• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1131-1138
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• 2001

This paper concerns the crashworthiness of the widely used vehicle structure, the spot welded hat and double hat shaped section members, which are excellent on the point of the energy absorbing capacity and low production cost. The target of this paper is to analyze the energy absorption capacity of the structure against the front-end collision, and to obtain useful information for designing stage. Changing the spot weld pitches on the flanges, the hat and double hat shaped section members were tested on the axial collapse loads in impact velocities of 4.72m/sec, 6.54m/sec, 7.19m/sec and 7.27m/sec. To efficiently review the collapse characteristics of these sections, the simulation have been carried out using explicit FEM package, LS-DYNA3D. The solutions are compared with results from the impact collapse experiments.

• Journal of Ship and Ocean Technology
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• v.5 no.3
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• pp.36-44
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• 2001

The collision energy absorbing characteristics of side structure of the LNG carriers which have the cargo containment systems of the spherical and the membrane types are compared. A failure mechanism of the double hull side structures of 130, 000 $m^3$ class LNG carriers under sideways collision event has been simulated by using the detailed finite element calculations. In ship collision analysis, the finite element method based on explicit time integration has been use[1 with much success. Finite element modeling techniques for detail description of structural members antral ship motion regarding the dynamic behavior allowed to investigate the effect of bow shape and the initial contact position on side shell of collided ship. In the numerical simulations of the ship-to-ship sideways collision, the effect of the colliding bow shapes and the change of the colliding ship draft are investigated. The critical collision energy which is absorbed by a side structure of a collided ship until the fore-end of colliding ship arrives at the boundary of the cargo tank is calculated. The critical speed of specified colliding ships which can not penetrate the boundary of the LNG cargo tank of the collided ship under collision accident if evaluated.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.235-240
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• 2010

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, energy absorbing members should be absorbed with collision energy sufficiently. But vehicle structure must be light weight for the environmentally-friendly aspect, in order to improve fuel efficiency and to reduce tail gas emission. Therefore, the light weight of vehicle must be achieved in a status of securing safety of crash. An aluminum or CFRP (Carbon Fiber Reinforced Plastics) is representative one among the light-weight materials. In this study, impact collapse behavior of circular hybrid thin-walled member is evaluated. The hybrid members are manufactured by wrapping CFRP prepreg sheets outside the aluminum circular members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties change with its stacking condition, special attention is given to the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member. Collapse mode and energy absorption capability of the hybrid thin-walled member are analyzed with change of the fiber orientation angle and interface number.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.85-96
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• 1996

Most protection systems such as seat belts and airbags are not effective means for side structure. There has been significant effort in the automobile industries in seeking other protective methods, such as stiffer structure and padding on the door inner panel. Therefore, a car-to-car side impact model has been developed using ATB occupant simulation program and validated for test data of the vehicle. Compared to the existing side impact models, the developed model has a more detailed vehicle side structure representation for the more realistic impact response of the door. This model include impact bar which effectively increases the side structure stiffness without reduction of space between the occupant and the door and padding for absorbing impact energy. The established model is applied to a 4-door vehicle. The parameter study indicated that a stiffer impact bar would reduce both the acceleration-based criteria, such as thoracic trauma index: TTI(d), and deformation-based criteria, such as viscous criterion(VC). Padding on the door inner panel would reduce TTI(d) while VC gives the opposite indication in a specified thickness range. For a 4-door vehicle, the stiffness enhancement of B-pillar is more beneficial than that of A-pillar for occupant injury severity indices.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.97-104
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• 2008

Many atypical structures on the roadside are exposed to traffics unshielded posing great danger. One way to shield an atypical structure to secure the occupant safety is to stack energy absorbing material modules in front of the structure. This paper presents the analysis method of module type crash cushion made of EPS blocks using simple energy balance of the car and crash cushion and numerical examples for 0.9ton-500km/h, 0.9ton-60km/h and 0.9ton-70km/h impact are presented. This method gives simple estimation of maximum acceleration, time of crash, whether or not the vehicle stops completely before whole cushion is being crushed. However, since the acceleration and velocity data from the analysis is so crudely spaced that calculation of safety indices such is RA and OIV is not possible. Problem is overcome by using data interpolation. The spline and linear interpolation is introduce and safety analysis is made and the results are compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.81-86
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• 2012

The shock absorber is very important in various mechanical field. Without the shock absorber, the structure might be broken. For lunar lander, honeycomb shock absorber to absorber the shock by using plastic deformation of honeycomb has been used. It is cheap and simple to use but impossible using again without changing the honeycomb. The oleo-pneumatic type shock absorber is not able to use in the cosmos because it is vacuum and its temperature. This study suggests the hybrid shock absorber combined spring-ratchet mechanical shock absorber and eddy current electromagnetic damper. The ratchet restricts rebound of lunar lander and the spring converts the impact energy to the potential energy of the spring. The eddy current damper dissipates the impact energy by eddy current force without contact between the parts. This hybrid shock absorber is reusable while the honeycomb shock absorber isn't. The impact absorbing test of the hybrid shock absorber was carried out. This paper shows that the compared results the hybrid shock absorber with ratchet and without ratchet and evaluates the possibility of using for lunar lander.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.27-31
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• 2013

The structure of a variable liquid column oscillator(VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system for absorbing the high kinetic energy of the accelerated motions of multiple floating bodies using an air-spring effect produced the installation of inner air chambers. Thus, a VLCO can improve the energy efficiency of the activating object type of wave energy converters made by the Pelamis Company. In this research, an experiment was performed in two cases: with the top valves closed and open. The floating bodies were connected by hinges. The effect of the internal flow was estimated by comparing the results for the closed and open valves.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1783-1790
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• 2023

Barium Bismuth Oxide Borate (BBOB) has been synthesized for the first time using solution combustion technique. SEM analysis reveal flower shape of the nanoparticles. The formation of the nanoparticles has been confirmed through XRD & FTIR studies which gives the physical and chemical structure of the novel material. The UV light absorption is observed in the range 200-300 nm. The present study highlights the radiation shielding ability of BBOB for different radiations like X/Gamma rays, Bremsstrauhlung and neutrons. The gamma shielding efficiency is comparable to that of lead in lower energy range and lesser than lead in the higher energy range. The bremsstrauhlung exposure constant is comparably larger for BBOB NPs than that of concrete and steel however it is lesser than that of lead. The beauty of BBOB nanoparticles lies in, high absorption of radiations and low emission of secondary radiations when compared to lead. In addition, the neutron shielding parameters like scattering length, absorption and scattering cross sections of BBOB are found to be much better than lead, steel and concrete. Thus, BBOB nanoparticles are highly efficient in absorbing X/Gamma rays, neutrons and bremsstrauhlung radiations.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.6
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• pp.273-282
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• 2015

In this study, shaking table test has been carried out for the dual frame passive control system for seismic performance verification of the proposed system. The proposed system was separated into two independent frameworks that are strength resistant core and frame structure by connecting to the damper. Moreover, the seismic performance improvement of the proposed system has been verified by comparing and analyzing the experimental results of the proposed system with an existing core system. As a result of the shaking table test, acceleration and displacement responses of dual-frame vibration control system are decreased than those of the existing strength resistant type core system. In the case of the core system, while the damage was concentrated on the column of first floor, the damage of the dual system was dispersed in each layer. The damage also was concentrated on the damper, almost no damage occurs to the structural members. It has been emphasized that installed dampers in the proposed dual system reduce the input energy of whole structure by absorbing seismic input energy, which leads overall system damage to be reduced.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.87-95
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• 2008

One way to shield an atypical structure to secure the occupant safety of an impact vehicle is to stack energy absorbing material modules around the structure. To be applicable to a cushion module, material must have enough energy absorbing capabilities while satisfying the safety requirements of the vehicle occupant. Static compression test of the potential materials gives a good indication which material is good for a slacking module. This paper presents the mechanical properties that a cushion material must have to satisfy the safety requirements. Static tests are performed for Quard-Guard system module, sand bag, recycled tires, Geo-Container, Geo-Cell and Expanded Polystyren (EPS) Blocks. Static test results are discussed and EPS block of $30kg/m^{3}$ density showed good potential for a cushion module. To check the dynamic effect of EPS block, drop tests have been made up to 35.6km/h impact speed. Drop test results are compared with static test results and no appreciable difference was found. To improve the EPS module property, making holes to the block is suggested and drop test are performed for the modified blocks. From the drop test results, design values are suggested.