H.B. Chen¹, Masa. Tanaka²

CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 19-42, 2010, DOI:10.3970/cmes.2010.069.019

Abstract Highly accurate calculation of derivative values to the field variable is a key issue in numerical analysis of engineering problems. The boundary integral equations (BIEs) of potential second derivatives are of third order singularities and obviously the direct calculation of these high order singular integrals is rather cumbersome. The idea of the present paper is to use an indirect algorithm which is based on the regularized BIE formulations of the potential second derivatives, following the work of the present first author and his coworkers. The regularized formulations, numerical strategies and example tests are given for both potential first and second… 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 >

Frederic L. Pellet¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 279-296, 2009, DOI:10.3970/cmes.2009.052.279

Abstract In this study, the contact and interaction between a tunnel lining support and a damage-susceptible viscoplastic medium is investigated. First, back-analysis of the time-dependent behaviour of a drift excavated across a carboniferous rock mass which exhibited large delayed displacements was undertaken. Drift closure was simulated using an elasto-viscoplastic constitutive model that included the strength degradation process. This 3D numerical simulation was performed taking into account both stage construction sequence and rate of excavation advancement. A comparison of the numerical results with the data measured on site allowed for the calibration of the model parameters. Subsequently, the installation of a concrete… More >

A.P.S.Selvadurai¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 259-278, 2009, DOI:10.3970/cmes.2009.052.259

Abstract The paper deals with a computational approach for modelling the fragmentation of ice sheets during their impact with stationary structures. The modelling takes into consideration the intact continuum behaviour of the ice as a rate-sensitive elastoplastic material. During impact, the ice sheet can undergo fragmentation, which is controlled by a brittle strength criterion based on the current stress state. The fragmentation allows the generation of discrete elements of the ice sheet, the movements of which are governed by the equations of motion. The contact between individual fragments is governed by a Coulomb criterion. The individual fragments can themselves undergo further… More >

S. Turrin¹, M. Hanss¹, A.P.S. Selvadurai²

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 237-258, 2009, DOI:10.3970/cmes.2009.052.237

Abstract Despite the continuing advances in rockfall analysis, the mathematical modeling and simulation of rockfall phenomena continues to be significantly influenced by a large amount of aleatory and epistemic uncertainty on significant number of model parameters. This paper focuses on the representation and quantification of epistemic uncertainties in rockfall modeling and simulation by fuzzy numbers. The propagation of the epistemic uncertainties considered is then calculated by the transformation method as a practical implementation of fuzzy arithmetic. Epistemic uncertainties on the material properties, on the boulder geometry and dimensions, on the kinematics of the impact and on the contact response between boulder… More >

A. Ferrari¹, L. Laloui^1,2, Ch. Bonnard^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 217-236, 2009, DOI:10.3970/cmes.2009.052.217

Abstract A coupled hydro-mechanical formulation is presented for the analysis of landslide motion during crisis episodes. The mathematical formulation is used to model a natural slope affected by a multiple slip surface failure mechanism, in which pore water pressure evolution was identified as the main cause for movement accelerations. An elasto-plastic constitutive model is adopted for the behaviour of slip surfaces. Material parameters are obtained by combining the available laboratory tests and the back analysis of some crisis episodes. After being calibrated and validated, the model is applied to improve the understanding of the physical processes involved and to predict the… More >

Anil Misra¹, Shiping Huang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 197-216, 2009, DOI:10.3970/cmes.2009.052.197

Abstract The behavior of contact between solid bodies with rough surfaces under combined normal and shear loading remains a problem of interest in many areas of engineering. In this paper, we have utilized a micromechanical methodology to derive an expression of stress-displacement relationship applicable to combined normal and shear loading conditions. The micromechanical methodology considers the mechanics of asperity contacts and the interface roughness in terms of asperity height and asperity contact orientation distribution. A numerical procedure is implemented to evaluate the derived expressions under complex and mixed loading conditions using an incremental approach. We find that the proposed numerical procedure… More >

F. Fleissner¹, T. Haag², M. Hanss², P. Eberhard¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 181-196, 2009, DOI:10.3970/cmes.2009.052.181

Abstract In alpine regions human settlements and infrastructure are at risk to be hit by landslides or other types of geological flows. This paper presents a new approach that can aid the design of protective constructions. An uncertainty analysis of the flow around a debris barrier is carried out using a chute flow laboratory model of the actual debris flow. A series of discrete element simulations thereby serves to compare and assess two different barrier designs. In this study, the transformation method of fuzzy arithmetic is used to investigate the influence of epistemically uncertain model parameters. It turns out that parameter… More >

H. T. Xiao¹, Z. Q. Yue²

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 159-180, 2009, DOI:10.3970/cmes.2009.052.159

Abstract This paper presents a three-dimensional boundary element method for contact problems of an elastic indenter on the surface of functionally graded materials (FGMs). The FGM elastic properties can have any irregular variations with depth. The indenter is subjected to the loading normal to the flat contact surface. The classical Kelvin solution is used for the mathematical formulation of the homogeneous elastic indenter. The generalized Kelvin solution is used for the mathematical formulation of the FGM base. The contact variables are defined with respect to each of the surfaces using local coordinate systems. The corresponding contact equations are used to couple… More >

Peter J. Ireman, Anders Klarbring¹, Niclas Strömberg

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 125-158, 2009, DOI:10.3970/cmes.2009.052.125

Abstract In this paper finite element approaches for fretting fatigue are proposed on the basis of a non-local model of continuum damage coupled to friction and wear. The model is formulated in the frame-work of a standard material. In a previous paper this was done in the spirit of Maugin, where an extra entropy flux is introduced in the second law in order to include the gradient of the internal variable in a proper manner. In this paper we follow instead the ideas of Frémond and others, where this extra entropy flux is no longer needed, but instead new non-classical balance… More >