• Journal of Welding and Joining
• /
• v.15 no.2
• /
• pp.43-53
• /
• 1997

The complete joining method for dissimilar press punch materials and its real-time evaluation method is not available at present. Brazing method has been used for joining them, but it is known that the welded joint by the brazing has the lower bonding efficiency and reliability than the diffusion welding. The friction welding with a diffusion mechanism in bonding was applied in this study. This work was carried out to determine the proper friction welding conditions and to analyze mechanical properties of friction welded joints of sintered carbide tool materials (SKNM50 for the blade part of press punch) to alloy steel (SCM440 for the shank part of press punch) using aluminum (A6061 for the interlayer material) as an insert material between the sintered carbide tool materials and the alloy steel. In addition, acoustic emission test was carried out during friction welding to evaluate the weld quality.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.277-277
• /
• 2022

급경사 산지하천은 호우 시 퇴적 하상이 붕괴하여 하천 유사량을 급격히 증가시키는 계곡형 토석류가 발생하고 도로와 교량에 피해를 일으키기도 한다. 이러한 하천재해를 저감하기 위하여 돌망태 낙차공을 설치하여 하상 안정을 강화하고 급경사에 따른 유수에너지를 줄일 수 있다. 급경사 하상에 설치한 돌망태 낙차공은 하류부 하상의 국부세굴에 따른 파괴위험이 완경사 하상의 경우에 비하여 높으므로 이를 줄이기 위한 연구가 필요하다. 이 연구에서는 광폭경사조절 개수로에 돌망태 낙차공을 설치하고 낙차공의 채움재가 복류의 특성에 미치는 영향을 파악하기 위하여 수리실험을 하였다. 수리실험에서는 최대 20º까지 경사를 조절할 수 있는 길이 1.44m, 폭 0.14m인 직사각형 단면 개수로에 SUS304 구슬을 사용하여 하상과 돌망태 낙차공을 설치하고 실험하였다. 구슬은 크기에 따라 작은구슬(10.31mm), 중간구슬(15.08mm), 큰구슬(20.63mm)을 사용하고, 하상에는 작은구슬을 깔았다. 낙차공의 크기는 길이 16cm이고 폭과 높이는 12cm이며, 돌망태는 작은구슬을 사용한 단일돌망태와 구슬 크기를 달리한 계층돌망태로 구분하였다. 계층돌망태의 상층은 작은구슬, 중층은 중간구슬, 하층은 큰구슬이 채움재로 사용되었다. 단일돌망태의 공극율은 0.399이고 계층돌망태의 공극률은 상층 0.393, 중층 0.517, 하층 0.54이다. 실험유량의 변화는 낙차공 하단부에서 표면류가 발생하지 않는 범위로 한정하였다. 낙차공 하단에서 상류 68cm 지점의 소류력과 낙차공 내부 복류의 수면경사를 측정하였다. 그 결과 단일돌망태보다 계층돌망태가 소류력과 수면경사가 더 작은 것으로 나타났으며 돌망태의 공극을 통한 통수능 차이 때문인 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.6
• /
• pp.991-998
• /
• 2016

The propose of this study is to demonstrate how efficiently and accurately the construction stages of cable-stayed bridges are analyzed using the unstrained length method (ULM) in which all unstrained element lengths are determined from a simplified analytical method (Jung et al., 2015). A forward analysis of cable-stayed bridges using the commercial FEA program, MIDAS is sequentially carried out considering the lack of fit force but the ULM is able to analyze a intermediate construction stage directly by taking the corresponding unstrained lengths of the construction stage model simply. The closing load step analysis is achieved by loading the pavement and counter weight forces in reverse. An Incheon bridge model is analyzed using the present ULM and the commercial program, respectively, and the two analysis results are compared.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.12
• /
• pp.5984-5989
• /
• 2011

The buckling strength of a pin-ended column may be increased significantly by reinforcing it with an assemblage of cross-arm members rigidly connected to the modpoint of the column and stayed members connecting the ends of the columns and cross-arm members. The purpose of the stays and cross-arm members is to introduce restraint against translation and rotation and thereby decrease the effective buckling length of the column. In this study, buckling strengths of the reinforced columns were quantitatively evaluated from analytical solutions and elastic/inelastic finite elements analysis and the results were compared each other. It was found that the reinforcing system may increase the buckling strength up to 8 times compared to ones without reinforcing system.

• Geotechnical Engineering
• /
• v.10 no.3
• /
• pp.5-16
• /
• 1994

This paper presents a new method to improve the bearing capacity of a square shallow foundation placed on a sand layer reinforced with geogrids which shows promise for further field work. The geogrid reinforcement will be necessary in the case of machine foundation, embankments for railroads, and foundations of structures in earthquake-prone areas. The ultimate bearing capacity (UBC) for the unreinforced sand and reinforced sand has been compared. Also, the effect of length, spacing, width of reinforcement on increasing the UBC have been evaluated. Based on the present model test results, it appears that significant improvement in the UBC of medium sand can be achieved by geogrid reinforcement.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.4
• /
• pp.915-922
• /
• 1994

This paper presents a new method of soil improvement by using semi-flexible vertical reinforcing elements which shows promise for future work. Load tests were conducted on two model footings in a sand box using unreinforced sand and also by reinforcing the sand with vertical reinforcing elements. The ultimate bearing capacity for the unreinforced and reinforced sand has been compared. The effect of length, spacing, lateral extent of the reinforcement, and the initial relative density of sand in increasing the ultimate bearing capacity have been evaluated. The effect of roughness of the reinforcing elements has also been investigated. Based on the results of these model footing tests, it appears that significant improvement in the ultimate bearing capacity of loose and medium sands can be achieved by reinforcing with vertical elements.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.6
• /
• pp.2169-2179
• /
• 2013

The compressive strengths of simply supported columns may be significantly increased by reinforcing them with an assemblage of cross-arms and stayed struts connecting both ends of the columns and the cross-arm members. The purpose of the stayed struts and cross-arms is to introduce partial restraints against translation and rotation, thereby decreasing the effective buckling length of the column. In this study, buckling strengths of the assembled column system have been quantitatively evaluated from the theoretical methods based on both the equivalent spring model and the stiffness matrix formulation. And the results were compared with those from elastic/inelastic analysis using a finite element analysis package program, ABAQUS, for verification purpose. Expected compressive strength curves have been proposed for the assembled column system as a function of slenderness ratio of the simply supported column.

• Journal of the Economic Geographical Society of Korea
• /
• v.15 no.1
• /
• pp.77-94
• /
• 2012

The purpose of this study is to analyze the process of vertical fragmentation of regional industries in Korea using Revealed Comparative Advantage index (RCA) and Average Propagation Length (APL). First of all, the competitiveness in regional export and substitution of regional imports were strong in the Electricity, Gas, and Water supply sector in Gyeongnam, and consumer-oriented Manufacturing sector in Incheon, Gyeongnam, and Gwangju. The high values of the APL were also found in the regions with common similarity with respect to the industrial structure and the sectors with indirect effects. In addition, the industrial sectors with high quality of infrastructure, and endowed services tended to be located in the beginning of the production chain. FInally, since manufacturing and service sectors in Seoul has higher APL, they could lead the growth of other related industries as key sectors, in the production fragmentation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.4
• /
• pp.443-449
• /
• 2014

To check the characteristics of nuclear fuels during an irradiation test, the nuclear fuel rod needs to be disassembled from the test rig located in the pool of the research reactor. Then, the disassembled fuel rod is delivered to the hot cell for intermediate examination. A fuel rod that passes the intermediate examination is delivered to the reactor pool to be reassembled into the test rig. The irradiation test is resumed with the reassembled test rig. Because nuclear fuel rods irradiated by neutrons are highly radioactive, all the disassembly and reassembly processes should be carried out in the pool of the research reactor to prevent operators being exposed to radiation. In particular, because a test rig is 5.4-m long and the reactor pool of HANARO is 6-m deep, special tools need to be developed for performing the disassembly and reassembly processes. In this study, a new assembly design of nuclear fuel rods for intermediate examination is introduced. Furthermore, tools for treating the irradiated fuel rod assembly are introduced, and their performance is verified by an out pile test.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.1533-1534
• /
• 2015

본 논문에서는 VDTA를 이용하여 플로팅 인덕터를 구현하기 위한 새로운 방법을 제안하였다. 제안된 방법은 [3]에서 사용하고 있는 방법을 개선하여 더 적은 수의 회로를 이용하여 양 기능 인덕터를 구현함으로써 변환방법이 용이하고 회로의 면적과 소비전력을 줄일 수 있는 방법이다. 2장에서는 VDTA에 대한 기본적인 개념과 새로운 양기능 인덕터의 구조제안 및 새롭게 제안한 능동 인덕터를 이용하여 2차 2MHz의 중간주파수를 갖는 대역통과 설계하고 그 유용성을 확인하였다. 2MHz의 중심주파수를 가지는 대역통과 필터와 그 필터의 특성을 시뮬레이션을 통하여 나타내었다. 그리고 3장에서 결론지었다.