Browsing by Author "Bao, Rui"
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Item Open Access Evaluating stress intensity factors due to weld residual stresses by the weight function and finite element methods(Elsevier Science B.V., Amsterdam., 2010-09-30T00:00:00Z) Bao, Rui; Zhang, Xiang; Yahaya, N. A.This paper presents a study on the application of the weight function and finite element methods to evaluate residual stress intensity factors in welded test samples. Three specimen geometries and various residual stress profiles were studied. Comparisons of the two different methods were made in terms of the accuracy, easiness to use, conditions and limitations. Calculated residual stress intensity factors by the two different methods are in general in good agreement for all the configurations studied. Computational issues involved in executing these methods are discussed. Some practical issues are also addressed, e.g. treatment of incomplete or limited residual stress measurements, influence of transverse residual stresses, and modelling residual stress in short-length specimens. The finite element method is validated by well-established weight functions and thus can be applied to complex geometries following the procedures recommended in this paper. (C) 2010 Elsevier Ltd. All rights reserved.Item Open Access Evaluation of the intrinsic crack growth rates of weld joints(Elsevier Science B.V., Amsterdam., 2011-04-30T00:00:00Z) Zhang, Xiang; Bao, RuiA method is presented for evaluating weld intrinsic fatigue crack growth rate (FCGR) by excluding the influence of residual stresses. The method is potentially useful for predicting crack growth lives of structural components using measured FCGR data from coupon specimens. Calculation procedures are developed and demonstrated via an example of crack growth across a longitudinal weld subjected to both constant amplitude loading and constant applied stress intensity factor ranges. Trends of intrinsic FCGR in different weld regions are identified. The methodology can also be used for establishing intrinsic FCGR laws for cracks propagating within and parallel with the weld joint.Item Open Access Fatigue crack growth behaviour and life prediction for 2324-T39 and 7050-T7451 aluminium alloys under truncated load spectra(Elsevier Science B.V., Amsterdam., 2010-07-01T00:00:00Z) Bao, Rui; Zhang, XiangThis paper presents a study of crack growth behaviour in aluminium alloys 2324- T39 and 7050-T7451 subjected to flight-by-flight load spectra at different low- stress truncation levels. Crack branching was observed in the higher truncation levels for the 2324 and in all truncation levels for the 7050. Mode I crack growth life can be predicted for the 2324 alloy by the NASGRO equation and the Generalised Willenborg retardation model. However, quantitative prediction of the fatigue life of a significantly branched crack is still a problem. Material properties, test sample’s orientation and applied stress intensity factor range all play dominant roles in the fracture procesItem Open Access An inverse method for evaluating weld residual stresses via fatigue crack growth test data(Elsevier Science B.V., Amsterdam., 2010-11-30T00:00:00Z) Bao, Rui; Zhang, XiangThis paper presents an inverse method for calculating the thermal residual stresses in welded specimens via measured fatigue crack growth rates. Firstly, fracture-mechanics superposition law has been used to extract the stress intensity factor due to residual stress contribution from measured crack growth rate. Secondly, a so-called B matrix has been established by performing finite element analysis. Residual stress distribution is then determined by solving linear algebraic equations relating the B matrix and residual stress intensity factors obtained from crack growth test data. The inverse method has been validated by a well-established residual stress distribution and corresponding stress intensity factor, and then applied to an M(T) sample in 2024-T3 alloy with a longitudinal weld. Agreement with the measured residual stresses is reasonably good and reasons for certain differences between the calculated and measured are discussed.