KwangsooHo¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.3, pp. 351-364, 2001, DOI:10.3970/cmes.2001.002.351

Abstract Negative, zero or positive rate sensitivity of the flow stress can be observed in metals and alloys over a certain range of strain, strain rate and temperature. It is believed that negative rate sensitivity is an essential feature of dynamic strain aging, of which the Portevin-Le Chatelier effect is one other manifestation. The viscoplasticity theory based on overstress (VBO), one of the unified state variable theories, is generalized to model zero (rate independence) and negative as well as positive rate sensitivity in a consistent way. The present model does not have the stress rate term in the evolution law for… More >

Xiaolin Chen, Yijun Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.3, pp. 337-350, 2001, DOI:10.3970/cmes.2001.002.337

Abstract An advanced boundary element method (BEM) is developed in this paper for analyzing thin layered structures, such as thin films and coatings, under the thermal loading. The boundary integral equation (BIE) formulation for steady-state thermoelasticity is reviewed and a special case, that is, the BIE for a uniform distribution of the temperature change, is presented. The new nearly-singular integrals arising from the applications of the BIE/BEM to thin layered structures under thermal loading are treated in the same way as developed earlier for thin structures under the mechanical loading. Three 2-D test problems involving layered thin films and coatings on… More >

H.-K. Ching, R. C. Batra¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.2, pp. 273-290, 2001, DOI:10.3970/cmes.2001.002.273

Abstract It is shown that the MLPG method augmented with the enriched basis functions and either the visibility criterion or the diffraction criterion successfully predicts the singular stress fields near a crack tip. Results are presented for a single edge-cracked plate and a double edge-cracked plate with plate edges parallel to the crack axis loaded in tension, the single edge-cracked plate with one plate edge parallel to the crack axis clamped and the other loaded by tangential tractions, and for a double edge-notched plate with the side between the notches loaded in compression. For the first three problems, the stress intensity… More >

Ru-Min Chao, Yen-Ji Chen, F.C. Lin¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 73-86, 2001, DOI:10.3970/cmes.2001.002.073

Abstract The two-dimensional elasticity problem of an isotropic material, containing a centered-crack with unknown boundary traction is studied by the inverse procedure. The dual boundary integral equations are used to analyze the problem. While solving the ill-posed inverse problem, both of the conjugate gradient method and the regularization method are used. A scaling factor depending upon the material constant μ is introduced into the sensitivity matrix in order to keep the order of magnitude the same throughout the formulation. The result by using the displacement measurement will be compared with those by stress measurement, and an extensive discussion will be given.… More >

A. El-Zafrany¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 27-38, 2001, DOI:10.3970/cmes.2001.002.027

Abstract In a recent publication, the author has introduced boundary integral equations for thick plate bending problems, for cases with generalized types of loading. Internal bending moments and shear forces, required for stress analysis, were calculated by means of a finite difference procedure, which requires fine boundary element meshes to achieve an acceptable degree of accuracy. In this paper, boundary integral equations for internal bending moments and shear forces are presented for thick Reissner plates in bending. Domain loading terms in those boundary integral equations have also been simplified for a variety of loading types including concentrated loading, linearly-distributed loading, and… More >

C.M. Müller-Karger¹, C.González², M.H.Aliabadi³, M.Cerrolaza⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 1-14, 2001, DOI:10.3970/cmes.2001.002.001

Abstract In this paper, a three-dimensional Boundary Element model of the proximal tibia of the human knee is described and stresses and displacements in the tibial plateau under static loading are computed. The geometry is generated via three-dimensional reconstruction of Computerized Tomographies and Magnetic Resonance Imaging. Various models of different lengths from the tibia plateau are calculated. The BEM results are compared with a Finite Element model having the same geometry and tibia FE models available in the literature. Also reported are investigations of some pathological situations, including fractures. The results of the comparisons show that BEM is an efficient and… More >

Z. Chen¹, W. Hu¹, E.P. Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.4, pp. 57-62, 2000, DOI:10.3970/cmes.2000.001.509

Abstract To simulate the dynamic failure evolution without using nonlocal terms in the strain-stress space, a damage diffusion equation is formulated with the use of a combined damage/plasticity model that was primarily applied to the case of rock fragmentation. A vectorized model solver is developed for large-scale simulation. Two-dimensional sample problems are considered to illustrate the features of the proposed solution procedure. It appears that the proposed approach is effective in simulating the evolution of localization, with parallel computing, in a single computational domain involving different lower-order governing differential equations. More >

N. Miyazaki¹, T. Tamura², K. Yamamoto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 99-106, 2000, DOI:10.3970/cmes.2000.001.099

Abstract Quantitative estimation of the failure of a gadolinium orthosilicate (Gd₂SiO₅, hereafter abbreviated as GSO) single crystal induced by thermal stress was investigated. A GSO cylindrical test specimen was heated in a silicone oil bath, then subjected to large thermal stress by room temperature silicone oil. Cracking occurred during cooling. The transient heat conduction analysis was performed to obtain temperature distribution in the test specimen at the time of cracking, using the surface temperatures measured in the test. Then the thermal stress was calculated using the temperature profile of the test specimen obtained from the heat conduction analysis. It is found… More >

Toru Ikeda¹, Isao Arase, Yuya Ueno, Noriyuki Miyazaki

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 91-98, 2000, DOI:10.3970/cmes.2000.001.091

Abstract In electronic devices, the corners of joined dissimilar materials exist between plastic resin and a die pad or a chip. Failure of the plastic resin is often caused from these corners during the assembly process or the operation of products. The strength evaluation of the corner is important to protect the failure of plastic packages. To evaluate the singular stress field around a corner, we utilize the stress intensity factors of the asymptotic solution for a corner of joined dissimilar materials. We show that the accurate stress intensity factor can be analyzed by the displacement extrapolation method using the displacement… More >

K. Garikipati¹, V.S. Rao², M.Y. Hao³, E. Ibok⁴, I. de Wolf⁵, R. W. Dutton⁶

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.1, pp. 65-84, 2000, DOI:10.3970/cmes.2000.001.065

Abstract This work is based upon a careful rendering of mechanics and mathematics to describe the phenomena that influence the stress engendered by the Shallow Trench Isolation process. The diffusion-reaction problem is posed in terms of fundamental mass balance laws. Finite strain kinematics is invoked to model the large expansion of SiO₂, dielectrics are modelled as viscoelastic solids and annealing-induced density relaxation of SiO₂ is incorporated as a history-dependent process. A levelset framework is used to describe the moving Si/SiO₂ interface. Sophisticated finite element methods are employed to solve the mathematical equations posed for each phenomenon. These include the incorporation of… More >