• Structural Monitoring and Maintenance
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• 제3권3호
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• pp.215-232
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• 2016

This paper presents a multi helical ultrasonic imaging approach for quantitative corrosion damage monitoring of cylindrical structures. The approach consists of two stages. First a multi helical ultrasonic imaging (MHUI) algorithm is used to provide qualitative images of the structure of interest. Then, an optimization problem is solved in order to obtain quantitative damage information, such as thickness map. Experimental tests are carried out on a steel pipe instrumented with six piezoelectric transducers to validate the proposed approach. Three thickness recesses are considered to simulate corrosion damage. The results show the efficiency of the proposed approach for quantifying corrosion location, area and remnant thickness.

• Journal of Welding and Joining
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• 제21권5호
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• pp.547-554
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• 2003

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive instrumented indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.291-298
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• 2001

It is very difficult to accomplish load tests of piles with large diameter constructed on the offshore area, because of requirement for large scaled loading equipment and bad testing conditions. Therefore, so far in many cases pile driving dynamic formulas have applied to quality control, and recently dynamic load test method is widely used for confirming bearing capacities of such piles. However, in cases of piles with very large diameter about 2,500mm, it is nearly impossible for regular type load test methods of piles such as static and dynamic to apply owing to very large design load. This is case studies of load tests such as modified static and dynamic load tests of piles and point load tests of rock samples for estimating rational allowable bearing capacity of very large diameter piles constructed on the marine area.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.371-378
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• 2001

The working load at pile is sometimes subjected to not only compression load but also lateral load and uplift forces. Pile foundation is essential and uplift load can be applied because of buoyancy, a typhoon, wind or seismic forces. This study was carried out to determine the uplift capacity of concrete pile foundation driven in clay. Pile was driven in clay, between pile and clay adhesion factor was estimated, and it is the mean value between the cast-in-situ-pile and steel pipe pile. When pile foundation is loaded for long time, creep behavior occurs. The behavior of creep is originated from the clay creep contacted with pile. The creep behavior of pile foundation embedded in clay is heavily depended on the thickness of clay around the pile shaft, pore water pressure in clay, and creep behavior of clay.

• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1212-1216
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• 2014

This study aims to find out the best anode location for buried pipelines. Numerical simulation program known as CATPRO (Elsyca, Belgium) were used for confirming the best location of anodes and the effects of impressed current cathodic protection system. Applied conditions for numerical simulation were similar to on-site environmental conditions for optimal application of cathodic protection system. Used criterion of cathodic protection was NACE SP 0169, which describes that minimum requirement for cathodic protection is -850mV vs. CSE. Various layouts for anodes' installation were applied, which were distance between anodes, anode installation location, and applied current. The areas where cathodic protection potential was lower than -850mV vs. CSE was limited up to 50m from anode installation locations. It was founded numerical analysis obtain cost-effective and efficient cathodic protection methods before design and application the impressed cathodic protection system to on-site environment.

• 안전기술
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• 제185호
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• pp.22-23
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• 2013

(주)해성기공은 건축물의 기초가 되는 철골 구조물만을 생산, 시공하는 강구조물(Steel Structure) 건물 건설업체다. 지난 1983년 창립된 이곳은 1997년 천안공장을 준공하면서부터 도약의 발판을 마련하게 된다. 가공설비를 구축하고 전문인력을 확충해 본격적으로 PIPE 구조물의 생산을 시작한 것이다. 이곳이 단순하게 강구조물을 제조하고 있다고 생각하면 오산이다. (주)해성기공은 인천문학경기장, 영종도 인천국제공항, KINTEX 국제전시장 등 국내 주요 랜드마크의 기초구조물을 공급한 것은 물론 일본의 해끼난, 이소보 화력 발전소에 자재를 납품했을 만큼 대내외적으로 기술력을 인정받고 있다. 이곳에서 안전관리업무를 맡고 있는 이가 오늘의 주인공인 강석훈 기사다. 강 기사는 이제 막 안전에 발을 내딛은 새내기라고 볼 수 있다. 갓 이립(而立, 30세)에 접어든 그는 지난 2011년 7월부터 본격적으로 안전관리 업무를 시작했다. 이는 곧 경력과 연륜에서 묻어나오는 안전관리를 기대하기 힘들다는 의미로 해석할 수 있다. 하지만 그는 남다른 열정과 각고의 노력을 통해 빈틈없는 자율안전관리를 전개하고 있는 것으로 지역 안전인들 사이에서 유명세를 타고 있다. 그가 어떻게 안전관리를 실시하고 있기에 이런 명성을 쌓고 있는지 만나봤다.

• 대한기계학회논문집A
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• 제27권2호
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• pp.285-293
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• 2003

This paper explores an optimal design methodology for an auto lever using a genetic algorithm. Components of the auto lever have been designed sequentially in the industry, but this study presents a novel design method to determine the design parameters of components simultaneously. The genetic algorithm approach is described to decide a set of design parameters for auto lever. The authors have attempted to model the design problem with the objective of minimizing the angle variation of detent spring subject to constraints such as modulus of elasticity of steel, geometry of shift pipe, and stiffness of spring. This method gives the promising design alternative.

• 대한기계학회논문집A
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• 제25권5호
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• pp.797-804
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• 2001

To obtain representative fatigue crack growth characteristic curve in residual stress field, fatigue crack growth test was carried out at various stress ratio and fatigue crack growth characteristic curve was represented using crack closure concept. Obtained results are as follows;K(sub)op/K(sub)max was independent of K(sub)max when R was lower than 0.5 and crack closure phenomenon was not observed when R is higher than 0.5. therefore neglecting crack closure behaviour, actual fatigue crack growth rate can be underestimated. Thus, considering crack closure phenomenon, fatigue crack growth characteristics curve of A 106 Gr B Steel weldment can be effectively estimated.

• 수산해양기술연구
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• 제33권3호
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• pp.194-201
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• 1997

Recently with the rapid development in the industries such as an iron mill and chemical plants, these are enlarged by the use of the piping. This piping was encountered the stress corrosion cracking(SCC) because of stress by water pressure and residual stress of welding etc. under industrial water. In this paper, the behaviour of stress corrosion cracking on the weld zone of steel pipe piping water(SPPW) were investigated according to pre-heat before welding in natural seawater(specific resistance : 25$\Omega$-cm). The main results obtained are as follows :1) The stress corrosion cracking for SPPW and SB 41 is most ready to propagate in heat affected zone of weldment. 2) The SCC sensitivity of SPPW on weldment is more susceptible than that of SB 41. 3) The stress corrosion cracking growth of heat affected zone is delayed by the preheat and dry of base metal and electrode before welding.

• 한국가시화정보학회지
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• 제4권2호
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• pp.76-80
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• 2006

The data for friction factor of the pipe correlated by Reynolds number and relative roughness have been reported well as a Moody chart. However, the results for corrugated shapes have been not investigated sufficiently. In this research, therefore, the pressure drop and friction factor are obtained. Flexible metal tubes with corrugations for the measurement are made of stainless steel plates. The kinds of tubes for the measurement are 5 annular types and helical types. The pressure drop & the velocity of the flow are obtained by micromanometer & digital pressure sensor, supplying dry air at several steps. Then the pressure drop is calculated for each tube, using the obtained data. The result shows that the pressure drop is strongly influenced by the viscous dissipation of kinetic energy due to the circulation of flows, rather than a viscous friction loss. The pressure drop increased consistently as the Reynolds number increases.