• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.5
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• pp.502-515
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• 2020

To identify the dynamic characteristics of the Auto-leveling system applied to the Tractor-Trailer type Transporter for mounting a large scale precision equipment, Dynamics Modeling & Simulation were performed using general Dynamics Analysis Program - RecurDyn(V9R2). The axial load data, transverse load data and pad trace data of leveling actuators were obtained from M&S. And they were analyzed and compared with each other by parameters, i.e. friction coefficients on the ground, landing ram speed of actuators, and direction & quantity of ground slope. It was observed that ground contact friction coefficients affected to transverse load and pad trace; the landing ram speed of actuators to both amplitude of axial & transverse load, and this phenomena was able to explain from the frequency analysis of the axial load data; the direction of ground slope to driving sequence of landing ram of actuators. But the dynamic behaviors on the two-directional slope were very different from them on the one-directional slope and more complex.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.328-335
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• 2005

For high speed railway vehicles, we consider a vibration of flexible track/wheel system. It is very important to deal with the complex phenomena of high-speed vehicles that can be occurred in the vertical vibration of the system. From a viewpoint of multibody dynamics, this kind of problem needs accurate analysis because the system includes mutual dynamic behaviors of rigid body and flexible body. The simulation technique for the complex problems is also discussed. We consider the high-speed translation, rail elasticity, elastic supports under the rail and contact rigidity. Eigen value analysis is also completed to verify the mechanism of the coupled vertical vibration of the system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.912-915
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• 2002

It has been known that general velocity and force of a rigid body in space can be described in forms of a twist and a wrench by use of screws. However, the geometrical meaning of acceleration has not been clearly disclosed. It has been a normal practice to analyze or synthesize the acceleration effect of manipulator using some complex mathematical equations, which do not represent any geometrical meanings. In other words, such a technique doesn't clearly provide information about the overall acceleration state of manipulator at that instant. In this study, the geometrical meaning of acceleration of a rigid body has been investigated and thereby a geometrical procedure which can be applied to inverse acceleration analysis of a general non-redundant manipulator is presented as an application.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.450-456
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• 1988

Dynamic analysis of a vehicle is carried out with rigid body and flexible body models. The chassis of the vehicle is treated as flexible body in the flexible body model, and vibration normal modes are considered to account for elastic deformation of the component. Using output from the modal analysis in the finite element program, input data for the dynamic analysis with flexible body is generated. To achieve the computational efficiency, SUPERELEMENT technique is used for the vehicle suspension subsisted. The computer simulation time with suspension superelement was much reduced due to the reduction of coordinates and no kinematic constraint in the system.

• Tribology and Lubricants
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• v.38 no.2
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• pp.33-40
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• 2022

In this study, we present rotor dynamic analysis and operation test of a turbo expander for a hydrogen liquefaction plant. The turbo expander consists of a turbine and compressor wheel connected to a shaft supported by two hydrostatic radial and thrust bearings. In rotor dynamic analysis, the shaft is modeled as a rigid body, and the equations of motion for the shaft are solved using the unsteady Reynolds equation. Additionally, the operating test of the turbo expander has been performed in the test rig. Pressurized helium is supplied to the bearings at 8.5 bar. Furthermore, we monitor the shaft vibration and flow rate of the helium supplied to the bearings. The rotor dynamic analysis result shows that there are two critical speeds related with the rigid body mode under 40,000 rpm. At the first critical speed of 36,000 rpm, the vibration at the compressor side is maximum, whereas that of the turbine is maximum at the second critical speed of 40,000 rpm. The predicted maximum shaft vibration is 3 ㎛, whereas sub-synchronous vibration is not presented. The operation test results show that there are two critical speeds under the rated speed, and the measured vibration value agrees well with predicted value. The measured flow rate of the helium supplied to the bearing is 2.0 g/s, which also agrees well with the predicted data.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.441-451
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• 2019

When a store is launched, the umbilical plug should be separated from the launcher without any physical interference and fragments. In order to satisfy these conditions, an umbilical plug and an umbilical separating device were designed. The plug is separated from the receptacle of the store while moving along inclined planes by the store thrust and the spring force connected from the launcher to the plug. As a result of the prototype test, the hanger on the store collided with the plug. Several tests were conducted after some actions were taken to prevent the collision. However, not only the same phenomenon was repeated, but also fragmentation occurred. In this study, the non-colliding conditions were analyzed through rigid and flexible multi-body dynamics analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.67-76
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• 2012

In this paper, collision analysis of the full rake for the Next Generation High-speed EMU is conducted using a 3D/1D hybrid model, which combines 3-dimensional (3D) front-end structure of finite element model and 1-dimensional (1D) multi-body dynamics model in order to analyze train collision with a standard 3D deformable obstacle. The crush forces, passengers' accelerations and energy absorptions of a full rake train can be easily obtained through a simulation of a 1D dynamics model composed of nonlinear springs, dampers and masses. Also the obtained simulation results are very similar to those of a 3D model if an overriding behavior does not occur during collision. The standard obstacle in TSI regulation has been changed from a rigid body to a deformable body, and therefore 3D collision simulations should be conducted because their simulation results depends on the front-end structure of a train. According to the obstacle collision analysis of this study, the obstacle collides with the driver's upper structure after overriding over the front-end module. The 3D/1D hybrid model is effective to evaluate a main energy-absorbing module that is frequently changed during design process and reduce the need time of the modeling and analysis when compared to a 3D full car body.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.751-755
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• 2004

This paper presents a simplified dynamics of railway vehicle for a tilting train simulator. The tilting train simulator has 6 electric-driven actuators and a visualization system with 1600mm-diameter dome screen. The each system shares the data by ethernet. In order to analyze the dynamics of railway vehicle and transfer the results of the analysis to the other system of the tilting train simulator in realtime base, We assumed the tilting train as a simplified rigid body model with primary and secondary suspensions. The simplified vehicle model has a 17-DOF. Through the running analysis on the tight curve with various radius, we verified the simplified vehicle model.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.47-57
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• 2010

This study analyzes the dynamic response of a floating crane with a cargo considering an elastic boom to evaluate(or for evaluation of) its flexibility effect on their dynamic response. Flexible multibody system dynamics is applied in order to establish a dynamic equation of motion of the multibody system, which consists of flexible and rigid bodies. In addition, a floating reference frame and nodal coordinates are used to model the boom as a flexible body. The study also simulates the coupled surge, pitch, and heave motions of the floating crane carrying the cargo with three degrees of freedom by numerically solving the equation. Finally, the simulation results of the elastic and rigid booms are comparatively analyzed and the effects of the flexible boom are discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.185-191
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• 2001

In many papers, the powertrain system generally has been madeled as one-dimensional torque model. One-dimensional powertrain model may calculate the torque correctly but it does not consider the non-rotational degrees-of-freedom of the powertrain components and the interaction of these degrees-of-freedom with the vehicle body frame and suspension. To consider the non-rotational degrees of freedom, the differential is modeled as a three-dimensional rigid body in this paper. A constant velocity joint is newly formulated and a relative constraint is also formulated to model the motion transfer due to gear ratio of the differential. Implementing the proposed powertrain system in the multibody model, more detail dynamic responses can be obtained. Obtained outputs such as reaction torques on the constant velocity joint and reaction forces on the rack can be useful data in the design of a powertrain.