Improvements for reduction of the brake squeal noise at Seoul metro rolling stock on tracks

김성걸 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.8

Experimental and theoretical methods were applied to find and understand the phenomenon of brake squeal noise of the Seoul Metro rolling stock on tracks. Generally, it is well known that brake squeal noise is strongly related to stick and slip between brake pad and disk. In most cases for rolling stock on tracks, trailer cars needed more particular attention through the tests, because they were the major sources of brake noise due to frictional braking. There are two types of rolling stocks in Seoul Metro: chopper and VVVF. Both types of rolling stocks for lines 1 and 3 in the Seoul Metro were used for experimental analyses. To study brake squeal noise under various braking conditions, dynamometer tests were performed at the S&T Brake, Co., which is one of major manufacturers of brake pads for rolling stock on tracks. For measuring brake squeal noise, acoustic tests were performed with a microphone in the Gunja depot. And modal tests for brake parts, which consisted of brake lining, brake lining pad, and back plates, were executed to obtain the natural frequencies related to the brake squeal noise. Also, modal tests of the whole brake assembly and lining block were performed at the heavy maintenance shop of the Gunja depot. The mode analysis using an ANSYS was simulated to determine the relations between the mechanisms of brake squeal noise. As the results of the tests and the simulations, it was found that specific natural frequencies of the brake parts affected squeal noise, and also, the reason to create squeal noise. Finally, improvements for reducing squeal noise were proposed, and applied to lines 2and 3 at Seoul Metro rolling stock on tracks.

북한 SLBM 기술 어디까지 왔나

김성걸 북한연구소 2016 北韓 Vol.- No.538

북한은 핵무기 개발과 함께 미사일의 개발에도 열을 올리고 있다. 개발된 핵무기를 사용하려면 투발수단인 미사일이 필요하기 때문이다. 지난 8월 하순에 실시된 북한 잠수함 발사 탄도미사일(SLBM)의 시험발사는 성공적이었던 것으로 드러나고 있다. 미사일 발사장소로 ‘수중(水中)’이 추가되면서, 한반도에 새로운 위협이 떠오르고 있다. 핵무기를 투발할 수 있는 북한 미사일 위협이 갈수록 도를 더하고 있는 것이다.

몰드물성 및 Chip의 크기차이에 따른 웨이퍼 레벨 SiP에 대한 열 피로 해석 모사

김성걸,김주영,정호동,김재호 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-

This paper describes in detail the life prediction models, and simulation of thermal fatigue under different mold compounds and chip sizes for wafer level embedded SiP. A 3D Finite element model was built to simulate the viscoplastic behaviors for mold compounds and chip sizes. Especially, bonding parts between mold and Silicon Nitride(Si₃N₄) were carefully modelled and distribution of strains was studied. Three different chip sizes were used and the effects of mold compounds were observed. Consequently, this numerical study shows that type-A has better fatigue life than other mold compounds. Also, 4×4 size chip has a shorter life than 6×6 and 8×8 size.

A study on the design of a new power transmission for wind turbines

김성걸 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.3

The single-rotor wind turbine remains the dominant design for energy production. However, this design requires improvements toovercome some of its limitations. The introduction of the dual rotor system regarded as improvement over the single-rotor system inKorea due to its high efficiency, despite Korea’s low wind quality. Many researchers have attempted to devise different dual rotor machinesand assess their power production capabilities under similar wind conditions to those in Korea. Existing power transmissions fordual-rotor wind turbines have issues with the complexity of design, difficulty in manufacturing, high costs and low efficiencies. Therefore,the aim of this study was to design a new power transmission for the dual-rotor wind turbine with an alternative to the bevelplanetarysystem by using a planetary system. This new method is dependent on the torque ratio and not the gear ratio as in common gearsystems. The design and analysis of each part, such as the gears, shafts, bearings and control mechanisms are included in this study. Thedesign is based on the power transmission of a motor vehicle. A prototype of the design is manufactured to verify the proposed method. The experimental results show that the new planetary-type gear box incurs fewer energy losses, has a high efficiency and low manufacturingcosts. It is anticipated that the proposed design might be suitable for use with commercial wind turbines.

부국강병과 국가적 자존심 상징이며 현대 군사과학의 결집체

김성걸 북한연구소 2008 北韓 Vol.- No.435

무연 솔더 접합부을 갖는 플립칩에서의 언더필 및 범프 피치 변화에 의한 열 피로 수명 예측 해석

김성걸,김주영,Kim, Seong-Keol,Kim, Joo-Young 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.2

This paper describes the thermal fatigue life prediction models for 95.5Sn-4.0Ag-0.5Cu solder joints of Flip chip package considering Under Bump Metallurgy(UBM). A 3D Finite element slice model was used to simulate the viscoplastic behavior of the solder. For two types of solder bump pitches, simulations were analyzed and the effects of underfill packages were studied. Consequently, it was found out that solder joints with underfill had much better fatigue life than solder joints without underfill, and solder joints with $300{\mu}m$ bump pitch had a longer thermal fatigue life than solder joints with $150{\mu}m$ bump pitch. Through the simulations, flip chip with lead-free solder joints should be designed with underfill and a longer bump pitch.

마그네틱 커플링을 사용한 축계의 동적해석 ( Dynamic Analysis of a Shaft System with Magnetic Coupling )

김성걸,이성진,이장무 대한기계학회 1993 대한기계학회 춘추학술대회 Vol.- No.-

자동차 시트 및 마네킹 시스템의 진동 Ⅱ ( Vibration of Car Seat and Mannequin System Ⅱ )

김성걸,김준현,박기홍 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.1 No.2

일본의 군사력과 군사기술

김성걸 원광대학교 2005 圓光軍事論壇 Vol.- No.1

Most people falsely believe that the Japanese military power is non-threatening. They are gravely mistaken. This misperception can be due to the fact that they are called it 'Self-Defence Forces' rather than an official army, or because defense spending that amounts to only 1% of national GDP seems miniscule. However, Japan's current year defense spending amounts to 4.8564 billion yen ($42 billion), which is second or third highest in the world. This means Japan spends 160,000 dollars per soldier compared to United States' 200,000 dollars. This is twice Germany's and triple Russia's spending per soldier. Japan's Self-Defense Forces may not be well manned, but they are well armed. One thing we need to place special focus on is Japan's military technology. Japan realized the importance of military technology after the World War II and has placed priority in technology accumulation and domestic industry participation in weapons procurement. Even when Japan had to procure defense systems from foreign countries, Japan chose licensing production over direct procurement so they can be prepared to get into indigenous production. After losing World War II, Japan fell behind when they lost the chance to evolve from propeller engines to jet engines, but by the time Japan went into co-production with the US on F-2 fighter jets through the FSX Program, Japan increased their technical capabilities to a level that could have challenged the United States. In the 1970s, Iran purchased F-14 fighter jets from the US, but was unable to procure spare parts after they strained diplomatic relations with the US. Lack of parts supplies prevented Iran from using their fighters in the Iran-Iraq War in the 1980s. Japan's world class technology allows Japan to be competitive in world trade. Japan possesses dual-use technology, which can be easily spun off to defense industry. As proof, we see Japan's capabilities including semi-conductor, rocket, electronics, laser, and stealth technology being applied to advanced weapons. In 1991, United States showed advanced warfare in the Gulf War but we need to realize that Japan supplied most parts for US's precision guidance missiles. Japan is involved in co-development of Missile Defense, which requires high technology, and this warrants a good cause for reassessing Japan's military power.

주파수 변화에 따른 태양전지 전기적 특성 분석

김성걸,홍창우,이경섭,Kim, Seong-Geol,Hong, Chang-Woo,Lee, Kyung-Sup 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.5

This study focused on the performance characteristics of solar cell using the impedance technique. We measured an impedance according to frequency from 1 Hz until 1 MHz. It could know that the impedance was decreased according to the frequency increases in solar cell. The impedance of single crystal solar cell was 0.61 ${\Omega}$ at 1 Hz, and kept almost settled value to $1{\times}10^2$ Hz. However, the impedance of polycrystal solar cell was $7{\times}10^3{\Omega}$ at 1 Hz.