Marcin Maździarz¹, Marcin Gajewski²

CMES-Computer Modeling in Engineering & Sciences, Vol.105, No.2, pp. 123-150, 2015, DOI:10.3970/cmes.2015.105.123

Abstract In this paper, the choice and parametrisation of finite deformation polyconvex isotropic hyperelastic models to describe the behaviour of a class of defect-free monocrystalline metal materials at the molecular level is examined. The article discusses some physical, mathematical and numerical demands which in our opinion should be fulfilled by elasticity models to be useful. A set of molecular numerical tests for aluminium and tungsten providing data for the fitting of a hyperelastic model was performed, and an algorithm for parametrisation is discussed. The proposed models with optimised parameters are superior to those used in non-linear mechanics of crystals. More >

Yonghua Zhou¹, Xun Yang¹, Chao Mi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.6, pp. 497-512, 2012, DOI:10.3970/cmes.2012.089.497

Abstract The movements of vehicles equipped with various positioning systems such as global and wireless positioning ones have provided beneficial channels to acquire abundant traffic flow information for total road network. However, not all vehicles are mounted with positioning systems and not all equipped positioning facilities are always active. This paper will address how to estimate the number and the states of unequipped vehicles through a series of observations on equipped ones. The proposed estimation process initiates employing the non-analytical microscopic traffic model for particle filter to estimate the number, positions and speeds of unequipped vehicles between an equipped one and… More >

Lior Banai

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.5, pp. 351-366, 2012, DOI:10.3970/cmes.2012.088.351

Abstract The explosive Engineering field is a costly one in which not every organization can effort the time and money it takes to performed field tests on its explosives. The purpose of this article is to present a program that was developed in the Israeli Navy for performance estimations and safety issues of warheads and explosives. With a relative small developing time one can create a tool that gives preliminary results in a few minutes without the need to design and order a field tests or run finite elements analyses. By implementing a few known models, in this tool, the user… More >

F. S. Lobato¹, V. Steffen Jr², A. J. Silva Neto³

CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 1-18, 2010, DOI:10.3970/cmes.2010.069.001

Abstract Differential Evolution Algorithm (DE) has shown to be a powerful evolutionary algorithm for global optimization in a variety of real world problems. DE differs from other evolutionary algorithms in the mutation and recombination phases. Unlike some other meta-heuristic techniques such as genetic algorithms and evolutionary strategies, where perturbation occurs in accordance with a random quantity, DE uses weighted differences between solution vectors to perturb the population. Although the efficiency of DE algorithm has been proven in the literature, studies indicate that the efficiency of the DE methods is sensitive to its control parameters (perturbation rate and crossover rate) and there… More >

Kuo-Ning Chiang¹, Chan-Yen Chou², Chung-Jung Wu²,Chao-Jen Huang², Ming-Chih Yew²

CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.1, pp. 85-96, 2008, DOI:10.3970/cmes.2008.037.085

Abstract An atomic-level analytical solution, together with a modified Morse potential, has been developed to estimate temperature-dependent thermal expansion coefficients (CTE) and elastic characteristics of bulk metals. In this study, inter-atomic forces are considered as a set of anharmonic oscillator networks which can be described by Morse potential, while the material properties can be defined by these inter-atomic forces; when temperature increases, the vibration of the anharmonic oscillator causes the phenomenon of temperature-dependent material properties. The results of analysis showed that the original Morse potential can give a reasonable prediction of the thermal expansion coefficients and elastic constants of metals at… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.2, pp. 69-86, 2006, DOI:10.3970/cmes.2006.015.069

Abstract In this paper we will study the numerical integrations of second order boundary value problems under the imposed conditions at t=0 and t=T in a general setting. We can construct a compact space shooting method for finding the unknown initial conditions. The key point is based on the construction of a one-step Lie group element G(u₀,u_T) and the establishment of a mid-point Lie group element G(r). Then, by imposing G(u₀,u_T) = G(r) we can search the missing initial conditions through an iterative solution of the weighting factor r ∈ (0,1). Numerical examples were examined to convince that the new approach… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.2, pp. 77-90, 2006, DOI:10.3970/cmes.2006.014.077

Abstract In this paper we derive the first-order and second-order one-step GPS applied to the estimation of thermophysical properties. Solving the resultant algebraic equations, which usually converges within ten iterations, it is not difficult to estimate the unknown temperature-dependent thermal conductivity and heat capacity simultaneously, if some supplemented data of measured temperature at a time T is provided. When the measured temperature in the conducting slab is contaminated by noise, our estimated results are also good. The new method does not require any prior information on the functional forms of thermal conductivity and heat capacity. Numerical examples are examined to show… More >

C. J. Reddy¹

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.5, pp. 455-462, 2004, DOI:10.3970/cmes.2004.005.455

Abstract This paper presents an efficient algorithm to evaluate multi-spectral and multi-angular monostatic radar cross section (RCS) of large objects with very fine increments. The technique is based on the combination of Model Based Parameter Estimation (MBPE) method with hybrid frequency domain formulations. A general approach to formulation of MBPE is presented along with a similar approach called the Asymptotic Waveform Evaluation (AWE). Various numerical examples are presented for multi-spectral response calculations using method of moments (MoM) and the hybrid Finite Element-MoM technique in conjunction with MBPE. Example application of MBPE for hybrid MoM-Physical Optics approach for multi-angular calculations is also… More >

V.A. Buryachenko^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.85, No.5, pp. 417-446, 2012, DOI:10.3970/cmes.2012.085.417

Abstract We consider a linearly elastic composite medium, which consists of a homogeneous matrix containing a statistically homogeneous set of multimodal spherical inclusions modeling the morphology of heterogeneous solid propellants (HSP). Estimates of effective elastic moduli are performed using the multiparticle effective field method (MEFM) directly taking into account the interaction of different inclusions. Because of this, the effective elastic moduli of the HSP evaluated by the MEFM are sensitive to both the relative size of the inclusions (i.e., their multimodal nature) and the radial distribution functions (RDFs) estimated from experimental data, as well as from the ensembles generated by the… More >

F. Guarracino ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.3, pp. 167-184, 2011, DOI:10.3970/cmes.2011.072.167

Abstract The design of many engineering problems requires accurate test results and interpretation in order to evaluate the carrying capacity of circular cylindrical shells subjected to various loads including bending. Apparently anomalous values of axial tensile and compressive strains from recent test results have been lately investigated and explained using Finite Element modeling. As a complement to numerical analyses, in the present paper a simple analytical formula for the estimation of the effects of local conditions in tubes testing and design is provided on the basis of an extended Ritz's approach and of the general linear theory of shells. The findings… More >