• 소음진동
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• 제11권3호
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• pp.449-454
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• 2001

The shock performance of hard disk drives has been a serious issue for portable computers and AV application HDD. Focusing on the motion of an actuator, we investigated non-operational shock mechanism and studied several parameters that affect the shock performance by experimental analysis. It was found that there are two important factors fort the actuator to endure high shock revel. One is a shock transmissibility and the other is a beating between the arm blade and the suspension. To generalize the shock transmissibility, the concept of shock response spectrum was introduced. The shock response spectrum of the actuator system was obtained experimentally and compared with that of an analytical single degree of freedom model. It was found that there was a good agreement. The first bending natural frequency of the arm blade was found to be the most important factor for the low shock transmissibility. By applying the shock response spectrum and avoiding the beating, we could design an actuator of high shock performance.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.215-220
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• 2008

A numerical method for gas-liquid two-phase flow is applied to solve shock-bubble interaction problems. The present method employs a finite-difference Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. By this method, a Riemann problem for shock tube was computed for validation. Then, shock-bubble interaction problems between cylindrical bubbles located in the liquid and incident liquid shock wave are computed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.215-220
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• 2008

A numerical method for gas-liquid two-phase flow is applied to solve shock-bubble interaction problems. The present method employs a finite-difference Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. By this method, a Riemann problem for shock tube was computed for validation. Then, shock-bubble interaction problems between cylindrical bubbles located in the liquid and incident liquid shock wave are computed.

• 정보저장시스템학회논문집
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• 제9권2호
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• pp.32-35
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• 2013

Nowadays, function related to anti-vibration and anti-shock of storage devices is required because of portability. Therefore, many hard disk drive (HDD) studies about external shock and vibration have been performed. Especially, many studies are performed with non-operational shock. Most studies have used the fixed condition between spindle system and base when they wanted to analyze dynamic behavior of inner parts in simulation. But spindle system has actually stiffness and damping coefficient. Maybe difference of value would be happened between fixed condition and spring condition. So, we measured FRF of spindle system to know stiffness and damping coefficient in HDD. And we studied on dynamic behavior of inner parts by using calculated stiffness and damping coefficient. As a result, we confirmed the difference as boundary condition of spindle system.

• 한국세라믹학회지
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• 제36권10호
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• pp.1069-1074
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• 1999

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.103-106
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• 2009

Fracture characteristics of plate shape using shock tube for glass filled ceramics was carried out. Glass filled ceramics have been considered as a promising candidate material for the dome port cover of air breathing engine. This part of the air breathing engine has an important role separating solid and liquid fuel, and needs the frangible characteristics that the fracture of a part should not affect the internal components of combustion. The objectives of this study are to evaluate the fracture pressures for various thicknesses and diameters of shock impact area. Also fracture phenomena of separated membrane using a shock tube are observed. The experimental apparatus of shock tube consists of a driver, a driven section and a dump tank. The used material is glass filled ceramic made from Corning company. Specimens are used 3, 4.5 and 6mm thickness. Also diameters of shock wave area are chosen 70, 60 and 50 mm. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.

• 한국재료학회지
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• 제27권1호
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• pp.25-31
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• 2017

This study investigates changes in the mechanical behaviors, especially hardness and indentation load-displacement curves, of thermal barrier coatings (TBCs) brought about by thermal shock. The TBCs on the Nickel-based bondcoat/superalloy was prepared with diameters of 25.4 mm and $600{\mu}m$ thickness. The results of thermal shock cycling test from $1100^{\circ}C$ of the highest temperature indicate that the thermal shock do not influence on the mechanical behavior, but a continuous decrease in porosity and increase in hardness were observed after 1200 thermal shock cycles; these changes are believed to be due to sintering of thermal barrier coating materials. The results that no degradation in the indentation load-displacement curves indicate that the coating shows good thermal shock resistance up to 1200 cycles at $1100^{\circ}C$ in air.

• 한국추진공학회지
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• 제9권1호
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• pp.27-34
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• 2005

본 논문은 기존 폭발볼트의 기능을 그대로 유지하면서 분리시 발생되는 파편 및 충격파의 악작용을 완벽히 제거할 수 있는 가스팽창분리형 볼트의 분리거동에 관한 연구이다. 가스팽창분리형 볼트는 분리화약을 사용하지 않고 압력카트리지의 압력만 이용하여 분리가 이루어지게 개발된 파이로 장치로써, 분리거동을 수치해석 함으로써 볼트의 설계인자를 최적화할 수 있었다. 수치해석 및 시험결과에서 노치는 쐐기형태를 가지며 내부 홈 깊이가 분리면과 일치하는 모델이 가장 좋은 분리현상이 나타났다. 본 연구에서 제시한 볼트 설계인자의 최적화 방법은 향후 다른 종류의 폭발볼트와 같은 파이로 장치 설계에 기초자료를 제공할 수 있다.

• 대한치과보철학회지
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• 제34권1호
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• pp.151-167
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• 1996

Temporary soft liners can be used to prevent chronic soreness from dentures or to aid in its treatment are as adjuncts in tissue conditioning, for temporary obturators, and to stabilize baseplate or surgical stent. The purpose of this study was to evaluate the shock absorption properties of several temporary soft denture liners using a free drop test with an accelerometer. The materials tested inclued Coe-comfort, Softone, Tissue conditioner and Viscogel. The specimens were fabricated with the thickness of 1, 2, 3mm and were stored in distilled water at $37^{\circ}C$ for a day, 1, 2, and 3 weeks. Six samples were made with each material for each test condition and the shock-absorbing behavior was evaluated according to material, thickness and duration. The results were as following : 1. Softone of 3mm thickness stored for a day showed the most excellent shock absorbability. 2. The shock absorbing behavior of duration according to materials and thickness showed a day to be the highest and decreased in 1 week, 2 weeks and 3 weeks in that order(p<0.05). And there was no significant difference between durations in Tissue conditioner. 3. The shock absorbability of thickness according to materials and duration showed 3mm to be highest and decreased in the order of 2mm, 1mm(p<0.05). 4. In comparison of the shock absorbability of temporary soft denture liners according to thickness, there was statistically significant difference between Softone and Visocgel, Tissue conditioner, Coe-comfort / Viscogel and Tissue conditioner, Coe-comfort in 1,2mm thickness, and between Softone, Viscogel and Tissue conditioner, Coe-comfort in 3mm thickness (p<0.05).

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 봄 학술발표회 논문집
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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.