• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.57-61
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• 2004

in order to improve the quality of the sheared surface in cutting of sandwich sheet metals the cut-off operation is mainly investigated which is the typical shearing process in sheet metal forming technology. For experiments the cut-off die is made which can be easily adjusted by die design variables such as blankholding force, pad force, and clearance. The sheet metals chose as specimen are clad304(STS304-Al1050-STS304) and anti-vibration sheet metal. The shearing process is visualized by the computer vision system installed in front of the cut-off die and the sheared surface before and after cut-off operation is measured and quantitatively compared with the help of the optical microscope. From test results the good sheared surface was shown when the clearance gets small with large blankholding force.

• 한국생산제조학회지
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• 제9권3호
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• pp.150-159
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• 2000

In-process diagnosis of the cutting state is essential for the automation of manufacturing systems. Especially when the cutting process becomes unstable it induces self-exited vibrations a frequent case of poor tool life rough surface finish damage to the workpiece and the machine tool itself and excessive down time. To ensure that the cutting process main-tains stable it is highly desirable to have the capability of real-time. To ensure that the cutting process main-tains stable it is highly desirable to have the capability of real-time monitoring and controlling chatter. This paper describes the detection method of chatter vibration using cutting force in turning process. In order to detect a chatter vibra-tion the dynamic fluctuation of radial force is analyzed since this components is sensitive to the chatter. The envelope sig-nal of radial force has been calculated by the use of FIR Hilbert transformer and it was useful to classify the chatter signal from the dynamically unstable circumstances. It was found that the mode and the mode width were closely correlated with the chatter amplitude was well. Finally back propagation(BP) neural network have been applied to the pattern recognition for the classification of chatter signal in various cutting conditions. The validity of this systed was confirmed by the experiments under the various cutting conditions.

• 한국소음진동공학회논문집
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• 제21권6호
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• pp.506-513
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• 2011

This paper is concerned with a study on the control effect of the MR damper using the cutout piston. The MR damper has passive damping force by the oil pressure and controllable damping force by the magnetic effect. As the velocity of the MR damper's piston increases the passive damping force increases and the ratio of the controllable damping force to the total damping force is decreased. Consequently, the control performance of the MR damper is reduced according to the increase of the velocity. In this paper, the cutout piston concept is applied to the MR damper to improve MR damper's control performance by reducing the passive damping effect. The MR damper with the cutout piston has been designed and manufactured and its hydraulic and electromagnetic analysis has been performed to predict its performance. The control performances of the MR damper with the cutout piston are verified through the comparison of experiment results and simulation results.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.258-264
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• 2016

This paper presents the experimental result and theoretical analysis result to investigate the correlation between the operating force and locking torque for vehicle hood frame. Also, we derived the experimental equations that using the results of experiment and theory. The hood frame is switching-devices used for opening and closing the vehicle hood. It needs the correlation data between locking torques of each joint and operating force of hood frame because the parameters affects the emotional quality of the vehicle. The correlation data for torque and force of hood frame obtained through experiment and theory analysis. Finally, two experimental equations of correlation are derived. Thus, the developed equations show that has high usefulness for the basic design of hood frame of vehicle.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1212-1217
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• 2006

This study is concerned with static and sinusoidal disturbance rejection for a single periodic input disturbance with known period. In the area of active elimination of a disturbance force, the control input should have two different kinds of gains: one is to deliver a stable control and the other is a force component to cancel the external disturbance force. In this paper we employ a simple state feedback control law to make the balance beam stable and employ a linear observer to estimate the states which represent the external disturbance force components. Simulation results verify our proposed control method to reject a static and sinusoidal disturbance force.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.146-152
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• 1997

This paper deals with a study of striker type impact hammer drill for improving the drilling performance. The study was performed through a numerical simulation of the impact hammer mechanism, an experimental comparison of the numerical simulation results and an optimization of the impact mechanism. The numerical model of the impact hammer drill takes into account the striker motion and the effects of the pressure in the cylinder as well as the friction acting on the striker. The equation of motion is solved with the pressure equation in the cylinder and the friction force. At the moment of impact, an ideal impact model that uses restitutiion codfficient is used to calculate the sudden change of the striker motion. The impact force numerically simulated shows a good agreement with the experimental results and thus, the validity of the numerical model is proven. Based upon the proposed model, an optimization was performed to improve the impact force of the hammer drill. The objective function is to maximize the impact force and the design variables are striker mass, frequency of piston, bit guide mass, cylindrical diameter and dimensions of the mechanism components. Each design variable and some other conditions that are essential to maintain normal operation of the hammer drill are considered as constraints. The optimized result shows remarkable improvement in impact force and an experimental proof was investigated.

• 한국철도학회논문집
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• 제10권4호
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• pp.414-419
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• 2007

The contact characteristics of the current collection system are investigated by analyzing data collected during a test run of the Korean high speed rail vehicle. For the analysis, the signals from accelerometers and load cells attached to the various parts of the pantograph are analyzed in both the time and frequency domains. In the frequency domain, the pantograph response consists of low frequency components related to the rigid-body motion of the panhead assembly and high frequency components due to the structural vibration modes of the pantograph. The analysis shows that the inclusion of the high frequency structural vibration modes of the pantograph in the contact force calculation has a negligible effect on the predicted mean value of the contact force but significantly affects the magnitude of its fluctuations. This finding implies that numerical simulations using lumped element models of the pantograph may accurately predict the mean contact force but is limited in its capacity for predicting the fluctuation about the mean. Since the ratio of the fluctuation to the mean in the contact force increases with increased train speed, the limitation of the predictions based on numerical simulation results becomes more pronounced at higher train speed.

• 한국소음진동공학회논문집
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• 제23권7호
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• pp.617-623
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• 2013

Accurate prediction of the radiated noise is important to reduce the noise of the washing machine. It is also necessary to predict the excitation force accurately because excitation force can induce noise. In order to predict the excitation force acting on the washing machine, this paper conducts source identification method by use of phase reference spectrum. In this method, the transfer function between the cabinet and the motor through FEM and the measured response from the surface of the cabinet is used. The analysis of the radiation noise from the identified exciting force has been investigated. The comparison between the predicted SPL and the measured SPL at 1m apart from the front side of the washing machine showed good tendency.

• 한국소음진동공학회논문집
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• 제12권11호
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• pp.904-913
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• 2002

In this study, a dynamic analysis of the reciprocating compression mechanism considering viscous friction force of a piston used in small refrigeration compressors is performed. The length of cylinder in this class of compressors is shortening to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder liner is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the compression mechanism dynamics, the change in bearing length of the piston and all corresponding viscous forces and moments are considered in order to determine the trajectories of piston and crankshaft. The piston orbits for viscous friction model and Coulomb friction model were used to compare the effect of the friction forces of piston on the dynamic trajectories of piston. To investigate the effect of friction force acting on the piston for the dynamic characteristics of crankshaft, comparison of the crankshaft loci is given in both viscous model and Coulomb model. Results show that the viscous friction force of piston must be considered in calculating for the accurate dynamic characteristics of the reciprocating compression mechanism.

• 대한물리의학회지
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• 제11권2호
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• pp.1-11
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• 2016

PURPOSE: This study was conducted to assess the effects of local vibration on ankle plantarflexion spasticity and clonus in patients with spinal cord injury. METHODS: The subjects were 14 inpatients with complete or incomplete spinal cord injury (SCI) whose scores were higher than 1 on the Modified Ashworth Scale (MAS) and Spinal Cord Assessment Tool for Spastic Reflexes (SCATS) scale of paraplegia. A randomized single-blind cross-over design was used. Vibration treatment involved a single application of vibration for 10 min in the sitting position, and placebo treatment involved the patient remaining in the sitting position for 10 min. One day after treatment, vibration and placebo treatments were crossed over. Spasticity was measured by using the MAS, and resistance force, by using a hand-held dynamometer; clonus was gauged by using the SCATS scale and clonus burst duration. Additionally, the burst maximal frequency and voluntary ankle dorsiflexion angle of the triceps surae were measured. RESULTS: The application of vibration treatment in the sitting position significantly reduced the MAS scores and resistance force, but significantly increased the dorsiflexion angle of the ankle joint (p<0.05). Furthermore, the vibration treatment diminished the clonus burst duration and SCATS score significantly (p<0.05). Although it reduced the burst maximal frequency of the lateral gastrocnemius and medial soleus, this was significant only for the lateral gastrocnemius. The placebo treatment did not significantly affect any of the test parameters. CONCLUSION: Vibration treatment in the sitting position was effective in cases of spasticity and clonus caused by SCI.