• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.1174-1179
• /
• 2001

차음성능 측정에 관한 국제간 신인도 향상을 위하여 home and away 테스트가 수행되었다. 동일 시편에 대한 비교 테스트 결과 대부분의 시편에서는 STC 1 ㏈ 이내의 차이를 보였다. 다만, 특정 시편의 경우 STC 5 ㏈의 차이가 발생하였다. 주원인으로는 잔향시간 측정 오차가 주원인으로 추정되며, 또한 부수적인 원인으로는 시편의 제작 및 설치의 차이 때문인 으로 사료된다.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.6
• /
• pp.11-18
• /
• 2011

Accurate modal identification analysis is required to reasonably perform a seismic qualification of safety-related electric equipment installed in nuclear power plants (NPPs). This study evaluates a variation of the modal properties of an electric equipment cabinet structure in NPPs according to the excitation levels. For the study, an actual electric equipment cabinet was selected as a specimen and was dynamically tested by using a portable exciter in accordance with the level of input vibration energy. Tests were classified into two sets: with-door cases, and without-door cases. Frequency response functions were computed from the signals of the acceleration responses and input motions measured from the vibration tests. A polynomial curve fitting algorithm was used to extract the modal properties from the frequency response functions. This study reviews the variation of the modal properties according to the variation of the excitation levels. The results of the study show that the modal frequencies and the modal dampings of the object specimen varies nonlinearly according to the excitation level of the test motion. Attaching the door increases the modal damping of the cabinet.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.768-768
• /
• 2011

선박/잠수함에 설치하는 소나(sonar)는 외부 해양 환경 및 유체 흐름을 위해 소나 돔을 설치하여 운용한다. 하지만 소나 돔 설치로 인해 핵심 기능인 음향신호 송/수신 기능 저하를 야기 시킨다. 따라서 소나돔을 설계시, 구조적으로는 수중 폭팔 등의 각종 하중으로부터 센서를 보호할 수 있도록 설계하고 음향적으로는 음파의 송수신 신호를 저하시키지 않는 재질을 고려하여 설계 및 제작을 하여야 한다. 소나돔에 의한 음향 손실을 최소화하기 위하여 설계 시, 소나돔음향창 시편을 통하여 음향신호가 이를 투과하면서 생기는 신호 왜곡 혹은 투과 손실 측정을 수행한다. 제한된 크기의 수조 시험장에서 투과 손실이 측정이 되는데, 음원 반사, 회절(diffraction) 등의 문제로 인하여 다양한 주파수 대역에서의 측정이 불가피 하다. 이때, 좁은 빔폭 (Beamwidth)을 갖는 Parametric array를 이용하여 음원 회절이 생기지 않는 범위 내에서 음향창 시편의 크기를 최소화 시킬 수 있으며 제한된 공간에서도 효율적으로 음향창 시편의 투과 손실을 측정 할 수 있다. 본 논문에서는 parametric array를 이용하여 음향창 시편의 크기를 최소화 하고 이를 이용하여 음향창 투과 손실을 측정하는 연구를 수행하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1991.04a
• /
• pp.133-138
• /
• 1991

일반적으로 고무를 비롯한 점탄성재료는 형상 및 크기를 적절히 조절함으로 써 한 방향 이상으로의 원하는 스프링상수를 얻을 수 있으며, 금속에 비하여 내부 마찰에 의한 에너지 발산이 매우 크기 때문에 강제 진동시의 진폭저감 및 충격에 따른 자유진동의 감쇠에 널리 이용되고 있다. 이와 같은 진동감쇠 에 점탄성재료를 효과적으로 사용하기 위해서는 복소탄성계수 즉, 탄성계수 와 손실계수를 정확하게 알아내는 것이 필요하다. 점탄성재료의 복소탄성계 수는 주파수, 온도 및 변형률등에 따라 변하므로 이와 같은 사용조건의 함수 로 구해야 한다. 복소탄성계수를 실험적으로 구하는 방법은 여러가지가 있으 며 실험의 용이성과 관심대상에 따라 적절한 방법을 선택하게 된다. 본 연구 에서는 주파수변화에 따른 복소탄성계수를 임피던스법으로 집중질량 모형을 이용하여 구하려고 할 때, 실험데이타로부터 보다 정확한 결과를 얻기 위하 여 적절한 시편의 크기를 결정하는 방법을 제시하고자 한다. 이를 위해서 시 편내의 파동전달효과와 포아송비와 관련된 양단제한효과 그리고 정하중시 압축변형에 대한 시편의 좌굴등을 고려하여 이론적으로 해석하였으며 실험 적으로도 검증하였다.

• Composites Research
• /
• v.35 no.3
• /
• pp.134-138
• /
• 2022

In this study, Ti powder/Polymer concrete composites were processed by adding the PZT powder, one of the piezoelectric materials, to improve the vibration damping effect of Polymer concrete. Ti powder was added at a constant ratio in order to maximize the vibration damping effect using the piezoelectric effect. Three types of composite material specimens were prepared: a specimen without PZT powder, specimens with 2.5 wt% and 5 wt% of PZT powder. The vibration characteristics and compression properties were analyzed for all specimens. As a result, it was confirmed that as the addition ratio of PZT powder increased, the Inertance value at the resonant frequency decreased due to the piezoelectric effect when the vibration generated from Ti powder/polymer concrete was transmitted. Especially, the Inertance value was decreased by about 19.3% compared to the specimen without PZT at the resonant frequency. The change in acceleration with time also significantly decreased as PZT powder was added, confirming the effect of PZT addition. In addition, through the compression strength test, it was found that the degree of deterioration in compression properties due to the addition of PZT up to 5 wt% was insignificant, and it was confirmed that the powder was evenly dispersed in the composites through the cross-sectional analysis of the specimen.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.14 no.5
• /
• pp.23-31
• /
• 2010

In this study, a shaking table test was performed for the evaluation of the failure capacity of an anchor foundation system in the case of an aged condition. For the shaking table test, three kinds of specimens were manufactured as follows: 1) a non-damaged anchor; 2) a specimen with cracks running through the anchor; and 3) a specimen with cracks along the expected corn-shape fracture away from the anchor. A dynamic characteristic was determined through a measurement of the frequency response function (FRF), and the seismic capacity was evaluated by using a shaking table test. Failure capacities were calculated using an acceleration response and it was compared with the anchor design code.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.11 no.5
• /
• pp.197-202
• /
• 2001

The influence of thermal treatment and cold drawing was investigated for poly(ethy1ene terephthalate) films fabricated with various experimental conditions. Samples were elongated at room temperature under stepwise-drawing condition with the cross-head speed kom 0.5 to 500 mrdmin in an universal tester. Stress oscillation was observed in the stress-stnin curve of the samples heat-treatd at 50, 72 and $129^{\circ}C$ for 30 min, but it was not observed in the samples heat-treatd at $83^{\circ}C$ for 30 min. Thermal analyses of the samples were carried out in differential scanning calorimeter at the heating rate df $10^{\circ}C$/min/min, and the glass transition temperature, crystallization peak, enthalpy of fusion and degree of crystallinity were measured. The dynamic mechanical analyses of the samples were also carried out in a multiplefimction internal kiction pendulum at 1 Hz with the heating rate of $1.5^{\circ}C$/min, and it was found that the elastic modulus increases in the order of non-treated, heat-treated, and elongated samples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1990.10a
• /
• pp.27-32
• /
• 1990

본고에서는 한국공업규격에서 정하고 있는 고무의 시험방법(공진법, 비공진 법)을 따라 고무의 탄성계수와 손실계수를 측정하고, 이 시험방법에서 발생 할수 있는 시험오차(시편의 질량효과, 비선형성)를 제시함으로써 이후 고무 의 동특성 시험을 위한 procedure의 제정에 도움이 되고자 한다.

• Polymer(Korea)
• /
• v.25 no.1
• /
• pp.56-62
• /
• 2001

When polyethylene terephthalate(PET) film specimen were stepwise elongated under tension with various speeds of about 0.5~500 mm/min, the necking area, consisted of transparent and opaque bands, was formed during plastic deformation. Stress oscillation was apparently obtained in the stress-strain curve of above specimen. However, stress oscillation was not obtained in the stress-strain curve of annealing specimen. Microstructure was examined dynamically using an optical microscopy and thermal analysis was carried out in a differential scanning calorimeter at a heating rate of 10${\circ}$/min. Also, orientation and crystallization were examined using monochromatic-pinhole technique and elastic modulus was measured by a dynamic mechanical analyzer in the temperature range of -150~70 ${\circ}$ with the frequency of 1 Hz. Transparent PET products were fabricated by use of the PET pellets annealed at 83${\circ}$ for 30 min in an electric furnace.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.5
• /
• pp.367-372
• /
• 2000

The film-type specimen of poly ethylene terephthalate (PET) was stepwise elongated under tension with various speed range of about 0.5~500 mm/min, and then the necking behavior during its plastic deformation was observed. When elongated at the speed range of about 20~100 mm/min, stress oscillation was apparently occurred in the stress-strain curve. When elongated at the speed range of about 200~500 mm/min, stress oscillation was not did. The transparent/opaque zone and cross-section area in the specimen elongated at the speed of about 50 mm/min were examined using the optical microscopy and scanning electron microscopy. The corrosion characteristic of the specimen elongated at the speed of about 50 mm/min in 3.8 M NaOH alkali solution was examined using the optical microscopy.