S.M. Häusler¹, P.M. Baiz², S.M.O. Tavares³, A. Brot⁴, P. Horst¹, M.H. Aliabadi², P.M.S.T. de Castro³, Y. Peleg-Wolfin⁴

Structural Durability & Health Monitoring, Vol.7, No.3, pp. 163-190, 2011, DOI:10.3970/sdhm.2011.007.163

Abstract This article represents the first part of a two-part article which presents, compares and discusses the different crack growth simulation models which were introduced for fatigue crack growth assessment during the DaToN project. The project was funded by the EC within the 6th framework program and was specifically devoted to investigate innovative manufacturing techniques for metallic structures with special focus on the effects of residual stresses on the fatigue crack growth and residual strength behaviour. Within this first part the different simulation approaches, including the residual stress modelling approaches will be introduced and stress intensity factor results will be presented… More >

A. Rama Chandra Murthy¹, G.S. Palani¹, Nagesh R. Iyer¹

Structural Durability & Health Monitoring, Vol.5, No.3, pp. 201-226, 2009, DOI:10.3970/sdhm.2009.005.201

Abstract This paper presents methodologies for residual strength evaluation of metallic structural components under fatigue loading. Structural components include plate panels of different crack configurations with and without stiffeners. For stiffened panels, stress intensity factor (SIF) has been computed by using parametric equations based on numerically integrated modified virtual crack closure integral (NI-MVCCI) technique. As a part of residual strength evaluation, remaining life has also been predicted by using standard crack growth models. Various methodologies for residual strength evaluation, namely, plastic collapse condition, fracture toughness criterion and remaining life approach have been described. From the studies, it has been observed that… More >

Kyousuke Yamaguchi¹, Nao-Aki Noda², Ker-Kong Chen³, Kiyoshi Tajima³, Seiji Harada¹, Xin Lan¹

Structural Durability & Health Monitoring, Vol.5, No.3, pp. 191-200, 2009, DOI:10.3970/sdhm.2009.005.191

Abstract Wedge-shaped defects are frequently observed on the cervical region of the human tooth. Previously, most studies explained that improper tooth-brushing causes such defects. However, recent clinical observation suggested that the repeated stress due to occlusal force may induce the formation of these wedge-shaped defects. In this study, a two-dimensional human tooth model after a wedge-shaped defect is restored with the composite resin is analyzed by using the finite element method. To obtain the intensity of the singular stress accurately, a method of analysis is discussed for calculating generalized stress intensity factors, which control the singular stress around the corner of… More >

G.S. Palani¹, B. Dattaguru², Nagesh R. Iyer¹

Structural Durability & Health Monitoring, Vol.4, No.2, pp. 77-94, 2008, DOI:10.3970/sdhm.2008.004.077

Abstract The objective of this paper is to present a generalized technique called as, numerically integrated Modified Virtual Crack Closure Integral (NI-MVCCI) technique for computation of strain energy release rate (SERR) for 2-D crack problems employing singular finite elements. NI-MVCCI technique is generalized one and the expressions for computing SERR are independent of the finite element employed. Stress intensity factor (SIF) can be computed using the relations between SERR and SIF depending on the assumption of plane stress/strain conditions. NI-MVCCI technique has been demonstrated for 8-noded Serendipity (regular & quarter-point) and 9-noded Lagrangian (regular & quarter-point) and 12-noded (regular & singular)… More >

C. Colombo¹, M. Guagliano^1,2, L. Vergani¹

Structural Durability & Health Monitoring, Vol.4, No.2, pp. 67-76, 2008, DOI:10.3970/sdhm.2008.004.067

Abstract With the aim of experimentally assessing the stress intensity factors under mixed-mode loading along a crack front, the case of an internal elliptical crack is analyzed. An experimental test is performed on a three-dimensional photoelastic model made in epoxy resin. This model contains an inner natural crack, created by thermal shock. The crack is inclined in the cylindrical model, loaded with a tensile stress field.
Exploiting the characteristics of the epoxy resin, and using the stress freezing technique, it is possible to keep memory of the stresses near to the crack tip, once the specimen is unloaded. The final specimen… More >

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 >

P.H. Wen¹, M.H. Aliabadi²

Structural Durability & Health Monitoring, Vol.3, No.2, pp. 107-120, 2007, DOI:10.3970/sdhm.2007.003.107

Abstract In the last decade, meshless methods for solving differential equations have become a promising alternative to the finite element and boundary element methods. Based on the variation of potential energy, the element-free Galerkin method is developed on the basis of finite element method by the use of radial basis function interpolation. An enriched radial basis function is formulated to capture the stress singularity at the crack tip. The usual advantages of finite element method are retained in this method but now significant improvement of accuracy. Neither the connectivity of mesh in the domain by the finite element method or integrations… More >

Abdulnaser M. Alshoaibi^1,2, M. S. A. Hadi², A. K. Ariffin²

Structural Durability & Health Monitoring, Vol.3, No.1, pp. 15-28, 2007, DOI:10.3970/sdhm.2007.003.015

Abstract An adaptive finite element method is employed to analyze two-dimensional linear elastic fracture problems. The mesh is generated by the advancing front method and the norm stress error is taken as a posteriori error estimator for the h-type adaptive refinement. The stress intensity factors are estimated by a displacement extrapolation technique. The near crack tip displacements used are obtained from specific nodes of natural six-noded quarter-point elements which are generated around the crack tip defined by the user. The crack growth and its direction are determined by the calculated stress intensity factors as the maximum circumference theory is also been… 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 >

L. Palermo Jr.¹, L.P.C.P.F. Almeida², P.C. Gonçalves³

Structural Durability & Health Monitoring, Vol.2, No.2, pp. 123-130, 2006, DOI:10.3970/sdhm.2006.002.123

Abstract The kernels of integrands are usually differentiated to obtain the general boundary integral equation (BIE) for stresses and its corresponding traction equation. An alternative BIE for stresses can be obtained when the tangential differential operator is introduced in problems using Kelvin type fundamental solutions. The order of the singularity is reduced with this strategy and the Cauchy principal value sense or the first order regularization can be used in the resultant BIE. The dual boundary element formulation with the BIE for tractions using the tangential differential operator is analyzed in the present study. Shape functions with same expressions for conformal… More >