• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.235-244
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• 2021

This study analyzes the applicability of limit state design method on bridge evaluation by considering the experiment of the existing bridge. The test strength of the member is obtained from the PSC beam bridge experiment. The test strength is compared with the calculated strength obtained from the statistical characteristics of material test strength and the two values are almost the same. The response modification factor and dynamic impact factor are obtained from the vehicle loading test. The rating factor is calculated by applying limit state design method as well as current evaluation method and the results are compared. The reliability index of the test bridge is calculated by using the statistical properties of the member strength obtained from material test and simulation. When the statistical properties of the PSC beam tested in this study are applied, the reliability index with a larger value was obtained than the reliability index obtained with the statistical properties of the design code.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.85-98
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• 2009

The in-situ Compaction test using sand cone (RC) and Plate Bearing Capacity Test (PBT) has been widely used for evaluating the subgrade and subbase condition on the pavement system. However, because the in-situ RC and PBT test are expensive and take plenties of time for operation, these are very difficult to figure out the in-situ characteristics of subgrade and subbase strength in detail. Therefore, for faster and economical operation, this study is to compare the Light Falling Weight Tests and propose the LFWD test as the in-situ Compaction test. This study suggests the relationship between in-situ RC value, $K_{30}$, $M_R$ and $E_{LFWD}$ of the subgrade and subbase materials in Korea using the laboratory and in-situ testing.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.282-283
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• 2012

국제표준규격(ISO 12215-5) 및 국내 플레저보트 검사지침의 개정에 따라 길이 6미터 미만의 플레저보트의 낙하시험에 의한 강도시험기준을 적용 가능하게 되었다. 하지만 현재 낙하시험은 자유낙하 시 내력 및 외력에 의한 선체 내부의 찌그러짐, 크랙, 박리, 파손 등을 육안으로 검사하는 방법으로 시험결과의 정량적인 판단이 이루어지지 않고 있다. 따라서 본 연구에서는 레저선박의 낙하시험을 위한 시스템 및 운용프로그램을 개발하여 플레저보트의 구조안전성의 정량적 평가가 가능한 시스템을 개발하고 다단 롤포밍 기법을 적용한 5m급 알루미늄레저보트에 적용하여 시스템의 성능을 검증하였다.

• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1062-1068
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• 1999

The flexural strength distribution of alumina ceramics was observed using ball-on-3 ball test after thermal shock into the distilled water of 25$^{\circ}C$ Crack distribution was also observed by dye-penetration after thermal shock test. Fracture probability of alumina ceramics by ball-on-3 ball test was studied and compared with that by 3-point bending test. The crack distance from the center of thespecimen showed the stronger effect on the flexural strength by ball-on-3 ball test than the crack density.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.102-106
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• 2003

An experimental modal analysis and dynamic stiffness evaluation of a moving body structure of a high speed machining center are presented in this paper. The natural frequencies and corresponding modes, and dynamic compliance of a moving body structure of high speed machining center are investigated by using F.E.M., hydraulic exciter test, and impulse hammer test. The lowest three natural frequencies were found to be 56.6 Hz, 112.7 Hz, and 142.7 Hz by FEA respectively, while those were 55 Hz, 112 Hz, 131 Hz by experimental analysis. Furthermore, both computed and measured absolute dynamic compliances of the moving body structure in iso-direction showed good agreement especially at the first two mode frequencies. With our experimental data, the dynamic characteristics of the machining center can be exploited to get a new development of structural dynamic design and modification.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.139-152
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• 1999

These days we broadly apply drilled shafts for deep foundations to build infrastructures. The defects of the deep foundations cause the decrease of their support load capacity and the increase of settlement, and the subsequent damage of the super-structures. In consequence, non-destructive testings techniques of concrete piles are important for their integrity evaluation. To improve understanding and reliable application of the impact echo method for the integrity evaluation of the drilled concrete piles, numerical studies of the impact response of concrete piles by using axi-symmetric three-dimensional finite element method are peformed for (a) sound piles: (b) piles containing necks, voids and layers of low-quality concrete: and (c) piles in soil and/or above rock. The results of these studies show that the finite element method is effective for evaluating the impact response of drilled concrete piles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.617-622
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• 2012

Structures are often subjected to various types of loading such as static, dynamic, or impact loading. Therefore, experimental and numerical methods have been employed to find adequate material properties according to the conditions. The Split-Hopkinson pressure bar (SHPB) test has frequently been used to test engineering materials, particularly those used under high strain rates. In this study, the compressive deformation behaviors of aluminum alloy under impact conditions have been investigated by means of the SHPB test. The experimental results were then compared with those of finite element analyses. It was shown that reasonably good agreement with the true stress-strain curves was obtained at strain rates ranging from 1000 $s^{-1}$ to 2000 $s^{-1}$. When the strain rate increased by 30%, the peak stress in particular increased by 17%, and the strain also increased by 20%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.91-96
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• 2010

The hydraulic hose can be divided with the low pressure, the medium pressure, and the high pressure hose according to the applied pressure. The power steering system in a passenger car can be divided with the high pressure and the low pressure hose. This study deals with the life prediction for high pressure hose to be given impulse pressure which was generated in turning the car. To adjust with external and internal condition, impulse pressure and oil temperature need to be controlled with impulse test system. The result, which is only controlled with the pressure and oil temperature, adapted Calibrated Accelerated Life Test(CALT) method to predict the life of the high pressure hose and analyzed the swagging part by finite element method during the impulse test.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.97-99
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• 2005

현장에서 사용중 고압전선에 고장이 발생한 6.6kV 건식변압기 고장의 원인분석을 위하여 설계와 제조방식이 동일하고 사용기간이 비슷한 건식변압기에 대한 전기적 열적 시험을 실시하였다. 전기적 시험으로서는 교류 및 충격 내전압시험, 부분방전시험을 실시하였고 열적시험으로는 단락법을 사용하여 온도를 상승시켰으며, 내부 및 외부권선표면의 온도분포와 열화상에 의한 온도분포를 측정하였다. 시험결과 부분방전특성이 기준치에 비하여 높게 나타났으며, 권선온도분포는 사용한계온도이하인 것으로 분석되었다.

• Composites Research
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• v.14 no.1
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• pp.1-7
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• 2001

In this study, damage evaluation of glass fiber reinforced thermoplastic composites was investigated with acoustic emission method. Specimens of 1.7mm thickness laminate were made from PET and 7 layers o171ass fabrics. Notch and impact loading were added to the specimen and normal tensile test and tensile test with the dead load were carried out. AE signal was measured as the functions of notch ratio to the width0 and impact energy in order to find out the correlation between fracture mode and AE parameters. The result has shown that low amplitude of AE signal was due to the microcrack of matrix and its growth, whereas the amplitude in the mid range was the response to the delamination and interfacial separation. In the range of high amplitude above 90dB. the fracture of glass fabric was found. Tensile strength decreased with increasing notch ratio to the width and impact energy because of tile effect or delamination, the cracking of matrix and stress concentration. In proportion to the size of damaged area. AE signal showed its wider range of frequency and energy as well as increased number of hits.