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Energy Balance Equation (energy + balance_equation)
Selected AbstractsIncremental model for fatigue crack growth based on a displacement partitioning hypothesis of mode I elastic,plastic displacement fieldsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 7 2007S. POMMIER ABSTRACT The mode I displacement field in the near crack tip region is assumed to be depicted by its partition into an elastic field and a plastic field. Then, each part of the displacement field is also assumed to be the product of a reference field, a function of space coordinates only, and of an intensity factor, function of the loading conditions. This assumption, classical in fracture mechanics, enables one to work at the global scale since fracture criteria can be formulated as a function of the stress intensity factors only. In the present case, the intensity factor of the plastic part of the displacement field measures crack tip plastic flow rate at the global scale. On the basis of these hypotheses, the energy balance equation and the second law of thermodynamics are written at the global scale, i.e. the scale of the K-dominance area. This enables one to establish a yield criterion and a plastic flow rule for the crack tip region. Then, assuming a relation between plastic flow in the crack tip region and fatigue crack growth allows an incremental model for fatigue crack growth to be built. A few examples are given to show the versatility of the model and its ability to reproduce memory effects associated with crack tip plasticity. [source] Multi-time-step domain coupling method with energy controlINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2010N. Mahjoubi Abstract A multi-time-step integration method is proposed for solving structural dynamics problems on multiple domains. The method generalizes earlier state-space integration algorithms by introducing displacement constraints via Lagrange multipliers, representing the time-integrated constraint forces over the individual time step. It is demonstrated that displacement continuity between the subdomains leads to cancelation of the interface contributions to the energy balance equation, and thus stability and algorithmic damping properties of the original algorithms are retained. The various subdomains can be integrated in time using different time steps and/or different state-space time integration schemes. The solution of the constrained system equations is obtained using a dual Schur formulation, allowing for maximum independence of the calculation of the subdomains. Stability and accuracy are illustrated by a numerical example using a refined mesh around concentrated forces. Copyright © 2010 John Wiley & Sons, Ltd. [source] Stationary solutions to an energy model for semiconductor devices where the equations are defined on different domainsMATHEMATISCHE NACHRICHTEN, Issue 12 2008Annegret Glitzky Abstract We discuss a stationary energy model from semiconductor modelling. We accept the more realistic assumption that the continuity equations for electrons and holes have to be considered only in a subdomain ,0 of the domain of definition , of the energy balance equation and of the Poisson equation. Here ,0 corresponds to the region of semiconducting material, , \ ,0 represents passive layers. Metals serving as contacts are modelled by Dirichlet boundary conditions. We prove a local existence and uniqueness result for the two-dimensional stationary energy model. For this purpose we derive a W1,p -regularity result for solutions of systems of elliptic equations with different regions of definition and use the Implicit Function Theorem. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparative thermal performance evaluation of an active solar distillation systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2007G. N. Tiwari Abstract In this paper, thermal models of all types of solar collector-integrated active solar stills are developed based on basic energy balance equations in terms of inner and outer glass temperatures. In this paper, hourly yield, hourly exergy efficiency, and hourly overall thermal efficiency of active solar stills are evaluated for 0.05 m water depth. All numerical computations had been performed for a typical day in the month of 07 December 2005 for the climatic conditions of New Delhi (28°35,N, 77°12,E, 216 m above MSL). The thermal model of flat-plate collector integrated with active solar still was validated using the experimental test set-up results. Total daily yield from active solar still integrated with evacuated tube collector with heat pipe is 4.24 kg m,2 day,1, maximum among all other types of active solar stills. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analysis of heat transfer in autoclave technologyPOLYMER COMPOSITES, Issue 5 2001Vincenza Antonucci In autoclave technology, polymer based composites are manufactured under the application of pressure and heat. The heat transferred between the energy carrying fluid and the bag-composite-tool element activates exothermic curing reactions, leading to composite consolidation. The convective heat transfer mechanism is the most relevant aspect controlling the rate of chemical and physical transformations associated with composite curing. Moreover, the fluidodynamic regime that results from the interactions between the autoclave and the tool geometry, even if totally predictable in theory, is unattainable in practice. In this study, the heat transfer phenomena occurring during the autoclave manufacturing cycle have been analyzed. The assumption of a negligible through-the-thickness thermal gradient led to simplified energy balance equations. In this case, the thermal evolution of the manufacturing elements has been completely determined by two parameters: the global convective heat exchange coefficient, setting the rate of the heat transfer between the autoclave environment and the bag-composite-tool element, and the adiabatic temperature rise, establishing the relevance of the polymerization exotherm. A scaling analysis has been performed in order to identify the dimensionless parameters controlling the autoclave process. The developed semitheoretical methodology has been extensively tested by comparison with experimental data from an industrial autoclave. [source] | |||||||||||||