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소산율 방정식의 개선을 통한 저레이놀즈수 k-.epsilon. 모형의 개발
송경,유근종,조강래,Song, K.,Yoo, G.J.,Cho, K.R. 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.5
Series of recent k-.epsilon. model modification have been carried out with the aid of DNS data to include the effect of near wall. Though these methods opened new way of turbulence modelings, newly developed turbulence models of its kind had yet shortcomings in prediction for the turbulent flows with various Reynolds numbers and various geometric conditions. As a remedy for these shortcomings, a new k-.epsilon. model proposed here by improving the dissipation rate equation and the damping function for eddy viscosity model. The new dissipation rate equation was modeled based on the energy spectrum and magnitude analysis. The damping function for eddy viscosity was also formulated on the ground of distribution of dissipation rate length scales near a wall and the DNS data. The new k-.epsilon. model was applied to the fully developed turbulent flows in a channel and a pipe with a wide range of Reynolds numbers. Prediction results showed that the present model represents properly the turbulence properties in all turbulent regions over a wide range of Reynolds numbers.
송경진(Song K.J.),김은겸(Kim E.K.),고승기(Koh S.K.) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Failure of an autofrettaged gun tube with a keyway groove at the outside surface occurs due to the fatigue crack initiation and propagation at the groove root. In order to predict the fatigue life of the autofrettaged gun tube, residual stress of the autofrettaged tube using finite element method was evaluated and fatigue properties of the tube steel were obtained from the fatigue tests. Fatigue life of a gun tube by summing the crack initiation and propagation lives was calculated as 2,598 cycles for an 80% autofrettaged tube subjected to a pulsating internal pressure of 424 ㎫.
송경진(Song, K.J.),조원용(Cho, W.Y.),김은겸(Kim E.K.),고승기(Koh S.K.) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In order to evaluate the endurance life of a vehicle suspension part, durability analysis and test were performed in this paper. Torque rod is a suspension part to improve the maneuvering stability of the commercial vehicle. The torque rod consisted of rod, end body, bush, and pin. Since the bush was made of rubber, uniaxial and equi-biaxial tests were performed to characterize the stress-strain behavior. Finite element stress analysis of the torque rod was performed to obtain the stress distributions and the critical location of the torque rod. Based on the stress analysis results, durability life was estimated. It was found that the pin groove was the most vulnerable to fatigue cracking, and verified in the durability fatigue tests. The durability life was improved by modifying the pin dimension to meet the specification of the torque rod.