• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.130-138
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• 1994

Bottom plates of empty hold are subjected to not only water pressure but also bi-axial inplane loads, specially in the alternate full loading full loading condition of bulk carrier. This kind of plate behaviours is very difficult to be explained and to be estimated using common buckling design guide in the initial design stage of hull structure, therefore, some more concrete studies for this plate structure was performed based on the currently developed buckling estimation formula. In this buckling formula, torsional stiffness effects of edge stiffener are included additionally and effects of elastic buckling strength of plate panel are treated as characteristic value problem. Also considering boundary stiffener effects and inplane and lateral loading, evaluation of bottom plate scantling using this formula, calculated results using various classification regulation of buckling strength and results of first report approach are compared each other and useful guides using developed formula for bottom plate scantling design are discussed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.24-31
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• 2003

In the gas cutting of plate steel, the quality of the cut surfaces and sections is strongly dependent on the cutting conditions such as cutting speed, kerf width, plate thickness, material, distance between tip and specimen, and cutting oxygen pressure etc. The cutting tests of plate steel were carried out using CNC gas cutting machine. This paper deals with cut surface and section characteristics of plate steel in CNC gas cutting. Both top and bottom widths of kerf, the surface roughness(Ra, Rmax) of cutting surfaces are measured under various cutting conditions such as cutting speed, material, distance between tip and specimen, and cutting thickness. The photographs of cut surface and cut section are also analyzed under various cutting conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.438-446
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• 1999

Crop minimization of the top and bottom ends of hot rolled plate, in a plate, in a plate mill, has been investigated. The existing model to determine the edging pattern at the finishing rolling pass was not reasonable to get high width accuracy and rolling yields. New models including width prediction have been formulated by using neural network model of back propagation learning algorithm and statistical analysis based on the actual production rolling data to give the optimal pattern for minimizing trimming loss. Using these models, at a given rolling condition of broadside pass and finishing pass and the permissible condition of width variation, it was possible to minimize crip at the top and bottom ends according to optimum procedure in plate mill. An application to improve the plan view pattern reduced width variation by 23% and crop length by 30% on average with an effective fishtail crop shape.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.2
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• pp.44-54
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• 1988

This study was carried out to investigate the applicability of the conventional design method for ground supported circular cylindrical shell structures. For this purpose, the ensiled farm silo was adopted as a model structures. Herein, the conventional design method was based on the assumption that such structures are clamped at the bottom edges or the ground pressure is independent of the deflection at the surface. In the present paper, the applicability of above assumption was checked out by comparison with an exact method considering soil-structure interaction. Some results of numerical calculation show us ; When the ground is very hard, for example Winkler's constant k is larger than 100 kg / cm$^2$ / cm, or the bottom plate of structures has a infinitely stiffness, for example the bottom plate thickness is larger than 100 cm, the sectional forces, obtained from the conventional method at any wall of structures resting on an elastic foundation, can used for design purpose. Therefore, if the above condition is satisfied then the conventional assumptions can be justified for the design purpose. In this case, the assumption that such structures are fixed at the lower edges was more realistic than the assumption that the reaction pressure acting on structures is uniformly disributed since the accuracy of results of the analysis by the former assumption was higher than that obtained from the latter assumption. But the sectional forces in the bottom plate resting on ground directly could not be evaluate correctly by the conventional method.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.79-86
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• 2014

The purpose of this study is to determine the proper fillet weld size for the stiffeners on hull bottom plate of crude oil tanker. To achieve it, the effective notch stress and hot spot stress of the fillet weld with leg length specified in the rule were evaluated by using comprehensive FE analyses. Based on the results, the fatigue damages at each location of weld were calculated. Meanwhile the transitional behavior of initial welding distortion in the hull bottom plate under the design conditions was investigated by using a non-linear FEA. Welding distortion and residual stress introduced during fabrication process were considered as initial imperfections. According to FE analysis results, if the fillet leg length satisfies the design criteria of the classification society, the concern on the root failure at the fillet welds in the bottom hull plate during the design life can be negligible. In addition, considering the transitional behavior of the distortion during the service life, the fillet leg length should be minimized.

• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.3-11
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• 1999

The atomic fuel rods between top and bottom end pieces of reactor need to be extended for high combustion rate of future-type fuel to increase the irradiation in the axial direction. For allowing axial extension of the fuel rods, the space between top and bottom end pieces should be expanded. Thus the thickness reduction of the flow plate is necessary. This study was carried out the mechanical strength test by using strain gages as a function of flow plate thickness, the existence of skirt and loading condition for the Korean Fuel Assembly(KOFA). The experimental apparatus was designed for load conditions, uniformly distributed load and displacement. Test method using whiffle tree of uniformly distributed load has been comparatively conservative. The test results were compared with those of finite element analysis and the test method on bottom end piece was established.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.3
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• pp.187-195
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• 2018

Ship's bottom slamming has been studied by many researchers for a very long time. But still some ships suffer structure damages caused by the bottom slamming impacts. This paper presents a practical computation method of the design impact pressure due to ship's bow bottom slamming. Large heave and pitch motions of a rigid hull ship are simulated by the nonlinear strip method in time domain and the relative colliding velocity between the bow bottom and the water surface is calculated using the simulated ship motions. The bottom slamming impact pressure is calculated as a product of the relative colliding velocity squared and the bottom slamming pressure coefficient that is obtained by modification of the SNAME pressure coefficients based on Ochi's slamming experiments. Not only the bottom slamming pressures but also the required bottom plate thicknesses are calculated and compared with those of the classification society rules. The comparisons show good agreements and it is confirmed that the present method is practically very useful for the bottom structure design against ship's bow bottom slamming impacts.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.149-154
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• 2003

The cutting tests of high tensile steel plate(AH36) were carried out using CNC plasma arc cutting machine. Both top and bottom width of kerf and the surface roughness(Ra, Rmax) of cut surface are measured under various cutting conditions such as cutting speed, steel plate thickness, etc. In the CNC plasma arc cutting, the surface roughness decreases as cutting speed increases. The hardness is high up to 4mm depth from the cutting surface. In the cutting speed 1300~2100mm/min, the ratio of proper kerf width(Wt/Wb) is around 2.6. Through the series the series of experiments, the satisfactory cutting conditions of high tensile steel plate were found.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.429-437
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• 1999

Width variation of the top and bottom ends of steel at finishing rolling in a plate, has been investigated. It was found that width variation after finishing rolling is affected by edging, broadside rolling ratio, longitudinal rolling ratio, width shape after broadside rolling, temperature, width-to-thickness ratio, and so on. A neural network modelling of back propagation has been conducted on the width variation during rolling. Based on these prediction models, a width control system, by which the roll opening and closing of the hydraulic AWC edger can be adjusted during edge rolling in finishing rolling passes, has been developed. Compared to conventional width model, the neural network model is much accurate in a model. The width control system is applied to a newly built production mill.

• Smart Structures and Systems
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• v.15 no.5
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• pp.1345-1362
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• 2015

The present paper deals with the free vibration analysis of the functionally graded solid and annular circular plates with two functionally graded piezoelectric layers at top and bottom subjected to an electric field. Classical plate theory (CPT) is used for description of the all deformation components based on a symmetric distribution. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness direction of the plate. The properties of plate core can vary from metal at bottom to ceramic at top. The effect of non homogeneous index of functionally graded and functionally graded piezoelectric sections can be considered on the results of the system. $1^{st}$ and $2^{nd}$ modes of natural frequencies of the system have been evaluated for both solid and annular circular plates, individually.