• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.11-18
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• 2011

This paper proposed a new 2-D multi-body dynamic modeling technique to analyze overriding behaviors taking place during train collision. This dynamic model is composed of nonlinear springs, dampers and masses by considering the deformable characteristics of carbodies as well as energy absorbing structures and components. By solving this dynamic model for rollingstock, energy absorbing capacities of collision elements, accelerations of passenger sections, impact forces applied to interconnecting devices, and overriding displacements can be well estimated. For a case study, we chose KHST (Korean High Speed Train), obtained crush characteristic data of each carbody section from 3-D finite element analysis, and established a 2-D multi-body dynamic model. This 2-D dynamic model was simulated under the train-to-train collision scenarios, and evaluated with 3-D virtual testing model. It was founded from the simulation results that this 2-D dynamic model could well predict overriding behaviors, and the modeling technique of carbody deformation was very important in overriding estimation.

• Wind and Structures
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• v.20 no.2
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• pp.169-189
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• 2015

To investigate the effects of "sudden change" of wind fluctuations on vehicle running performance, which is caused by the artificial discrete simulation of wind field, a three-dimensional vehicle model is set up with multi-body dynamics theory and the vehicle dynamic responses in crosswind conditions are obtained in time domain. Based on Hilbert Huang Transform, the effects of simulation separations on time-frequency characteristics of wind field are discussed. In addition, the probability density distribution of "sudden change" of wind fluctuations is displayed, addressing the effects of simulation separation, mean wind speed and vehicle speed on the "sudden change" of wind fluctuations. The "sudden change" of vehicle dynamic responses, which is due to the discontinuity of wind fluctuations on moving vehicle, is also analyzed. With Principal Component Analysis, the comprehensive evaluation of vehicle running performance in crosswind conditions at different simulation separations of wind field is investigated. The results demonstrate that the artificial discrete simulation of wind field often causes "sudden change" in the wind fluctuations and the corresponding vehicle dynamic responses are noticeably affected. It provides a theoretical foundation for the choice of a suitable simulation separation of wind field in engineering application.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.4
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• pp.330-337
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• 2015

When a tower crane is carried by a transporter in shipyard, the height and length of the tower crane should be adjusted to meet the safety guidelines. Since the guidelines came from the field experience, the safety limitation needs to be analyzed by a computer simulation. In this paper, modeling methods are addressed to implement the appropriate transportation simulation of a tower crane. For the relation between the tower crane and the transporter, normal contact force, friction force, and kinematic constraints are compared. Assignment of relevant linear acceleration and angular velocity is considered for the transporter to start or move on an inclined ground surface. By using the examined modeling methods, the dynamic motion of tower crane transportation is analyzed by a dynamic simulation program, and comparison between the simulation result and analytic solution is made to verify the feasibility of the modeling methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.115-120
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• 2011

The dynamic responses of a 5 MW wind turbine lifted by a floating crane with two elastic booms are analyzed. Dynamic equations of motions of a multibody system that consists of a floating crane, two elastic booms, and a wind turbine are derived. The six-degree-of-freedom (DOF) motions for the floating crane and the wind turbine are considered in the equations of motions. The hydrostatic force, the hydrodynamic force due to a regular wave, the mooring force, the wire rope force, and the gravitational force are considered as external forces. By solving the equations numerically, the dynamic responses of cargo are simulated. The simulation results are compared with those in the case of one elastic boom. Finally, the dynamic responses of the wind turbine lifted by the floating crane are analyzed under regular wave condition.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.28-34
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• 2014

In this paper, a concept design of a rail type ultra-high-speed train is proposed and its dynamic characteristics are analyzed. Instead of the existing solid axle, a new type bogie system and independently rotating wheels are applied in the proposed train. In order to analyze the dynamic characteristics, a multibody dynamic model of a vehicle is developed and the basic validity is verified by eigenvalue analysis. Also, it is shown that the critical speed is improved in comparison to that of existing high-speed train model HEMU-430X. Finally, through 7000R curved track driving analysis at a speed of 550 km/h, the lateral force of the wheels and the derailment quotient are estimated and the applicability of the new concept railway vehicle is confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.175-181
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• 2010

This paper presents the dynamic analysis method for estimating the performance of flat-type blades in wiper systems. The blade has nonlinear characteristics since the rubber is a hyper-elastic material. Thus, modal coordinate and absolute nodal coordinate formulations were used to describe the dynamic characteristic of the blade. The blade was structurally analyzed to find the bending characteristics of the cross section of the blade. According to the analysis results, the blade section is divided into three deformation bodies: rigid, small, and large. For the small deformation body, the modal coordinate formulation is used, while the absolute nodal coordinate formulation is used for the large deformation body. To verify the dynamic analysis result, an experiment was performed. The simulation and experiment results were compared to verify the flexible multi-body dynamic model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.501-509
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• 2010

A floating crane is a crane-mounted ship and is used to assemble or to transport heavy blocks in shipyards. In this paper, the static and dynamic response of a floating crane and a heavy block that are connected using elastic booms and wire ropes are described. The static and dynamic equations of surge, pitch, and heave for the system are derived on the basis of flexible multibody system dynamics. The equations of motion are fully coupled and highly nonlinear since they involve nonlinear mass matrices, elastic stiffness matrices, quadratic velocity vectors, and generalized external forces. A floating frame of reference and nodal coordinates are employed to model the boom as a flexible body. The nonlinear hydrostatic force, linear hydrodynamic force, wire-rope force, and mooring force are considered as the external forces. For numerical analysis, the Hilber-Hughes-Taylor method for implicit integration is used. The dynamic responses of the cargo are analyzed with respect to the results obtained by static and numerical analyses.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1559-1565
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• 2013

This study aims to investigate the dynamic interaction characteristics between Maglev vehicles and an elevated guideway. A more detailed model for the dynamic interaction of the vehicle/guideway is proposed. The proposed model incorporates a 3D full vehicle model based on prototyping, flexible guideway by a modal superposition method, and levitation electromagnets including the feedback controller into an integrated model. The proposed model was applied to an urban transit Maglev developed for a commercial application to analyze the dynamic response of the vehicle and guideway, and the effect of the surface roughness of the rail, mid-span guideway deflections, and air gap variations are then investigated from the numerical simulation.

• Transactions of the KSME C: Technology and Education
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• v.3 no.2
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• pp.141-148
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• 2015

In this study, the VCB(Vacuum Circuit Breaker) has been developed using the Recurdyn that is widely used on multibody dynamics analysis. The VCB consists of three main circuits with the VI(Vacuum Interrupter) and the main frame with the operating mechanism. This analytic model is validated by comparing the simulation results and the experimental results. Generally, in order to reliably cut off the breaking current, the opening speed of the VCB after contact separation has to be a 0.9~1.1m/s. Therefore, the study of the design parameters of the VCB is needed. To improve the opening velocity, Taguchi design method is applied to optimize the design parameters of a VCB with a lot of linkages. In addition, to evaluate the improvement of the operating characteristics, the simulation results are compared with the Recurdyn and experimental results with improved prototype sample.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1231-1237
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• 2014

It is essential to perform driving performance tests of military vehicles on rough terrain. A full car test is limited by cost and time constraints, because of which a dynamic analysis via computer simulation is preferred. In this study, a vehicle model is developed using MSC.ADAMS, a commercial multibody analysis program, and compared via experiments. FTire is modeled using the results of a tire performance test to obtain the vertical stiffness. A nonlinear damper is modeled by a characteristic experiment. Leaf springs are modeled with beam force elements and consisted to a vehicle model. The vertical force and acceleration response of the wheel are identified when vehicle is passing over a simple bump as well as a sinusoidal road. The developed vehicle model is verified with the results of a full car test.