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노우진(Roh, Woo-Jin),이종원(Lee, Chong-Won) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.5
It is important to improve the initial launch conditions of golf ball at impact between golf club and ball to get a long flight distance. The flight distance is greatly influenced by the initial launch conditions such as ball speed, launch angle and back spin rate. It is also important to analyze the mechanism of ball spin to improve the initial conditions of golf ball. Back spin rate is created by the contact time and force. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of ball, and the tangential force creates the spin. Especially, the tangential force is known to take either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail in the literature. In this paper, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and time at impact between golf club head and ball are computed using FEM and compared with previous results. In addition, we investigate the impact phenomenon between golf club head and ball by FEM and clarify the mechanism of ball spin creation accurately, particularly focusing on the effect of negative tangential force on ball spin rate.
노우진(Woo-Jin Roh),이종원(Chong-Won Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
This paper reviews and develops green dynamics, and the run of a golf ball. We analyze green dynamics using stimpmeter and Werner and Greig's empirical equations. Reasonable empirical equations are suggested to satisfy mechanical principles. The resistance moment is calculated to find rolling resistance of a golf ball on the green. Then, the rolling friction coefficient is deduced using previous results. Finally, it is found that the bounce form of forward or backward is caused by landing backspin and the coefficient of kinetic friction.
노우진(Roh, Woo-Jin),이종원(Lee, Chong-Won) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.11
Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.
노우진(Woo-Jin Roh),이종원(Chong-Won Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In a previous study, the motion of a rolling golf ball on a sloped green was modeled. In this paper, the equation of motion for a golf ball interacting with a hole on a sloped green are found. The capture process is studied by numerically solving the equations for rolling without slipping on the rim.
Dynamic Substructuring 기법을 이용한 APR 1400 원자로 내부구조물의 동적 거동 고찰
이상정(Sang-Jeong Lee),박노철(No-Cheol Park),최영인(Youngin Choi),박영필(Young-Pil Park),김진성(Jinsung Kim),박찬일(Chanil Park),노우진(Woo-Jin Roh) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
In order to identify dynamic behavior of complex structure as nuclear reactor, vibration analysis is mostly conducted as using finite element method (FEM). If the structure is complicated, high computational cost and time is demanded at vibration analysis using FEM. After model reduction is fulfilled with using dynamic substructuring method, it is objective to decrease the computational cost and time at vibration analysis of complex structures in this study. With applying selecting method of mater degree of freedom (MDOF) whose validity was identified in previous study, accuracy of vibration analysis is guaranteed. We apply the method to APR 1400 nuclear reactor internals which are one of complex structures. Because the result of application shows that vibration analysis data from dynamic substructuring method are well matched with original method, we confirm the effect of Vibration analysis using dynamic substructuring method.