G. Davì¹, A. Milazzo¹

Structural Durability & Health Monitoring, Vol.3, No.4, pp. 229-238, 2007, DOI:10.3970/sdhm.2007.003.229

Abstract An original and alternative single domain boundary element formulation and its numerical implementation are presented for the analysis of orthotropic two-dimensional cracked bodies. The problem is formulated employing the classical displacement boundary integral representation and an alternative integral equation deduced on the basis of the stress function theory. This integral equation written on the crack provides the relations needed to determine the problem solution in the framework of linear elastic fracture mechanics. Numerical examples are reported and discussed to demonstrate the accuracy of the proposed approach. More >

S. Beyer¹, Ch. Zhang², S. Hirose³, J. Sladek, V. Sladek⁴

Structural Durability & Health Monitoring, Vol.3, No.3, pp. 177-190, 2007, DOI:10.3970/sdhm.2007.003.177

Abstract This paper presents a hypersingular time-domain boundary element method (BEM) for transient dynamic crack analysis in two-dimensional (2-D), homogeneous, anisotropic and linear elastic solids. A finite crack in an infinite or a finite solid subjected to impact loading conditions is investigated. A combination of the classical displacement boundary integral equations (BIEs) on the external boundary and the hypersingular traction BIEs on the crack-faces is applied. The present BEM uses the time-domain dynamic fundamental solutions for anisotropic solids derived by Wang and Achenbach (1994). An explicit time-stepping scheme based on collocation method is developed. Numerical examples for computing the dynamic stress… More >

C.P. Providakis¹

Structural Durability & Health Monitoring, Vol.2, No.4, pp. 249-254, 2006, DOI:10.3970/sdhm.2006.002.249

Abstract This paper explores the concept of strain energy density rate in relation to the crack initiation in fracture analysis problems arising in creeping cracked structural components. The analysis of the components is performed by using the boundary element methodology in association with the employment of singular boundary elements for the modeling of the crack tip region. The deformation of the material is assumed to be described by an elastic power law creep model. The strain energy density rate theory is applied to determine the direction of the crack initiation for a center cracked plate in tension which is subjected to… More >

E.J. Sapountzakis¹, V.G. Mokos¹

Structural Durability & Health Monitoring, Vol.2, No.4, pp. 207-224, 2006, DOI:10.3970/sdhm.2006.002.207

Abstract In this paper a boundary element method is developed for the second-order analysis of frames consisting of composite beams of arbitrary constant cross section, taking into account shear deformation effect. The composite beam consists of materials in contact, each of which can surround a finite number of inclusions. The materials have different elasticity and shear moduli with same Poisson's ratio and are firmly bonded together. Each beam is subjected in an arbitrarily concentrated or distributed variable axial loading, while the shear loading is applied at the shear center of the cross section, avoiding in this way the induction of a… More >

G. Davì¹, A. Milazzo¹

Structural Durability & Health Monitoring, Vol.2, No.3, pp. 177-182, 2006, DOI:10.3970/sdhm.2006.002.177

Abstract An alternative single domain boundary element formulation and its numerical implementation are presented for the analysis of two-dimensional cracked bodies. The problem is formulated employing the classical displacement boundary integral representation and a novel integral equation based on the stress or Airy's function. This integral equation written on the crack provides the relations needed to determine the problem solution in the framework of linear elastic fracture mechanics. Results are presented for typical problems in terms of stress intensity factors and they show the accuracy and efficiency of the approach. More >

V. Mallardo, C. Alessandri¹

Structural Durability & Health Monitoring, Vol.2, No.3, pp. 165-176, 2006, DOI:10.3970/sdhm.2006.002.165

Abstract The formation of cracks and their propagation in brittle materials has been intensively studied in the last years. The main difficulty is related to the theoretical and numerical possibility to follow the development of regions of highly localised strains. The nonlinear phenomenon is physically different from the one which occurs in ductile materials: it starts with a narrow fracture process zone containing a large number of distributed microcracks which could lead to the formation of macrocracks and eventually to rupture. In the present paper, a simple nonlocal damage model is coupled to the crack analysis in order to describe the… More >

Y.C. Shiah¹, Y.M. Lee², Chi-Chang Wang²

CMC-Computers, Materials & Continua, Vol.33, No.3, pp. 229-255, 2013, DOI:10.3970/cmc.2013.033.229

Abstract In this paper, the boundary integrals for treating 3D field problems are fully regularized for planar elements by the technique of integration by parts (IBP). As has been well documented in open literatures, these integrals appear to be strongly singular and hyper-singular for the associated fundamental solutions. In the past, the IBP approach has only been applied to regularize the integrals for 2D problems. The present work shows that the IBP can also be further extended to treat 3D problems, where two variables of the local coordinates are involved. The presented formulations are fully explicit and also, most importantly, very… More >

Leiting Dong^1,2, Satya N. Atluri^1,3

CMC-Computers, Materials & Continua, Vol.33, No.2, pp. 111-154, 2013, DOI:10.3970/cmc.2013.033.111

Abstract In this study, SGBEM Voronoi Cells (SVCs), with each cell representing a grain of the material at the micro-level, are developed for direct micromechanical numerical modeling of heterogeneous composites. Each SVC can consist of either a (each with a different) homogenous isotropic matrix, and can include micro-inhomogeneities such as inclusions, voids of a different material, and cracks. These inclusions and voids in each SVC can be arbitrarily-shaped, such as circular, elliptical, polygonal, etc., for 2D problems. Further, the cracks in each SVC can be fully-embedded, edge, branching, or intersecting types, with arbitrary curved shapes. By rearranging the weakly-singular boundary integral… More >

Jai Hak Park¹, Maan Won Kim², Gennadiy P. Nikishkov³

CMES-Computer Modeling in Engineering & Sciences, Vol.68, No.3, pp. 269-296, 2010, DOI:10.3970/cmes.2010.068.269

Abstract A SGBEM-FEM alternating method had been proposed by Nikishkov, Park and Atluri for the analysis of three-dimensional planar and non-planar cracks and their growth. In the method, the symmetric Galerkin boundary element method is used for the crack solution in an infinite body and the finite element method is used to perform stress analysis for the uncracked body only. In this paper the method is extended further to analyze through-thickness cracks. Adequate shape of boundary element mesh is examined and it is found that the fictitious portion of the boundary element mesh, which is located outside the body, plays an… More >

A. Cruz-Estrada^1,2, E. Ruiz-Sánchez², I.L. Medina Baizabal¹, E. Balam-Uc¹ and M. Gamboa-Angulo^1,*

Phyton-International Journal of Experimental Botany, Vol.88, No.2, pp. 161-170, 2019, DOI:10.32604/phyton.2019.05809

Abstract The development of plant-derived products to control Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) is an urgent need for production of horticultural crops. Plant extracts and essential oils of several species of the genus Eugenia (Myrtaceae) have shown insecticidal activity. In southern Mexico, leaf extracts from Eugenia winzerlingii showed nematicidal effect but its insecticidal properties have not been explored. Therefore, the objective of this study was to evaluate the insecticidal effect of aqueous and organic extracts from E. winzerlingii leaves on B. tabaci egg, nymph and adult stages, and else to explore its nursery propagation. Then, extracts of this species were obtained… More >