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Abstract: The objective of this paper is to develop a probabilistic model for a stiffened panel subjected to correlated growth of cracks in the stiffener and plate elements. The geometry functions of the correlated cracks in the plate and in the stiffener are defined based on the stress intensity factors calculated by finite element analysis. A validation of the stress intensity factor and the geometry function calculation has been performed for an isolated crack in a plate with a central/edge through thickness crack. The Paris–Erdogan law is used to predict the crack propagation. Monte Carlo simulation is employed to define the statistical descriptors of the crack growth in the stiffened panel under different correlation functions and a probabilistic model of crack size as a function of time are presented adopting a truncated normal distribution to describe the probability density function of the crack size in the plate and in the stiffener. A procedure for the development of a probabilistic crack growth model for a stiffened panel has been proposed, allowing for the existence of multiple cracks both in the stiffeners and in the plate and accounting for the correlation between them. The developed probabilistic model may be used for fatigue crack growth analysis and is suitable for reliability assessment of a stiffened panel subjected to correlated crack growth. [Copyright &y& Elsevier]

Abstract: In this paper creep crack growth behaviour of P92 welds at 923K are presented. Creep crack growth behaviour for P92 welds are discussed with C * parameter. Creep crack growth behaviour of P92 welds has been compared with that of P91 welds with C * parameter. NSW and NSW–MOD model were compared with the experimental creep crack growth data. Plane strain NSW model significantly overestimates the crack growth rate, and plane stress NSW model underestimates it. Whilst, NSW–MOD model for plane stress and plane strain conditions gives lower and upper bound of the experimental data, respectively. FE analysis of creep crack growth has been conducted. Constrain effect for welded joints has been examined with C * line integrals of C(T) specimens. As a result, constant C * value using the material data of welded joint gives 10 times lower than that of only HAZ property. Whilst, the predicted CCG rates for welded joint are 10 times higher than those for only HAZ properties. Compared with predicted CCG rate from FE analysis and the experimental CCG rate, it can be suggested that creep crack growth tests for lower load level or for large specimen should be conducted, otherwise the experimental data should give unconservative estimation for components operated in long years. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism underlying plasticity-induced shielding of a crack tip under fatigue loading has been already experimentally investigated by means of photoelasticity using a recently-developed mathematical model which considers stress field near the crack tip and along the flanks. Stress intensification factors have also been defined to describe shielding effects on the applied elastic field. In this paper a new application of this model is developed through a numerical simulation of the experimental tests, which were previously performed. The study is aimed to analyze the shielding effect related to constant amplitude cycling loading and a single overload peak, considering numerical simulation. By means of the models developed by XFEM technique, the plastic region is reproduced finding a good agreement with the experimental data, and a systematic procedure is proposed to evaluate the stress intensity factors. A good correspondence is found by comparing the numerical with the experimental parameters, obtained from the mathematical model. [Copyright &y& Elsevier]

Abstract: This paper focuses on the dynamic fracturing process of jointed rock masses due to blast wave loading. A coupled numerical method using both LS-DYNA (a transient dynamic finite element program) and UDEC (an universal discrete element code) is outlined first. The blast-induced fracture extension in two representative jointed rock masses is studied subsequently. Besides, the effects of loading density of explosive charge on fracture evolution and the effects of the preexisting earth stress and free face on the fracturing process of rock masses are also explored in detail. The numerical results capture some of the well-known phenomena observed in the field and expected theoretically, and thus can offer useful guidelines to blasting design in rock masses. [Copyright &y& Elsevier]