• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.2
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• pp.25-31
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• 2004

Machinability in metal cutting processes depends on cutting input conditions such as cutting velocity, feed rate, depth of cut, types of work material and tool shape factors. In this study, to assess chip breaking characteristics of a turning process, an equivalent oblique cutting system to this has been established. And the equivalent effective rake angle was determined using side rake angle, back rake angle and side cutting edge angle of the tool. A non-dimensional parameter, Chip breaking index(CB), was used to assess Chip breaking characteristics of chip in conjunction with the equivalent effective rake angle. In case of positive rake angles of the equivalent effective rake, the back rake angle has little effect on the chip breaking characteristics however, in case of negative ones, the side rake angle has some effect on Chip breaking characteristics.

• Journal of Navigation and Port Research
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• v.28 no.7
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• pp.619-627
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Ulsan Harbor and Ulsan New Port, etc. due to construction of New Port in Ulsan Bay. We also considered the increase of water depth at the entrance channel by dredging work up to 15 meters depth in order to see the dredging effect. Among several model analyses, the nonlinear and breaking wave conditions are showed the most applicable results. This type of trial might be a milestone for port development in macro scale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.405-416
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• 2005

The rubblization technique is breaking the aged concrete pavement slab into rubblized concrete aggregate, and use it as an base material at its original position, then builds overlay above the rubblized base. This method has been successively used in USA due to the advantage of good contructibility, cost-effectiveness as well as the capability of preventing of reflection cracks. However, constructibility and economic performance of rubblization on typical Korean concrete pavements needed to be investigate since to typical Korean concrete pavements have thick slab, as well include lean concrete subbase course. This stud explored optimum breaking depth and suggested minimum 10cm based on reflection crack simulation test. Also proper head shape and impact energy were investigated based on small breaking field tests. It was found that $127kg/cm^2$ of stress with 52.3% of head contact area are breaking requirement. Also, Multi-head type breaker suitable for Korean condition was designed and developed. This multi-head type breaker was designed to rubblize old concrete to the suggested optimum rubblized-depth and rubblized-concrete-aggregate size to prevent reflection crack and maintain high bearing capacity. This machine was used for the test of rubblization of old concrete pavement on a non-use old concrete and a in-serviced road. In these two tests, engineering properties of rubblized base and constructability and cost were investigated. In both tests, the old concrete rubblized to targeted size and depth, and high-level bearing capacity was achieved. Also, superior constructability and lower cost compared with traditional reconstruction was examined.

• Proceedings of the Korean Quaternary Association Conference
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• 2002.12a
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• pp.66-67
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• 2002

• Journal of Korea Water Resources Association
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• v.37 no.6
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• pp.461-466
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• 2004

This study presents a combined experimental and numerical effort to investigate wave breaking of sinusoidal waves in a surf zone. Numerical predictions are verified by comparing to laboratory measurements. The model solves the Reynolds equations and$textsc{k}$-$\varepsilon$ models for the turbulence analysis. To track the free surface displacement, the volume of fluid method is employed. As the height of incident wave increases, the wave breaking occurs at a closer point of the slope in the numerical model and laboratory experiments with the same depth and period. When a wave breaking occurs, the ratio of wave height becomes larger, with the same wave height and depth, as the period increases.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.2
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• pp.37-49
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• 2024

To date, numerous empirical formulas have been proposed through hydraulic model experiments to predict the wave breaker index, including wave height and depth of wave breaking, due to the inherent complexity of generation mechanisms. Unfortunately, research on the characteristics of wave breaking and the prediction of the wave breaker index for gravel beaches has been limited. This study aims to forecast the wave breaker index for gravel beaches using representative linear-based machine learning techniques known for their high predictive performance in regression or classification problems across various research fields. Initially, the applicability of existing empirical formulas for wave breaker indices to gravel seabeds was assessed. Various linear-based machine learning algorithms were then employed to build prediction models, aiming to overcome the limitations of existing empirical formulas in predicting wave breaker indices for gravel seabeds. Among the developed machine learning models, a new calculation formula for easily computable wave breaker indices based on the model was proposed, demonstrating high predictive performance for wave height and depth of wave breaking on gravel beaches. The study validated the predictive capabilities of the proposed wave breaker indices through hydraulic model experiments and compared them with existing empirical formulas. Despite its simplicity as a polynomial, the newly proposed empirical formula for wave breaking indices in this study exhibited exceptional predictive performance for gravel beaches.

• Journal of Korean Port Research
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• v.15 no.1
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• pp.47-56
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• 2001

A numerical model for practical use based on the 1-line theory is presented to simulate shoreline changes due to construction of offshore structures. The shoreline change model calculates the longshore sediment transport rate using breaking waves. Before the shoreline change model execution, a wave model, adopting the modified Boussinesq equation including the breaking parameters and bottom friction term, was used to provide the longshore distribution of the breaking waves. The contents of present model are outlined first. Then to examine the characteristics of this model, the effects of the parameters contained in this model are clarified through the calculations of shoreline changes for simple cases. Finally, as the guides for practical application of this model, several comments are made on the parameters used in the model, such as transport parameter, average beach slope, breaking height variation alongshore, depth of closure, etc. with the presentation of typical examples of 3-dimensional movable bed experimental results for application of this model. Here, beach change behind the offshore structures is represented by the movement of the shoreline position. Analysis gives that the transport parameters should be taken as site specific parameters in terms of time scale for the shoreline change and adjusted to achieve the best agreement between the calculated and the observed near the structures.

• Journal of Navigation and Port Research
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• v.28 no.8
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• pp.753-757
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• 2004

The free-surface flow is simulated to make clear the viscous interaction of stem waves and the sub-breaking phenomena around a high speed vehicle. The Navier-Stokes equation is solved by a finite difference method where the body-fitted coordinate system, the wall function and the triple-grid system are invoked They are applied to study precisely on the stem flow of S-103 as to which extensive experimental data are available. Computations are extended to the submerged revolutional body. The numerical result shows that the gradient of M/Us is greatly influenced by the submerged depth And the stem wave is influenced by the separation due to the bow wave.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.891-894
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• 2001

In this work, an effort is made to investigate the behavior of a chip, from its initial flow to its final breaking stage. The expression for chip flow in grooved tools is verified analytically using FEM. Cutting parameters like velocity and depth of cut have a profound influence on chip flow behavior. Chip curling increases and, for a given tool geometry, effectiveness of the groove increases with increasing depth of cut. The feasibility of tool design using FEM simulations is also demonstrated. Optimization of tool geometry results in better chip control.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.101-106
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• 2001

In this work, an effort is made to investigate the behavior of a chip, from its initial flow to its final breaking stage. The expression for chip flow in grooved tools is verified analytically using FEM. Cutting parameters like velocity and depth of cut have a profound influence on chip flow behavior. Chip curling increases and, for a given tool geometry, effectiveness of the groove increases with increasing depth of cut. The feasibility of tool design using FEM simulations is also demonstrated. Optimization of tool geometry results in better chip control.