Sanjay Mittal¹, Anubhav Dwivedi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.113, No.2, pp. 219-237, 2017, DOI:10.3970/cmes.2017.113.229

Abstract Linear Stability Analysis (LSA) of parallel shear flows, v ia local and global approaches, is presented. The local analysis is carried out by solving the Orr-Sommerfeld (OS) equation using a spectral-collocation method based on Chebyshev polynomials. A stabilized finite element formulation is employed to carry out the global analysis using the linearized disturbance equations in primitive variables. The local and global analysis are compared. As per the Squires theorem, the two-dimensional disturbance has the largest growth rate. Therefore, only two-dimensional disturbances are considered. By its very nature, the local analysis assumes the disturbance field to be spatially periodic in the… More >

T. V. Viknesh¹, V. Manik,an

CMES-Computer Modeling in Engineering & Sciences, Vol.113, No.1, pp. 109-116, 2017, DOI:10.3970/cmes.2017.113.107

Abstract The working of Canonical switching cell (CSC) converter was studied and its equivalent circuit during ON and OFF states were obtained. State space model of CSC converter in ON and OFF states were developed using the Kirchhoff laws. The state space matrices were used to construct the transfer functions of ON & OFF states. The step response of the converter was simulated using MATLAB. The step response curve was obtained using different values of circuit components (L, C1, C2 and RL)and optimized. The characteristic parameters such as rise time, overshoot, settling time, steady state error and stability were determined using… More >

Li Bin^1,2,3, Fang Hongyuan^1,2,3,*, He Wei⁴, Sun Bin¹

CMES-Computer Modeling in Engineering & Sciences, Vol.113, No.1, pp. 57-69, 2017, DOI:10.3970/cmes.2017.113.054

Abstract The cutter head will be stuck when the shield machine pass through the area existing anchor left by foundation construction of surrounding high-rise building. Subsurface excavation method is an efficient way to remove the existed anchor. In this paper, a three-dimensional finite element model is developed to study stability of cross-channel excavation. The time-spatial effects of arch crown settlement, intrados uplift and side wall horizontal convergence are analyzed according to different excavation size, lining thickness and lining order. The results show that the excavation size is the main factor to control the deformation of the surrounding soil, especially in arch… More >

Di Wu¹, Wei Gao^1,2, Chongmin Song¹, Zhen Luo³

CMES-Computer Modeling in Engineering & Sciences, Vol.108, No.5, pp. 331-373, 2015, DOI:10.3970/cmes.2015.108.331

Abstract Two novel mathematical programming approaches are proposed to separately assess non-deterministic behaviour and stability of engineering structures against disparate uncertainties. Within the proposed computational schemes, uncertainties attributed by the material properties, loading regimes, as well as environmental influences are simultaneously incorporated and modelled by the interval approach. The proposed mathematical programming approaches proficiently transform the uncertain structural analyses into deterministic mathematical programs. Two essential aspects of structural analysis, namely linear structural behaviour and bifurcation buckling, have been explicitly investigated. Diverse verifications have been implemented to justify the accuracy and computational efficiency of the proposed approaches through practically motivated numerical examples. More >

Delfim Soares Jr.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.3, pp. 223-247, 2015, DOI:10.3970/cmes.2015.107.223

Abstract In this work, an explicit time marching procedure, with solution-adaptive time integration parameters, is introduced for the analysis of hyperbolic models. The proposed technique is conditionally-stable, second-order accurate and it has controllable algorithm dissipation, which locally adapts at each time step, according to the computed solution. Thus, spurious modes can be more effectively dissipated and accuracy is improved. Since this is an explicit time integration technique, the new procedure is very efficient, requiring no system of equations to be dealt with at each time-step. Moreover, the technique is simple and easy to implement, being based just on displacement-velocity relations, requiring… More >

Marcin Kamiński², Jacek Szafran³

CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.1, pp. 27-57, 2015, DOI:10.3970/cmes.2015.107.027

Abstract Basic probabilistic characteristics and reliability indices of critical forces for high steel skeletal towers are numerically modeled by using the Stochastic, perturbation-based Finite Element Method. It is implemented together with the Weighted Least Squares Method and compared with the Monte-Carlo simulation as well as with the semi-analytical Probabilistic FEM. The Finite Element Method solution to the stability problem for a full 3D model of a tower accounts for both first and second order effects known from the engineering codes as the so-called P-delta effect. Two different Gaussian input random variables are adopted here – Young modulus of steel as well… More >

Delfim Soares Jr.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.105, No.5, pp. 341-360, 2015, DOI:10.3970/cmes.2015.105.341

Abstract In this work, a second-order time-marching procedure for dynamics is discussed, in which enhanced accuracy is enabled. The new technique is unconditionally stable (according to its parameter selection), it has no amplitude decay or overshooting, and it provides reduced period elongation errors. The method is based on displacement-velocity relations, requiring no computation of accelerations. It is efficient, simple and very easy to implement. Numerical results are presented along the paper, illustrating the good performance of the proposed technique. As it is described here, the new method has no drawbacks when compared to the Trapezoidal Rule (TR), which is one of… More >

Letícia Fleck Fadel Miguel¹, Leandro Fleck Fadel Miguel², João Kaminski Jr.³

CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.2, pp. 87-104, 2015, DOI:10.3970/cmes.2015.104.086

Abstract Since the half of the XX century, attention was given to the instability of structures under parametric excitation, especially under periodic loads. On the other hand, the instability of bars subjected to axial loads of impulsive type has been little studied, in spite of the practical importance of the topic. Thus, in Engineering Design it is frequently supposed, without tests or additional verifications, that an axial load of short duration can exceed the Euler critical load of the bar without inducing damage in the same.
Within this context, this paper proposes the use of the truss-like Discrete Element Method… More >

Haitao Liao

CMES-Computer Modeling in Engineering & Sciences, Vol.103, No.3, pp. 155-187, 2014, DOI:10.3970/cmes.2014.103.155

Abstract The improved constrained optimization harmonic balance method(COHBM) is presented to solve the Duffing oscillator with time delayed term. Within the framework of the proposed method, the analytical gradients of the objective function and nonlinear quality constraints with respect to optimization variables are formulated and the sensitivity information of the Fourier coefficients can also obtained. The general formulas of the geometrically nonlinear and time delayed terms are analytically derived, which makes the calculations of nonlinear differential equations in the frequency domain easily. A stability analysis method based on the analytical formulation of the nonlinear equality constraints is presented for the nonlinear… More >

Yidong Bao^1,2, Dongmei Wu^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.100, No.4, pp. 277-294, 2014, DOI:10.3970/cmes.2014.100.277

Abstract Aiming at the shortcomings of mass-spring model, this paper, on the basis of preliminary studies, established a new viscoelastic soft tissue model based on meshless structure. The model is consisted of a large quantity of filled spheres, with every three spheres being connected by a spring and a Kelvin structure, which can further enhance the real-time virtual simulation operability while ensure the viscoelasticity of basic model. The stress relaxation and creep equation of the model can be derived from formula derivation. Through setting different parameters to the filled spheres, this model, with certain universal property, can create a virtual liver,… More >