Chul Ki Song

Active vibration control for structural–acoustic coupling system of a 3-D vehicle cabin model

Abstract This paper presents an active vibration control system for use with structural–acoustic coupling system using piezoelectric actuators and piezoelectric sensors. For modelling a complicated 3-D vehicle cabin model, the structural–acoustic coupling system is analyzed by combining the structural data from modal testing with the acoustic data from the finite element method. Through the structural–acoustic analysis program, the control plate and the control modes are selected, which are most effective for attenuating its noise. A robust LQG controller with two sensor signal filters is designed to remove the experimental problems such as the spillover effect due to uncontrolled modes. The robust LQG controller for the structural–acoustic coupling system can reduce the interior noise of the cavity as well as the structural vibration of the cabin.

Laser-marking process for liquid-crystal display light guide panel

Abstract A light guide panel is an element of the liquid-crystal display backlight unit, which is extensively used for display devices. In this study, a laser-marking process is applied to the fabrication of light guide panels, and the new fabrication process may replace existing manufacturing methods such as silk screen printing, stamping, or V-cutting methods. The objective of this research is to evaluate the feasibility of the laser patterning system. A series of light guide patterns were made with a 50 W CO2 laser (continuous wave) to understand the effects of laser power and scanning speed on the geometry of groove patterns. The width and depth of the fabricated grooves increased with increasing laser power and decreasing scanning speed. In order to analyse surface geometry, scanning electron microscopy (SEM) photography was used and, for luminance measurement, a Topcon-BM7 was used. As a result, the marking conditions of the laser patterning, 5W and 0.4m/s, were suggested.

Structure Evaluation for the Level Luffing Crane' Boom

Abstract Structure evaluation for 70/15 T×105 m LLC(Level Luffing Crane)’s boom was conducted by Finite Element Method. Boom modeled with beam element was fixed by luff rope and boom mount and was received loads from self weight, luff hoisting, traveling motion, slewing motion, and wind force, etc. These applied loads were calculated using various factors presented in the reference standards and were inputted in the analysis model after considering about the adverse conditions of LLC. In the research, deformation, stresses, buckling of boom were evaluated by ANSYS. Structural safety of boom was confirmed in the results of numerical analysis. 기호설명 K : 후크의 하중조건, 하중횟수에 따른 효 β 율 계수(duty factor) Ψ : 리프트 작동에 의한 발생되는 충격계 수 (impact factor) F i : 관성력(N) W i : 호이스팅 하중과 구성품 질량(kg) G : 중력 가속도(m/s 2 ) Q : 풍하중에서의 속도압(N/m 2 ) C : 풍력계수 A : 파이프의 2단면적(m ) β TL : 주행(Traveling)시 발생되는 관성력에 의한 계수 SL : 선회(Slewing)시 발생되는 관성력에 의한 계수

Structural Evaluation of the 300 Ton Goliath Crane

Key Words : Finite Element Analysis(유한요소해석), Goliath Crane(골리앗크레인), Dead Load(자중), WindLoad(풍하중), Earthquake Load(지진하중)초록: 본연구는유한요소해석에의해300톤골리앗크레인의구조해석및평가를하였다. 300톤골리앗크레인의구조는110m의스판과50m의높이로구성되어있다. 크레인은자중, 크레인의주행관성력, 트롤리의주행관성력, 풍하중, 지진하중을받는다. 다양한하중조건을입력하여크레인의구조해석을수행하였다. 크레인의등가응력과전체변형량을ANSYS Workbench에서얻은결과를이용하여크레인의구조안전성여부를판단하였다.Abstract: Structural analysis and evaluation for the 300ton Goliath Crane were conducted with an FEM tool.The Golliath Crane has a 300 ton hoisting weight, a 110 m span and a 50 m lift. All loads such as theself weight, crane traveling load, trolley traveling load, wind load, and earthquake force, etc., that are indicatin the reference standards, were inputted as various severe conditions affecting the crane. The deformationand equivalent stress (von Mises stress) were evaluated for the crane structures

A Study on Performance of Cooling Fan for Auto Transmission Oil Cooler in the Large-Size Diesel Engine

This study has investigated numerically and experimentally the flow characteristic of air-cooling fan for transmission oil cooler in the large-size diesel engine. Impellers of cooler were composed of eight normal-scale and eight small-scale blades in the zig-zag pattern. In order to increase the discharge pressure of cooling fan, turbo type of fan blade is proposed in the impeller for transmission oil cooler. The fluidic performance of cooling fan has been estimated numerically by using the commercial code and experimentally carried out with reference on AMCA Standard 210-99. As a result, it is confirmed that the numerical result for performance curve is in good agreement with experimental data.

Fuzzy Estimation of Vehicle Speed

The absolute longitudinal speed of a vehicle is estimated by using data from an accelerometer of the vehicle and wheel speed sensors of a standard 50-tooth antilock braking system. An intuitive solution to this problem is, “When wheel slip is low, calculate the vehicle velocity from the wheel speeds; when wheel slip is high, calculate the vehicle speed by integrating signal of the accelerometer.” The speed estimator weighted with fuzzy logic is introduced to implement the above concept, which is formulated as an estimation method. And the method is improved through experiments by how to calculate speed from acceleration signal and slip ratios. It is verified experimentally to usefulness o estimation speed of a vehicle. And the experimental result shows that the estimated vehicle longitudinal speed has only a 6 % worst-case error during a hard braking maneuver lasting a few seconds.Copyright

The Noise Reduction Effect by the Enclosure of Gas Turbines

A gas turbine is the main equipment used in a combined heat and power plant. It generates a high sound pressure noise level. To reduce the noise level, an enclosure is installed around the turbine. The sound insulation performance of the enclosure affects the amount of external noise reduction. In this study, a sound transmission loss analysis is performed using the boundary element method to predict sound insulation performance according to the numbers and shapes of the supporter. Radiated noise analysis is also performed for the main external points of the enclosure using ray-acoustics. The results of these analyses are presented and a design plan is proposed that reduces the sound pressure noise level of the enclosure.

Design Improvement for a Planetary Gear System in Hydraulic Drive System

1 경상대학교 공학연구원 (Engineering Research Institute, Gyeongsang National University) 2 (주)영동테크 (Young Dong Tech Co. Ltd.) 3 경상대학교 대학원 기계설계학과 (Graduate School, Department of Mechanical Design and Production Engineering, Gyeongsang National University) 4 경상대학교 기계공학부, 공학연구원 (School of Mechanical Engineering, Engineering Research Institute, Gyeongsang National University) Corresponding author: cksong@gnu.ac.kr, Tel: +82-55-772-1633

Finite Element Analysis of an Elongation Rolling Process for Manufacturing Seamless Pipes

Elongation rolling process is an intermediate process to make the uniform thickness and uniform surface roughness during producing seamless pipes. The thickness and surface roughness of seamless pipes are generally affected by the distance of rolls and guide shoes, the roll shape, and its cross angle. In this study, finite element analysis for shape forming process is based on the analysis model of elongation rolling mill with guide shoes. This paper shows how the cross angle of the roll, the rolling rpm, and the distance of the guide shoe influence on the outer diameter and the thickness of seamless pipes. The rolling rpm did not give much influence on outer diameter.

Structural Analysis for a 70/15 ton×105 m Level Luffing Crane

Evaluation of the structural analysis for a 70/15 ton×105 m LLC (Level Luffing Crane) was conducted with an FEM Tool. Due to a discordance of the modeling and element type, the LLC was progressively analyzed after dividing it into the boom, main structure and rocker. All loads such as slewing, traveling and wind load, etc., that are indicated in the reference standards, were inputted as various severe conditions of the LLC. The deformation, equivalent stress(Von Mises stress), buckling characteristics were evaluated for the LLC structures. The stress concentrated areas over the allowable stress were identified, and reinforcement work was performed with a stiffener.