P. Ramamurty Raju¹, B. Satyanarayana², K. Ramji³

Structural Durability & Health Monitoring, Vol.4, No.3, pp. 161-172, 2008, DOI:10.3970/sdhm.2008.004.161

Abstract This paper presents the details of method of sample size determination to estimate the characteristic fatigue life of aluminum alloy. The characteristic fatigue life of Aluminum alloy A356.2-T6 has been estimated by assuming a two parameter Weibull distribution model. A stepwise procedure is outlined to determine the number of specimens required at a predetermined stress amplitude to estimate the fatigue life within an acceptable error at a given probability and confidence level. The percentage of error is calculated at various probabilities and confidence levels (C.L). The probabilities considered are 50%, 90% and 95% whereas C.Ls considered are 90%, 95% and… More >

G. Savaidis¹, N. Pitatzis¹, A. Savaidis¹, Ch. Zhang²

Structural Durability & Health Monitoring, Vol.4, No.3, pp. 145-160, 2008, DOI:10.3970/sdhm.2008.004.145

Abstract This paper presents an elastic-plastic finite element analysis of a circumferentially notched cylinder subjected to multiaxial non-proportional fatigue loading. Two different load combinations are investigated: (1) constant tension with cyclic torsion and (2) constant torsion with cyclic tension. The multilayer plasticity model of Besseling in conjunction with the von Mises yield criterion is applied to describe the elastic-plastic material behaviour. The parametrical study contains a coarse and a fine finite element mesh with and without mid-nodes as well as three different types of multilinear approximations of the material law, namely, a twenty-segments, a five-segments and a three-segments one. The comparison… More >

B.K.Raghuprasad¹, N.Lakshmanan², N.Gopalakrishnan², K.Muthumani²

Structural Durability & Health Monitoring, Vol.4, No.3, pp. 117-144, 2008, DOI:10.3970/sdhm.2008.004.117

Abstract The reduction in natural frequencies, however small, of a civil engineering structure, is the first and the easiest method of estimating its impending damage. As a first level screening for health-monitoring, information on the frequency reduction of a few fundamental modes can be used to estimate the positions and the magnitude of damage in a smeared fashion. The paper presents the Eigen value sensitivity equations, derived from first-order perturbation technique, for typical infra-structural systems like a simply supported bridge girder, modelled as a beam, an end-bearing pile, modelled as an axial rod and a simply supported plate as a continuum… More >

J. Useche, P. Sollero, E.L. Albuquerque¹, L. Palermo²

Structural Durability & Health Monitoring, Vol.4, No.2, pp. 107-116, 2008, DOI:10.3970/sdhm.2008.004.107

Abstract The fracture analysis of cracked thick plates repaired with adhesively bonded composite patches using a boundary element formulation is presented. The shear deformable cracked isotropic plate was modeled using the dual boundary method. In order to model the repair, a three parameter boundary element formulation was established. This formulation is based on Kirchhoff's theory for symmetric layer composite plates and considers the transversal deflection and two in-plane rotations. Interaction forces and moments between the cracked plate and the composite repair were modeled as distributed loading, and discretized using continuous and semi-discontinuous domain cells. Coupling equations, based on kinematic compatibility and… More >

B. M. Singh, J. Rokne, R. S. Dhaliwal¹

Structural Durability & Health Monitoring, Vol.4, No.2, pp. 95-106, 2008, DOI:10.3970/sdhm.2008.004.095

Abstract Under the permeable electric boundary condition the problem of two collinear anti-plane shear cracks situated at the interface of two bonded dissimilar piezoelectric layers is considered. It is assumed that applied longitudinal shear stress and electric loading at the layer surfaces are prescribed. By the use of Fourier transforms we reduce the problem to solving a set of triple integral equations with a cosine kernel. The triple integral equations are further reduced to a Fredholm integral equation of the second kind whose iterative solution has been obtained. Analytical expressions for the stress intensity factors are obtained. Numerical results are presented… 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 >

A. Brasiliano¹, W.R. Souza², G.N. Doz³, J.L.V. Brito⁴

Structural Durability & Health Monitoring, Vol.4, No.2, pp. 53-66, 2008, DOI:10.3970/sdhm.2008.004.053

Abstract It can be observed that usually, during structures useful life they are submitted to deterioration processes that, depending on the intensity, may affect their performance and load capacity and, as a result, their safety. In this case, it is necessary to accomplish an inspection in order to evaluate the conditions of the structure and to locate and quantify the intensity of the damage. Another important point is to study the behavior of brittle material beams with cracks, as an attempt of understanding the rupture mechanism and crack propagation phenomenon. In this paper, the Residual Error Method (Genovese, 2000) is applied… More >

F.R. Biglari¹, A. Agahi¹, O. Nikfarjam², B. M. Dariani¹, K. Nikbin³

Structural Durability & Health Monitoring, Vol.4, No.1, pp. 47-52, 2008, DOI:10.3970/sdhm.2008.004.047

Abstract A modified sensitivity analysis has been applied to an elastic-plastic finite element analysis 3D blank design in sheet metal forming. In recent literature, the sensitivity method has successfully been applied to several arbitrary shapes. However, in the present paper the sensitivity coefficients are not considered constant during the analysis. The presented approach computes the new coefficients from the two last iterations. This method can produce an initial blank boundary shape that has any arbitrary flange shape. A cup with uniform flange has been studied in detail and results show a faster solution convergence than the published sensitivity method. Experimental tests… More >

H. Ghasemnejad¹, H. Hadavinia^1,2, D. Marchant¹, A. Aboutorabi¹

Structural Durability & Health Monitoring, Vol.4, No.1, pp. 29-46, 2008, DOI:10.3970/sdhm.2008.004.029

Abstract In this paper the crashworthiness capabilities of thin-walled corrugated crash boxes in axial crushing relative to flat sidewall boxes from the same material are investigated. In order to achieve this, various design of corrugated aluminium alloy 6060 temper T4 crash boxes were chosen and their axial crushing behaviour under impact loading was studied by developing a theoretical model based on Super Folding Element theory and by conducting finite element analysis using LS-DYNA in ANSYS. From the theoretical and FE analysis the crush force efficiency, the specific energy absorption and the frequency and amplitude of fluctuation of the dynamic crush force… More >