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Artykuły w czasopismach na temat "Arc-Length Solver"
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Reynolds, Quinn G., Thokozile P. Kekana i Buhle S. Xakalashe. "A Computational Magnetohydrodynamic Modelling Study on Plasma Arc Behaviour in Gasification Applications". Mathematical and Computational Applications 28, nr 2 (12.04.2023): 60. http://dx.doi.org/10.3390/mca28020060.
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The application of direct-current plasma arc furnace technology to the problem of coal gasification is investigated using computational multiphysics models of the plasma arc inside such units. An integrated modelling workflow for the study of DC plasma arc discharges in synthesis gas atmospheres is presented. The thermodynamic and transport properties of the plasma are estimated using statistical mechanics calculations and are shown to have highly non-linear dependencies on the gas composition and temperature. A computational magnetohydrodynamic solver for electromagnetically coupled flows is developed and implemented in the OpenFOAM® framework, and the behaviour of three-dimensional transient simulations of arc formation and dynamics is studied in response to different plasma gas compositions and furnace operating conditions. To demonstrate the utility of the methods presented, practical engineering results are obtained from an ensemble of simulation results for a pilot-scale furnace design. These include the stability of the arc under different operating conditions and the dependence of voltage–current relationships on the arc length, which are relevant in understanding the industrial operability of plasma arc furnaces used for waste coal gasification.
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Bharali, Ritukesh, Somdatta Goswami, Cosmin Anitescu i Timon Rabczuk. "A robust monolithic solver for phase-field fracture integrated with fracture energy based arc-length method and under-relaxation". Computer Methods in Applied Mechanics and Engineering 394 (maj 2022): 114927. http://dx.doi.org/10.1016/j.cma.2022.114927.
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Hou, Jiatong, Bo You, Jiazhong Xu i Qiaomu Hu. "Numerical simulation for expansion of preform and optimization of preform in thermoset composites". Advances in Mechanical Engineering 13, nr 5 (maj 2021): 168781402110170. http://dx.doi.org/10.1177/16878140211017002.
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The expansion of preform and the optimization of preform have become important steps in the molding process. At present, there are some questions in the expansion of thermoset composite material preform and precompression, for example, the inaccurate dimensions, cracks, and wrinkles. For the expansion of preform, the finite element inverse algorithm is used as the expansion algorithm, and then the initial solution is optimized by the arc length mapping method, the expansion of preform is realized by the iterative equation which is solved by the ABAQUS solver. The effectiveness of the expansion of preform is verified through the comparison between the finite element inverse algorithm with DYNAFORM. The optimization of the precompression process is researched in order to solved the problems of cracks and wrinkles in the integral precompression method of preform. Firstly, the precompression sequence is adjusted by the precompression method, and then the precompression direction is optimized by the genetic algorithm. Through numerical simulation, the maximum thinning rate is reduced to 13%, and the maximum thickening rate is reduced to 6%, which improve the problems of cracks and wrinkles of preform, and the effectiveness of the optimization method is verified.
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Shamal, Souad Jabbar, Luay Sadiq Al-Ansari, Ahmed Niameh Mehdy Alhusseny i Adel Gharib Nasser. "Roughness Effect on Thermo-Elasto-Hydrodynamic Performance of a 170ᵒ -Arc Partial Journal Bearing". Journal of Engineering 27, nr 1 (1.01.2021): 16–34. http://dx.doi.org/10.31026/j.eng.2021.01.02.
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In the current analysis, the effects of circumferential scratches along the inner surface of a 170ᵒ -arc partial journal bearing has been numerically investigated. Their impact on the thermo-elasto-hydrodynamic performance characteristics, including maximum pressure, temperature, deformation, and stress, has been examined thoroughly. The ANSYS Fluent CFD commercial code was employed to tackle the iterative solution of flow and heat transfer patterns in the fluid film domain. They are then applied to the ANSYS Static Structure solver to compute the deformation and stress resulted in the solid bearing zone. A wide range of operating conditions has been considered, including the eccentricity ratio ( ) and scratch depth ( ). In contrast, the bearing length-diameter ratio (L/D) and the rotation speed (N) have been fixed at 0.77 and 1500 rpm, respectively. The thermo-hydrodynamic pressure, temperature, stress, and deformation have all been computed. It was found that the scratch depth has a direct effect on the thermo-hydrodynamic performance of the partial bearings. Meanwhile, the deep central scratches are important, especially at scratch depth equal to 0.224 mm.
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Shamal, Souad Jabbar, Luay Sadiq Al-Ansari, Ahmed Niameh Mehdy Alhusseny i Adel Gharib Nasser. "Roughness Effect on Thermo-Elasto-Hydrodynamic Performance of a 170ᵒ -Arc Partial Journal Bearing". Journal of Engineering 27, nr 1 (1.01.2021): 16–34. http://dx.doi.org/10.31026/10.31026/j.eng.2021.01.02.
Pełny tekst źródłaStreszczenie:
In the current analysis, the effects of circumferential scratches along the inner surface of a 170ᵒ -arc partial journal bearing has been numerically investigated. Their impact on the thermo-elasto-hydrodynamic performance characteristics, including maximum pressure, temperature, deformation, and stress, has been examined thoroughly. The ANSYS Fluent CFD commercial code was employed to tackle the iterative solution of flow and heat transfer patterns in the fluid film domain. They are then applied to the ANSYS Static Structure solver to compute the deformation and stress resulted in the solid bearing zone. A wide range of operating conditions has been considered, including the eccentricity ratio ( ) and scratch depth ( ). In contrast, the bearing length-diameter ratio (L/D) and the rotation speed (N) have been fixed at 0.77 and 1500 rpm, respectively. The thermo-hydrodynamic pressure, temperature, stress, and deformation have all been computed. It was found that the scratch depth has a direct effect on the thermo-hydrodynamic performance of the partial bearings. Meanwhile, the deep central scratches are important, especially at scratch depth equal to 0.224 mm.
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Barbieri, Ettore, Federica Ongaro i Nicola Maria Pugno. "AJ-integral-based arc-length solver for brittle and ductile crack propagation in finite deformation-finite strain hyperelastic solids with an application to graphene kirigami". Computer Methods in Applied Mechanics and Engineering 315 (marzec 2017): 713–43. http://dx.doi.org/10.1016/j.cma.2016.10.043.
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Soria, Antonio, i Pierre Pegon. "An arc length control procedure to solve parabolic problems". Computer Methods in Applied Mechanics and Engineering 106, nr 1-2 (lipiec 1993): 27–50. http://dx.doi.org/10.1016/0045-7825(93)90183-x.
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Chucheepsakul, S., C. M. Wang, X. Q. He i T. Monprapussorn. "Double Curvature Bending of Variable-Arc-Length Elasticas". Journal of Applied Mechanics 66, nr 1 (1.03.1999): 87–94. http://dx.doi.org/10.1115/1.2789173.
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This paper deals with the double curvature bending of variable arc-length elasticas under two applied moments at fixed support locations. One end of the elastica is held while the other end portion of the elastica may slide freely on a frictionless support at a prescribed distance from the held end. Thus, the variable deformed length of the elastica between the end support and the frictionless support depends on the relative magnitude of the applied moments. To solve this difficult and highly nonlinear problem, two approaches have been used. In the first approach, the elliptic integrals are formulated based on the governing nonlinear equation of the problem. The pertinent equations obtained from applying the boundary conditions are then solved iteratively for solution. In the second approach, the shooting-optimization method is employed in which the set of governing differential equations is numerically integrated using the Runge-Kutta algorithm and the error norm of the terminal boundary conditions is minimized using a direct optimization technique. Both methods furnish almost the same stable and unstable equilibrium solutions. An interesting feature of this kind of bending problem is that the elastica can form a single loop or snap-back bending for some cases of the unstable equilibrium configuration.
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Kalitkin, N. N., i I. P. Poshivaylo. "Guaranteed accuracy for the Cauchy problem solved using the arc length method". Doklady Mathematics 88, nr 2 (wrzesień 2013): 601–4. http://dx.doi.org/10.1134/s1064562413050219.
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Gao, Liyang, i Weiguo Wu. "Forward kinematics modeling of spatial parallel linkage mechanisms based on constraint equations and the numerical solving method". Robotica 35, nr 2 (19.06.2015): 293–309. http://dx.doi.org/10.1017/s0263574715000508.
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SUMMARYIn order to solve general kinematics modeling problems and numerical stability problems of numerical methods for spatial parallel linkage mechanisms, a general modeling method and its numerical solving algorithm is proposed. According to the need for avoiding direct singular configurations, valid joint variable space and valid forward kinematics solutions (VKSs) are defined. Taking numerical convergence near singular points into account, the pseudo-arc length homotopy continuation algorithm is given to solve the kinematics model. Finally as an example, the joint variable space of the general Stewart platform mechanism is analyzed, which is proved to be divided into subspaces by direct singular surfaces. And then, forward kinematics solutions of 200 testing points are solved separately using the pseudo-arc length homotopy continuation algorithm, the Newton homotopy continuation algorithm and the Newton–Raphson algorithm (NRA). Comparison of the results shows that the proposed method is convergent to the same solution branch with the initial configuration on all the testing points, while the other two algorithms skip to other solution branches on some near singular testing points.
Rozprawy doktorskie na temat "Arc-Length Solver"
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Roy, Suprateek. "Quasi-Static and Implicit-Dynamic Finite Element Solution of Large Deformation Elastic Adhesive Contacts Using a Volumetric Interaction Scheme". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5699.
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Adhesive forces, mediated by van der Waals’ and other interactions, dominate the contact response in the micron and sub-micron regimes. Understanding adhesion is especially important in biological systems (interaction of cells with pathogens, bio-locomotion, and drug delivery), mechanical systems (nano-indentation), and Micro-Electro-Mechanical Systems (MEMS), among many others. Classical adhesive contact models like the JKR, DMT, and Maugis’ models apply in the small-deformation regime for regular bodies. Despite attempts by Shull, Lin, and others, enabling large deformation and arbitrary shapes is infeasible in such semi-analytical schemes, necessitating the use of finite element analysis (FEA).
Existing FE models use volume-to-volume (V2V), surface-to-surface (S2S), point to volume (P2V) or point to surface (P2S) interactions. S2S (e.g. Fan et al.) are computationally efficient but are not accurate enough to simulate strong adhesion in soft bodies due to inherent approximations. In these paradigms, a well-known FE scheme is the Coarse-Grained-Contact-Model (CGCM) developed by Sauer and co-workers. While CGCM is quite general, it uses a modification of the classical continuum, which is complicated to implement. More importantly, adhesion involves inherent ‘jump-to’ and ‘jump-off’ instabilities, which have not received adequate attention in the existing simulation literature. Moreover, these instabilities are more pronounced in soft materials, and necessitate new supporting algorithms and computational approaches for successful simulation. Lastly, for applications, it is important for solvers to demonstrate the ability to simulate adhesive systems with realistic material and interaction parameters.
In the present work, a V2V, interaction-based, continuum FE model is developed for large deformation plane strain adhesive contacts, with all interacting bodies considered to be elastic. A tree-based, ultra-fine, structured mesh generator is developed to accurately model interactions while reducing the associated computational expense. A k-d tree based algorithm is implemented to compute the interactions, reducing the computational cost. Both quasi-static and implicit dynamic solvers are developed. The quasi-static solver uses a custom path-following algorithm which can tackle ‘jump-to’ and ‘jump-off’ instabilities for a wide range of problems. The dynamic solver provides an alternative solution strategy to resolve only the stable branches of the solution curve and is especially useful for soft materials with strong adhesion.
The solutions obtained by the quasi-static solver and the dynamic solver in the low-velocity limit show good agreement, except, obviously, in the snap-back zone. In the past, dynamics solvers for adhesive problems (Johnson et al.; Jayadeep et al.) have typically focused on the impact ('unforced') regime rather than on the constant-velocity ('forced') regime, which is often more important in applications.
Some studies were carried out to validate various aspects of these solvers, including checks on the accuracy of interaction force calculations, mesh convergence behavior, and various limiting cases. Several model applications were considered to study and test these solvers, including cylinders and elliptical cylinders interacting with half-spaces, and a multi-body problem involving two cylinders and a half-space. Apart from the load-displacement and load-gap curves, a complete set of sub-surface strain fields and transmitted contact tractions is presented. The temporal evolution of the pressure peaks near the edges of contact is clearly revealed, flipping from tensile to compressive as the bodies approach each other very closely. The simulations show that tensile peaks always occur near the 'edge of contact' even in a highly repulsion-dominated regime. The solvers developed in the present work are expected to be useful to explore a spectrum of adhesive contact problems that arise in applications.
Części książek na temat "Arc-Length Solver"
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Busby, C. J., T. L. Pavlis, S. M. Roeske i B. Tikoff. "The North American Cordillera during the Mesozoic to Paleogene: Selected questions and controversies". W Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(31).
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ABSTRACT The North American Cordillera experienced significant and varied tectonism during the Triassic to Paleogene time interval. Herein, we highlight selected questions and controversies that remain at this time. First, we describe two tectonic processes that have hindered interpretations of the evolution of the orogen: (1) strike-slip systems with poorly resolved displacement; and (2) the closing of ocean basins of uncertain size, origin, and mechanism of closure. Next, we divide the orogen into southern, central, and northern segments to discuss selected controversies relevant to each area. Controversies/questions from the southern segment include: What is the origin of cryptic transform faults (Mojave-Sonora megashear vs. California Coahuila transform fault)? Is the Nazas an arc or a continental rift province? What is the Arperos basin (Guerrero terrane), and did its closure produce the Mexican fold-and-thrust belt? How may inherited basement control patterns of deformation during subduction? Controversies/questions from the central segment include: Can steeply dipping mantle anomalies be reconciled with geology? What caused high-flux events in the Sierra Nevada batholith? What is the origin of the North American Cordilleran anatectic belt? How does the Idaho segment of the orogen connect to the north and south? Controversies/questions from the northern segment include: How do we solve the Baja–British Columbia problem? How big and what kind of basin was the Early Cretaceous lost ocean basin? What connections can be found between Arctic geology and Cordilleran geology in Alaska? How do the Cretaceous tectonic events in the Arctic and northern Alaska connect with the Cordilleran Cretaceous events? What caused the Eocene tectonic transitions seen throughout the northern Cordillera? By addressing these questions along the length of the Cordillera, we hope to highlight common problems and facilitate productive discussion on the development of these features.
Streszczenia konferencji na temat "Arc-Length Solver"
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Borjesson, E., M. Fagerstrom i J. Remmers. "An Arc-Length Solver with Dissipation Path-Following for Complex Analysis of Brittle Failure and Stability of Composite Structures". W VIII Conference on Mechanical Response of Composites. CIMNE, 2021. http://dx.doi.org/10.23967/composites.2021.120.
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Khatri, Rasish, i Dara W. Childs. "An Experimental Investigation of the Dynamic Performance of a Vertical-Application Three-Lobe Bearing". W ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25483.
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Dynamic performance test results are provided for a vertical-application three-lobe bearing, geometrically similar to a three-lobe bearing tested by Leader [1] to stabilize a vertical sulfur pump. The bearing has the following specifications: 100° pad arc angle, 0.64 preload, 100% offset, 101.74 mm bore diameter, 0.116 mm radial pad clearance, 76.3 mm axial length, and 100° static load orientation from the leading edge of the loaded pad. The bearing is tested at 2000 rpm, 4400 rpm, 6750 rpm, and 9000 rpm. This bearing is tested in the no-load condition and with low unit loads of 58 kPa and 117 kPa. The dynamic performance of this bearing is evaluated to determine (1) whether a fully (100%) offset three-lobe bearing configuration is more stable than a standard plain journal bearing (0.5 whirl-frequency ratio), and (2) whether a fully offset three-lobe bearing provides a larger direct stiffness than a standard fixed-arc bearing. Hot and cold clearances are measured for this bearing. Dynamic measurements include frequency-independent stiffness and damping coefficients. Bearing stability characteristics are evaluated using the whirl-frequency ratio (WFR). Test results are compared to numerical predictions obtained from a fixed-arc bearing Reynolds equation solver. Dynamic tests show that the vertical-application three-lobe bearing does not improve stability over conventional fixed-arc bearings. The measured WFRs for the vertical-application bearing are approximately 0.4–0.5 for nearly all test cases. Predicted WFRs are 0.46 at all test points. The vertical-application bearing dimensionless direct stiffness coefficients were compared to those for a 70% offset three-lobe bearing. Dimensionless direct stiffness coefficients at 0 kPa are larger for the vertical-application bearing by 45–48% in the loaded direction and larger by 15–26% in the unloaded direction. Thus, the vertical-application bearing does impart a larger centering force to the journal relative to the 70% offset bearing, in the no-load condition. Predictions using both the measured hot clearance and measured cold clearance as inputs to the code are compared to the measured dynamic data. In general, the predicted direct stiffness coefficients using both the hot and cold clearances as inputs were higher than measured direct stiffnesses. The two sets of predicted cross-coupled stiffness coefficients straddle the measured cross-coupled stiffness coefficients. Predicted direct damping coefficients using both solutions were higher than measured values in most cases, but agreement between predictions and measurements improved significantly at high speeds and when applying light loads.
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Ju, Ren, Wei Fan i Weidong Zhu. "A Universal Nonlinear Analyzer for Rigid Multibody Systems Based on the Efficient Galerkin Averaging-Incremental Harmonic Balance Method". W ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-68548.
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Abstract The bridge between the multibody dynamic modeling theory and nonlinear dynamic analysis theory is built for the first time in this work by introducing an efficient Galerkin averaging-incremental harmonic balance (EGA-IHB) method for steady-state nonlinear dynamic analysis of index-3 differential algebraic equations (DAEs) for general rigid multibody systems. The multibody dynamic modeling theory has made significant advances in generality and simplicity, and multibody systems are usually governed by DAEs. Since the fast Fourier transform and EGA are used, the EGA-IHB method has excellent robustness and computational efficiency. Since the Floquet theory cannot be directly used for stability analysis of periodic responses of DAEs, a new stability analysis procedure is developed, where perturbed, linearized DAEs are reduced to ordinary differential equations with use of independent generalized coordinates. A modified arc-length continuation method with a scaling strategy is used for calculating response curves and conducting parameter studies. Three examples are used to show the performance and capability of the current method. Periodic solutions of DAEs from the EGA-IHB method show excellent agreement with those from numerical integration methods. Amplitude-frequency and amplitude-parameter response curves are generated, and stability and period-doubling bifurcations are analyzed. The EGA-IHB method can be used as a universal solver and nonlinear analyzer for obtaining steady-state periodic responses of DAEs for general multibody systems.
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Hanin, Leonid. "Efficiency of a New Straight Cooling Fin". W ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72376.
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In 1926 E. Schmidt [1] discovered his optimum parabolic straight cooling fin. The most critical premise used in his analysis was the “length-of-arc” assumption that consists of neglecting the curvature of the fin exposed surface. The problem of optimum straight cooling fin design without the “length-of-arc” assumption was solved in [2] which led to the discovery of the optimum circular fin. In the present work, thermal efficiency of this new optimum straight cooling fin is computed.
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Petrasch, Jo¨rg, i Aldo Steinfeld. "A Novel High-Flux Solar Simulator Based on an Array of Xenon Arc Lamps: Optimization of the Ellipsoidal Reflector and Optical Configuration". W ASME 2005 International Solar Energy Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/isec2005-76009.
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The optical characteristics of a high-flux solar simulator that comprises an array of Xe-arc lamps with ellipsoidal specular reflectors of common focus is examined using the Monte Carlo ray tracing technique. The parameters varied are arc diameter, focal length, eccentricity, truncation diameter, and angular error of specular reflection. The geometrical design of the truncated ellipsoidal reflector is optimized for maximum transfer efficiency, defined as the portion of radiation intercepted by a circular target centered at the common focal point. An array of ten 15 kW Xe-arc lamps of 9 mm electrode gap and 35% electrical-to-radiant efficiency, each closed-coupled with an ellipsoidal reflector of optimum design, should be capable of delivering an average radiative power flux exceeding 5900 kW/m2 over a 6 cm-diameter circular target, with an overall transfer efficiency of 31.9%.
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Zhang, Lu, Peng Wu i DaZhuan Wu. "Analyses of Pressure Fluctuation and Fluctuation Reduction of an Automobile Fuel Pump". W ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7820.
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The automobile fuel pump studied in this paper is a mini regenerative pump consisting of a casing with an axial channel and an impeller with 33 radial blades. In this study, the pressure fluctuation characteristics of the regenerative pump were analyzed with the method of unsteady CFD analysis. To investigate the pressure fluctuation, the unsteady Reynolds-averaged Navier-Stokes equations (URANS) were solved with realizable k-ε turbulence model using the CFD code FLUENT. To study the effect of arc length of stripper on the pressure fluctuation, the pressure fluctuations at several locations of pumps with strippers of different arc length were analyzed in time and frequency domain. The static pressure contours at different times were presented to reveal the generating mechanism of pressure fluctuation of the regenerative pump. For the purpose of pressure fluctuation reduction, a random modulation of blade spacing method was applied to design a new impeller with uneven spaced blades. The pressure fluctuations of four different pump units of the combination of different blade distribution impellers with casings of different arc length of stripper were studied and discussed. The pressure fluctuation of the pump unit of combination of random blade distribution impeller and large arc length stripper is significantly reduced. In this paper, the generating mechanism of pressure fluctuation for regenerative pump is uncovered, and a good solution to the fundamental pressure fluctuation reduction of regenerative pump is put forward.
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Seo, Jong-Hwi, Hiroyuki Sugiyama i Ahmed A. Shabana. "Spatial Finite Element Formulation for the Pantograph/Catenary Systems". W ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84060.
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This paper describes a three-dimensional large deformation finite element formulation for the analysis of the multibody pantograph/catenary systems. The large deformation of the catenary is modeled using the three-dimensional finite element absolute nodal coordinate formulation. A non-generalized arc-length parameter is introduced in order to be able to formulate the joint between the catenary and pan-head and to accurately predict the location of the contact point. The resulting system of differential and algebraic equations formulated in terms of reference coordinates, finite element absolute nodal coordinates, and non-generalized arc-length and contact surface parameters are solved using computational multibody system algorithms. A method is also proposed to deal with the problem of the loss of contact between the pan-head and the catenary cable.
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Ardakani, Esmaeil Safaei, i Javad Mostaghimi. "Numerical Study of the Arc Fluctuations in DC Plasma Torch". W ITSC2015, redaktorzy A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen i C. A. Widener. ASM International, 2015. http://dx.doi.org/10.31399/asm.cp.itsc2015p0836.
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Abstract Plasma spray technology is widely employed by industry to apply coatings on different components to protect them from corrosion, wear and high temperature environments. The gases introduced into the DC plasma torch are heated by the arc and a plasma jet exits the torch. Powders are injected into the plasma jet where they are then accelerated, heated, and melted before impacting the substrate, which is placed at some distance from the outlet of plasma spray torch. Plasma arc exhibits strong voltage fluctuations which correspond to the movement of the anode arc root attachment. Understanding the arc movement within the torch and how it affects the flow and temperature fields of the plasma jet exiting the torch is of great importance. Understanding the flow, temperature and electromagnetic fields within the DC plasma torch is extremely challenging and there is a limited number of investigations in the literature. In order to provide unique sets of surface characteristics, e.g., thermal barriers, wear and corrosion resistance, a high quality coating with appropriate combination of powder and base materials must be produced. To produce a high quality coating, powder particles should be uniformly heated and accelerated, and then deposited onto the substrate. In this paper, an unsteady 3-dimensional model of the arc movement within the plasma torch is reported. The proposed model is employed to solve electric potential and magnetic vector potential equations in addition to continuity, momentum and energy equations. The k-ε turbulence model was used to model the turbulence of the flow field inside a non-transferred DC argon plasma torch. The geometry of the torch was that of SG-100 torch (Praxair). TO study the effect of the arc length on the voltage, first a steady-state model was considered for a range of arc lengths and arc-root radii. The results of this model provided the relation between arc length and arc voltage for a set of arc root radii and given argon flow rate. Then, given voltage fluctuation profile, the unsteady, arc root attachment movement was simulated from the estimation which found from steady models. Results show that the effects of velocity and temperature fluctuations at the outlet of the torch (where the particles are injected) are not negligible and such fluctuations exceed 15% of their average values. These will in turn affect the particle heating history and will negatively impact the microstructure of the coating.
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Ramachandran, K., J. L. Marqués, R. Vaßen i D. Stöver. "Modelling the Plasma Torch: Numerical and Analytical Models to Describe the Temperature and Velocity Distribution Inside a F4 Torch". W ITSC2005, redaktor E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0337.
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Abstract One of the most sensitive factors for the simulation of the gas flow outside the plasma torch is the determination of the velocity and temperature profiles at the torch outlet. It requires the solution of the flow and electric potential equations within the torch. In this work this problem is solved through numerical simulations, with two free parameters: the radius of the plasma core near to the cathode and the length of the electric arc (or alternatively the potential between cathode and anode). In order to reduce the number of the free parameters to only one, an analytical model is also developed, which solves the same equations as the numerical simulations but in a simplified way. The reduction of parameters is achieved in this simple model through the additional condition that the physical plasma corresponds to an extremal value in the entropy production. Since the results of the simplified analytical model are compared to more detailed numerical simulations, the free parameter can be adjusted. The effect of high hydrogen content on the gas flow is thus studied, showing that the velocity profile at the outlet displays a more pronounced peak, as expected experimentally.
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Qureshi, Ejaz M., Afzaal M. Malik i Naeem Ullah Dar. "Thermo-Mechanical Analysis of Residual Stresses in Arc Welded Thin-Walled Cylinders". W 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48431.
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The problem of reduced strength of the structures in and around the weld zone due to the residual stresses in arc welding process is a major concern of the welding industry for decades. The prediction of the transient and residual stress fields during and after the completion of the welding process is of critical importance to ensure the structural integrity of welded structures. Circumferentially welded thin-walled cylinders are widely utilized in many engineering applications including the oil transportation system, boiler and pressure vessel industries. This paper presents a detailed three-dimensional finite element (FE) study to investigate the welding induced residual stresses in circumferentially welded thin-walled cylinders. The complex phenomenon of arc welding is numerically solved by sequentially coupled transient, non-linear thermo-mechanical analysis approach to simulate Gas Tungsten Arc (GTA) Welding process. Single pass butt-welded geometry with single “V” groove for two 300 mm outer diameter cylinders with 3 mm wall thickness and 150 mm length are used in numerical simulations. Temperature dependent thermo-mechanical behavior for low carbon steel is modeled and filler metal deposition by using the element birth and kill features is incorporated. Widely accepted double ellipsoidal GOLDAK heat source model for arc welding is introduced and implemented. Simulation of the entire welding process is accomplished by using author written subroutines in ANSYS®, general purpose FE software. The accuracy of the developed FE simulation strategy is validated with experimentation for temperature distribution and residual stresses.