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김홍건,강영우,유기현 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-
An electric vehicle uses the system to a power source whether it limps a high efficiency, without environmental pollution. It coincides the best at the 21th century environmental regulation and energy frugality. The motor control system using DC-DC converter is carried out in this study. The present control system is structured the better condition than that of the AC-DC converter with DC-AC inverter. Further, a vehicle dynamics analysis is performed for the case of Mini-Baja. It is found that the analysis dynamic system for the Mini-Baja gives a good design parameters.
직조유리섬유강화 PET수지 복합체의 인장특성에 관한 연구
김홍건,최창용 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.1
Tensile strength of the woven glass fiber reinforced PET(Poly-Ethylene-Terephthalate) matrix composite manufactured by rapid press consolidation technique was investigated and evaluated. During pre-heating, consolidation and solidification stages, the optimal manufacturing conditions for this composite were discussed based on the void content and tensile properties depending on vacuum condition. It is found that the effect of vacuum condition during preheating gives a substantial difference on the strength as well as microstructure. It is also found that the failure micromechanism shows several energy absorption processes enhancing fracture toughness.
김홍건,양성모,노홍길 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.4
In discontinuous composite mechanic, shear lag theory is one of the most popular model because of its simplicity and accuracy. However, it does not provide sufficiently accurate strengthening predictions in elastic regime when the fiber aspect ration is small. This is due to its neglect of stress transfer across the fiber ends and the stress concentrations that exist in the matrix regions near the fiber ends. To overcome this shortcoming, a more simplified shear lag model introducing the stress concentration factor which is function of several variables, such as the modulus ratio, the fiber volume fraction, the fiber aspect ratio, is proposed. It is found that the modulus ratio (E_f/E_m) is the essential variable among them. Thus, the stress concentration factor is expressed as a function of modulus ratio in the derivation. It is found that the proposed model gives a good agreement with finite element results and has the capability to correctly predict the values of interfacial shear stresses and local stress variations in the small fiber aspect ratio regime.
Nano positioning control for dual stage using minimum order observer
김홍건 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.3
A nano positioning control is developed using the ultra-precision positioning apparatus such as actuator, sensor, guide, power transmission element with an appropriate control method. Using established procedures, a single plane X-Y stage with ultra-precision positioning is manufactured. A global stage for materialization with robust system is combined by using an AC servo motor with a ball screw and rolling guide. An ultra-precision positioning system is developed using a micro stage with an elastic hinge and piezo element. Global and micro servos for positioning with nanometer accuracy are controlled simultaneously using an incremental encoder and a laser interferometer to measure displacement. Using established procedures, an ultra-precision positioning system (100 mm stroke and ±10 nm positioning accuracy) with a single plane X-Y stage is fabricated. Its performance is evaluated through simulation using Matlab. After analyzing previous control algorithms and adapting modern control theory, a dual servo algorithm is developed for a minimum order observer to secure the stability and priority on the controller. The simulations and experiments on the ultra precision positioning and the stability of the ultra-precision positioning system with single plane X-Y stage and the priority of the control algorithm are secured by using Matlab with Simulink and ControlDesk made in dSPACE.
Investigation of a Stress Field Evaluated by Elastic-Plastic Analysis in Discontinuous Composites
김홍건 한국자동차공학회 2007 International journal of automotive technology Vol.8 No.4
A closed form solution of a composite mechanics system is performed for the investigation of elasticplastic behavior in order to predict fiber stresses, fiber/matrix interfacial shear stresses, and matrix yielding behavior in short fiber reinforced metal matrix composites. The model is based on a theoretical development that considers the stress concentration between fiber ends and the propagation of matrix plasticity and is compared with the results of a conventional shear lag model as well as a modified shear lag model. For the region of matrix plasticity, slip mechanisms between the fiber and matrix which normally occur at the interface are taken into account for the derivation. Results of predicted stresses for the small-scale yielding as well as the large-scale yielding in the matrix are compared with other theories. The effects of fiber aspect ratio are also evaluated for the internal elastic-plastic stress field. It is found that the incorporation of strong fibers results in substantial improvements in composite strength relative to the fiber/matrix interfacial shear stresses, but can produce earlier matrix yielding because of intensified stress concentration effects. It is also found that the present model can be applied to investigate the stress transfer mechanism between the elastic fiber and the elastic-plastic matrix, such as in short fiber reinforced metal matrix composites.
Hydrox Gas 절단과 LPG 절단의 열적특성에 관한 연구
김홍건,곽이구,Kim, Hong-Gun,Kwac, Lee-Ku 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.2
Cutting procedures where qualities are determined by various demand factors largely influences shipbuilding productivity. Particularly, defects in cutting shapes and cutting surface results in delay for post shipbuilding stages such as in welding and assemblage lines which could become factors for reduced economic viability of the project. Existing cutting procedures utilize fossil fuels such as propane or ethylene as the main fuel component and these methods applied particularly to ship plate cutting gives relatively slow cutting speed and generates large quantities of harmful and sometimes poisonous polluting fumes of which warrants an urgent need to look for alternative cutting methods. Recent introduction of hydrox gas generated by electrically dissociating water into hydrogen and oxygen components to be utilize as an alternative cutting fuel has resulted not just in visible improvement on cutting quality and speed over the existing methods but it has also been welcomed as an environmentally friendly clean fuel source. This paper has been prepared to serve as the basis for accommodating this environmentally friendly hydrox gas cutting method into actual working environment by observing and recording hydrox gas cutting thermal characteristics.
Evaluation of elastic modulus for unidirectionally aligned short fiber composites
김홍건,곽이구 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.1
An analytical approach of to reinforcement for of short fiber reinforced composites has been extended to include the estimation of elastic modulus. The model is based on the theoretical development of shear lag theory developed by Cox for unidirectionally Aligned aligned Short short Fiber fiber Compositescomposites. Thus, the evolution of conventional models is described in detail along with the effect on the modulus of various parameters. Results are shown with experimental data as well as the comparison of other theories. It is found that the present model agrees well with experimental data and resolves some of the discrepancies among the previous models. It is also found that the present model is very accurate yet relatively simple to predict Young's modulus of discontinuous composites and has the capability to correctly predict the effects of fiber aspect ratio, fiber volume fraction, and fiber/matrix modulus ratio.