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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]