• Composites Research
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• v.34 no.3
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• pp.155-160
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• 2021

Metamaterials are complexes of elements that can create properties not found in naturally occurring materials, such as changing the direction of forces, creating negative stiffness, or altering vibration and impact properties. In the case of wood pile metamaterials that are easy to manufacture and have excellent performance in reducing vibration and shock in the vertical direction, basic research on variables affecting shock transmission is needed to reduce shock. Although research on impact reduction according to geometrical factors is being conducted recently, studies on the effect of material variables on impact reduction are insufficient. In this paper, finite element analysis was carried out by variablizing the geometrical properties (lamination angle, diameter, length) and material properties (modulus of elasticity, specific gravity, Poisson's ratio) of wood pile cylinders. Through finite element analysis, the shape of the wooden pile cylinder delivering impact was confirmed, and the effect of each variable on the reduction of impact force and energy was considered through main effect diagram analysis, and frequency band analysis was performed through fast Fourier transform. proceeded In order to reduce the impact force and vibration, it was found that the variables affecting the contact area of t he cylinder have a significant effect.

• Journal of KSNVE
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• v.10 no.1
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• pp.160-167
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• 2000

This paper addresses issues encountered in using the ISO and national standard codes to assess the hazards of whole-body vibration and repeat shocks. Their assessment methods are given in ISO 2631-1 (1974, 1985, 1997) and BS 6841 (1987) that are now available to us. Two standard codes can yield unfortunately different assessment results even for a single measured vibration signal. Possible reasons for such different results are pointed out and, furthermore, related questions that should be re-examined in the future are raised in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.609-610
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• 2012

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.67-74
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• 2019

In this paper the response factor is investigated for middle and small size-RC slab aged bridges. The response factor consists of static and dynamic response factors and is a main parameter in the frequency based-bridge load carrying capacity prediction model. Static and dynamic response factors are determined based on the frequency variation and the impact factor variation respectively between current and previous (or design) states of bridges. Here, the impact factor variation is figured out using the impact factor response spectrum which provides the impact factor according to the natural frequency of bridges. In this study, four actual RC slab bridges aged over 30 years after construction are considered and their span length is 12m. The dynamic loading test in field using a dump truck and eigenvalue analysis with FE models are conducted to identify the current and previous (or design) state-natural frequencies of the bridges, respectively. For more realistic considerations in the moving loading situation, the impact factor response spectrum is developed based on tri-axle moving loads representing the dump truck load distribution and various supporting conditions such as simply supported and both ends fixed conditions. From the results, the response factor is widely ranged from 0.21to 0.91, showing that the static response factor contributes significantly on the results while the dynamic response factor has a small effect on the result. Compared to the results obtained from the impact factor response spectrum based on the single axle-simply supported condition, the maximum percentage difference of the response factors is below 3.2% only.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.06a
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• pp.55-72
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• 1993

Dynamic compaction may cause some demages to structures becasue it uses the impact energy of heavy weight with high drop height. This study measured and analyzed the vibrations at the (bnamic compaction site which was composed of man-made land fill. From the vibration analysis, it was found that the particle velocity and attenuation was greatest in longitudinal direction and smallest in transversal direction, the dominant frequency ranged from 7 Hz to 9 Hz and the structural damage could be prevented by reducing the drop height at the vicinity of the vibration sentialive structures. Also, the damage to the office equipment could be prevented by doing the dynamic compaction work curing closed-office hours.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.272-279
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• 2005

In this study the optimal isolation system for the prototype HIFD(high impulsive force device) is investigated. For this purpose, firstly, the dynamic behavior of a human body and a transmitted force under specific operation conditions are analyzed through a series of experimental works using the devised test setup. In order to design the optimal dynamic absorbing system, the parameter optimization process is performed using the simplified isolation system model based on the experimental results of linear impulse and transmitted force. Finally, under the parameters satisfying the constraints of the buffering displacement and the transmitted force, the performance of the designed isolation system for the prototype HIFD is evaluated by experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.509-512
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• 2004

규준화 바닥충격음레벨 평가시 잔향시간은 흡음력 보정을 위해서 필수적으로 고려해야 할 사항이다. 그러나, 잔향시간의 측정 편차가 심하기 때문에 이로 인해 규준화 바닥충격음레벨이 5dB 이상씩 변동하는 경우가 생긴다. 잔향시간 측정 편차의 원인은 실의 형상에 따른 고유모드 분포로 설명할 수 있으며, 측정시 계측기에서의 원인, 특히 동특성에 따라 측정 편차가 심하다는 것을 실험을 통해 알 수 있었다. 또한, 잔향곡선은 직선적인 형태일 경우에 정확한 측정이 가능하나, 저주파수 대역에서는 잔향곡선에 요철이 많이 생기므로 측정 데이터들을 이용하여 잔향시간을 산출할 때 세심한 주의가 요구된다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.588-593
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• 2012

Nowadays, various forms of electro-optical rifle scope have been developed and used in order to enhance the accuracy of small arms. However, firing shock acceleration has characteristics of pyroshock having a big acceleration value with very short duration time, which the electro-optical scopes should be designed to sustain. In this paper, the firing shock acceleration, which is transmitted to the electro-optical scope, was measured and SRS (Shock Response Spectrum) analysis was performed by using the measured firing shock acceleration. Furthermore, a shock test condition using a drop-table shock tester, which can simulate the actual firing shock acceleration, was devised. The devised shock test condition will be utilized to test the electro-optical scope itself before attaching it to the small arms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.397-398
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• 2013

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.352-358
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• 1996

원자력발전소의 지진에 대한 절대안전성을 확보하기 위하여 설치된 지진감시설비망에 과도진동이 유발되는 사례가 자주 발생하여, 이에 대한 원인을 분석하고 대책을 강구하는 연구를 수행하였다. 현재 울진1,2호기 배관상에 설치되어 있는 가속도계 및 응답스펙트럼기록기에 작업자의 실수로 인한 인위적인 충격이나 배관진동에 의해 과도한 진동이 발생할 수 있다는 개연성을 밝혀 내고 이러한 지진감시설비의 개선 및 적합한 설치장소에 대하여 의견을 제시할 수 있는 계기를 마련하였다.