T. Nishioka¹, F. Stan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.1, pp. 119-140, 2003, DOI:10.3970/cmes.2003.004.119

Abstract In this paper we investigate the essentially unexplored area of three-dimensional dynamic fracture mechanics. The general objective sought by this investigation is the understanding of three-dimensional dynamic crack propagation and arrest, and, specifically, the effect that the specimen thickness has on the dynamic fracture mechanism. In particular, in the context of the present paper, it is intended to provide a summary of the achievements on the issue of three-dimensional dynamic fracture parameters. Furthermore, the behavior of the three-dimensional field near the crack front is investigated. The issue that will be addressed is the extent of More >

Jian Chen¹, Huang Yuan², Folker H. Wittmann³

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 743-754, 2002, DOI:10.3970/cmes.2002.003.743

Abstract Experimental observation confirms that micro-hardness of metallic materials depends significantly on the indentation depth. In the present paper we discuss simulations of micro-indentation tests based on the gradient plasticity model using the finite element method. The role of intrinsic material length parameters in the gradient plasticity model is investigated. The computational results confirm that the gradient plasticity model is suitable to simulate micro-indentation tests and predicts the depth-dependent hardness in micro- and nano-indentations. Variations of micro-hardness is correlated with the intrinsic material length parameters. More >

J. Choi¹, M.D. Bryant²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 431-446, 2002, DOI:10.3970/cmes.2002.003.431

Abstract This paper presents an updated bond graph model of a gearbox, which now includes bending of shafts. The gearbox system has an input shaft, layshaft, output shaft, spur gears, bearings, and housing. The bond graph model integrates separate sub-models into a composite model. Sub-modules include tooth-to-tooth contact, rotor dynamics of shafts, global dynamics of the gearbox housing structure, and shaft bending modeled by finite element modeling. The tooth-to-tooth model includes tooth bending; shaft torsion; gear inertia; conversion of gear torque into tooth forces; tooth contact mechanics; and multiple tooth contact. To analyze shaft dynamics more More >

T. Nishioka¹, J. Furutuka¹, S. Tchouikov¹, T. Fujimoto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 129-146, 2002, DOI:10.3970/cmes.2002.003.129

Abstract The governing condition of dynamic crack bifurcation phenomena had not been fully elucidated until our recent experimental studies. We found from the experimental results that the energy flux per unit time into a propagating crack tip or into a fracture process zone governs the crack bifurcation. Regarding the numerical simulation of dynamic crack bifurcation, to the authors' knowledge, no accurate simulations have been carried out, due to several unresolved difficulties. In order to overcome the difficulties, for the analysis of dynamic crack bifurcation, we developed a moving finite element method based on Delaunay automatic triangulation. More >

Chyou-Chi Chien, Tong-Yue Wu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.2, pp. 213-226, 2001, DOI:10.3970/cmes.2001.002.213

Abstract This study presents a novel computational method for implementing the time finite element formulation for the equations of linear structural dynamics. The proposed method adopts the time-discontinuous Galerkin method, in which both the displacement and velocity variables are represented independently by second-order interpolation functions in the time domain. The solution algorithm derived utilizes a predictor/multi-corrector technique that can effectively obtain the solutions for the resulting system of coupled equations. The numerical implementation of the time-discontinuous Galerkin finite element method is verified through several benchmark problems. Numerical results are compared with exact and accepted solutions from More >

S. Rugonyi, K. J. Bathe¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.2, pp. 195-212, 2001, DOI:10.3970/cmes.2001.002.195

Abstract The solution of fluid flows, modeled using the Navier-Stokes or Euler equations, fully coupled with structures/solids is considered. Simultaneous and partitioned solution procedures, used in the solution of the coupled equations, are briefly discussed, and advantages and disadvantages of their use are mentioned. In addition, a simplified stability analysis of the interface equations is presented, and unconditional stability for certain choices of time integration schemes is shown. Furthermore, the long-term dynamic stability of fluid-structure interaction systems is assessed by the use of Lyapunov characteristic exponents, which allow differentiating between a chaotic and a regular system More >

C.P . Providakis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 123-130, 2000, DOI:10.3970/cmes.2000.001.425

Abstract Boundary and Finite Element methodologies for the determination of the inelastic response of thick plates resting on Winkler-type elastic foundations are compared and critically discussed. For comparison reasons the domain/boundary element and the finite element methodology use isoparametric elements of the same accuracy level. After a discretizaton of the integral equations of motion in both methodologies an efficient step-by-step time integration algorithm is used to solve the resulting matrix equations. Comparison studies are shown for impacted elastoplastic thick plates with smooth boundaries and supported on different Winkler-type foundations. The numerical results reveal that boundary element More >

N. D. Ngo, K. K. Tamma¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 57-72, 2000, DOI:10.3970/cmes.2000.001.359

Abstract In the process modeling via Resin Transfer Molding (RTM) for thick composite sections, multi-layer preforms with varying thermophysical characteristics across the different layers, or for geometrically complex mold geometries with varying thicknesses, the assumption of a thin shell-like geometry is no longer valid. The flow in the through thickness direction is no longer negligible and current practices of treating the continuously moving flow front as two-dimensional and the temperature and cure as three-dimensional are not representative of the underlying physics. In view of these considerations, in the present study, the focus is on the non-isothermal… More >

H. Okumura¹, M. Kawahara¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 71-78, 2000, DOI:10.3970/cmes.2000.001.231

Abstract This paper presents a new approach to a shape optimization problem of a body located in the unsteady incompressible viscous flow field based on an optimal control theory. The optimal state is defined by the reduction of drag and lift forces subjected to the body. The state equation used is the transient incompressible Navier--Stokes equations. The shape optimization problem can be formulated to find out geometrical coordinates of the body to minimize the performance function that is defined to evaluate forces subjected to the body. The fractional step method with the implicit temporal integration and More >

K. Kaminishi¹, M. Iino², H. Bessho², M. Taneda³

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 107-110, 2000, DOI:10.3970/cmes.2000.001.107

Abstract An FEA (finite element analysis) program employing a new scheme for crack growth analysis is developed and a prediction method for crack growth life is proposed. The FEA program consists of the subroutines for the automatic element re-generation using the Delaunay Triangulation technique, the element configuration in the near-tip region being provided by a super-element, elasto-inelastic stress analyses, prediction of crack extension path and calculation of fatigue life. The FEA results show that crack extension rate and path are controlled by a maximum opening stress range, Δσ_θmax, at a small radial distance of r = d, where More >