• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.542-549
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• 2002

Computer simulation is essential to design the suspension elements of railway vehicle. By computer simulation, engineers can assess the feasibility of given design variables and chance them to get a bettor design. Even though commercial simulation codes are used, the computational time and cost remains non-trivial. Therefore, malty researchers have used a mesa model made by sampling data through simulation. In this paper, four mesa-models for each index group such as ride comfort, derailment Quotient, unloading radio and stability index, are constructed by use of neural network. After these meta models are constructed, multi-objective optimization are achieved by using the differential evolution. This paper shows that the optimization of design variables using the neural network model is very efficient to solve the complex optimization Problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.609-617
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• 2013

This paper presents a near-minimum time path planning algorithm for autonomous driving. The problem of near-minimum time path planning is an optimization problem in which it is necessary to take into account not only the geometry of the circuit but also the dynamics of the vehicle. The path planning algorithm consists of a candidate path generation and a velocity optimization algorithm. The candidate path generation algorithm calculates the compromises between the shortest path and the path that allows the highest speeds to be achieved. The velocity optimization algorithm calculates the lap time of each candidate considering the vehicle driving performance and tire friction limit. By using the calculated path and velocity of each candidate, we calculate the lap times and search for a near-minimum time path. The proposed algorithm was evaluated via computer simulation using CarSim and Matlab/Simulink.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.245-250
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• 2010

In this work, the stability and safety analysis are carried out to predict the performance of a next generation high-speed railway vehicle (HEMU-400X). Since the safety of the high-speed railway vehicles is very important, it is meaningful to predict the dynamic performance and stability of the railway vehicles using a numerical model at a railway vehicle design step. The critical speed of the dynamic model depending on the conicity of the wheel is calculated in the stability analysis. The critical speed calculated in this analysis is over 400km/h for the conicity value of 0.15, which is determined on the basis of representative international standard, UIC 518. Also, the lateral and vertical accelerations at several points of the same dynamic model are calculated for the safety analysis. In the simulation, the dynamic model runs at the test speed of 440km/h, which is determined considering a maximum target speed, and the total driving distance is 30km. And those estimated values are less than the allowed maximum acceleration values of UIC 518.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.86-92
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• 2017

In this study, a running performance evaluation and roller rig test was conducted to evaluate the applicability of a composite bogie frame, which has the role of the primary suspension. The composite bogie frame was made of a GEP224 glass/epoxy prepreg. Vehicle dynamic analysis was carried out on the composite bogie with three different kinds of side beam thicknesses (50 mm, 80 mm, and 150 mm). From the results, the composite bogie with a side beam thickness of 80 mm satisfied all the dynamic design requirements. Although the composite bogie with the side beam thickness of 50mm also met the design requirements, its critical speed was just a 2% margin to the requirement. In contrast, the model of the side beam thickness of 150mm did not meet the ride comfort. In addition, a composite bogie frame with the side beam thickness of 80 mm was fabricated and installed on a complete bogie. Moreover, the roller rig test using the fully equipped bogie was performed to evaluate the critical speed. During the test, the lateral excitation was imposed on the wheelsets to realize the rail irregularity. There was no divergence of the lateral displacement of the wheelsets while increasing the speed. The measured critical speed was similar to the predicted result.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.699-705
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• 2012

The role of a seat belt in a vehicle is to protect the driver from injury when a crash occurs. However when a large crash occurs, the driver slips forward and receives a strong impact. To prevent this situation, improvement of seat belts is essential. In this study, the new concept of a dynamic locking tongue (DLT) for seat belts is developed. The DLT device is used to reduce the impact to the driver's chest by tightening the webbing, so the driver is protected from severe injury in a large crash. First, a finite element model of the DLT device is created using SAMCEF and structural analysis is conducted with boundary conditions similar to those found in experiments. Then, the stress in the DLT device can be calculated. Second, the shape of the DLT device is optimized using the response surface analysis method in order to minimize the stress and weight. The validity of the optimization of the DLT device is verified using structural analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.415-425
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• 2017

Stresses occur in the spent nuclear fuel disposal canister due to the impulsive forces incurred in the accidental drop and impact event from the transportation vehicle onto the ground during deposition in the repository. In this paper, the comparative study of finite element analysis for stresses occurring in various models of the spent nuclear fuel disposal canister due to these impulsive forces is presented as one of design processes for the structural integrity of the canister. The main content of the study is about the design of the structurally safe canister through this comparative study. The impulsive forces applied to the canister subjected to the accidental drop and impact event from the transportation vehicle onto the ground in the repository are obtained using the commercial rigid body dynamic analysis computer code, RecurDyn. Stresses and deformations occurring due to these impulsive forces are obtained using the commercial finite element analysis computer code, NISA. The study for the structurally safe canister is carried out thru comparing and reviewing these values. The study results show that stresses become larger as the wall encompassing the spent nuclear fuel bundles inside the canister becomes thicker or as the diameter of the canister becomes larger. However, the impulsive force applied to the canister also becomes larger as the canister diameter becomes larger. Nonetheless, the deformation value per unit impulsive force decreases as the canister diameter increases. Therefore, conclusively the canister is structurally safe as the diameter increases.

• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.572-578
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• 2012

In the electric railway vehicles, securing stable current collection performance is an important factor which determines the quality of operation and the maximum speed. In order to predict such current collection performance, various analysis methods have been proposed for a long time. Also, investigations for improving the accuracy of the results and the efficiency of the analysis process have been performed. In this paper, a method for the efficiency improvement has been proposed. This method is based on the basic concept that the system equations of motion of a catenary numerical model include only interactive range with a pantograph. In this paper, an algorithm and generalized process for applying proposed method are introduced. Also, validity of the results and utility of the method was verified and studied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1447-1453
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• 2012

For an electromagnetic suspension (EMS)-type urban Maglev train using U-shaped electromagnets, both the vertical and the lateral air gaps for levitation are maintained only by the electromagnet. The train can run over curved rails without active lateral air gap control because the U-shaped electromagnet simultaneously produces both a levitation force and a guidance force, which is dependent on the levitation force. Owing to the passive control of the lateral air gap, the lateral vibration could exceed the limits of the lateral air gap and acceleration. In this study, dynamic analysis of a Maglev train is carried out, and the effectiveness of a lateral damper for vibration reduction is investigated. To more accurately predict the lateral vibration, a Maglev vehicle multibody model including air-sparing, guideway irregularities, electromagnets, and their controls is developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.837-842
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• 2010

The wiper system of a vehicle is important because it wipes the windshield, thereby enabling drivers to see through the windshield even under conditions of rain and snow. The blade is the key component of the wiper system because it wipes the windshield. When wiper-arm spring causes the blade to be pressed on the windshield optimum performance of wiping can be achieved when appropriate contact pressure is maintained. In this study, a dynamic analysis of the wiper system is carried out. A three-dimensional finite-element model of the wiper system is generated using SAMCEF, a commercial structural dynamic analysis program. The distribution of the contact pressure of the blade in its dynamic state is calculated. The simulation result is compared to the experiment result. Using the results of this study, the contact pressure of the blade can be estimated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.437-442
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• 2012

To analyze a multibody system, this paper proposes an implicit numerical integration method for joint coordinates subsystem synthesis method. To verify the proposed method, a multibody model for an unmanned robot vehicle, which consists of six identical independent suspension systems, is developed. The symbolic method is applied to compute the system Jacobian matrix for the implicit integration method. The proposed method is also verified by performing rough terrain run-over simulation in comparison with the conventional implicit integration method. In addition, to evaluate the efficiency of the proposed method, the CPU time obtained by using this method is compared with that obtained by using the conventional implicit method.