• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.1
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• pp.38-44
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• 2015

In this paper, a finite element dynamic simulation study was performed to gain an insight about the blast wall test details for the offshore structures. The simulation was verified using qualitative and quantitative comparisons for different materials. Based on in-depth examination of blast simulation recordings, dynamic behaviors occurred in the blast wall against the explosion are determined. Subsequent simulation results present that the blast wall made of high energy absorbing high manganese steel performs much better in the shock absorption. In this paper, the existing finite element shock analysis using the LS-DYNA program is further extended to study the blast wave response of the corrugated blast wall made of the high manganese steel considering strain rate effects. The numerical results for various parameters are verified by comparing different material models with dynamic effects occurred in the blast wall from the explosive simulation.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.103-108
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• 2013

The operation of a Doppler wind LIDAR in a mobile environment is very sensitive to shocks and vibrations, which can cause critical failures such as misalignment of the optical path and damage to optical components. To be able to stabilize the LIDAR and to perform wind field measurements in motion, a shock absorption and vibration isolation system was designed and implemented. The performance of the vehicle-mounted Doppler wind LIDAR was tested in motion, first in a circular test route with a diameter of about 30 m and later in regular expressway traffic. The vibration isolation efficiency of the system was found to be higher than 82% in the main vibration area and shock dynamic deflection was smaller than maximal deflection of the isolator. The stability of the laser locking frequency in the same mobile environment before and after the vibration isolation system installation was also found to be greatly improved. The reliability of the vibration isolation system was confirmed by good results of the analysis of the LIDAR data, in particular the plane position indicator of the line of sight velocity and the wind profile.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.65-74
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• 2016

A finite element dynamic simulation is performed to gain an insight about the stiffened blast wall structures subjected to blast loading. The simulation was verified using qualitative and quantitative comparisons for different materials. Based on in-depth examination of blast simulation recordings, dynamic behaviors occurred in the blast wall against the explosion are determined. Subsequent simulation results present that the blast wall made of the high performance steel performs much better in the shock absorption. In this paper, the existing finite element shock analysis using the LS-DYNA program is further extended to study the dynamic response of the stiffened blast wall made of the high-performance steel considering high strain-rate effects. The numerical results for various parameters were verified by comparing different material models with dynamic effects occurred in the stiffened blast wall from the explosive simulation.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.25-29
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• 2009

High temperature high humidity and thermal shock reliability tests were performed for the board level COB(chip-on-board) flip chip packages using self-formulated and commercial NCPs(non-conductive pastes) to ensure the performance of NCP flip chip packages. It was considered that the more smaller fused silica filler in prototype NCPs is more favorable for high temperature high humidity reliability. The failure of NCP interconnection was affected by the expansion of epoxy due to moisture absorption rather than the fatigue due to thermal stress. It was considered that the NCP having more higher adhesive strength seems to be more favorable to increase the thermal shock reliability.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.128-134
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• 2009

This paper aims to design a variable-stiffness type economical safety joint for service robots. The safety joint was designed to have a passive shock absorbing mechanism for protecting human from a catastrophic collision under service condition of robots. A simple mechanism composed of two action disks for switching the load transfer, a spring and a screw for pre-load was proposed. In order to evaluate the performance of the safety joint a testing platform which can carry out the static and impact tests was also designed and fabricated. From the test results, the designed safety joint was proved to have a variable load-carrying capacity and about 42% impact absorption capacity with simple manipulation of the control screw.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.933-938
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• 2007

These days, up-to-date humanoid robots are continuously developed. Among them, Qrio, Asimo[1,2] are famous for its unique walking technology and natural movement. These robots could show manufacturers' technological improvement and leave a good impression to the customer. In accordance with global trends, Samsung is also producing humanoid robot. The humanoid robot, however, could walk like a human compared to the industrial robot fixed in the factory. This feature could cause another dynamic effect while walking. In this paper, the robot's feet were examined to find out parameters that affect stability of the humanoid robot's feet. With the sensitivity analysis, the optimization procedure in design of experiments finds the most suitable performance of robot. Maximum deflection of the frame upon various cases was minimized, and rubber coefficients for shock absorption were optimized.

• Steel and Composite Structures
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• v.6 no.4
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• pp.303-317
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• 2006

The connection with combined cross diaphragm is developed for the connection of square CFT column and steel beam and proposed to be used for the frame with asymmetric span length. The structural characteristics of this connection lie in the penetration of the beam flange in the direction of major axis through the column for the smooth flow of stress. The purpose of this study is to analyze the dynamic behavior and stress flow of suggested connection and to evaluate the resistance to shock of connection. Four T-type CFT column-to-beam specimens; two with combined cross diaphragm and the others with interior and through diaphragms, the existing connection types, were made for cyclic load test guided by the load program of ANSI/AISC SSPEC 2002. The results show that the proposed connection is more efficient than existing ones in terms of strength, stress flow and energy absorption and satisfies the seismic performance required in the region of weak/moderate earthquakes.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.8
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• pp.661-668
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• 2016

Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.367-375
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• 2006

Sequencing Batch Reactor (SBR) is well adopted for community wastewater treatment for its simplicity, performance and various advantageous treatment options. SBR is now drawing attention for its process modification such as coupled with membrane bioreactor, reverse osmosis or applying different media to achieve high removal efficiency. This study focused on the improved efficiency of carbon, nitrogen and phosphorous removal by applying zeolite materials called bioceramics to the SBR. Two laboratory-scale SBR units were operated in the same operating conditions - one with bioceramics called Bioceramic SBR (BCSBR) and the other without bioceramics used as control. Routine monitoring of COD, TP, $NH_3-N$, $NO_3-N$ was performed throughout this study. COD removal was about 80% to 100% and phosphorous removal was about 60% in the process whereas $NH_3-N$ removal efficiency was found to be 99.9% in the BCSBR unit. Addition of bioceramics also improved sludge characteristics such as sludge dewaterability, specific gravity and particle size. BCSBR can withstand high ammonia shock loading leading to the better treatment capacity of high ammonia containing wastewater. The cause of improved removal efficiencies within the biological reactor could be attributed to the biochemosorption mechanisms of bioceramics. Absorption/adsorption or desorption capacity of bioceramics was tested through laboratory experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.519-526
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• 2012

Recently fuel cell is considered to be a new technology that can substitute the ICE(Internal Combustion Engine) as well as overcome environmental issues. In military applications, fuel cell has an unique advantages, which are quietness, namely, stealth. The environmental requirement such as shock and vibration in military application, however, is very severe comparing to civilian demand. Especially, the safety concerning hydrogen storage is the most important problem. Among the candidate methods to store hydrogen, the metal hydride storage is promising method owing to the storage mechanism of chemical absorption of hydrogen to metal hydrides. In this study, the new composition of Ti-Zr type metal hydride(A composition) was suggested and investigated to increase the hydrogen storage capacity. For comparison, the hydrogen charge-discharge properties were investigated with the commercialized Ti-Zr type metal hydride(B composition) using PCT(Pressure-Composition-Temperature) measurement. Also two hydrogen storage cylinders were loaded with each metal hydride and their hydrogen charging and discharging characteristics were investigated. As a result, it was found that the new Ti-Zr type metal hydride has a slightly higher hydrogen storage capacity compared to commercial Ti-Zr type metal hydride.