P. H. Wen¹, M. H. Aliabadi¹, A. Young²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 1-10, 2002, DOI:10.3970/cmes.2002.003.001

Abstract In this paper, applications of the boundary element method to damaged and undamaged aircraft curved panels with mechanical repairs are presented. The effects of fastened repairs are replaced by uniform distribution forces in the area of cross-section of the rivet and can be determined from the compatibility condition of displacements. A coupled boundary integral formulation of a shear deformable plate and two dimensional plane stress elasticity is used to determine the bending and membrane forces on the rivets. Domain integrals in each integral equation are determined using the dual reciprocity method. The stress intensity factors due to bending and membrane… More >

G.P.Nikishkov², J.H.Park³, S.N.Atluri²

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.3, pp. 401-422, 2001, DOI:10.3970/cmes.2001.002.401

Abstract An efficient and highly accurate, Symmetric Galerkin Boundary Element Method - Finite Element Method - based alternating method, for the analysis of three-dimensional non-planar cracks, and their growth, in structural components of complicated geometries, is proposed. The crack is modeled by the symmetric Galerkin boundary element method, as a distribution of displacement discontinuities, as if in an infinite medium. The finite element method is used to perform the stress analysis for the uncracked body only. The solution for the structural component, containing the crack, is obtained in an iteration procedure, which alternates between FEM solution for the uncracked body, and… 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 >

K. Nishimura¹, N. Miyazaki²

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.2, pp. 143-154, 2001, DOI:10.3970/cmes.2001.002.143

Abstract In this paper, we present a classical molecular dynamics algorithm and its implementation on Cray C90 and Fujitsu VPP700. The characters of this algorithm consist in a grid based on the block division of the atomic system and a neighbor list based on the use of a short range potential. The computer program is used for large scale simulations on a Cray C90 and a 32-node VPP700, and measurements of computational performance are reported. Then, we examine the interaction between a crack propagating and a tilt grain boundary under uniaxial tension using this computer program. The Johnson potential for α-Fe… 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 >

Y. Wei, C.L. Chow¹, C.T. Liu²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.4, pp. 71-78, 2000, DOI:10.3970/cmes.2000.001.523

Abstract The paper presents a numerical simulation for mixed mode crack initiation based on the concepts of damage mechanics. A model with two scalar damage variables is introduced for characterization of damage in a material element. Then a tangent modulus tensor is derived for damage-coupled constitutive equations. A failure criterion is developed with the concept of damage accumulation not only to identify the location of damaged element where the crack initiation angle but also to determine the critical load for mixed mode fracture. The damage model developed is incorporated in a general-purpose finite element program ABAQUA through its UMAT subroutine. The… More >

L. Ma¹, A.S. Kobayashi², S. N. Atluri³, P.W. Tan⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.4, pp. 19-26, 2000, DOI:10.3970/cmes.2000.001.471

Abstract Experimentally determined T_ε^* and CTOA resistance curves were used to simulate numerically, stable crack growth and the ensuing crack linkup in 0.8 mm thick 2024-T3 aluminum tension specimen with multiple site damage (MSD) subjected to monotonically/cyclically increasing loading. The T_ε^* integral correctly predicted the crack growth and linkup history as well as the onset of rapid fracture in MSD specimens. The CTOA criterion also predicted the crack growth history but in its present form, could not predict crack linkup and rapid fracture. More >

S. Guimarães¹, J.C.F. Telles²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.3, pp. 131-139, 2000, DOI:10.3970/cmes.2000.001.433

Abstract The paper discusses further applications of the hyper-singular boundary integral equation to obtain the Green's function solution to general geometry fracture mechanics problems, such as curved multifracture crack simulation, static and transient dynamic in 2-D, 3-D and plate bending problems. This numerical Green's function (NGF) is implemented into alternative boundary element computer programs, as the fundamental solution, to enhance the scope of alternative applications of the NGF procedure.
The results to some typical linear fracture mechanics problems are presented. More >

J. Lufrano¹, P. Sofronis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 119-132, 2000, DOI:10.3970/cmes.2000.001.279

Abstract Transient hydrogen diffusion and hydride formation coupled with material deformation are studied in Zr-2.5Nb alloys used in the pressure tubes of CANDU nuclear generating stations. The energetics of the hydride formation is revisited and the terminal solid solubility of hydrogen in solution is defined on the basis of the total elastoplastic work done on the system by the forming hydride and the external loads. Probabilistic precipitation of hydride is modeled in the neighborhood of a crack tip under mode I plane strain loading and a uniform initial hydrogen concentration below the stress free terminal solid solubility. Finite element analysis is… 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 d is chosen… More >