• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.175-181
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• 1998

The coil spring is used in the suspension of automotive vehicles and small omnibus. Recently, it can be adopted hardening type spring which spring constant is accompanied by increasing displacement to increase passenger comfortability. One of methods which assert this characteristic is cylindrical-taper section coil spring. In this paper we calculate ideal spring characteristic curve from the given vehicle conditions, and show the design method of the cylindrical-taper section coil spring.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.292-292
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• 2000

Since high-power CO$_2$ Laser can be make a high densed energy to Local processing area, manufacturing processes using the laser can be processed for very Localized areas at a very fast rate with minimal or no distortion. Accordingly, the laser has been widely used in the fields of thermal manufacturing processes such as welding, fusion cutting, grooving, and heat treatment of metals. In particular, interest in the laser heat treatment process has grown tremendously in the past few years. In this process, maintaining the uniform hardening depth is important problem to obtain good quality products and to reduce heat induced distortion and residual stress. For achieving this objective, we introduced a new design technique of a fuzzy logic controller that greatly simplified the design procedure by defining several simplified design parameters. In the design procedure, the major design parameters of the controller are characterized by identifying several common aspects. From a series of simulation results, we found that the proposed design technique can be effectively used to design of a fuzzy logic controller for the LASER surface hardening process.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.579-585
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• 2008

Numerous experimental investigations on metallic materials and solid polymers have shown that relaxation behavior is nonlinearly dependent on prior strain rate. The stress drops in a constant time interval nonlinearly increase with an increase of prior strain rate. And the relaxed stress associated with the fastest prior strain rate has the smallest stress magnitude at the end of relaxation periods. This paper deals with the performance of three classes of unified constitutive models in predicting the characteristic behaviors of relaxation. The three classes of models are categorized by a rate sensitivity of kinematic hardening rule. The first class uses rate-independent kinematic hardening rule that includes the competing effect of strain hardening and dynamic recovery. In the second class, a stress rate term is incorporated into the rate-independent kinematic hardening rule. The final one uses a rate-dependent format of kinematic hardening rule.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.676-679
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• 1995

Practically, induction surface hardening is used widely to enhance the local strength of structure. In this study, Fatigue limit and its S-T characteristic for raw and induction hardened specimen of SCM440 is studied experimentally. The life prediction was considered by Juvinall's equation and its predicted result is compared with experiment.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.496-501
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• 2005

Precipitates, present in most commercial alloys, can have a strong influence on strength and hardening behavior of a single crystal. The effect of thin precipitates on the anisotropy of initial slip resistance and hardening behavior of crystals is modeled in this article. For the convenience of the computational derivation and implementation, the material formulation is given in the unrelated intermediate configuration mapped by the plastic part of the deformation gradient. Material descriptions for the considered two phased aggregates consisting in lattice hardening as well as isotropic hardening and kinematic hardening are suggested. Numerical simulations of various loading cases are presented to discuss and assess the performance of the suggested model. From the results of the numerical simulation, it is found that the suggested model represents the initial plastic anisotropy at least qualitatively well and that it has an improved representation of various characteristic hardening behaviors in comparison with conventional hardening descriptions where the precipitate structure is not reflected.

• Corrosion Science and Technology
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• v.11 no.4
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• pp.151-156
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• 2012

The cavity formed by the ultrasonic generation in the fluid with the application of water cavitation peening collides into the metal surface. At this time, the surface modification effect such as the work hardening presents by the compressive residual stress formed due to the localized plastic deformation. In this investigation, the water cavitation peening technology in the distilled water with the lapse of time was applied to 5052-O aluminum alloy for aluminum ship of a high value. So, the optimum water cavitation peening time on the effect for surface hardening and anti-corrosion property was investigated. Consequently, the water cavitatin peening time on excellent hardness and corrosion resistance characteristic presented 3.5 min. and 5.0 min, respectively. The surface hardness in the optimum water cavitation peening time was improved approximately 45% compared to the non-WCPed condition. In addition, corrosion current density was decreased.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.211-216
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• 2000

Foamed concrete is applied ad filling, material of On-dol, bur it has much trouble in controlling the quality because of not establishing the detailed related criteria and recommendation for the construction and quality control practice. Therefore, this study will investigate the as-placed density and air content of formed slurry before hardening and its physical characteristics after hardening, analyzed the relation of each characteristic, and finally provide the proper method for the quality control foamed concrete.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.877-881
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• 1996

승용차나 소형승합차에는 현가장치의 스프링으로 코일스프링을 많이 사용하고 있으며 최근 들어 승차감의 상을 위해 변위의 증가와 함께 스프링 정수가 증가하는 경화 특성 스프링(hardening type spring)을 많이 채택하고 있는데, 이 특성을 나타낼 수 있는 방법 중 하나가 등반경-테이퍼 소재의 코일스프링이다. 이 논문에서는 주어진 차량조건으로부터 이상적인 스프링 특성곡선을 계산하고 이 곡선을 분할하여 직선의 연결로 근사시켜 분할한 수만큼의 직선적 특성의 스프링으로 직렬 연결되어 있다고 가정하여 이 곡선에 근접된 특성을 가지는 등반경-테이퍼 소재 코일 스프링의 설계방법을 제시하고자 한다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.209-214
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• 2007

This study is concerned with working hardening of bending operation on hydroforming parts. Generally, hydroforming parts having the complicated shape of the automobile, require a 3-dimentional bending operation. This operation involves several variations in the tube which are the thickness, the mechanical characteristics, the hardness, the circumference etc., on original tube. So, we study those variations and the affect on the hydroforming operation and hydroforming parts. We used two methods, one of which was computer simulation and the other the actual test in the plant.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.639-640
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• 2007