• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.88-97
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• 1995

The leaf spring is used in the suspension of most buses and trucks due to its compactness, which reduces the shock-force and the vibration from the road, and increases passenger comfortability and carlife. Of the various kinds of leaf springs, the leaf spring without eyes can be found easily in the heavy duty truck, and has different characteristics to the leaf spring with eyes in the case of large free camber. Because of radius change, the leaf without eyes slips on the supports, which makes the deflection. The difference is due to this deflection. In this paper, we show the general method of characteristic analysis, for example, Pandan method, can be no more applicable to these springs. Thus considering the geometry deflection by slip, we have developed the equation of the characteristic of the leaf spring without eyes and prove the effectiveness of this equation by experiment. From the result, at large camber the slip deflection is large and as camber smaller, this is smaller. At the camber behind some value, the effect of slip no longer influence to the characteristic of leaf springs.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.35-41
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• 2016

Ceramic-metal based high power LED array package was developed via thick film LTCC technology using a glass-ceramic insulation layer and a silver conductor patterns directly printed on the aluminum heat sink substrate. The thermal resistance measurement using thermal transient tester revealed that ceramic-metal base LED package exhibited a superior heat dissipation property to compare with the previously known packaging method such as FR-4 based MCPCB. A prototype LED package sub-module with 50 watts power rating was fabricated using a ceramic-metal base chip-on-a board technology with minimized camber deformation during heat treatment by using partially covered glass-ceramic insulation layer design onto the aluminum heat spread substrate. This modified circuit design resulted in a camber-free packaging substrate and an enhanced heat transfer property compared with conventional MCPCB package. In addition, the partially covered design provided a material cost reduction compared with the fully covered one.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.8-19
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• 1998

Nonlinear flow characteristics of a hydrofoil running under the free surface are investigated based on potential flow theory using singularity distribution techniques. Following Hess & Smith's method[12], sources and vortices are distributed on the surface of the foil and Rankine sources are distributed at a distance above the undisturbed free surface to solve the nonlinear free surface waves(so called Raised Panel Method). Using the linearized Neumann-Kelvin solution, the conversed solutions which rigidly satisfy the nonlinear free surface condition is obtained through an iterative technique. It is validated that the nonlinear solutions are compared with Duncan's experimental results(NACA 0012, $\alpha=5^{\circ}$), showing good correlations with each other. At a very shallow submergence and a very high speed the converged solutions are obtained. As the speed increases higher, it is shown that the difference between the nonlinear and linear solutions are trivial. Finally, the effects of the camber and thickness on the nonlinear flow characteristics of the foil are investigated.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.63-68
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• 2007

A number of process problems should be solved in the multi-layered ceramic devices such as EMI filter. In particular, it is essential to control the sintering shrinkage in co-firing of different materials for obtaining defect-free samples such as crack, camber, and delamination which usually occur near the surface and interface. We studied the effect of the powder properties of ferrite on the co-firing behavior of green ceramic layers composed of ferrite and varistor. Three kind of ferrite powder samples as a function of milling time (24, 48, and 72 hr) were prepared. Varistor and ferrite ceramic green sheet were made by means of doctor blade process using slurry (ceramic powder and binder solution). Here, slurry was prepared by mixing 55 wt% powder with 45wt% binder solution. Varistor and ferrite green sheets were laminated at $80 kg/cm^2$, and co-fired at $900^{\circ}C$ and $1000^{\circ}C$ for 3 hr. We obtained the camber-free and co-fired ferrite/varistor layer structure by controlling the milling time and sintering temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.979-984
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• 2001

The Sang-Jin bridge constructed by the Free Cantilever Method in 1985 is 4-span concrete rahmen bridge with a hinge at midspan. Due to the effect of creep, shrinkage of concrete and relaxation of tendon, the Sang-Jin bridge exposed the excessive displacement at midspan with the passage of time. In order to improve the load-carrying-capacity and durability of the bridge, needs to repair and rehabilitate the structure emerged. New rehabilitation methods were applied such as external prestressing of concrete box, application of pier pre-camber and steel truss jacking. Structural analysis and several tests including static load test, dynamic load test and ambient vibration test were executed to verify the improvement. The test result showed that the displacement of the midspan was improved by 10mm and it was verified that the stiffness of the bridge was increased. Totally, the load-carrying-capacity of Sang-Jin bridge was increased at least 1.56times which was attributed to the new rehabilitation method.

• International Journal of Fluid Machinery and Systems
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• v.6 no.2
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• pp.105-112
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• 2013

The application of contra-rotating rotors for higher specific speed pump has been proposed in our studies, which is in principle effective for reducing the rotational speed and/or the pump size under the same specification of conventional axial flow pump. In the previous experiments of our prototype, the cavitation inception at the tip region of the rear rotor rather than that of the front rotor and the strong potential interaction from the suction surface of the rear rotor blade to the pressure surface of the front one were observed, indicating the possibility to further improve the pump performance by optimizing rotational speed combination between the two rotors. The present research aims at the design of rear rotor with lower rotational speed. Considering the fact that the incoming flow velocity defects at the tip region of the rear rotor, an integrated inflow model of 'forced vortex' and 'free vortex' is employed. The variation of maximum camber location from hub to tip as well as other related considerations are also taken into account for further performance improvement. The ideas cited above are separately or comprehensively applied in the design of three types of rear rotor, which are subsequently simulated in ANSYS CFX to evaluate the related pump performance and therefore the whole low speed design idea. Finally, the experimental validation is carried out on one type to offer further proofs for the availability of the whole design method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.10
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• pp.955-965
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• 2010

The MH-75 propeller for the MAV propulsion is designed using a free vortex design method which considers design parameters such as the hub-tip ratio, the twist angle distribution, the maximum camber location and the chord length of the propeller blade. Aerodynamic characteristics of the MH-75 propeller are predicted by changing the flight speed using the frequency domain panel method. And, the thrust characteristics of the MH-75 propeller are measured using the balance system of the subsonic wind tunnel for the validation of numerical results. The performance characteristics of the MH-75 propeller satisfied with design requirements. Numerical results of the MH-75, which are predicted by the frequency domain panel method, are more agree with experimental results compare with XFOIL.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.97-108
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• 2015

In the design of sailing yachts, para-glider, or high-sky wind power, etc., the analysis of side-wind aerodynamic forces exerted on a cambered 3-D model is very important to predict the performance of various machinery systems. To understand the essential flow physics around the three-dimensional shape, simplified rigid-body models are proposed in this study. Four parameters such as free stream velocity, angle of attack, aspect ratio, and camber are considered as the independent variables. Lift and drag coefficients are computed with CFD technique using ANSYS-CFX, and the results with the visualization of post-processed flow fields are analyzed in the viewpoint of fluid dynamics.