coupling coefficient, air resistance, and other parameters on its vibration and stability. The results show that different parameters of the moving electronic laminated membrane have different effects on its stability, and some parameters are not positively correlated with stability. This study can serve as a theoretical guide for improving the transmission stability and high-precision fabrication of roll-to-roll, flexible electronic laminated membranes.
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Керестень, И. А., И. А. Попов et М. В. Ховайко. « Numerical simulation of underwater cable laying with account of non-uniform hydrostatic force at Arctic basin condition ». MORSKIE INTELLEKTUAL`NYE TEHNOLOGII), no 3(53) (27 août 2021) : 267–73. http://dx.doi.org/10.37220/mit.2021.53.3.032.
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Статья посвящена моделированию динамического равновесия установившегося движения протяженной кабельной линии с учетом действия гидродинамических сил сопротивления и неоднородной гидростатической силы. Учитывая различные условия и глубины укладки, а также требования функционального назначения и защиты от враждебных факторов морского дна, необходимо рассмотреть широкий диапазон кабелей с различными механическими характеристиками: трехжильный кабель с одиночным бронированием 2XS2YRAA, одножильный кабель с одиночным бронированием ZS-YJQ41 и одножильный кабель с двойным бронированием – аналог GASLMLTV. Целью работы является развитие цифровой технологии по моделированию укладки подводных коммуникационных и силовых кабелей, позволяющей учитывать многочисленные физико-механические явления, имеющие место при проведении реальных морских работ. Для достижения поставленной цели работы используется программная среда Matlab Math Works с использованием разработанного комплекса программ для инженерной оценки формы и натяжения провисающего участка кабеля. Научная новизна состоит в апробации модели подводной укладки кабеля, учитывающей действие неоднородной гидростатической силы. Результаты моделирования представлены в виде формы и натяжения провисающей части кабеля при различных углах схода кабеля с движущегося судна при различных механических параметрах кабелей. Практическое значение работы состоит в повышении эффективности освоения перспективных месторождений, путем определения характеристик укладки кабеля в условиях Арктического бассейна: газовое месторождение Лудловское, газоконденсатное месторождение Ленинградское, нефтяное месторождение Медынское-море. This article studies the numerical simulation of underwater steady motion of the cable line with account of hydrodynamic water resistance forces and non-uniform hydrostatic force. It is necessary to consider distinctive types of cables due to various depths, laying conditions, functional requirements and protection requirements against adverse factors of seabed. Three-core single armoured cable 2XS2YRAA, one-core single armoured cable ZS-YJQ41 and one-core double armoured cable – analogue GASLMLTV are considered in this article. The aim of the research consists in digital technology development for underwater cable laying modeling, which allows taking into account numerous physical and mechanical features. These features occur during real marine operations for communication and power cables. Programming and numeric computing platform Matlab Math Works with developed software package is chosen as the research method. Simulation results are presented in dimensionless form for cable shape and tension for engineering purposes. The novelty of the work consists in approbation of underwater cable laying analytical model considering non-uniform hydrostatic force. Simulation results are presented for underwater cable laying during reeling from spool mounted on the vessel, moving with constant speed for distinctive types of cables. The influence of the cable run-off angle on the investigated characteristics was also considered. The practical value of the research consists in increasing of efficiency of exploration of oil, gas and condensate fields by determining underwater cable laying characteristics for perspective fields. At the end of the paper, the results of estimation of the shape and tension of the cable being laid undersea were presented for several fields at Arctic basin condition: gas field Ludlovskoe, condensate field Leningradskoe and oil field Medinskoe sea.
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Liu, Jie, et Sheng Liu. « Dynamics Behaviors of Droplet on Hydrophobic Surfaces Driven by Electric Field ». Micromachines 10, no 11 (14 novembre 2019) : 778. http://dx.doi.org/10.3390/mi10110778.
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Droplet microfluidic technology achieves precise manipulation of droplet behaviors by designing and controlling the flow and interaction of various incompatible fluids. The electric field provides a non-contact, pollution-free, designable and promising method for droplet microfluidics. Since the droplet behaviors in many industrial and biological applications occur on the contact surface and the properties of droplets and the surrounding environment are not consistent, it is essential to understand fundamentally the sessile droplet motion and deformation under various conditions. This paper reports a technique using the pin-plate electrode to generate non-uniform dielectrophoresis (DEP) force to control sessile droplets on hydrophobic surfaces. The electrohydrodynamics phenomena of the droplet motion and deformation are simulated using the phase-field method. It is found that the droplet moves along the substrate surface to the direction of higher electric field strength, and is accompanied with a certain offset displacement. In addition, the effect of pin electric potentials, surface contact angles and droplet volumes on the droplet motion and deformation are also studied and compared. The results show that higher potentials, more hydrophobic surfaces and larger droplet volumes exhibit greater droplet horizontal displacement and offset displacement. But for the droplet vertical displacement, it is found that during the first revert process, the release of the surface tension can make the droplet with low potentials, small contact angles or small droplet volumes span from negative to positive. These results will be helpful for future operations encountered in sessile droplets under non-uniform electric fields towards the droplet microfluidics applications.
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Umeno, Yoshitaka, et Takayuki Kitamura. « Criterion of Mechanical Instability in Inhomogeneous Atomic System ». Materials Science Forum 482 (avril 2005) : 127–30. http://dx.doi.org/10.4028/www.scientific.net/msf.482.127.
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The mechanical stability of a material is a fundamental issue in strength of atomic systems. Although the criterion of the mechanical stability of homogeneous structures such as perfect crystals have been successfully investigated so far, the criterion has not been able to be precisely evaluated in the cases of non-uniform deformations or bodies of inhomogeneous atomic structures. Now we present an instability criterion of an arbitrary atomic structure based on the energy balance of the whole system. This method gives the mathematically rigorous condition for the onset of an unstable deformation in any inhomogeneous atomic system. Furthermore, the method can be applied to any type of potential field, which means that ab initio evaluations of the mechanical instability of inhomogeneous structure under non-uniform deformation will be possible. The validity of the method is clarified by the application to tension of a cracked body. The onsets of unstable deformations and their deformation modes are precisely evaluated by the method.
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Gao, Yang. « Singular Problems of Spherically Uniform Anisotropic Piezoelectric Solids ». Advanced Materials Research 415-417 (décembre 2011) : 19–24. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.19.
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A material is radially anisotropic piezoelectric when its generalized Hooke’s law at each material point referred to a spherical coordinate system is the same everywhere. In a recent paper by Ting, the remarkable nature at the center of a sphere has been shown when a spherically uniform linear anisotropic elastic material is subjected to a uniform traction at the surface of the sphere. This paper extends elastic material for piezoelectric material, and shows that the singular problems also prevail in piezoelectric material. When a sphere of piezoelectric material is subjected to a uniform traction and electric potential at the surface of the sphere, for a certain range of material parameter, the stress, the electric field and the electric potential at the center of the sphere are infinite. When the sphere is subjected to a uniform tension, a cavitation occurs at the center of the sphere. If the applied traction is a uniform pressure, a black hole occurs at the center of the sphere. The singular problems depend only on one non-dimensional material parameter and the direction of the applied traction, while is independent of the magnitude of the traction.
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Syngellakis, Stavros. « Stress amplification in three-dimensional narrow zones created by cavities ». Theoretical and Applied Mechanics 39, no 1 (2012) : 71–97. http://dx.doi.org/10.2298/tam1201071s.
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The paper is concerned with a particular case of stress amplification arising from the proximity of a spherical cavity to the boundary of a loaded elastic solid. The performed approximate analysis yields distributions of stresses and displacements in the narrow region formed between a spherical cavity and the faces of a thin flat layer subjected to a far field uniform radial tension. The narrow region is modelled as a circular plate of non-uniform thickness undergoing coupled membrane and flexural deformation. Series solutions are obtained for both membrane forces and bending moments leading to estimates for the stress concentration factor at minimum thickness. These predictions are found consistent with those obtained from both the exact analytical solution and finite element modelling of the problem. Cross-validated results from the two latter methods also provide trends for the stress amplification due to the narrowness of the region.
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Sun, Peng, Jin Huang, Jiaying Zhang et Fanbo Meng. « Wrinkling Patterns and Stress Analysis of Tensile Membrane with Rigid Elements ». Applied Sciences 12, no 13 (30 juin 2022) : 6630. http://dx.doi.org/10.3390/app12136630.
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Heterogeneous membrane structures with rigid elements are often used in flexible electronic and aerospace structures. In heterogeneous membrane structures under tension, the disturbance stress caused by the rigid element changes the stress distribution of the membrane, and it is difficult to calculate the stress distribution of the heterogeneous membrane structure using the traditional stress functions method. In this article, we propose a method for calculating the non-uniform stress field based on the Eshelby elastic inclusion theory, which states that tension membrane structures contain square rigid elements. The wrinkle distribution of the rigid element at different positions is predicted by a stress analysis, and the influence of the position and size of the rigid element on the wrinkle distribution of the membrane is studied by a finite-element simulation. The research results show that the wrinkle pattern of the stretched membrane can be controlled by changing the position of the rigid element to meet some special needs.
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Siva, Dr M. M. « Elevated Percentage Mechanical Properties of in-situ Synthesized TiB2/Al Matrix Composites ». International Journal for Research in Applied Science and Engineering Technology 10, no 6 (30 juin 2022) : 2172–76. http://dx.doi.org/10.22214/ijraset.2022.44199.
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Abstract: Make use of TiB2 salts with Al-2011 fabricated by stir cast method. In the composites of Particulate reinforced varies in non-uniform microstructure and the composition in a 5 and 10 percentage of TiB2 in functional performance of a component with continuously changing properties. In mechanical, aeronautical and marine field Al 2011 is used due to its good mechanical and corrosion resistance. TiB2 is combined with Al 2011 also increases the mechanical corrosion resistance properties. MMc of Al-2011 by stir cast method titanium and boride salt were used. InTiB2 5% and 10% the tension tests and hardness tests were performed on the as cast or after heat treated samples to find the microstructure and the effect of reinforcement on the mechanical properties.
Actes de conférences sur le sujet "Non-uniform tension field"
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Narendra Sekhar, Gummadi, Jayalatha Gopal et Prakash Revanna. « Thermorheological and Magnetorheological Effects on Rayleigh-Bénard-Marangoni Convection in Ferromagnetic Liquids With Non-Uniform Basic Temperature Gradient ». Dans ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64522.
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A linear stability analysis of buoyancy and surface tension driven convection in temperature and magnetic field sensitive Newtonian ferromagnetic liquid is studied. The importance of this problem lies in the interesting possibility of regulating convection using a heat source (sink). The problem discussed in this paper leads to a situation that the basic temperature gradient here is non-uniform. The governing equations thereby are of variable coefficients. The principle of exchange of stabilities is shown to be valid. The critical values are obtained using higher order Galerkin technique. The influence of various magnetic and nonmagnetic parameters on the onset of convection has been analyzed. It is found that there is tight coupling between Rayleigh and Marangoni numbers, with an increase in one resulting in a decrease in the other. Variable viscosity parameter and heat source destabilize the system. The effect of heat sink is to stabilize the system. Buoyancy magnetization parameter destabilizes the system both in presence/absence of heat source/sink.
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Song, Suping, et Ben Q. Li. « Surface Deformation and Thermal Convection in Electrostatically-Positioned Droplets Under Microgravity ». Dans ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1120.
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Abstract Electrostatically positioned droplets are very useful for the fundamental study of solidification phenomena and the measurement of thermal physical properties. This paper descries a numerical analysis of surface deformation and surface tension driven flows in electrostatically positioned droplets in microgravity. The analysis is based on a fully coupled boundary element and finite element solution of the Maxwell equations, the Navier-Stokes equations and the energy balance equation. Results show that an applied electrostatic field results in a nonuniform electric stress distribution along the droplet surface, which, combined with surface tension, causes the droplet to deform into an ellipsoidal shape in microgravity. Laser heating induces a non-uniform temperature distribution in the droplet, which in turn produces Marangoni convection in the droplet. It is found that the viscous stress contribution to the deformation is small for a majority of cases. Also, a higher temperature gradient produces a stronger Marangoni convection in droplets with higher melting points that require more laser power. The internal recirculating flow may be reduced by more uniform laser heating. During the undercooling of the droplet, both temperature and fluid flow fields evolve in time such that the temperature gradient and the tangential velocities along the droplet surface subside in magnitude and reverse their directions.
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Farrow, Gary H., Simon Dimopoulos et Andrew A. Kilner. « Investigations Into Fatigue of OPB Loaded Offshore Mooring Chains ». Dans ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18609.
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Abstract The Chain FEARS (Finite Element Analysis of Residual Strength) JIP developed a correlated FEA method for determining fatigue life of Tension-Tension (T-T) loaded offshore mooring chain. The developed first principles method incorporated the non-linear effects of proof loading, accounted for mean chain tension, accounted for material grade, employed a multi-axial fatigue method to account for complex stress fields within the chain, and was based on a parent material S-N curve. It was anticipated that this high fidelity approach could be applied more universally to successfully address a broader spectrum of emergent factors experienced in-field which have caused chain fatigue life reduction and adversely impacted mooring system integrity. These emergent factors include an array of chain degradation modes including; uniform, pitting and mega pitting corrosion; preferential butt weld corrosion; abrasive, contact and interlink wear; and load duties other than Tension-Tension (TT) such as Out-Of-Plane Bending (OPB), In-Plane-Bending (IPB) and Bending-Tension (BT). The objective of the investigations conducted by AMOG Consulting following completion of the Chain FEARS JIP research was to explore the extent to which the developed fatigue method could be applied more universally to address these emergent factors as they pertained to residual fatigue life. Application of the method identified a number of trends in fatigue performance for links subject to hawse pipe and fairlead interaction, and demonstrated good correlation against available guidance on fairlead performance and against OPB fatigue test data. The investigation confirms that the first principles FEA fatigue method can be applied more universally to successfully address a broader spectrum of emergent factors experienced in-field relating to fatigue life reduction.
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ladicola, Mark A., et John A. Shaw. « An Experimental Setup for Measuring Unstable Thermo-Mechanical Behavior of a Shape Memory Alloy Wire ». Dans ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1685.
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Abstract An experimental arrangement is demonstrated that overcomes some difficulties in thermo-mechanical testing of thin Shape Memory Alloy (SMA) wires under uniaxial tension. It is now well known that stress-induced transformations in some SMAs under uniaxial loading can lead to mechanical instabilities and propagating phase transformation fronts. Critical parameters, such as nucleation barriers are difficult to measure by conventional testing techniques and are often masked by unavoidable stress concentrations at grips. In addition, simultaneous full field measurements of localized deformation and temperature fields are difficult to obtain for different ambient conditions. The current scheme uses a temperature-controlled conduction block and a non-uniform temperature field induced by thermoelectric modules to uncover the underlying thermo-mechanical response of the wire. The approach also allows access for optical and infrared imaging of the specimen deformation and temperature fields.
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Milner, Justin L., et Thomas Gnäupel-Herold. « Design of an Octo-Strain Specimen for Biaxial Tension Testing ». Dans ASME 2018 13th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/msec2018-6612.
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A custom biaxial testing fixture was designed to evaluate a new specimen geometry for complex loading paths. Biaxial testing is commonly used to evaluate work-hardening behavior of sheet metal in biaxial tension to study the accumulation of plastic strains to determine the anisotropic yield loci. The current state-of-the-art specimen geometry that is used for biaxial testing is the cruciform specimen. Cruciform specimens are machined into a geometry that resembles a cross with four arms arranged at 90 degrees. However, this geometry is prone to premature failure and non-homogenous strain distribution within the gauge region. These problems persist even with the addition of complex features (e.g., slits and multi-step pockets). Therefore, the primary goal of the new specimen geometry is to achieve a large and uniform strain field within the gauge region. One of the main problems of the cruciform specimen is the formation of stress concentration within the gauge region. Therefore, the proposed specimen geometry is comprised of four additional arms between the existing cruciform arms. This geometry is termed an ‘Octo-Strain’ specimen after the eight arms that are arranged in a 45-degree planar pattern. It is hypothesized that the additional arms will stabilize the stress concentrations and, thus, achieve increased failure strain and uniformity as compared to the cruciform geometry. This work focuses on the comparison of the cruciform specimen to the Octo-Strain specimen during balanced biaxial deformation of mild steel. It is found that the Octo-Strain specimen achieved twice the failure strain and increased strain uniformity within the gauge region as compared to the cruciform specimen.
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Huang, Kevin, Hamn-Ching Chen et Chia-Rong Chen. « Vertical Riser VIV Simulation in Uniform Current ». Dans ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79349.
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Recently some riser vortex-induced vibrations (VIV) experimental data have been made publicly available (oe.mit.edu/VIV/), including a 10m riser VIV experiment performed by MARINTEK and donated by ExxonMobil URC. This paper presents our numerical simulation results for this 10m riser and the comparisons with the experimental results in uniform current. The riser was made of a 10m brass pipe with an OD of 0.02m (L/D = 482), and mass ratio of 1.75. The riser was positioned vertically with top tension of 817N, and pinned at its two ends to the test rig. Rotating the rig in the wave tank would simulate the uniform current. In the present numerical simulation the riser’s ends were pinned to the ground, and a uniform far field incoming current was imposed. The riser and its surrounding fluid were discretized using 1.5 million elements. The flow field is solved using an unsteady Reynolds-Averaged Navier-Stokes (RANS) numerical method in conjunction with a chimera domain decomposition approach with overset grids. The riser is also discretized into 250 segments. Its motion is predicted through a tensioned beam motion equation with external force obtained by integrating viscous and pressure loads on the riser surface. Then the critical parameters including riser VIV a/D, vorticity contours, and motion trajectories were processed. The same parameters for the experimental data were also processed since these data sets are in “raw time-histories” format. Finally, comparisons are made and conclusions are drawn. The present numerical method predicts similar dominant modes and amplitudes as the experiment. It is also shown that the cross flow VIV in the riser top section is not symmetric to that of the bottom section. One end has considerably higher cross flow vibrations than the other end, which is due to the non-dominant modal vibrations in both in-line and cross flow directions. The computational fluid dynamics (CFD) simulation results also agree with the experimental results very well on the riser vibrating pattern and higher harmonics response. The higher harmonics were studied and it is found they are related to the lift coefficients, hence the vortex shedding patterns. It is concluded that the present CFD approach is able to provide reasonable results and is suitable for 3D riser VIV analysis in deepwater and complex current conditions.
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Dong, Xuanliang Neil, Qing Luo, Bijay Giri et Xiaodu Wang. « Progressive Post-Yield Behavior of Human Cortical Bone in Shear ». Dans ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53677.
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Post-yield behavior is important for bone fragility since it accounts for the major part of energy dissipation of bone. Therefore, it is essential to study the post-yield behavior of bone to understand the different pathways for energy dissipation [1]. The post-yield behavior of bone may depend on the different loading modes. Previous studies have utilized a novel progressive loading scheme to study the post-yield behavior of cortical bone at tension [2] and compression [3]. However, few studies have reported post-yield behaviors of cortical bone in shear [4]. One of major challenges in shear tests of cortical bone is to achieve a uniform stress field over a test region. For example, the notches of the Iosipescu test may cause non-constant stress fields and locally high stresses when small amounts of bending are present [5]. The objective of this study was to develop the progressive loading scheme of shear in bone using an inclined double notch shear test, in which homogeneous shear stress fields were produced [5].
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Nezhad, Hamed Yazdani, Noel P. O’Dowd, Catrin M. Davies, Ali N. Mehmanparast et Kamran M. Nikbin. « Influence of Prior Deformation on Creep Crack Growth Behaviour of 316H Austenitic Steels ». Dans ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78680.
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The influence of pre-strain and pre-stress on creep crack growth behaviour of 316H austenitic steels is studied experimentally and numerically in this paper. Compact tension, C(T), specimens (25mm thickness) have been extracted from two steam headers, one as-received and one uniformly compressed to the strain value of 8%. The C(T) specimen extracted from the as-received header was compressed, introducing a non-uniform strain field. Creep crack growth (CCG) tests were performed at 550°C. Comparisons have been provided with the results from as-received C(T) specimens. Finite element (FE) analysis has been carried out to simulate the CCG behaviour of the C(T) specimens. By choosing the problem parameters appropriately, good agreement may be achieved between the FE predictions and the creep data.
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Ho, Peng-Ching, Yit Fatt Yap, Nam-Trung Nguyen, John Chai Chee Kiong, Teck Neng Wong et Levent Yobas. « A Numerical Investigation of Thermally Mediated Droplet Formation in a T-Junction ». Dans ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82056.
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The present article presents a numerical investigation on the effect of thermal forcing for droplet formation in a T-junction. Thermal forcing, generated by a heater embedded into the channel wall, induces a non-uniform temperature field which results in the variation the fluids’ properties and affects the droplet formation process in a desirable manner. In the present article, droplet formation process is posed as an incompressible immiscible two-phase flow problem with the motion of the two-phases strongly coupled via the related interfacial conditions. It is governed by the three-dimensional Navier-Stokes and the energy equations. The interface is captured with a narrow-band particle level-set method. Solutions are obtained using a finite volume method on a staggered mesh. The numerical model is validated against droplet formation in a cross junction. With the formation of water droplet in oil within the squeezing formation regime as a case study, the physics underlying droplet formation process in a T-junction affected by a thermal forcing is investigated. The combined effect of variations in both viscosities and surface tension result in a larger droplet. It is believed that the behavior of fluids system under an imposed thermal forcing depends strongly on the characteristics of temperature dependent viscosities and surface tension.
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Wang, Z. X., R. F. Zhang, Y. J. Chao et P. S. Lam. « Elastic-Plastic Constraint Analysis of Semi-Elliptic Surface Cracks in X100 Pipeline Steel ». Dans ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57715.
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In the framework of the J-A2 fracture theory, the crack driving force J and the crack tip constraint parameter A2 are used to describe the near crack tip stress and deformation fields. These two parameters, J and A2, were calculated from three-dimensional finite element results for semi-elliptic surface cracks with various lengths and depths in X100 pipeline steel. It was found that, under a uniform far field tensile loading, A2 increases rapidly to a nearly constant value along the crack front from the free surface to the deepest part of the crack. A similar trend was found for the J-integral distribution except in the case of a semi-circular crack. In addition, for a given elliptic crack configuration, A2 showed significant J-integral dependence when the crack front approached the free surface, where a strong three-dimensional effect is apparent. On the other hand, at the deepest part of the crack, A2 converged to a constant value. Two-dimensional plane strain calculations were also performed for single edge-notched tension specimens (SENT), where the crack length corresponds to the depth of the surface crack. The constraint of these two configurations (semi-elliptic crack and SENT) were compared under the same crack driving force (J-integral). In general, the constraint at the deepest crack front of an elliptic crack is higher than that of the corresponding SENT, especially in mid- to large scale yielding condition where J-integral is relatively large. It can be concluded that using fracture toughness determined from SENT specimens to predict surface flaw stability may lead to non-conservative result.