Tae Won Park

Analysis of dynamic interaction between catenary and pantograph with experimental verification and performance evaluation in new high-speed line

Understanding the dynamic interaction between the catenary and pantograph of a high-speed train is the one of the most important technical issues in the railway industry. This is because the catenary–pantograph system plays a crucial role in providing electric power to the railway vehicle for stable operation. The aim of the present paper is to estimate the current-collection performance of this system by using numerical analysis, in particular, the flexible multibody dynamic analysis technique. To implement large deformable catenary wires, an absolute nodal coordinate formulation is used for the cable element. Additionally, an efficient contact element and an interactive model for the catenary–pantograph system are introduced. Each developed model is then used for analytical and experimental verification. Actual on-line test results of existing high-speed railway vehicles are presented and used to verify the analysis model. Finally, the performance characteristics of a new 400 km/h-class high-speed line are estimated and evaluated on the basis of international standards.

An Optimum Design of a Gas Circuit Breaker Using Design of Experiments

Abstract In this study, a gas circuit breaker (GCB) used to interrupt or apply an electric current in a high-voltage system is optimized using design of experiments. A multibody dynamic simulation model of the GCB is created and the performance of the system is optimized according to the optimization procedure presented in this paper. Sensitivity analysis is performed on the basis of a Plackett–Burman design table. Then, through the response surface analysis, the objective function is estimated and the reliability of the function is verified by an analysis of variance table. Using the sequential quadratic programming method, the values of design parameters that minimize the objective function and satisfy the constraint conditions are obtained. The performance of the current and optimized system is compared and by conducting an actual test of the GCB, the reliability of the simulation model and the usefulness of the optimal design method presented are verified.

Structural Vibration Analysis of Electronic Equipment for Satellite under Launch Environment

The impulse between the launch vehicle and the atmosphere can generate a lot of noise and vibration during the process of launching a satellite. In this situation, random vibrations can cause the malfunction of the electronic equipment of the device. In general, the safety of the electronic equipment is related to the natural frequency, shapes of mode and the dynamic deflection of the PCB in the electronic equipment. Structural vibration analysis of PCBs and their electronic components can be performed using either FEM or a vibration test. In this study, the natural frequency and dynamic deflection of a PCB were measured by FEM, and the safety of the electronic components of the PCB were evaluated according to the results. This study presents a unique method for the finite element modeling and analysis of PCBs and their electronic components. The results of the FEA were verified using a vibration test. The method proposed herein may be applicable to various designs ranging from satellite’s electronic equipment to home electronics. Introduction The electronic equipment installed in the satellite is box-shaped, and frames inside the satellite support many of the PCBs, there are also various types of electronic components in the PCBs. The agitation of the satellite caused by the random vibration during the launch process is transmitted to the PCB’s electronic components, thereby causing fatigue fracture. In particular, when the frequency of the random vibration is identical to the natural frequency of the PCB, fatigue fracture can occur at the connection of the electronic components and the PCB. It is generally known that the safety of electronic components is related to their natural frequency, mode shape and dynamic deflection [2]. This study uses a RDU (Remote Drive Unit), which is one of the electronic devices on a satellite, as a model to validate the relationship between launch condition, dynamic deflection, natural frequency, and the safety of PCBs’ electronic components. It will do this by modeling and simulating the PCBs fixed on the inside frame with a 1DOF system. During the process, FEA (Finite Element Analysis) was conducted on the PCB, including the electronic components, in order to find out the natural frequency of the PCB. A natural frequency test was also done on the PCB. The test and FEA results were compared and analyzed to guarantee the reliability of the analysis. At the same time, the safety of the electronic components was also evaluated. Analysis of the Safety of Electronic Components of the PCB The electronic components are soldered to the PCB with lead wire and are installed over a wide area so that they can endure the very harsh conditions present during the dynamic deflection of the PCB Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 1440-1445 doi:10.4028/www.scientific.net/KEM.270-273.1440

Analysis of the Current-Collection Performance of a High-Speed Train Using Finite Element Analysis Method

In this study, a simulation model to estimate the current-collection performance of a high-speed train was developed by using a commercial finite element analysis software, SAMCEF. A three-dimensional springDdamperDmass model of a pantograph was created, and its reliability was validated by comparing the receptance of the model to that of the actual pantograph. The wave propagation speed of the catenary model was compared with the analytical wave propagation speed of the catenary system presented in the UIC 799 OR standard. The length of the droppers was controlled, and the pre-sag of the contact wire due to gravity was considered. The catenary and the pantograph were connected by using a contact element, and the contact force variation when the pantograph was moved at velocities of 300 km/h and 370 km/h was obtained. The average, standard deviation, maximum, and minimum values of the contact force were analyzed, and the effectiveness of the developed simulation model was examined.

Estimation of Contact Pressure of a Flat Wiper Blade by Dynamic Analysis

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.

Fatigue strength optimisation of friction stir welded A6005-T5 alloy sheets

Abstract In this study, the friction stir welding process is optimised to improve the fatigue strength of the joints of A6005-T5 alloy sheets. The welding speed, rotational speed and tilting angle of the tool tip are chosen as design variables. Fifteen friction stir welding experiments are performed according to the central composite design table. The regression model function is estimated using the response surface analysis method. Using the model function, sensitivity analysis is carried out and the effect of each design variable on the fatigue strength of the joint is discussed. The optimum values of design variables are determined using the sequential quadratic programming algorithm.

Experimental Study on the Fatigue Strength of the Bogie Frame for Tilting Railway Vehicles

This paper shows the experimental study to evaluate the fatigue strength of a bogie frame for Korean tilting train. The various load cases were established based on the international standard (UIC615-4) and the special tilting load case, which is unique in the tilting train, was derived by dynamic analysis and logical assumption of operation under worst tilting condition. The experimental study was conducted by means of two ways, both static and fatigue loading test. Through the static load test, the safety against fatigue was assessed using Goodman diagram of the material used. The fatigue load test was carried out up to 1x107cycles. The fatigue strength was assessed by fatigue crack inspection by means of NDT test at the stage of 6x106cycles and 1x107cycles.

Computation of Dynamic Stress in Flexible Multi-Body Dynamics Using Absolute Nodal Coordinate Formulation

Recently, the finite element absolute nodal coordinate formulation (ANCF) was developed for the large deformation analysis of flexible bodies in multi-body dynamics. This formulation is based on the finite element method and the general continuum mechanics theory to represent the elastic forces. In this paper, a computational method of dynamic stress in flexible multi-body dynamics using absolute nodal coordinate formulation is proposed. Numerical examples, based on the Euler-Bernoulli beam theory, are shown to verify the efficiency of the proposed method. This method can be applied to predict the fatigue life of a mechanical system. In conclusion, it is possible to improve the reliability of a product by analyzing the dynamic stress time history in the design stage of product development using computer simulation. Moreover, this study demonstrates that structural and multi-body dynamic models can be unified into one numerical system. Introduction In various fields of mechanics, a part’s periodic or non-periodic elastic deformation resulting from the system’s light weight and high speed is considered to be the main cause of fatigue crack. In order to solve this problem, there have been many studies to calculate the dynamic stress, a main factor of fatigue, through dynamic analysis of the mechanical system considering a part’s elastic deformation [1-2]. In particular, computer simulation techniques have proven useful as a more economical means of predicting a product’s fatigue life than durability tests. These include the flexible multi-body dynamics analysis method [3-4] adopting modal coordinates, and the use of the commercial finite analysis program. The flexible multi-body dynamics analysis method, which employs modal coordinates, considers only a small number of a system’s generalized coordinates and thus offers numerical efficiency. However, it cannot adequately express large deformable motion, which takes into account rotational freedom. Furthermore, in order to find the body’s elastic deformation modes, a finite element analysis has to be carried out as well and the dynamic stress time history, which is required to predict fatigue life, must be calculated, proving to be a tedious process. The commercial finite element analysis program not only provides vibration and static analysis, but may also include dynamic analysis for a nonlinear mechanical system, and can be used to calculate a comparatively accurate dynamic stress, although much time and effort is required for analysis. Recently, a dynamic analysis method using absolute nodal coordinates applicable to even large deformation problems was introduced [5-6]. Due to the limitations of the existing flexible multi-body dynamics method using modal coordinates, this method employs nodal coordinates, and its reliability is being verified by large deformation experiments [7]. Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 1427-1433 doi:10.4028/www.scientific.net/KEM.270-273.1427

A Study of the Vibration Characteristics of a Haptic Vibrator for Horizontal and Vertical Magnetization

This paper describes the study of the design procedure for the step-by-step setup parameters and of the magnetizing method for performance and size reduction in the development of a haptic vibrator. The study of magnetization was accomplished by comparing the electromagnetic force in accordance with the horizontal and the vertical magnetization. The theoretical results indicated that the horizontal magnetization resulted in a better performance. The systematic design of a step-by-step procedure for establishing the design parameters was verified by testing the characteristics of the fabricated prototype product. The vibration response function analysis and electric field analysis were processed by decoupling of the analytical method, and these were determined to be in good agreement with the test results. The design parameters to contributing to the product reliability included the spring height, the welding position, and the coil position. The sensitivity of the electromagnetic field and the performance change were analyzed based on the design parameters. As a result, we proposed a design method to implement a reliability-based, high performance haptic vibrator.

Analysis of Hot Judder of Disc Brakes for Automotives by Using Finite Element Method

Thermal energy generated because of the friction between the disc and pad is transferred to both sides and causes thermal expansion of the material, which affects the contact pressure distribution. This phenomenon, which is called thermoelastic instability (TEI), is affected by the natural mode of a disc. TEI results in the formation of a hot spot and causes hot judder vibrations. In this study, three-dimensional analysis of the hot judder of a ventilated disc for automotives was performed by using the commercial finite element analysis program, SAMCEF. The intermediate processor based on a staggered approach was used to exchange the result data of the mechanical and thermal model. The hot spot was formed on the surface of the disc, and the number of hot spots was compared with the natural mode of the disc.