• Journal of the Society of Naval Architects of Korea
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• v.60 no.3
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• pp.193-201
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• 2023

A developed code based on the unified conservation laws of incompressible/compressible fluids is applied to analyze similarity in pressure oscillations caused by pulsating air pockets in sloshing tanks. It is shown that the nondimensional time histories of pressure show good agreements under Froude and geometric similarities, provided that there are no pulsating entrapped air pockets. However, the nondimesional period of pressure oscillation due to the pulsating air pocket becomes longer as the size of the sloshing tank increases. The discrepancy in the nondimensional period is attributed to the compressibility bias of the entrapped air. To get rid of the compressibility bias, the ullage pressure in a sloshing tank is adjusted based on the Bagnold's impact number. The variation in the period of pressure oscillation according to the ullage pressure is explained based on the spring-mass system. It is shown that the nondimensional period of pressure oscillation is virtually constant when the ullage pressure is adjusted based on the Bagnold's impact number, regardless of tank size. It is found that the Bagold's impact number should be the same, if the time history of pressure is important while an entrapped air pocket pulsates.

• Journal of the Ergonomics Society of Korea
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• v.21 no.2
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• pp.13-23
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• 2002

Human dummies are essential tools in the development of such products as vehicle have been actively used not only in reach and view field tests. but also in impact perception evaluations. This study attempted to obtain geometric and dynamic model body segments from Korean anthropometric data. The investigation focused on the de both human and dummy for the geometric and inertial properties. The dynamic modeli being suggested is based on rigid body dynamics using fifteen individual body segments by joins. The segments are connected at the locations representing the physical joint body so that each segment has its mass and moment of inertia. For visual three-dimensional graphic was used for easier implementation of the dumn applications. For applications, proposed Korean dummies Were used in dynamic crash and driver's view and reach test modules were developed in virtual environment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.441-448
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• 1998

In this study, an explicit transient analysis program considering material and geometric nolinearities has been developed and used to analyze the dynamic behaviors of circular, parabolic, sinusoidal and catenary arches according to the change of shapes and boundary conditions. To understand dynamic behaviors of arches, first of all, the results of free vibration analysis for four kinds of arches are discussed. The results of transient analysis under impact loads we discussed in respect of boundary condition, change of height, and arch-shape. The dynamic behaviors of arches by nonlinear transient analysis considering both material and geometric nolinearities are also discussed.

• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.795-802
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• 2016

Gas pipelines are types of structures that are highly susceptible to corrosion. Sometimes, the pipes are subjected to a thinning of the wall thickness at the inside or outside wall due to erosion/corrosion. Therefore, it is important to evaluate the strength of the pipes undergoing corrosion to maintain the integrity of the piping systems. The main purpose of this study is to understand failure aspects caused by degradation of metal due to corrosion through. The ASME standard offers a relationship for the yielding pressure of the corroded pipes which was compared with the finite element results. The results demonstrate to obtain accurate results, the ASME relationship is unreliable. Moreover, pitting corrosion must be considered critical more than of other types.

• Steel and Composite Structures
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• v.30 no.4
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• pp.305-313
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• 2019

Creating different cutout shapes in order to make doors and windows, reduce the structural weight or implement various mechanisms increases the likelihood of buckling in thin-walled structures. In this study, the effect of cutout shape and geometric imperfection (GI) is simultaneously investigated on the critical buckling load and knock-down factor (KDF) of composite cylindrical shells. The GI is modeled using single perturbation load approach (SPLA). First, in order to assess the finite element model, the critical buckling load of a composite shell without cutout obtained by SPLA is compared with the experimental results available in the literature. Then, the effect of different shapes of cutout such as circular, elliptic and square, and perturbation load imperfection (PLI) is investigated on the buckling behavior of cylindrical shells. Results show that the critical buckling load of a shell without cutout decreases by increasing the PLI, whereas increasing the PLI does not have a great impact on the critical buckling load in the presence of cutout imperfection. Increasing the cutout area reduces the effect of the PLI, which results in an increase in the KDF.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.43-57
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• 2023

The hypervelocity impact simulations of space objects and structures are performed using LS-DYNA. Space objects with spherical, conical, and hollow cylindrical shapes are modeled using the Smoothed Particle Hydrodynamics (SPH). The direct and indirect impact zones of a space structure are modeled using the SPH and finite element methods, respectively. The Johnson-Cook material model and Mie-Grüneisen Equation of State are used to represent the nonlinear behavior of metallic materials in hypervelocity impact. In the hypervelocity impact simulations, various impact conditions are considered, such as the shape of the space object, the thickness of the space structure, the impact angle, and the impact velocity. The shapes of debris clouds are quantitatively classified based on the geometric parameters. Conical space objects provide the worst debris clouds for all impact conditions.

• Steel and Composite Structures
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• v.22 no.5
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• pp.1085-1114
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• 2016

This paper investigates the transverse impact response for ultra lightweight cement composite (ULCC) filled pipe-in-pipe structures through a parametric study using both a validated finite element procedure and a validated theoretical model. The parametric study explores the effect of the impact loading conditions (including the impact velocity and the indenter shape), the geometric properties (including the pipe length and the dimensions of the three material layers) as well as the material properties (including the material properties of the steel pipes and the filler materials) on the impact response of the pipe-in-pipe composite structures. The global impact responses predicted by the FE procedure and by the theoretical model agree with each other closely. The parametric study using the theoretical approach indicates the close relationships among the global impact responses (including the maximum impact force and the maximum global displacement) in specimens with the equivalent thicknesses, proposed in the theoretical model, for the pipe-in-pipe composite structures. In the pipe-in-pipe composite structure, the inner steel pipe, together with the outer steel pipe, imposes a strong confinement on the infilled cement composite and enhances significantly the composite action, leading to improved impact resistance, small global and local deformations.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.2
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• pp.152-165
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• 1993

This study was performed at eleven small-sized plating factories located in Seoul, Incheon, Ansan, and Taejeon from July 21 to October 6, 1992. The major objectives of this study were to evaluate worker exposure to hexavalent chromium and local exhaust ventilation (L.E.V.) systems at the chromium plating operations. The most suitable L.E.V. systems for chromium plating tanks were designed as examples for recommendation to the industry. The results are summarized as follows. The range of chromium plating operations investigated included decorative, hard, and black chromium plating on several kinds of parts. Most of plating tanks were not equipped with proper control methods against emission of hexavalent chromium mists and workers were not wearing appropriate personal protectives. The ariborne hexavalent chromium concentrations showed an approximate lognormal distribution. The geometric means of both personal and area samples were within the Korean and ACGIH standards, $50{\mu}g/m^3$. However, in comparison with the NIOSH criterion, $1{\mu}g/m^3$, the geometric means of personal samples at two factories and the geometric means of area samples at two factories exceeded it. The geometric means of personal and area samples of high exposure groups (above the NIOSH criterion) were 7 and 27 times higher than those of low exposure groups (below the NIOSH criterion), respectively. The L.E.V. systems of high exposure groups were improperly designed, and the factory with the highest exposure level had no L.E.V. systems at all on chemical etching process. Whereas at factories of low exposure groups, mist control methods such as mist suppressants, tank cover, and/or auxillary L.E.V. systems were added to L.E.V systems. The evaluation of L.E.V. systems showed that there was no chromium plating operation satisfying the ACGIH criteria for capture velocity, slot velocity, and exhaust rate simultaneously. To increase performance of L.E.V. systems, it must be designed to minimize the impact of boundary layer separation. Push-pull ventilation hood and downward plenum ventilation hood were suggested for the Korean industry.

• Journal of the Korean Operations Research and Management Science Society
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• v.13 no.2
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• pp.72-77
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• 1988

Subjective scoring by different groups on different status of morbidity are compared to objective data obtained from legal awards. A power law is tested between subjective and objective scores. Regression analysis by means of a power function provides a measure of consistency in its regression coefficient. Power functions fitting also leads to a justified use of geometric averaging of individual scores into group scores.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.489-494
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• 2001

This paper deals with a dynamic modeling of artillery system loaded by gun charge explosion during firing condition. Geometric and elastic gun data are used to modify a projectile interaction model. The maximum impact force on gun barrel was 15,000 N and the gun barrel moved about 1.3 m. A cannon bal] was presented to travel in the flexible gun, the traveling distance was about 23,000 m, and the angular velocity was about 10rad/sec. The artillery dynamic system using the multi-body dynamics enables us to obtain the data for the fatigue analysis.