• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.110-115
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• 2002

In this paper, the results of an analysis of the dynamic behavior of the eddy current brake(ECB) system are presented. The measured irregularity of the track in Korean high speed line and the track irregularity given by ERRI(high level) were used for simulation. The wheel-rail profile combination were analyzed with different rail gauges. A model of the bogie with an substitute body for the carbody was implemented in the Multi-body-Simulation Program SIMPACK. The ECB frame was modelled both as flexible body and as rigid body. Four different driving conditions were analyzed. In this study dynamic behavior in general were performed to evaluate the design of eddy current brake system and specially the effect of damper was also studied. A comparison of simulations with and without damper shows that the damper have most effect for lower speed. The simulation results will be verified by comparison with measured data from on line test and also used for improving design.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.466-477
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• 2021

There are three different well-known methods for predicting the manoeuvrability of ships: (1) free running model test, (2) direct manoeuvring simulation using CFD and (3) system-based manoeuvring simulation. In this paper, the manoeuvrability of the KVLCC2 was estimated using CFD with rigid body motion and body force propeller method. The free running manoeuvre at the different time steps were also simulated. The yaw checking ability and the turning ability of KVLCC2 were predicted using CFD and could have been confirmed that the IMO criteria was satisfied. When the results were compared with the model test and system-based method, the free running simulation showed better agreement to that of the model test. It could also be confirmed that the results vary depending on the time step. Overall, the CFD results using the body force propeller method estimated most accurately the test results.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.59-69
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• 2019

This paper focuses on the numerical simulation of ice abrasion induced by unbreakable ice floe. Under the assumption that unbreakable floes behave as rigid body, the Discrete Element Method (DEM) was applied to simulate the interaction between a fixed structure and ice floes. DEM is a numerical technique which is eligible for computing the motion and effect of a large number of particles. In DEM simulation, individual ice floe was treated as single rigid element which interacts with each other following the given interaction rules. Interactions between the ice floes and structure were defined by soft contact and viscous Coulomb friction laws. To derive the details of the interactions in terms of interaction parameters, the Finite Element Method (FEM) was employed. An abrasion process between a structure and an ice floe was simulated by FEM, and the parameters in DEM such as contact stiffness, contact damping coefficient, etc. were calibrated based on the FEM result. Resultantly, contact length and contact path length, which are the most important factors in ice abrasion prediction, were calculated from both DEM and FEM and compared with each other. The results showed good correspondence between the two results, providing superior numerical efficiency of DEM.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.10-22
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• 1998

In the present work the elastic-plastic FE formulations using dynamic explicit time integration schemes are used for numerical analysis of a large auto-body panel stamping processes. For analyses of more complex cases with larger and more refined meshes, the explicit method is more time effective than implicit method, and has no convergency problem and has the robust nature of contact and friction algorithms while implicit method is widely used because of excellent accuracy and reliability. The elastic-plastic scheme is more reliable and rigorous while the rigid-plastic scheme require small computation time. In finite element simulation of auto-body panel stamping processes, the roobustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry conditions. The performnce of the dynamic explicit algorithms are investigated by comparing the simulation results of formaing of complicate shaped autobody parts, such as a fuel tank and a rear hinge, with the experimental results. It has been shown that the proposed dynamic explicit elastic-plastic finite element method enables an effective computation for complicated auto-body panel stamping processes.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.428-435
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• 2001

In this paper, the design factors of stacker crane for the automatic warehouse are verified by dynamic simulation process. Simulation model is designed as the form of rigid elements and discrete flexible beam connections. The various result for structural design of stacker crane is produced by dynamic simulation and experiment. For the simulation of structural dynamics, ADAMS which is a software for kinematic & dynamic simulation, is used. In order to verify the analysis method, simulation and experiment result are compared.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.45-50
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• 2002

Airbag systems have improved the occupant safety in reducing the injuries of driver and passenger during collisions. They have occasionally caused fatalities; especially to small occupant and children. Recent airbag related fatalities of children have raised serious concerns on how to evaluate the safety of children in various crash environments. This paper present the development of the 3-year-old human model. Child human model is composed of skin, skeleton and joints. The positions of joint and mass properties of body segments are calculated from ARB(Ariticulated Rigid Body) program GEBOD. To verify the developed human model, ROM simulation and OOP simulations are conducted.

• Journal of Korea Game Society
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• v.9 no.5
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• pp.43-52
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• 2009

This paper analyzes the four game physics engines in terms of real time techniques. Real time physics is the technology that simplifies the physics-based simulation to apply for the real time applications such as game. Our study includes two commercial physics engines, Havok's Physics SDK and NVIDIA's PhysX SDK, and two open source projects, Open Dynamics Engine and Bullet physics engine. As a result, most of them covers rigid body dynamics and some include either deformable body simulation or fluids simulation, or both. For real time simulation, they adopt the simplified numerical methods, the effective in collision detection/response, and also use the parallel processing hardwares, i.e., multi core CPU, Physics processing unit(PPU), or graphics processing unit(GPU).

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.305-311
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• 2005

This research presents a three-dimensional modeling technique for a flexible sheet. A relative coordinate formulation is used to represent the kinematics of the sheet. The three-dimensional flexible sheet is modeled by multi-rigid bodies interconnected by out-of-plane joints and plate force elements. A parent node is designated as a master body and is connected to the ground by a floating joint to cover the rigid motion of the flexible sheet in space. Since the in-plane deformation of a sheet such as a paper and a film is relatively small, compared to out-of-plane deformation, only the out-of-plane deformation is accounted for in this research. The recursive formulation has been adopted to solve the equations of motion efficiently. An example is presented to show the validity of the proposed method.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.909-922
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• 2015

The dynamic response and the mooring line tension of a 1/75 scale model of spar-type platform for 2.5 MW floating offshore wind turbine subject to one-dimensional regular harmonic wave are investigated numerically and verified by experiment. The upper part of wind turbine which is composed of three rotor blades, hub and nacelle is modeled as a lumped mass the scale model and three mooring lines are pre-tensioned by means of linear springs. The coupled fluid-rigid body interaction is numerically simulated by a coupled FEM-cable dynamics code, while the experiment is performed in a wave tank with the specially-designed vision and data acquisition system. The time responses of surge, heave and pitch motions of the scale platform and the mooring line tensions are obtained numerically and the frequency domain-converted RAOs are compared with the experiment.