• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.189-201
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• 2001

For a design of multi-layer armor, the extensive full scale or sub-scale penetration test data are required. In generally, the collection of penetration data is in need of time-consuming and expensive processes. However, the application of numerical or analytical method is very limited due to poor understanding about penetration mechanics. In this paper, we have developed a neural network analyzer which can be used as a design tool for a new armor. Calculation results show that the developed neural network analyzer can predict relatively exact penetration depth of a new armor through the effective analysis of the pre-existing penetration database.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.76-82
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• 2000

In this study, three-dimensional heat flow in laser beam welding for deep penetration was analyzed by using F.E.M common code, and then the results were compared with the experimental data. The models for analysis are full penetration welds and are made at three different laser powers (6, 9.9, 4.5 kW) with two different welding speeds (5.8mm/s, 5mm/s). The characteristics of thermal absorption by the workpiece during deep penetration laser welding can be represented by a combination of line heat source through the workpiece and distributed heat source at the top surface due to the plasma plume above the top surface. This gives an insight into the way in which the beam interacts with the material being welded. The analyses performed with the combined heat source models show comparatively good agreement between the experimental and calculated melt temperature isotherm, i.e, the fusion zone boundary. The results are used to explain the "nail head" appearance of fusion zone, which is quite common in laser beam welds.eam welds.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.04a
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• pp.31-35
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• 2011

Factors influencing penetration kinetics of PVAm solution into paper were investigated with ultrasonic Penetration Evenness Analyzer (PEA). Paper structure was varied by changing basis weight, freeness of pulp, calendering, number of plies and filler addition and hydrophobicity of paper was varied by adding AKD. Important factors affecting liquid penetration are found to be pore structure and hydrophobicity of paper. Pore structure of paper can be designed by controlling refining degree and filler addition. Hydrophobicity of paper can be controlled by internal sizing.

• Computers and Concrete
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• v.8 no.1
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• pp.111-123
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• 2011

Severe element distortion problem is observed in finite element mesh while performing numerical simulations of high velocity steel projectiles penetration/perforation of concrete targets using finite element method (FEM). This problem of element distortion in Lagrangian formulation of FEM can be resolved by using element erosion methodology. Element erosion approach is applied in the finite element program by defining failure parameters as a condition for element elimination. In this study strain parameters for both compression and tension at failure are used as failure criteria. Since no direct method exists to determine these values, a calibration approach is used to establish suitable failure strain values while performing numerical simulations of ogive-nose steel projectile penetration/perforation into concrete target. A range of erosion parameters is suggested and adopted in concrete penetration/perforation tests to validate the suggested values. Good agreement between the numerical and field data is observed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.820-824
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• 1997

In order to investigate the effect of surface treatment(Anodizing) and rolling in Al 5083-H131 alloy, ballistic testing was conducted. Ballistic resistance of these materials. was measured by protection ballistic limit(V$_{50}$), a statical velocity with 50% probability for incomplete penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, are observed respectfully, resulting from V$_{50}$ test and Projectile Through Plates(PTP) test at velocities greater than V$_{50}$. PTP tests were conducted with 0$^{\circ}$obliquity at room temperature were also conducted with projectiles that were able to achieve near or complete penetration during PTP tests. Resistance to penetration, and penetration modes of Al 5052-H34 alloy, compared to those of Al 5083-H131 alloy.alloy.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.594-597
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• 2006

Chloride ion penetration and carbonation are the most important factors in the durability problems of reinforced concrete structures. Most of the existing studies on those subjects are focused on the no-crack concrete, though the existence of crack may strongly affect the chloride ion penetration and carbonation. To evaluate the influence of crack on the chloride ion penetration and carbonation and to assess the service life of reinforced concrete more accurately, finite volume analyses (FVA) were performed based on the FV mesh containing the ideal crack whose width is uniform along the depth. Analytical results show that the influence of crack width and depth is much more pronounced for the chloride ion penetration than for the carbonation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.87-88
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• 2010

A permeability of concrete is a very important factors evaluating durability. So, we are carrying out a lot of relational data bases and experiment regarding a permeability. In order to evaluate a permeability of concrete, we are proceeding study on the water penetration and diffusion in concrete by water pressure. Because a way to evaluate a permeability of concrete has a limit. We will present a good method of evaluating durability of concrete using the water penetration depth of concrete by water pressure. To carry this out, we executed experiment with penetration depth of concrete by water pressure and verified it though FEM analysis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.197-207
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• 1992

Fatigue life and penetration behavior were examined analytically by variety of initial front face crack length and initial crack depth. The fatigue crack shape before penetration is almost semielliptical, and the aspect ratio by calculation using the Newman-Raju's formula is smaller than the value obtained by the experiment. It is found that the crack growth behavior on the back surface after penetration is unique and can be divided into three stage a, b and c. By using the K value proposed by the authors, particular crack growth behavior and the change in crack shape can be evaluated quantitatively. It is found that fatigue life and penetration behavior were more dependent on initial front face crack length than initial crack depth.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.2
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• pp.321-325
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• 2011

After investigating the analytic model to predict penetration depth, we propose an analytical model which can be used in estimating the normal penetration characteristics of small projectiles, when they are impacted to the concrete targets with ordnance velocities. The major parameters of this model are nose factor of penetrator, compressive strength and density of targets, and impact velocity. We can predict accelerations, velocities, displacements of projectiles and applied forces by this proposed model. Estimated penetration depths were shown 5% error. We also verified the usefulness of the new method with laboratory impact test data.

• Journal of the Korean Society of Costume
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• v.11
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• pp.51-60
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• 1987

The penetration force of needle and penetration energy kave been investigated, in order to research into the sewing factors that influence the weft knitted fabric with high elastic property. The results of the studies are a follows: (1) As the results have showed a high correlativity between the needle penetration energy and force, it proves that the dynamic energy produced by the friction of the needle as it penetrates and withdraws from the knitted fabric contributes to the heat growth of the needle. (2) To reduce frictional force the use of thin needles, medium ball point needle and super needle are effective. (3) The reduction in number of plies of fabric or also in the case of a decrease in penetration speed have been effective in lowering the penetration energy and force.