• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.187-191
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• 1995

An experimental study to analyze thd hot extrusion processes of regular square section through square dies is carried out by using plasticine as a model material at room temperature. The experimental setup for the extrusion of squared section from round billets through square dies is designed and manufactured. In order to visullize the plastic flow in the extrusion process the technique of gridding on the planes of the sysmmetries and a stacking the desks with different colors are employed. Velocity fields on the symmetry planes are obtained by using grid distortion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.548-554
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• 1996

A new method to locate modular fixtures using an optimization technique is proposed. The optimal fixture arrangement is derived to minimize the elastic deformation of a workpiece. That is, a fixture arrangement is regarded better if it minimized the elastic deformation of the workpiece while fixing a workpart of course. In this approach, the workpiece is projected into two dimensional domain to simplify the 3-dimensional fixture arrangement problem into 2-dimensional one. Thus the problem is reduced to find the optimal positions of one horizontal clamp and three locators which minimize the total deformation of the workpiece and the design variables are the location of the contact points between the boundary of the workpiece and the 4-fixels. The Genetic Algorithm is used for the optimization by mapping each design variables to a gene of a chromosome. The fitness value is the total strain energy of the workpiece calculated by the fin element analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.852-859
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• 1994

Optmal topology design is to search the optimal layout of the structure which can be used fot the shape of the conceptual design stage. Our objective is to maximize the stiffness of the structure under a material usage constraint. The density of each finite element is the design variable and its relationship with Young's modulus is expressed by quadratic form. The shape is represented by the entire density distribution, the structural analysis is performed by finite element method and the optimization is achieved by feasible direction method. Unlike optimality criteria method,feasible direction method can handle various problems simultaneously, that is, multi- objectives and multi-constraints. Total optimization time can be reduced by the approximation of the material property and fewer design variables than homogenization method. Topology optimization is applied to design the shape of ribs.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.148-159
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• 1999

A numerical method is presented for the dynamic analysis of spur gears rotating with very high angular speeds. For an efficient computation each gear is assumed to consist of a rotating rigid disk and an elastic tooth having mass, and finite element formulations are used for the equations of motion of the tooth. The geometric constraint is imposed between the rigid disk and the elastic tooth to fix them, and contact condition is imposed between the meshing teeth of the gears. At each iteration of each time step the Lagrange multiplier and contact force are revised by using the constraint error vector, and then the whole equations of motion are time integrated with the given Lagrange multiplier and contact force. For the accurate solution the velocity and acceleration constraints as well as the displacement constraint are satisfied by the monotone reductions of the constraint error vectors. Computing procedures associated with the iterative schemes are explained and numerical simulations are conducted with the spur gears.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.26-31
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• 2000

There are various noises generated by friction. Among the rest, eliminating squeal noise generated during braking is an important task for the improvement of vehicle passengers' comfort. The parameters affecting brake squeal noise are the material properties of the braking pad, the dynamic properties of the brake parts and the dimensions of the brake assembly etc. Also, the squeal noise changes its inherent form with the normal load and sliding speed. In this study, the characteristics of brake squeal noise generated by friction is analyzed experimentally. The experiment focused on the analysis of friction self-excited vibration and squeal noise level. Friction self-excited vibration is caused by the dry friction between pads and rotor, and occurs as a function of their relative sliding speeds. And Friction self-excited vibration is raised the brake squeal noise.

• The tire
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• s.86
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• pp.37-47
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• 1980

국제연합무역개발회의(UNCTAD)가 1976년 제4회 나이로비 총회이후, 추진해온 일차산품 종합계획 중 천연고무에 관한 교섭은 79년 10월초에 정리되어 정식으로 천연고무 상품협정이 발족하게 되었다. 동협정은 80년 1~6월간에 제네바에서 각국이 서명하고, 7~9월에 각국에서 비준하여 10월에 발족될 전망이다. 완충재고를 중심으로 한 동협정은 UNCTAD의 18개품목의 협정 중, 경제조항과 의무분담을 골자로 한 협정으로서는 처음 있는 일로서 주목되고 있다. 동협정은 천연고무가격의 안정과 공급안정을 목적으로 한 것이나, 동협정이 발효되더라도 현재에는 최고가격인 270싱가포르센트 이상으로 되어 있으므로 당분간은 아무런 효과도 거두지 못할 것으로 보인다. 고무업계에서는, 「천연고무가격이 안정되는 것은 환영하고 있으나 고가안정으로 (주석협정과 같이) 될 두려움마저 있다」고 평하고 있으며, 원재료앙등에 고심하고 있다. 전문 68조로 된 천연고무 국제협정의 내용은 다음과 같다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.982-987
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• 2012

Inconel 718 alloy has been widely used in the aerospace, heavy industry and electronic industry. However, the machinability of this alloy is very poor, which is attributed to their inherent high strength that is maintained at elevated temperatures. The tool life is dominant problem in machining difficult-to-cut materials, so it is necessary to select the efficient cutting conditions for the improvement of tool life. In this study, the cutting force, tool wear and surface roughness are investigated in end milling machining under various cutting conditions. By this experiment, the efficient machining condition of this alloy is suggested to adopt in various industries.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.680-688
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• 1986

In order to obtain the optimal estimation method of fracture toughness of dual phase steel in which martensitic phase encapsulated islands of ferritic phase, the stretched zone (SZ) method and the R-curve method of the JSME S 001 was discussed. The results obtained are as follows. (1) The $J_{IC}$ values estimated by the SZ method are overestimated as compared with those by the R-curve method. (2) The $J_{IC}$ by the R-curve method decreases with the increase of the ferrite grain size and the martensite hardness. (3) The overestimation of $J_{IC}$ by the SZ method is due to the continuous plastic blunting of ferrite after the formation of stable crack which affects the critical stretched zone width.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.194-201
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• 1997

Recently with the rapid development in the industries such as an iron mill and chemical plants, these are enlarged by the use of the piping. This piping was encountered the stress corrosion cracking(SCC) because of stress by water pressure and residual stress of welding etc. under industrial water. In this paper, the behaviour of stress corrosion cracking on the weld zone of steel pipe piping water(SPPW) were investigated according to pre-heat before welding in natural seawater(specific resistance : 25$\Omega$-cm). The main results obtained are as follows :1) The stress corrosion cracking for SPPW and SB 41 is most ready to propagate in heat affected zone of weldment. 2) The SCC sensitivity of SPPW on weldment is more susceptible than that of SB 41. 3) The stress corrosion cracking growth of heat affected zone is delayed by the preheat and dry of base metal and electrode before welding.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.124-127
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• 2008

현장방염처리 물품의 방염성능평가시 실내 인테리어 공사가 끝난 후 시험 시료를 채취하여 연소시험을 실시하게 되어있다. 그러나 이러한 절차로 인해 검사 소요시간이 길어지고 여러 민원이 발생하여 이를 대처할 시험 방법이 필요하다. 따라서 연소시험 대신 도막두께 측정 시험 방법을 도입하여 방염성능평가에 따른 문제점들을 해결하고자 한다. 도막두께 측정 시험의 경우 도막두께 측정용 라벨을 방염도료를 칠해야 하는 합판이나 목재 위에 붙이고 도료 작업이 끝나고 나면 관할 소방서에 이 라벨을 떼어서 제출하여 기준 도막 두께와 비교 측정하였을 때 기준 도막두께보다 두꺼우면 방염성능을 인정해주고 만약 기준 도막두께보다 얇게 칠해지면 현장 검사 또는 시료 채취 후 연소시험을 병행하여 검사함으로서 안전하고, 책임 있는 방염성능 시공을 할 수 있도록 관리 감독할 수 있을 것이다.