B. Ch,rasekhar¹, Sadasiva M. Rao²

CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.1, pp. 67-80, 2007, DOI:10.3970/cmes.2007.021.067

Abstract In this work, a simple and robust numerical method to calculate the scattered acoustic fields from fluid bodies of arbitrary shape subjected to a plane wave incidence is presented. Three formulations are investigated in this work$viz.$ the single layer formulation (SLF), the double layer formulation (DLF), and the combined layer formulation (CLF). Although the SLF and the DLF are prone to non-uniqueness at certain discrete frequencies of the incident wave, the CLF is problem-free, eliminates numerical artifacts, and provides a unique solution at all frequencies. Further, all the three formulations are surface formulations which implies More >

S.Y. Wang^1,2, K.M. Lim^2,3, B.C. Khoo^2,3, M.Y. Wang⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.1, pp. 1-40, 2007, DOI:10.3970/cmes.2007.021.001

Abstract The level set method is a numerical technique for simulating moving interfaces. In this paper, an unconditionally BIBO (Bounded-Input-Bounded-Output) time-stable consistent meshfree level set method is proposed and applied as a more effective approach to simultaneous shape and topology optimization. In the present level set method, the meshfree infinitely smooth inverse multiquadric Radial Basis Functions (RBFs) are employed to discretize the implicit level set function. A high level of smoothness of the level set function and accuracy of the solution to the Hamilton-Jacobi partial differential equation (PDE) can be achieved. The resulting dynamic system of… More >

J. Perko¹, B. Šarler²

CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.1, pp. 55-68, 2007, DOI:10.3970/cmes.2007.019.055

Abstract This work introduces a procedure for automated determination of weight function free parameters in moving least squares (MLS) based meshless methods for non-uniform grids. The meshless method used in present work is Diffuse Approximate Method (DAM). The DAM is structured in 2D with the one or two parameter Gaussian weigh function, 6 polynomial basis and 9 noded domain of influence. The procedure consists of three main elements. The first is definition of the reference quality function which measures the difference between the MLS approximation on non-uniform and hypothetic uniform node arrangements. The second is the… More >

S.Y. Wang^1,2, K.M. Lim^2,3, B.C. Khoo^2,3, M.Y. Wang⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.3, pp. 155-182, 2007, DOI:10.3970/cmes.2007.018.155

Abstract In this paper, a geometric deformation constrained level set method is presented as an effective approach for structural shape and topology optimization. A level set method is used to capture the motion of the free boundary of a structure. Furthermore, the geometric deformation of the free boundary is constrained to preserve the structural connectivity and/or topology during the level set evolution. An image-processing-based structural connectivity and topology preserving approach is proposed. A connected components labeling technique based on the 4-neighborhood connectivity measure and a binary image is used for the present region identification. The corresponding… More >

Heng Cheng Lin^1,2, Chieh Kung³, Rong Sheng Chen²

CMC-Computers, Materials & Continua, Vol.6, No.1, pp. 43-50, 2007, DOI:10.3970/cmc.2007.006.043

Abstract Presented herein are the evaluation results of the BGA solder ball shape using energy method, two types of solder, viz. Sn37Pb and Sn80Pb, are selected .The geometry of the solder bump is firstly estimated using free computer software, the Surface Evolver, an interactive program which is an energy-based approach for the study of liquid droplet surfaces shaped by surface tension and other energies. The solder bump is then numerically constructed in a finite element model that simulates a BGA package. The influences of both upper and bottom solder pad radii, the surface tension on the… More >

Cheng-Hung Huang¹, Hsin-Hsien Wu²

CMC-Computers, Materials & Continua, Vol.5, No.3, pp. 197-212, 2007, DOI:10.3970/cmc.2007.005.197

Abstract The conjugate gradient method (CGM) is applied in an inverse fin design problem in estimating the optimum shapes for the non-Fourier spine and longitudinal fins based on the desired fin efficiency and fin volume at the specified time. One of the advantages in using CGM in the inverse design problem lies in that it can handle problems having a huge number of design parameters easily and converges very fast.
The validity of using CGM in solving the present inverse design problem is justified by performing the numerical experiments. Several test cases involving different design fin efficiency, More >

Kanchi Venkatesulu Reddy¹, Ranjan Ganguli²

CMC-Computers, Materials & Continua, Vol.5, No.2, pp. 79-98, 2007, DOI:10.3970/cmc.2007.005.079

Abstract This paper investigates the effect of damage on beams with fixed boundary conditions using Fourier analysis of the mode shapes in spatial domain. A finite element model is used to obtain the mode shapes of a damaged fixed-fixed beam. Then the damaged beams are studied using a spatial Fourier analysis. This approach contrasts with the typical time domain application of Fourier analysis for vibration problems. It is found that damage causes considerable change in the Fourier coefficients of the mode shapes. The Fourier coefficients, especially the higher harmonics, are found to be sensitive to both More >

A. H. Muhr¹

CMC-Computers, Materials & Continua, Vol.5, No.1, pp. 11-30, 2007, DOI:10.3970/cmc.2007.005.011

Abstract The mechanics of laminates of elastomer and shims of high modulus material are reviewed. Such structures are often built to provide engineering components with specified, and quite different, stiffnesses in different modes of deformation. The shims may either be rigid or flexible, flat or curved, but are usually close to inextensible, being made of a high modulus material such as steel. On the other hand, rubber has an exceptionally low shear modulus, about one thousandth of its bulk modulus, so that shear of the rubber layers and flexure of the high modulus layers (if thin)… More >

Wendong Shi^∗,†, Xi-Qiao Feng^*, Huajian Gao^†

Molecular & Cellular Biomechanics, Vol.3, No.3, pp. 121-126, 2006, DOI:10.3970/mcb.2006.003.121

Abstract When pulling a vesicle adhered on a substrate, both the force-displacement profile and the maximum force at pull-off are sensitively dependent upon the substrate shape. Here we consider the adhesion between a two-dimensional vesicle and a rigid substrate via long-range molecular interactions. For a given contact area, the theoretical pull-off force of the vesicle is obtained by multiplying the theoretical strength of adhesion and the contact area. It is shown that one may design an optimal substrate shape to achieve the theoretical pull-off force. More >

S.Y. Wang^1,2, M.Y. Wang³

CMES-Computer Modeling in Engineering & Sciences, Vol.13, No.2, pp. 119-148, 2006, DOI:10.3970/cmes.2006.013.119

Abstract In this paper, an implicit free boundary parametrization method is presented as an effective approach for simultaneous shape and topology optimization of structures. The moving free boundary of a structure is embedded as a zero level set of a higher dimensional implicit level set function. The radial basis functions (RBFs) are introduced to parametrize the implicit function with a high level of accuracy and smoothness. The motion of the free boundary is thus governed by a mathematically more convenient ordinary differential equation (ODE). Eigenvalue stability can be guaranteed due to the use of inverse multiquadric… More >