• Computers and Concrete
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• v.14 no.6
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• pp.675-694
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• 2014

Annular and solid concrete specimens with different aspect ratios and static unconfined compressive strengths were studied for impact loading using SHPB test setup. Numerical simulations in LSDYNA were also carried out and results were validated. The stress-strain curves obtained under dynamic loading were also compared with static compressive tests. The mode of failure of concrete specimen was a typical ductile failure at high strain rates. In general, the dynamic increase factor (DIF) of thin solid specimens was higher than thick samples. In the numerical study, the variation of axial, hydrostatic and radial stresses for solid and annular samples was studied. The core phenomenon due to confinement was observed for solid samples wherein the applied loads were primarily borne by the innermost concrete zone rather than the outer peripheral zone. In the annular samples, especially with large diameter inside hole, the distribution of stresses was relatively uniform along the radial distance. Qualitatively, only a small change in the distribution of stresses for annular samples with different internal diameters studied was observed.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.131-144
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• 2000

본 연구는 비검측공 시험법으로서 널리 사용되고 있는 충격반향기법(impact-echo test)의 적용서을 수치해석 및 실내 실험을 통하여 분석해 보았다. 즉, 결함이 없는 말뚝과 결함이 있는 말뚝에 대하여 1차원 및 2차원 축대칭 유한요소해석을 실시하였으며, 또한 모노캐스트라고 하는 일종의 플라스틱 원형 봉의 말뚝에 축대창 공극, 비축대칭 공극, 병목부 및 단면 확대부와 같은 결함을 각각 크기와 깊이를 변화시켜 제작한 후 공기 중과 지반 내부에서 충격반향기법 실험을 수행하였다. 실험결과 충격반향기법의 말뚝 결함 탐지능력은 수치해석에서 얻은 결과와 함께 결함의 크기와 위치에 영향을 받는 것으로 나타났으며 결함의 크기가 커질수록 탐지의 정확도가 향상되는 것을 알 수 있었다. 결함의 상대면적이 말뚝 단면적의 50% 이상이면 충격반향기법에 의하여 결함의 위치를 파악할 수 있는 것으로 나타났으며, 공기 중 보다 지반에 근입 된 말뚝의 경우가 더욱 명확한 신호를 제공해주는 것으로 나타났다. 그리고 시간영역의 신호가 주파수 영역의 신호 보다 말뚝의 결함 크기에 더 민감히 반응하므로 주파수 영역에서 탐지할 수 없는 작은 크기의 결함을 시간 영역에서는 탐지할 수 있는 것으로 나타났다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.37-40
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• 2004

The impact/sliding wear tests have been performed in high temperature high pressure water in order to evaluate the effect of spring shape on the wear behavior of a spring supported tube for nuclear fuel fretting study. The results indicate that the tube wear volume and the size of the wear scar are closely related to each spring shape. From the analysis of the wear scar, it is possible to extract the real worn area (Aw) from the size of the wear scar (At). In addition, we found that the wear volume has a linear relation with the real worm area rather than the size of wear scar and this was only determined by each spring shape in the high temperature and pressure water condition. From the above results, it is possible to evaluate the wear resistant spring using the correlation between the variation of the real worn area and the wear behavior at each spring.

• Journal of the Korean Operations Research and Management Science Society
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• v.36 no.4
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• pp.63-79
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• 2011

In this research, we have investigated the impact of servitization on firm value focused on Fortune 500 company's alliance announcement. The Firms are categorized to understand the impact of servitization and productization. The data includes Fortune 500 companies (2009, USA). Samples used for the hypothesis tests consist of 1,057 American companies that are opened on NYSE and NASDAQ, for the years 1990 through 2010. We test four research hypotheses based upon the various theoretical perspectives in servitization. The market is selective in reacting to alliance category; service company ${\rightarrow}$ manufacturing company, service company ${\rightarrow}$ service company. The findings show that alliance is significant between service company and manufacturing company. Also, the result shows significant relationship inter-service company's alliance. We have a significant relationship between company's alliance announcement and the market value of firms and shows significant AR in financial performance. Finally, this study presents implications for manufacturing companies that pursue service-led expansion as a strategic approach and are seeking to improve market value through alliance, partnership and cooperation. Continual effort must be placed to sustain market value of the firms.

• The Journal of Asian Finance, Economics and Business
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• v.6 no.4
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• pp.249-260
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• 2019

The study examines the impact of financial risk, convenience risk, non-delivery risk; return policy risk and product risk on online consumer behavior of Malaysian consumers. The research employed a self-administered survey to collect empirical data from 245 Malaysian online shoppers by using convenience sampling. Cronbach alpha was calculated to confirm the reliability of the data and then normality was assessed. Confirmatory Factor Analysis was then conducted to test the model using the goodness-of-fit tests. And finally, structural equation modeling is used to test the hypotheses and draw conclusions. IBM SPSS AMOS version 22.0 was utilized for data analysis. The research indicates that product risk, convenience risk, and return policy risk have a significant and positive impact on online shopping behavior. Financial risk is found to have insignificant and negative effects on consumer behavior. In addition, the non-delivery risk is found to have a significant and negative impact on online shopping behavior. The findings provide a useful model for measuring and managing perceived risk in online shopping which may result in an increase in participation of Malaysian consumers and reduce their cognitive deficiencies in the e-commerce environment. Several managerial implications are discussed along with the scope for future research.

• Journal of Korea Foundry Society
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• v.34 no.1
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• pp.6-13
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• 2014

The mechanical properties of low-pressure die cast (LPDC) A356-T6 automotive road wheels are evaluated and correlated with their corresponding microstructures. In this study, two types of alloy wheels processed using different LPDC gating system are investigated. The yield stress, tensile stress, and elongation values tested at room temperature are correlated with the secondary dendrite arm spacing (SDAS) with respect to the gating system, and are also compared with similar studies. The SDAS and precipitates are examined using optical microscopy, scanning electron microscopy (SEM) and energy-dispersive spectroscopy. The phase information is also investigated using X-ray diffraction. Charpy impact tests are also performed from $-100^{\circ}C$ to $200^{\circ}C$, and the fracture surfaces are examined using SEM. The impact energy is demonstrated to increase with increasing temperatures without exhibiting specific transition behaviors as in other nonferrous alloys. The fracture toughness is also evaluated using three point bend test with single-edged bend specimens. The obtained fracture toughness values are in good agreement with those in similar studies.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.9-10
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• 2010

In this study, the static and low velocity impact tests for two-way concrete specimens strengthening with the CFRP sheets were carried out. The specimens that had a dimension of $50{\times}350{\times}350mm$ with 40 MPa plain concrete and steel fiber reinforced concrete which had same mixture to plain concrete and 0.75% steel fibers were fabricated. The specimens reinforced with the CFRP or steel fibers showed mixed failure modes, splitting and punching, also splitting cracks and fragments were much reduced than plain concrete specimens'. Two-way concrete members reinforced with the CFRP and steel fiber simultaneously dissipated 6.8 times larger energy than not-retrofitted members' under the low-velocity impact loading.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.17-22
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• 2011

Ultimate goals in vehicle design can be summarized as environment-friendliness and safety. Along with these requirements, the importance of natural environment conservation has been focused lately. Therefore, reduced emission from vehicle and improved efficiency has become the top priority projects throughout the world. CFRP(Carbon Fiber Reinforced Plastics) of the advanced composite materials as structure materials for vehicles, has a widely application in lightweight structural materials of air planes, ships and automobiles because of high strength and stiffness. This study is to investigate the energy absorption characteristics of CFRP hat-shaped section members under the axial impact collapse test. The CFRP hat-shaped section members which manufactured from unidirectional prepreg sheets were made of 8plies. The axial impact collapse tests were carried out for each section members. The collapse mode and energy absorption characteristics were analyzed for CFRP hat-shaped section member according to the interface numbers(2, 3, 4, 6 and 7).

• Nuclear Engineering and Technology
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• v.19 no.1
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• pp.1-9
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• 1987

The fracture toughness of SA 533 Grade B Class 1 steel has been studied with the Charpy impact test specimens in a range of temperature between -4$0^{\circ}C$ and 288$^{\circ}C$. The dynamic fracture toughness is measured by the instrumented precracked Charpy impact test while the static fracture toughness is by the 3-point bend test based on the unloading compliance method. The results are compared with the data obtained from the large specimens. It is known through the studies that temperature dependence of the appropriate (a low bound) value of the fracture toughness can be estimated by taking the static fracture toughness above the transition temperature and the dynamic fracture toughness below the temperature and it is also shown that the tests are satisfied with the requirements of ASTM E 813 when the side-groove is more than 14%.

• Journal of the Society of Disaster Information
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• v.12 no.4
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• pp.432-439
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• 2016

To make a model of a Impact/Blast resistant composite material and perform the analysis, material properties of the composite material are required. In order to obtain such a property value, it is necessary to input the result obtained by performing a lot of material tests by the calculation formula of the situation, and there is a lot of difficulty in the case of a special purpose material which is not a general material. In this study, modeling and structural analysis of composite fiber panels for protection and explosion - proofing were performed in ACP(ANSYS Composite PrePost) and AUTODYN by applying the application properties of composites provided in Ansys Workbench environment.