• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.99-110
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• 2000

The damages due to wave impact loads are largely affected by impact pressure impulse and impact load area. The objective of this study is, as the third step, to perform dynamic structural analysis of bow flare structure of 300,000 DWT VLCC using LS/DYNA3D code, and to verify its dynamic structural behaviors. The impact load areas of stiffener space $1.5s{\times}1.5s$ and $2.5s{\times}2.5s$ are applied to bow flare structure part with relatively flexible stiffeners, and with stiff members such as stringers, webs etc., respectively, under the wave impact load with peak height 6.5MPa, tail 1.0MPa, and duration time 5.0msec. Through the dynamic structural analysis in this study, it might be thought that the structural strength of bow flare structure is generally sufficient for these wave impact load and areas, except that large damages were found at bow flare structure area with flexible wide span stiffeners.

• Computers and Concrete
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• v.22 no.3
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• pp.337-353
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• 2018

The present study focuses on examining the structural behaviour of steel-fibre-reinforced concrete (SFRC) beams under high rates of loading largely associated with impact problems. Fibres are added to the concrete mix to enhance ductility and energy absorption, which is important for impact-resistant design. A simple, yet practical non-linear finite-element analysis (NLFEA) model was used in the present study. Experimental static and impact tests were also carried out on beams spanning 1.3 meter with weights dropped from heights of 1.5 m and 2.5 m, respectively. The numerical model realistically describes the fully-brittle tensile behaviour of plain concrete as well as the contribution of steel fibres to the post-cracking response (the latter was allowed for by conveniently adjusting the constitutive relations for plain concrete, mainly in uniaxial tension). Suitable material relations (describing compression, tension and shear) were selected for SFRC and incorporated into ABAQUS software Brittle Cracking concrete model. A more complex model (i.e., the Damaged Plasticity concrete model in ABAQUS) was also considered and it was found that the seemingly simple (but fundamental) Brittle Cracking model yielded reliable results. Published data obtained from drop-weight experimental tests on RC and SFRC beams indicates that there is an increase in the maximum load recorded (compared to the corresponding static one) and a reduction in the portion of the beam span reacting to the impact load. However, there is considerable scatter and the specimens were often tested to complete destruction and thus yielding post-failure characteristics of little design value and making it difficult to pinpoint the actual load-carrying capacity and identify the associated true ultimate limit state (ULS). To address this, dynamic NLFEA was employed and the impact load applied was reduced gradually and applied in pulses to pinpoint the actual failure point. Different case studies were considered covering impact loading responses at both the material and structural levels as well as comparisons between RC and SFRC specimens. Steel fibres were found to increase the load-carrying capacity and deformability by offering better control over the cracking process concrete undergoes and allowing the impact energy to be absorbed more effectively compared to conventional RC members. This is useful for impact-resistant design of SFRC beams.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.67-76
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• 2011

In this present study, to evaluate a behavior characteristics of the sea dyke coastal covering stone by sea waves. sea waves act on coastal structures as an impact load. During impact loading, erosion and bluff slumping occur in the coastal structures. Also, the covering stone are worn down by wave impact. The sea dyke has been used near coastal region for protection of infra-structure since 1970s in Korea. The sea dyke consist of dredged sand and covering stone mainly. The damage type of covering stone has been reported since 1970s. However, the interaction of impact load by sea wave with the covering stone has not been investigated yet properly. Mainly damage type of covering stone is an abrasion. But the study of covering stone abrasion is not sufficient. Hence, In this study, it was analyzed the interaction of impact load by sea wave and the covering stone during sea wave action on coastal structures. In order to analyze the behavior characteristics of coastal covering stone considering the magnitude and period of impact loading and to evaluate the displacement increment of covering stone during impact load, numerical analysis was carried out considering impact loading by sea wave.

• Journal of Auto-vehicle Safety Association
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• v.3 no.2
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• pp.5-10
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• 2011

Under the full frontal crash event, seatbelt system is the most typical and primary restraint device that prevents the second impact between an occupant and vehicle interior parts by limiting the forward motion of an occupant in the vehicle occupant packaging space. Today's restraint systems typically include the three-point seat belt with the pretensioner and the load limiter. A pretensioner preemptively tightens the seat belts removing any slack between a passenger and belt webbing which leads to early restraint of a passenger. After that a load limiter controls level of belt load by releasing the belt webbing to reduce occupant injurys. In this study, load characteristics of load limiters are optimized by the computer simulation with a MADYMO model for a frontal impact against the rigid wall at 56kph and then we suggest performance requirements. We derived optimum load characteristic from the results using four vehicle simulation models represented by the vehicle. Based on the results, we suggest the performance from the results of the second optimization using the simulation considering the design and the standardization. Finally, the performance requirements is verified by the sled tests including the load limiter device for the full vehicle condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.191-197
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• 2016

RCAR low speed impact test estimates repair cost of the impacted vehicle. In this study, for a mid-size vehicle front body model, structural performance for RCAR low speed impact were analyzed with changing the bumper stay shape and size. First, for improving the impact load transfer mechanism to side member the stay rear section shape at connecting area with side member was modified and the stay outer was redesigned to be normal to the barrier. Next, the investigation on stay thickness effect was carried out and the performances of several models with different forming shape were compared. The final design showed 13mm decrease in the maximum barrier intrusion distance and greatly reduced side member deformation. Additional analyses explained the validity of the final design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.403-407
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• 2009

It is reported that the heavy weight floor impact noise of a slab system is very sensitive to the location of microphone and impact load. In addition, it is known that the aspect raio, thickness and boundary condition of a slab also have great effect on the noise induced by impact load. However, the effect has been mainly evaluated by experimental test and numerical analysis is nearly performed to verify the effect quantitatively. In this study, the effect of the aspect ratio, thickness and boundary condition on the heavy weight floor impact noise is examined through numerical analysis for simple rectangular slab system. The results show that the thickness and boundary condition have a strong correlation with the noise of the slab, on the contrary, the aspect ratio has little relation with the noise.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.195-201
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• 2000

The fundamental spot welded sections of automobiles (hat-shaped and double hat-shaped sections) absorb most of the energy in a front impact collision. The sections of various thickness, shape and weld width on the flange lave been tested on axial impact crush load (Mass 40kg, Velocity 7.19m/sec) using a vertical air pressure crash est device Characteristics of impact collapse have been reviewed and a structure of optimal energy absorbing capacity is suggested.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.6
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• pp.286-290
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• 2003

The high temperature superconducting bulk can be used as the bearing of induction motors. This paper presents the fabrication and test results of an induction motor with superconducting bearings using HTS bulks. The bearing had eight hexahedron type YBCO bulks. Height, width and thickness of the HTS bulk were 30mm, 30mm and 10mm, respectively. Single phase induction motor was used to drive the shaft made of aluminum and the rotor of a conventional induction motor. To estimate the performance of the HTS bulk magnetic bearing, no load test, load test and Impact test were carried out. Load tests were performed by using air resistance caused by the shaft-mounted thin cylinder with buckets. Impact tests by axial direction and vertical direction impact showed that the vibration of the shaft gradually decayed. The induction motor with HTS bulk magnetic bearing rotated silently and smoothly throughout the tests. According to the test results, conventional bearings can be replaced with superconducting magnetic bearings made of HTS bulks.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.170-177
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• 1997

In this study, an analysis technique using simple beam model for predicting structure crashworthiness of the passenger car side impacted with an angle by another passenger car was investigated. The simple model was composed of major beam-like side structure which carry almost all side impact load. A procedure of component collapse test, calculation of load carrying capability and dynamic simulation was carryed out sequentially. Transient dynamic algorithms and a computer program to simulate deformations and motions of the impacted car was developed. The developed procedure was applied to a 3 door passenger car side impacted with an angle of 75 degree and the analysis results show good agreements with the actual test results.

• 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.