Zai You Yan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.46, No.1, pp. 1-20, 2009, DOI:10.3970/cmes.2009.046.001

Abstract It is well-known that the velocity potential and its first normal derivative on the structure surface can be easily found in the boundary element method for problems of potential flow. Based on an investigation in progress, the gradient of the normal derivative of the velocity potential will be very helpful in the treatment of the so-called hypersingular integral. Through a coordinate transformation, such gradient can be expressed by the combination of the first and the second normal derivatives of the velocity potential. Then one interesting problem is how to find the second normal derivative of 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, 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 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 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 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 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. 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 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,… More >

Shueei-Muh Lin¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.1, pp. 105-124, 2009, DOI:10.3970/cmes.2009.052.105

Abstract In this study, the mathematical model of a non-constant rotating beam is established. It is an in-plane moving mass problem. Due to the effect of non-constant rotation, this model is composed of a governing differential equation with time-dependent coefficients and forcing term and three homogenous boundary conditions and one non-homogeneous boundary condition with time-dependent coefficients and forcing term. It is basically different to the system with constant rotation speed [Lin, 2008] and the linear moving beam system [Lin, 2009]. Obviously, a moving mass problem with time-dependent coefficients and forcing term is very complicated. A new… More >