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 >

Y.F. Nie^1,2, S.N. Atluri², C.W. Zuo¹

CMES-Computer Modeling in Engineering & Sciences, Vol.12, No.2, pp. 137-148, 2006, DOI:10.3970/cmes.2006.012.137

Abstract Owing to the meshless and local characteristics, moving least squares (MLS) methods have been used extensively to approximate the unknown function of partial differential equation initial boundary value problem. In this paper, based on matrix analysis, a sufficient and necessary condition for the existence of inverse of coefficient matrix used in MLS methods is developed firstly. Then in the light of approximate theory, a practical mathematics model is posed to obtain the optimal radius of support of radial weights used in MLS methods. As an example, while uniform distributed particles and the 4^th order spline weight function are adopted in… More >

Zhen Luo^1,2, Nong Zhang^1,3, Yu Wang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.1, pp. 73-96, 2012, DOI:10.3970/cmes.2012.083.073

Abstract This paper aims to present a physically meaningful level set method for shape and topology optimization of structures. Compared to the conventional level set method which represents the design boundary as the zero level set, in this study the boundary is embedded into non-zero constant level sets of the level set function, to implicitly implement shape fidelity and topology changes in time via the propagation of the discrete level set function. A point-wise nodal density field, non-negative and value-bounded, is used to parameterize the level set function via the compactly supported radial basis functions (CSRBFs) at a uniformly defined set… More >

Zhen Yang¹, Xingsheng Gu², Xiaoyi Liang^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 161-182, 2011, DOI:10.3970/cmes.2011.074.161

Abstract Mesoporous carbons are synthesized by organic-organic self-assembly of triblock copolymer F127 and a new type of carbon precursor as resorcinol-furfural oligomers. Some factors will impact the mesoporous carbons pore structure and properties were studied. The main factors, such as the ratio of triblock copolymer F127 and oligomers, degree of polymerizstry of resorcinol-furfural oligomers, the ratio of resorcinol-furfural oligomers - F/R, and their mutual relations were identified. Aimed at balancing the complex characteristic of mesoporous structure and adsorption properties, a classification and optimization model based on support vector machine is developed. The optimal operation conditions of Barret-Joyner-Halenda (BJH) adsorption cumulative volume… More >

Shuncai Li^1,2,3, Zhengzhu Dong², Dan Ma²

CMES-Computer Modeling in Engineering & Sciences, Vol.71, No.2, pp. 93-110, 2011, DOI:10.3970/cmes.2011.071.093

Abstract Weak local support is a very common phenomenon in roadway support engineering. It is a problem that needs to be studied thoroughly at the theoretical level. So far, the literature on stress field theory of rock surrounding a roadway is largely restricted to analytical solutions of stress for roadways with a uniform support or no support at all. The corresponding stress solution under conditions of local or weak local support has not been provided. Based on a mechanical model of weak local support at the boundary of a circular roadway and the boundary element method on boundary value problems of… More >

S. Tangaramvong, F. Tin-Loi

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.3, pp. 269-296, 2009, DOI:10.3970/cmes.2009.049.269

Abstract We consider the optimal synthesis, namely minimum weight design, of rigid perfectly-plastic structures for which some supports involve unilateral frictional contact. This problem is of interest as it is not only encountered in practice but it also involves, in the general friction case, a nonassociative complementarity condition that makes it theoretically and numerically challenging. For simplicity of exposition, we focus on the class of bar structures for which yielding is governed by either pure bending or by combined axial and flexural forces. In view of possible multiplicity of solutions due to nonassociativity, a direct optimization formulation may lead to an… More >

G. C. Bourantas¹, E. D. Skouras^2,3,4, G. C. Nikiforidis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.43, No.1, pp. 1-26, 2009, DOI:10.3970/cmes.2009.043.001

Abstract The extent of application of meshfree methods based on point collocation (PC) techniques with adaptive support domain for strong form Partial Differential Equations (PDE) is investigated. The basis functions are constructed using the Moving Least Square (MLS) approximation. The weak-form description of PDEs is used in most MLS methods to circumvent problems related to the increased level of resolution necessary near natural (Neumann) boundary conditions (BCs), dislocations, or regions of steep gradients. Alternatively, one can adopt Radial Basis Function (RBF) approximation on the strong-form of PDEs using meshless PC methods, due to the delta function behavior (exact solution on nodes).… More >

C. Zheng¹, S. C. Wu^2,3,4, X.H.Tang¹, J. H. Zhang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.38, No.2, pp. 149-178, 2008, DOI:10.3970/cmes.2008.038.149

Abstract A novel meshfree poly-cell Galerkin method is developed for problems of elasticity and fracture. To improve accuracy, a poly-cell support is proposed to ensure the alignment of shape function support and the integration domain. By orthonormalizing basis functions, the improved moving least-square is formulated soundly, in which frequent matrix inversions are avoided. The Nitsche's method is introduced to treat the essential boundary conditions. It is found that computed solutions are more accurate than those obtained using the circle support used in standard MLS. Furthermore, numerical results present the superconvergent property, compared with the theoretical values in both displacement and energy… More >

C. P. Providakis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.3, pp. 247-258, 2007, DOI:10.3970/cmes.2007.018.247

Abstract The method of Domain/Boundary Element is used to achieve a dynamic analysis of elastoplastic thick plates resting on internal supports. All possible boundary conditions on the edge of the plate with any interior support conditions such as isolated points (column), lines (walls) or regions (patches) can be treated without practical difficulties. The formulation presented includes the effects of shear deformation and rotatory inertia following Reissner-Mindlin's deformation theory assumptions. The method employs the elastostatic fundamental solution of the problem resulting in both boundary and domain integrals due to inertia, plasticity and interior support effect terms. By discretizing the integral equations and… More >

B. F. Romanowicz¹, M. H. Zaman¹, S. F. Bart¹, V. L. Rabinovich¹, I. Tchertkov¹, S. Zhang¹, M. G. da Silva¹, M. Deshpande¹, K. Greiner¹, J. R. Gilbert¹, Shawn Cunningham²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 45-64, 2000, DOI:10.3970/cmes.2000.001.045

Abstract Development of micro-electro-mechanical systems (MEMS) products is currently hampered by the need for design aids, which can assist in integration of all domains of the design. The cross-disciplinary character of microsystems requires a top-down approach to system design which, in turn, requires designers from many areas to work together in order to understand the effects of one sub-system on another. This paper describes current research on a methodology and tool-set which directly support such an integrated design process. More >