• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.232-239
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• 1997

The phenomenology of shock loading effects in brittle mass has been of interest to researchers and engineers. The shock loading as blasting causes strong stress waves in the structures. Discontinuous faces due to shock waves interrupt the tensile stress wave propagation and reflect the stress wave propagation. To predict the fracturing behavior of brittle mass, it is required for the numerical method that can analyze the colliding and slipping behavior of discontinuous faces and the wave propagation in the mass, simultaneously In this study, the wave propagation in the brittle materials is analyzed using the modified distinct element method to be able to predict the behavior of discontinuous structures. The behavior of an unsupported bar subjected to loading at the end is analyzed to verify the rigid body motion of a bar and the relative displacement in the bar. The colliding behavior of two bars is analyzed to investigate the propagation of stress waves in the bar. The fracturing behavior of a bar due to impact loading is analyzed to investigate the propagation of stress waves in the bar with and without the discontinuous faces. The applicability of the modified distinct element method to the wave propagation problems is investigated.

• Journal of Aerospace System Engineering
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• v.4 no.3
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• pp.1-5
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• 2010

Understanding the crushing behaviour of aluminum honeycombs under dynamic loading is useful for crash simulations of vehicles and for design of impacting energy absorbers. In the study of honeycomb crushing under quasi-static, dynamic loading, the most important parameter is crush strength. Crush strength is indicated to energy absorption characteristic of aluminum honeycomb. In this study, Using Finite Element Analysis carried out crush strength of hexagonal aluminum honeycomb then the results was compared with Quasi-static test. Consequently, Crush strength is different in quasi-static loading and dynamic loading about 16%.

• Geotechnical Engineering
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• v.4 no.4
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• pp.19-28
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• 1988

An underground explosion crests shock waves, which propagate to a buried structure through the이 ground. Due to the explosion, very high stresses and large deformation occur in the ground so that the shock waves decay gradually. In this study the numerical simulation of the ground shock attenuation has teen performed. One dimensional wave equation is presented and the finite difference method is applies. A Cap model is adopted to describe the stress-strain behavior of the ground. The results are expressed by the attenuation of the peak stress and the particle vrelocity by the time and the distance.

• Environmental Engineering Research
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• v.11 no.5
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• pp.285-291
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• 2006

Biofiltration is a simple, effective, economically viable and the most widely used gas treatment technique for treating malodors at low concentrations and high flow rates. This paper reports the performance of two lab scale immobilized cell biofilters operated in continuous mode for hydrogen sulfide ($H_2S$) and ammonia ($NH_3$) removal. The removal efficiency (RE, %) and the elimination capacity (EC, $g/m^3{\cdot}hr$) profiles were monitored by subjecting the biofilters to different loading rates of $H_2S$ (0.3 to $8\;g/m^3{\cdot}hr$) and $NH_3$ (0.3 to $4.5\;g/m^3{\cdot}hr$). The removal efficiencies were greater than 99% when inlet loading rate to the biofilters were upto $6\;gH_2S/m^3{\cdot}hr$ and $4\;gNH_3/m^3{\cdot}hr$ respectively. The performance of the biofilters were also ascertained by conducting shock loading studies at a loading rate of $10\;gH_2S/m^3{\cdot}hr$ and $6\;gNH_3/m^3{\cdot}hr$. The results from this study show high removal efficiency, good recuperating potential and stability of the immobilized microbial consortia to transient shock loads.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.791-799
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• 2005

The phased isolation intra-clarifier ditch system used in this study is a simplified novel process enhancing simultaneous removal of biological nitrogen and phosphorus in municipal wastewater in terms of elimination of additional pre-anaerobic reactor, external clarifier, recycle of sludge, and nitrified effluent recirculation by employing intrachannel clarifier. Laboratory-scale phased isolation ditch system was used to assess the treatability on municipal wastewater. When the system was operated at the HRTs of 6~12hours, SRTs of 9~31days, and cycle times of 2~8hours, the system showed removals of BOD, TN, and TP as high as 88~97%, 70~84%, and 65~90%, respectively. The rainfall in Korea is generally concentrated in summer because of site-specific characteristics. Especially, the wet season has set in on June to August. In combined sewers, seasonal variations are primarily a function of the amount of stormwater that enters the system. In order to investigate the effect of hydraulic shock loading on system performance, the laboratory-scale system was operated at an HRT of 6hours (two times of influent flowrate) during two cycles (8hours). The system performance slightly decreased by increasing of influent flowrate and decreasing of system HRT. Nitrification efficiency and TN removal were slightly decreased by increasing of influent flowrate (decreasing of system HRT), whereas, the denitrification was not affected by hydraulic shock loading. However, the higher system performance could be achieved again after four cycles. Thus, the phased isolation technology for enhanced biological nutrient removal in medium- and small-scale wastewater treatment plants suffering fluctuation of influent quality and flowrate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.189-194
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• 2004

As a disk drive becomes widely used in portable environments, one of the important requirements is durability under severe environmental condition, especially, resistance to mechanical shock. An important challenge in the disk recording is to improve disk drive robustness in shock environments. If the system comes In contact with outer shock disturbance, the system gets critical damage in head-gimbal assembly or disk. This paper describes analysis of a HGA(head-gimbal assembly) in micro MO drives to shock loading during both non-operating state and operating state. A finite element model which consists of the disk, suspension, slider and air bearing was used to find structural response of micro MO drives. In the operational case. the air bearing is approximated with four linear elastic springs. The commercially available finite element solver, ANSYS/LS-DYNA, is used to simulate the shock response of the HGA in micro MO drives. In this paper, the mechanical robustness of the suspension is simuiated considering the shock responses of the HGA.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.581-589
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• 2019

Guided missiles assembled with the bolted joint are subjected to various shock loading conditions while flying in the air and operating on the ground or platform. Especially, It is important to analyze the effect of the shock load on the structure because it affects the structure for a short duration time while its acceleration magnitude is quite large. In this study, mechanical shock tests on the structure with the bolted joint have been carried out to measure the acceleration changes of the structure against external shock loads by electrical exciter. Variation of dynamic characteristics of a structure with fastening methods and fastening forces has been investigated through Shock Response Spectrum analysis.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.39-43
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• 2003

An experimental study was conducted to develop and understanding of fracture behavior of ceramic thermal barrier coating when subjected to a thermal shock loading. The thermal loading was applied using a 1.5kW $CO_2$ laser. In the experiments, beam-shaped specimens were subjected to a high heat flux for 4sec and cooling of 7sec in air. The interface crack length was increased as the crack density, the surface pre-crack legth and the coating thickness were increased. The center surface crack length was increased as the maximum surface temperature got higher and the surface pre-crack length for shorter.

• Journal of Biosystems Engineering
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• v.30 no.2 s.109
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• pp.89-94
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• 2005

The compression strength of corrugated fiberboard container for packaging the agricultural products rapidly decreases because of various environmental conditions during distribution of unitized products. Among various environmental conditions, the main factors affecting the compression strength of corrugated fiberboard are absorption of moisture, long-term accumulative load, and fatigue caused by shock and vibration. An estimated rate of damage for fruit during distribution is about from 30 to 40 percent owing to the shock and vibration. This study was carried out to characterize the durability of corrugated fiberboard container for packaging the fruit and vegetables under simulated transportation environment. The vibration test system was constructed to simulate the land transportation using truck. After the package with corrugated fiberboard container was vibrated by vibration test system at various experimental conditions, the compression test for the package was performed. The compression strength of corrugated fiberboard container decreased with loading weight and vibrating time. The multiple nonlinear regression equation for predicting the decreasing rate of compression strength of corrugated fiberboard containers were developed using four independent variables such as input acceleration level, input frequency, loading weight and vibrating time. The influence of loading weight on the decreasing rate of corrugated fiberboard container was larger than other variables.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.17-26
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• 2011

Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.