共查询到20条相似文献,搜索用时 31 毫秒
1.
A computational thermo-metallographic and thermoelastoplastic model for the analysis of the quenching process is developed
and validated. The diffusive transfor-mations are modeled according to the Johnson–Mehl–Avrami–Kolmogorov model and the Scheil’s
additivity rule. Two different models are investigated for the non-diffusive transformation—the Koistinen–Marburger model
and the Yu model. A large displacement formulation is assumed for the deformation analysis, modeling the plastic behavior
of the material according to the Prandtl–Reuss model. Two different bilinear hardening models—the isotropic and the kinematic
hardening model—are used and compared. The model allows to evaluate the transient stress and strain distributions during the
quenching process, the final phases and hardness distributions, and to predict the residual stress and the final deformation
of the processed part. A good agreement between computational results and reference data is found 相似文献
2.
A numerical study of mixed convection in a vertical channel filled with a porous medium including the effect of inertial forces
is studied by taking into account the effect of viscous and Darcy dissipations. The flow is modeled using the Brinkman–Forchheimer-extended
Darcy equations. The two boundaries are considered as isothermal–isothermal, isoflux–isothermal and isothermal–isoflux for
the left and right walls of the channel and kept either at equal or at different temperatures. The governing equations are
solved numerically by finite difference method with Southwell–Over–Relaxation technique for extended Darcy model and analytically
using perturbation series method for Darcian model. The velocity and temperature fields are obtained for various porous parameter,
inertia effect, product of Brinkman number and Grashof number and the ratio of Grashof number and Reynolds number for equal
and different wall temperatures. Nusselt number at the walls is also determined for three types of thermal boundary conditions.
The viscous dissipation enhances the flow reversal in the case of downward flow while it counters the flow in the case of
upward flow. The Darcy and inertial drag terms suppress the flow. It is found that analytical and numerical solutions agree
very well for the Darcian model.
An erratum to this article is available at . 相似文献
3.
The effects of viscous dissipation on unsteady free convection from an isothermal vertical flat plate in a fluid saturated
porous medium are examined numerically. The Darcy–Brinkman–Forchheimer model is employed to describe the flow field. A new
model of viscous dissipation is used for the Darcy–Brinkman–Forchheimer model of porous media. The simultaneous development
of the momentum and thermal boundary layers are obtained by using a finite difference method. Boundary layer and Boussinesq
approximation have been incorporated. Numerical calculations are carried out for various parameters entering into the problem.
Velocity and temperature profiles as well as local friction factor and local Nusselt number are shown graphically. It is found
that as time approaches infinity, the values of friction factor and heat transfer coefficient approach steady state. 相似文献
4.
C.G. Speziale 《Theoretical and Computational Fluid Dynamics》1999,13(3):161-166
A resent extension of the nonlinear K–ε model is critically discussed from a basic theoretical standpoint. While it was said in the paper that this model was formulated
to incorporate relaxation effects, it will be shown that the model is incapable of describing one of the most basic such turbulent
flows as is obvious but is described for clarity. It will be shown in detail that this generalized nonlinear K–ε model yields erroneous results for the Reynolds stress tensor when the mean strains are set to zero in a turbulent flow
– the return-to-isotropy problem which is one of the most elementary relaxational turbulent flows. It is clear that K–ε type models cannot describe relaxation effects. While their general formalism can describe relaxation effects, the nonlinear
K–ε model – which the paper is centered on – cannot. The deviatoric part of the Reynolds stress tensor is predicted to be zero
when it actually only gradually relaxes to zero. Since this model was formulated by using the extended thermodynamics, it
too will be critically assessed. It will be argued that there is an unsubstantial physical basis for the use of extended thermodynamics
in turbulence. The role of Material Frame-Indifference and the implications for future research in turbulence modeling are
also discussed.
Received 19 February 1998 and accepted 23 October 1998 相似文献
5.
A model of kinetics of phase transitions in a substance in a metastable state is proposed, where the probability of extensive
nucleation owing to homogeneous mechanisms is rather large; the model is an alternative to Kolmogorov’s model. The use of
this model is demonstrated to offer analytical solutions that describe both the crystallization processes with similar densities
of the liquid and solid phases and, for instance, the kinetics of nucleation and growth of bubbles in surface boiling. Solutions
obtained by Kolmogorov’s model and by the present model coincide at the initial stage of the process where the volume fraction
of the new phase is small.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 75–80, March–April, 2007. 相似文献
6.
S. P. Kiselev 《Journal of Applied Mechanics and Technical Physics》2006,47(6):857-866
A mathematical model is proposed for the development of a shear band in crystals. The model is based on the mechanism of double
cross-slips of screw-dislocation segments. Equations are derived to study instability of the uniform distribution of dislocations.
A solution is found in the form of a traveling wave, which describes the shear-band structure.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 102–113, November–December, 2006. 相似文献
7.
David E. Zeitoun Yves Burtschell Irina A. Graur Mikhail S. Ivanov Alexey N. Kudryavtsev Yevgeny A. Bondar 《Shock Waves》2009,19(4):307-316
Numerical simulations of shock wave propagation in microchannels and microtubes (viscous shock tube problem) have been performed
using three different approaches: the Navier–Stokes equations with the velocity slip and temperature jump boundary conditions,
the statistical Direct Simulation Monte Carlo method for the Boltzmann equation, and the model kinetic Bhatnagar–Gross–Krook
equation with the Shakhov equilibrium distribution function. Effects of flow rarefaction and dissipation are investigated
and the results obtained with different approaches are compared. A parametric study of the problem for different Knudsen numbers
and initial shock strengths is carried out using the Navier–Stokes computations.
相似文献
8.
A multi-dimensional mathematical thermal model of the oil-fired furnace has been developed. Radiation calculation of this
model is based on the Hottel's zone method incorporating with the statistical Monte Carlo method to determine the total exchange
areas. The whole furnace is divided into 4 gaseous zones and 18 surface zones. The Monte Carlo method integrated with the
least square smoothing technique considering both conservation and reciprocity is used to evaluate the total exchange areas,
i.e. surface–surface, surface–gas, gas–gas and gas–surface, directly for both the absorbing and emitting media. A better accuracy
is achieved in the determination of the total exchange areas by using the proposed smoothing Monte Carlo method.
Received on 10 April 2000 相似文献
9.
R. A. Abirov 《Journal of Applied Mechanics and Technical Physics》2009,50(1):107-111
A model of plasticity for a transversely isotropic material with allowance for complex loading is developed, based on results
of experiments with homogeneous cylindrical specimens of isotropic materials. An empirical model of plasticity for isotropic
metals is constructed with allowance for vector properties of the material. The model is extended to a particular case of
anisotropy.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 1, pp. 128–133, January–February, 2009. 相似文献
10.
This article describes a semi-analytical model for two-phase immiscible flow in porous media. The model incorporates the effect
of capillary pressure gradient on fluid displacement. It also includes a correction to the capillarity-free Buckley–Leverett
saturation profile for the stabilized-zone around the displacement front and the end-effects near the core outlet. The model
is valid for both drainage and imbibition oil–water displacements in porous media with different wettability conditions. A
stepwise procedure is presented to derive relative permeabilities from coreflood displacements using the proposed semi-analytical
model. The procedure can be utilized for both before and after breakthrough data and hence is capable to generate a continuous
relative permeability curve unlike other analytical/semi-analytical approaches. The model predictions are compared with numerical
simulations and laboratory experiments. The comparison shows that the model predictions for drainage process agree well with
the numerical simulations for different capillary numbers, whereas there is mismatch between the relative permeability derived
using the Johnson–Bossler–Naumann (JBN) method and the simulations. The coreflood experiments carried out on a Berea sandstone
core suggest that the proposed model works better than the JBN method for a drainage process in strongly wet rocks. Both methods
give similar results for imbibition processes. 相似文献
11.
V. A. Vinnikov V. L. Shkuratnik 《Journal of Applied Mechanics and Technical Physics》2008,49(2):301-305
A model for the thermal emission memory effect in rocks under cyclic heating with the temperature amplitude increasing from
cycle to cycle is validated. The model is used to consider one of the possible mechanisms of the effect related to the temperature
gradient on the faces of cracks dividing structural elements of a geomaterial.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 172–177, March–April, 2008. 相似文献
12.
Raffaella Rizzoni 《Continuum Mechanics and Thermodynamics》2011,23(4):319-335
The theory of thin wires developed in Dret and Meunier (Comptes Rendus de l’Académie des Sciences. Série I. Mathématique 337:143–147,
2003) is adapted to phase-transforming materials with large elastic moduli in the sense discussed in James and Rizzoni (J Elast
59:399–436, 2000). The result is a one-dimensional constitutive model for shape memory wires, characterized by a small number of material
constants. The model is used to analyze self-accommodated and detwinned microstructures and to study superelasticity. It also
turns out that the model successfully reproduces the behavior of shape memory wires in experiments of restrained recovery
(Tsoi et al. in Mater Sci Eng A 368:299–310, 2004; Tsoi in 50:3535–3544, 2002; S̆ittner et al. in Mater Sci Eng A 286:298–311, 2000; vokoun in Smart Mater Struct 12:680–685, 2003; Zheng and Cui in Intermetallics 12:1305–1309, 2004; Zheng et al. in J Mater Sci Technol 20(4):390–394, 2004). In particular, the model is able to predict the shift to higher transformation temperatures on heating. The model also
captures the effect of prestraining on the evolution of the recovery stress and of the martensite volume fraction. 相似文献
13.
A non-linear relationship of the Reynolds stresses in function of the strain rate and vorticity tensors, with terms up to
third order, is developed. Anisotropies in the normal stresses, influence from streamline curvature or rotation of the reference
frame, and swirl effects are accounted for. The relationship is linked to ak–ε model with a modified transport equation for the dissipation rate. A new low-Reynolds source term is introduced and a model
parameter is written in terms of dimensionless rate-of-strain and vorticity. The model is checked on different realizability
constraints. It is shown that practically all constraints are fulfilled. The model is numerically tested on a fully developed
channel and pipe flow, both stationary and rotating. The plane jet–round jet anomaly is addressed. Finally, the model is applied
to the flow over a backward-facing step. Results are compared with a linear low-Reynolds k–ε model and the shear stress transport model.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
V. Yu. Liapidevskii 《Journal of Applied Mechanics and Technical Physics》1999,40(2):238-248
A mathematical model for the propagation of nonlinear long waves is constructed with allowance for nonhydrostatic pressure
distribution and the development of a surface boundary layer due to wave breaking. The problem of the structure of a bore
in a homogeneous liquid is solved. In particular, the transition of a wave bore to a turbulent bore as its amplitude increases
is described within a single model.
Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 2, pp. 56–68, March–April, 1999. 相似文献
15.
A new general constitutive model in terms of the principal stretches is proposed to reflect limiting chain extensibility resulting
in severe strain-stiffening for incompressible, isotropic, homogeneous elastic materials. The strain-energy density involves
the logarithm function and has the general Valanis–Landel form. For specific functions in the Valanis–Landel representation,
we obtain particular strain-energies, some of which have been proposed in the recent literature. The stress–stretch response
in some basic homogeneous deformations is described for these particular strain-energy densities. It is shown that the stress
response in these deformations is similar to that predicted by the Gent model involving the first invariant of the Cauchy–Green
tensor. The models discussed here depend on both the first and second invariants.
相似文献
16.
We prove the global existence of solutions for a shape-memory alloys constitutive model at finite strains. The model has been
presented in Evangelista et al. (Int J Numer Methods Eng 81(6):761–785, 2010) and corresponds to a suitable finite-strain version of the celebrated Souza–Auricchio model for SMAs (Auricchio and Petrini
in Int J Numer Methods Eng 55:1255–1284, 2002; Souza et al. in J Mech A Solids 17:789–806, 1998). We reformulate the model in purely variational fashion under the form of a rate-independent process. Existence of suitably
weak (energetic) solutions to the model is obtained by passing to the limit within a constructive time-discretization procedure. 相似文献
17.
A turbulent wake model, based on the Reynolds, energy and turbulence dissipation equations together with the closing relations
for the turbulent transport coefficients, is proposed. A comparative investigation of swirled momentumless wakes with zero
and nonzero angular momentum is carried out.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 13–22, January–February,
1994. 相似文献
18.
Yu. N. Voroshilova M. A. Rydalevskaya 《Journal of Applied Mechanics and Technical Physics》2008,49(3):369-374
A formula for the velocity of sound, which is valid not only for barotropic gases, is derived on the basis of methods of the
kinetic theory of gases. This formula is specified for various stages of relaxation of a high-temperature diatomic gas in
the approximation of the model of anharmonic oscillators. A dependence between the populations of vibrational levels of molecules
and the velocity of sound is found.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 28–34, May–June, 2008. 相似文献
19.
Based on a seven-degree-of-freedom shear deformable beam model, a geometrical nonlinear analysis of thin-walled composite
beams with arbitrary lay-ups under various types of loads is presented. This model accounts for all the structural coupling
coming from both material anisotropy and geometric nonlinearity. The general nonlinear governing equations are derived and
solved by means of an incremental Newton–Raphson method. A displacement-based one-dimensional finite element model that accounts
for the geometric nonlinearity in the von Kármán sense is developed to solve the problem. Numerical results are obtained for
thin-walled composite beam under vertical load to investigate the effects of fiber orientation, geometric nonlinearity, and
shear deformation on the axial–flexural–torsional response. 相似文献
20.
We show that the Reissner–Mindlin plate bending model has a wider range of applicability than the Kirchhoff–Love model for
the approximation of clamped linearly elastic plates. Under the assumption that the body force density is constant in the
transverse direction, the Reissner–Mindlin model solution converges to the three-dimensional linear elasticity solution in
the relative energy norm for the full range of surface loads. However, for loads with a significant transverse shear effect,
the Kirchhoff–Love model fails.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献