• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.1033-1038
• /
• 1995

NC 공작기계의 contour 운동 오차를 측정하기 위하여 사용되는 Ball-Bar에 의한 원호 보간 시험 데이터를 이용하여 NC controller의 성능을 평가 할 수 있는 S/W에 의한 방법을 제시한다. 본 논문에서 지금까지는 분석이 어려웠던 Masrer-Slave Changeover의 분석을 가능하게 하였으며, Ball-Bar로 부터 얻어지는 데이터를 Weighted Residual Method에 의한 종합적인 분석을 하였으며, 오차 원인별 비교를 위해 Eztra Sum of Squares Method를 도입하였다. 본 연구의 실제 적용을 위한 측정 및 분석 S/W를 개발하였으며, 결과적으로 NC controller의 성능평가에 유용함을 알 수 있었다. 무부하 조건에서의 Ball-Bar에 의한 분석 데이터와의 비교를 위하여 원형 시편을 가공하고, 진원도 측정 및 분석을 통하여 유사한 오차 pattern을 가짐을 알 수 있었다.

• Architectural research
• /
• v.10 no.1
• /
• pp.13-23
• /
• 2008

It is the purpose of this study to evaluate the structural performance of steel pipe splice for SD500 high-strength reinforcing bar, through a cyclic loading test. The experimental variables adopted in this study include the development length of rebar, the type of sleeve, and size of reinforcing bar, among others. The results of this study showed that the developed steel pipe splice system for SD500 high-strength reinforcing bar, retained the structural performance required in domestic, ACI and AIJ code. It is considered that the study result presented in this paper can be helpful in developing a reasonable design method for a steel pipe splice system for SD500 high-strength reinforcing bar.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.39 no.1
• /
• pp.48-53
• /
• 1997

The sand bar has developed at the junction of the Kum-ho River and Shin-ryoung River. The sediment transported from the Kumho River basin has decreased since the Youngchon Dam has been functioning. Sand bar and the vicinity of the bottleneck at the upstrem of Kumho River and Osu Island which is consisted of sand bar have inundated frequently. This study was carried out through the hydraulic model test to calibrate the hydraulic effect from removal of sand bar in the river and straightening the river course by land reclamation. The water level of river at the vicinity of bottleneck can be lowered as much as 0.40~0.7m when the sand bar is removed. When river is straightened the river course by land reclamation the water level can be lowered as half of removal of sand bar.

• Journal of the Society of Disaster Information
• /
• v.3 no.2
• /
• pp.147-169
• /
• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.478-481
• /
• 2004

An experimental investigation on the relationship between corrosion of reinforcement and bond strength in pull-out test specimen has been conducted to establish the allowable limit of rust of reinforcement in the construction field. The reinforcing bars used in this study were rusted before embedded in pull-out test specimen. The first component of this experiment is to make reinforcing bar rust electrically based on Faraday's theory to be 2, 4, 6, 8 and $10\%$ of reinforcing bar weight. For estimation of the amount of rust by weight, Clarke's solution and shot blasting were adopted and compared. Parameters also include 24 and 45MPa of concrete compressive strengths and diameter of reinforcing bar (16, 19 and 25mm). Pull-out tests were carried out according to KS F 2441 and ASTM C 234. Results show that up to $2\%$ of rust increases the bond strength regardless of concrete strength and diameter of reinforcing bar. As expected, the bond strength increases as compressive strength of concrete increases and the diameter of bar decreases.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.12
• /
• pp.2209-2219
• /
• 1997

A split hopkinson bar could be used for obtaining the high strain rate material properties of sheet metals for an autobody. In high speed tensile tests of sheet matals, a new design of a tension split Hopkinson bar apparatus is needed. The design of grips and an anvil length are numerically analyzed with ABAQUS/Explicit for the new apparatus of split Hopkinson bars. From the experiments with the new apparatus, the material properties of SPCEN in the high strain rate state have been acquired and compared with quasi-static experimental results. The material properties of SPCEN as well as other sheet metals in an autobody are indispensible for the analysis of crashworthness. Nevertheless the experiment of sheet metal in the high strain rate state has not been done or reported.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.05a
• /
• pp.231-238
• /
• 2010

Combustion stability rating tests under condition low pressure of a 75-$ton_f$ liquid rocket engine(LRE) thrust chamber were carried out. Mixing head with decreased number of injectors than that of the other but with the same mass flow rate to the combustion chamber showed self-oscillation instability in chamber pressure of 30 bar. The other combustion chamber with increased number of injectors showed that high frequency combustion stability was maintained under condition of same pressure, but self-oscillation instability was generated in chamber pressure of 20 bar which can be considered as stability boundary region of this mixing head.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.5
• /
• pp.559-568
• /
• 2019

Recently, the infrastructure of the marine environment has been increasing. Therefore, there has been increasing interest in increasing the durability of structures. The FRP Hybrid Bar with improved durability against corrosion was developed in recent years. On the other hand, studies that evaluate the corrosion resistance are insufficient. In this study, the corrosion resistance according to the type of rebar in concrete was assessed and analyzed. The experiment used steel bars and FRP Hybrid Bar. The corrosion test method was a galvanic current and half-cell potential method. The accelerated corrosion test was carried out by four levels (0%, 1.5%, 3%, and 6%) of chloride added to the concrete. The galvanic current measurements revealed no corrosion current in the FRP Hybrid Bar. The half-cell measurement also showed the corrosion resistance of the FRP Hybrid Bar. Therefore. FHB can be used as an alternative steel for structures where a marine environment and steel corrosion are predicted.

• International Journal of Highway Engineering
• /
• v.14 no.6
• /
• pp.37-43
• /
• 2012

PURPOSES : This study is to evaluate the feasibility of setting the standard of cement alkali content by using ASTM C 1260(accelerated mortar bar test) METHODS : This study analyzes the ASR(alkali silica reaction) expansion of cement mortar bar based on the changes in the aggregate type(fine, coarse), cement type(ordinary, low alkali), and replacement contents of fly ash. ASR tests were conducted according to ASTM C 1260. RESULTS : In this test results, There is no big difference in the ASR expansion between ordinary cement and low alkali cement. From this test results, it was found that the variation of cement alkali content did not have a effect on ASR expansion because mortar bar was placed in a container with sufficient alkali aqueous solution at high temperature during the test process of ASTM C 1260. CONCLUSIONS : It is evidently clear that the alkali content of cement have a effect on ASR. But ASTM C 1260 is difficult to assess this effect.

• Structural Engineering and Mechanics
• /
• v.65 no.2
• /
• pp.155-162
• /
• 2018

A smart glass fiber reinforced polymer (SMFRP) reinforcing bar with a fiber Bragg grating (FBG) sensor was fabricated using a pultrusion technique, while ribs were formed to improve bonding between concrete and SMFRP. Then, strain of SMFRP bars were measured for a uniaxial tension test of an SMFRP bar, and a four-point bending test of concrete beams reinforced with SMFRP bars. The results of a uniaxial tension test illustrate that the strain obtained from an FBG sensor agrees well with that obtained from electrical resistance strain gauge (ERSG). Additionally, concrete beams reinforced with SMFRP bars were fabricated, and actual flexural test were performed while the strain of with an FBG sensor was compared with that of ERSG. The experimental results demonstrate that SMFRP bars can be used as reinforcement of concrete member while providing deformation information. Furthermore, SMFRP bars may provide stronger durability and smart monitoring to reinforced concrete members under corrosive environments during a service life.