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Article Citation - WoS: 15Citation - Scopus: 21Comparison of Various Preforms for Hot Forging of Bearing Rings(Elsevier Science Sa, 2005) Arbak, M; Tekkaya, AE; Özhan, FProduction of bearing rings by hot forging is investigated in this study. The aim of the study is to determine a feasible preform at the first station of the forming process such that the tool wear is prolonged and tool fracture is prevented. For this purpose, it is assumed that the contact pressure at the interface between tools and workpiece is the predominant process parameter. The contact pressures are determined by precise thermo-mechanical coupled finite element analyses based on elastic-plastic material description. Material flow curves for various temperatures and strain-rates are determined in velocity controlled upsetting tests. Cooling experiments are used to determine the heat transfer coefficients. Accuracy of the numerical models has been verified by extensive numerical convergence studies and finally by comparing with experimental measurements. The analysed preforms are evaluated using a scheme of weight-factors for the various tool parts. Finally, a preform is suggested for which the weighted total tool pressure could be reduced by 15%. (c) 2005 Elsevier B.V. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 5Higher Order Isoparametric Finite Element Solution of Stokes Flow(Elsevier Science inc, 2005) Eid, RA finite element method of the penalization type, using higher order shape functions with rectangular elements, is presented for the solution of the Stokes flow. The fluid is viscous and the flow is slow, steady and incompressible. The solution has been obtained in terms of velocity field while the pressure terms are eliminated using the penalty function approach. The degree of the finite element approximation can be increased as much as one needs with this higher order shape function formulation. The method is tested in a lid-driven square cavity and it is found that there is a relationship between the viscosity and penalty parameter. From one solution one can obtain all the other solutions only by arranging one of the parameters since the product of these parameters has been shown that is a fixed constant. Selected graphs of the velocity field are given showing these behaviors. (C) 2004 Elsevier Inc. All rights reserved.
