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Thixforming 을 위한 Al-7%Si-0.3%Mg 합금의 유도 가열 조건이 구상화 조직에 미치는 영향
정홍규,강충길 ( Hong Kyu Jung,Chung Gil Kang ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.5
N/A The optimal reheating conditions to apply the thixoforging and semi-solid die casting process were investigated by changing the reheating time, the holding time, the reheating temperatures, the capacity of the induction heating system, and the adiabatic material size. In the case of solid fraction fs=50% (for semi-solid die casting), the microstructure of SSM (specimen size:d76×l90) at the condition of the first elevating time of 4 min, holding time of 1 min and holding temperature of 350˚C, the second elevating time of 3 min, holding time of 3 min and holding temperature of 575˚C, the third elevating time of 1 min, holding time of 2 min and holding temperature of 584˚C, capacity of Q=8.398KW is obtained with globular microstructure and finest. In addition, in the case of solid fraction fs=55% (for thixoforging), the SSM (specimen size:d76xl90) at the condition of the first elevating time of 4 min, holding time of 1 min and holding temperature of 350˚C, the second elevating time of 3 min, holding time of 3 min and holding temperature of 570˚C, the third elevating time of 1 min, holding time of 2 min and holding temperature of 576˚C, capacity of Q=12.04KW is obtained with the finest globular microstructure. We saw that the most important factor in a three-step reheating process is the final holding time. (Received May 22, 1998)
Thixoforming 을 위한 A1-6%Si-3%Cu-0.3%oMg 합금의 유도 가열 공정에 관한 연구
정홍규(Hong Kyu Jung),강충길(Chung Gil Kang) 한국주조공학회 1999 한국주조공학회지 Vol.19 No.3
The optimal induction heating conditions are proposed to obtain a uniform temperature, which affects a uniformity of solid fraction, throughout the billet during the thixoforming process. Heating method for providing a homogeneous temperature profile in overall cross section of the billet has been introduced. The optimal design of the induction coil has been identified as a function of coil size, ratio of semi-solid material diameter and coil one. The optimal coil design process of semi-solid aluminum alloy with d × l = 76 × 70 (㎜) to reduce the temperature gradient of the billet and to obtain the globular microstructure was theoretically proposed. The suitability of the coil design has been demonstrated by induction-heating experiments. The effect of the induction heating conditions on globular microstructure, grain growth and the solutions avoiding the coarsening phenomena has been discussed through the grain growth mechanism of Al-6%Si-3%Cu-0.3%Mg alloy. (Received January 5, 1999)
내마모계 AI - Si 재료의 레오로지 성형기술 개발 ( I ) - 충진거동 및 결함분석 -
정홍규(Hong Kyu Jung),강성수(Sung Soo Kang),문영훈(Young Hoon Moon),강충길(Chung Gil Kang) 한국주조공학회 2000 한국주조공학회지 Vol.20 No.6
N/A Rheology forming technology has been accepted as a new method for fabricating near net shaped products with lightweight aluminum alloys. The rheology forming process consists of reheating process of billet, billet handling, filling into the die cavity and solidification of rheology formed part. The rheology forming experiments are performed with two different die temperatures (T_d = 200℃, 300℃) and orifice gate type. The filling behavior and various defects of Al-Si materials with wear resistance (A357, A390 and ALTHIX 86S) fabricated in rheology forming process are evaluated in terms of alloying elements and surface non-uniformity. Finally, the methods to obtain the rheology formed products with high quality are described by solutions for avoiding the surface and internal defects.
김상섭(Sang-sup Kim),정홍규(Hong-kyu Jung) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.5_2
This paper presents a vehicle dynamic modeling method for five body lumped parameter model, that includes kinematic characteristics of suspensions more accurately. The relative displacement and orientation of a wheel with respect to car body are represented as a function of the vertical displacement of the wheel. A unique representation of the cartesian relative velocity and acceleration of the wheel is derived using the suspension displacement function. The system equations of motion for functional suspension model are systematically derived by using velocity transformation method. The comparison of the simulation results between multibody and functional model of suspension demonstrates the validity of the proposal modeling method.<br/>
군용화 트럭의 동역학 해석 및 차체프레임의 내구도 분석
이철훈(Chul-hoon Lee),김상섭(Sang-sup Kim),정홍규(Hong-kyu Jung),어하준(Ha-joon Eo),고병성(Byoung-sung Ko),김준원(Joon-won Kim) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, the durability analysis of military and commercial truck frame is performed, and possibility of using the commercial truck as military is evaluated. For accurate durability analysis, a full vehicle truck is modeled as multibody in ADAMS including the front & rear suspension, tire, cab & cargo and the flexible frame. This paper investigated dynamic behaviors of military and commercial truck with flexible frame for dynamic loads, while the vehicle is running over a bump, APG9, and TRC durability road. By using the dynamic stresses through modal stress recovery method, the fatigue life is analyzed by S-N method. This paper shows the effectiveness of the durability analysis and evaluation method by combining multibody dynamics and FE fatigue analysis.<br/>
차체의 유연체 특성을 고려한 차량의 조종 안정성과 승차감 해석
김상섭(Sang-sup Kim),이상범(Sang-bum Lee),정홍규(Hong-kyu Jung),손희성(Hoo-sung Son) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_2
This paper presents a method of flexible vehicle dynamic analysis. The trimmed body model is constructed by using MSC/NASTRAN. A comprehensive chassis system model is created by using ADAMS/CAR. The two model is successfully combined using component mode synthesis method. The simulation results show that the car body structual compliance has significant effect on the ride as well as handling response of the vehicle.
Development of Real-time Vehicle Dynamics Model for HILS System of Active Chassis Control
Kim, Sang-Sup,Jung, Hong-Kyu 국민대학교 생산기술연구소 2004 공학기술논문집 Vol.27 No.-
A functional suspension model is proposed as a kinematic describing function of the suspension, that represents the relative wheel displacement in polynomial form in terms of the vertical displacement of the wheel center and steering rack displacement. The relative velocity and acceleration of the wheel is represented in terms of first and second derivatives of the kinematic describing function. The system equations of motion for the full vehicle dynamic model are systematically derived by using velocity transformationmethod of multi-body dynamics. The comparison of test and simulation results demonstrates the validity of the proposed functional suspension modeling method. The model is computationally very efficient to achieve real-time simulation on TMS 320C6711 150MHz DSP board of HILS system for ECU evaluation of semi-active suspension.
Thixoforging 을 위한 다출력 유도가열 공정의 응용
강충길,정홍규 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.7
For the thixoforging process, multi-power induction heating process (with rapid change of the power) and inductive coil design are very important due to the reduction of the lead time for induction heating and forming. The multi-power induction heating process is indispensable to adopt a power-time beating pattern which manages to conciliate complete eutectic melting at the core with limited overheating at the periphery. Generally, high power is used for the rapid reheating of the billet to the eutectic temperature range (about 10℃ lower than eutectic temperature) and low power for the remelting of the desired solid fraction and for the radial homogeneization of the solid faction. The suitability of multi-power induction heating conditions would be verified through the comparison to general beating (without rapid change of the power) and Garat's data. It is found that if the billet is rapidly reheated at high power range, T_(h2) is important from the point of securing a fine distribution of solid and liquid.
Thixoforging 공정에 있어서 반용융 알루미늄 합금의 충전거동과 기계적 성질
강충길,정홍규 한국주조공학회 1999 한국주조공학회지 Vol.19 No.4
The filling behavior and various defects of thixoforged Al alloy products were observed. The microstructures and the mechanical properties were investigated for variation of process parameters such as applied pressure and die temperature. The thixoforging experiments were performed at f_s=55%. Punch speed was 200 ㎜/sec. Die temperature was changed from 250˚C to 400˚C Applied pressures were changed to 100MPa and 150MPa, respectively. Various defects were observed particularly at the lower die temperatures. To uniformly distribute the regions of solid and liquid phase around the specimen during forming, it is necessary to increase the punch speed and design the optimal gate. Furthermore, dense microstructures were found for lower die temperature and higher applied pressure. The tensile properties yielded that the higher the applied pressure, the higher the ultimate strength, yield strength, and elongation. ( Received April 12 , 1999)