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Temperature-dependent Properties (temperature-dependent + property)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

Explicit coupled thermo-mechanical finite element model of steel solidification

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2009
Seid Koric
Abstract The explicit finite element method is applied in this work to simulate the coupled and highly non-linear thermo-mechanical phenomena that occur during steel solidification in continuous casting processes. Variable mass scaling is used to efficiently model these processes in their natural time scale using a Lagrangian formulation. An efficient and robust local,global viscoplastic integration scheme (Int. J. Numer. Meth. Engng 2006; 66:1955,1989) to solve the highly temperature- and rate-dependent elastic,viscoplastic constitutive equations of solidifying steel has been implemented into the commercial software ABAQUS/Explicit (ABAQUS User Manuals v6.7. Simulia Inc., 2007) using a VUMAT subroutine. The model is first verified with a known semi-analytical solution from Weiner and Boley (J. Mech. Phys. Solids 1963; 11:145,154). It is then applied to simulate temperature and stress development in solidifying shell sections in continuous casting molds using realistic temperature-dependent properties and including the effects of ferrostatic pressure, narrow face taper, and mechanical contact. Example simulations include a fully coupled thermo-mechanical analysis of a billet-casting and thin-slab casting in a funnel mold. Explicit temperature and stress results are compared with the results of an implicit formulation and computing times are benchmarked for different problem sizes and different numbers of processor cores. The explicit formulation exhibits significant advantages for this class of contact-solidification problems, especially with large domains on the latest parallel computing platforms. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Average power-handling capability of the signal line in coplanar waveguides on polyimide and GaAs substrates including the irregular line edge shape effects

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2005
Wen-Yan Yin
Abstract The average power-handling capability (APHC) of the signal line in finite-ground coplanar waveguides (FGCPWs) on polyimide and GaAs substrates is evaluated in this paper. In our approach, the ohmic loss of metal lines is characterized in different ways, and the effects of an irregular edge shape are also considered. The rise in temperature of the signal line is determined by single- and double-layer thermal models, with the temperature-dependent properties of the thermal conductivity of GaAs material treated appropriately. Parametric studies are carried out to investigate the overall effects of signal-line width, thickness, conductivity, edge-shape angle, and polyimide thickness on APHC. Some possible ways to enhance the APHC of these FGCPWs are also proposed. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

Weak solutions of a phase-field model for phase change of an alloy with thermal properties

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 14 2002
José Luiz Boldrini
The phase-field method provides a mathematical description for free-boundary problems associated to physical processes with phase transitions. It postulates the existence of a function, called the phase-field, whose value identifies the phase at a particular point in space and time. The method is particularly suitable for cases with complex growth structures occurring during phase transitions. The mathematical model studied in this work describes the solidification process occurring in a binary alloy with temperature-dependent properties. It is based on a highly non-linear degenerate parabolic system of partial differential equations with three independent variables: phase-field, solute concentration and temperature. Existence of weak solutions for this system is obtained via the introduction of a regularized problem, followed by the derivation of suitable estimates and the application of compactness arguments. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Dynamic mechanical properties of extruded nylon,wood composites

POLYMER COMPOSITES, Issue 4 2008
Jianmin Chen
Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon,wood composite in under-the-hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon,wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (Tg), physical aging effects, long-term performance prediction, and comparisons to similar products. The storage modulus of the nylon,wood composite was found to be more temperature stable than pure nylon 66. The Tg range of the nylon,wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon,wood composites have good temperature-dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon,wood composite with other similar products shows that nylon,wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source]