• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.16 no.1
• /
• pp.65-73
• /
• 2020

Integrity evaluations on a platen superheater were conducted as per ASME Section VIII Division 2(hereafter 'ASME VIII(2)') which was originally used for design with implicit consideration of creep effects. A platen superheater subjected to severe loading conditions of high pressure and high temperature at creep regime in a supercritical thermal plant in Korea was chosen for present study. Additional evaluations were conducted as per nuclear-grade high-temperature design rule of RCC-MRx that takes creep effects into account explicitly. Comparisons of the two results from ASME VIII(2) and RCC-MRx were conducted to quantify the conservatism of ASME VIII(2). From present analyses, it was shown that the design evaluation results exceeded allowable limits of RCC-MRx for the plant design conditions although limits of ASME VIII(2) were satisfied regardless of operation time, which means that design as per ASME VIII(2) might be potentially non-conservative in case of operation in creep range. A high-temperature design evaluation program as per RCC-MRx, called 'HITEP_RCC-MRx' has been used and it was shown that pressure boundary components can be designed reliably with the program especially for the loading conditions of long-term creep conditions.

• Journal of the Korean Society of Safety
• /
• v.35 no.4
• /
• pp.23-31
• /
• 2020

In the construction sector, there were 99 fatalities from falls associated with steel tube and system scaffolds for three years from 2016 to 2018 and out of which 27.3 percent (27 workers) were found to have occurred during installing and dismantling procedure. To erect scaffolding which is installed for the work at height, the work platforms are generally installed first and the safety guardrails are installed and vice versa to dismantle. As a result, workers are exposed to the risk of falling because they erect and dismantle scaffolding without guardrails. To minimize the risk of falling, it is necessary to study a new construction method that can erect or dismantle scaffolding while guardrails are installed (called advanced guardrail system). This study analyzed advanced guardrail system in terms of safety regulation, workability and economic efficiency by investigating the domestic situation on the use of scaffolding, reviewing domestic and foreign standards for guardrails and conducting economic feasibility study. The results of this study is expected to greatly contribute to preventing falls in scaffolding installation and dismantlement procedure. As a follow-up study, empirical research is required including physical test of scaffolding with advanced guardrail system and effectiveness analysis after trial applications.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 2006.03a
• /
• pp.195-203
• /
• 2006

The crossing construction under railroad have two methods which are cut and cover and trenchless method. first, cut and cover method is an extremely limited method concerning non-running time. Whereas, trenchless method is free from restriction such as train speed and running time, and has the strong points of safe and rapid construction. Front Jacking method, one of the trenchless methods, is frequently applied recently due to its stability during construction and vantage of assuring schedule reliability. The procedure is that after minimizing interlocking friction with structure and earth pressure due to jacking the small steel tube, pulling the precast box manufactured at the field in the ground using PC strand and hydraulic Jack. This method is able to be applied regardless of section size and length of box and condition of ground. And that is also pro-environmental. This paper presents the case of Daejeon E. W. perforate Road Project applied with the Front Jacking method.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.61-64
• /
• 2008

A combination of CFT column and RC flat plate without formworks is very effectively rapid constructions. This paper verified the lateral resisting capacity of CFT column-RC flat plate exterior connection in comparison with general RC column-flat plate connection and detected moment capacity and ductility capacity of connection according to moment-displacement ratio. We made and tested specimens which have different variables respectively and as a result derive a following conclusion. In CFT-E2 specimen a critical section was extended and maximum moment increased 20% respectively in comparison to general RC column specimen. In BME and CFT-E1 specimens generally shear governed behaviors and CFT-E2 specimen complemented with seismic band, flexure behavior region of slab was extended and also ductility ratio and energy absorptance increased.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.5
• /
• pp.561-565
• /
• 2011

The structural vehicles are steel members of square or circle tube with definite shape. These members support various components and absorb impact energy to protect passengers during accidentswhen crash happen. Structural members need to be lightweight and stable. In this study, we do an impact simulation of a CFRP square member using finite element analysis program Ls-Dyna in order to predict fracture shape and energy absorb feature of CFRP member. Also, we make square member shape of CFRP and do an impact experiment. We compare the analytical and experimental results and consider the fracture shape and energy features of CFRP members.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.26 no.5
• /
• pp.343-352
• /
• 2006

In the present paper, the nondestructive test method was suggest to establish the bonding status of a motor case assembly composed of a steel motor case, adiabatic rubber layer and an ablative composite tube with strain data, AE(acoustic emission) signals and UT(ultrasonic test) data. And, finite element analysis was conducted to verify quantitatively the bonding status of motor case assembly under inner pressure loading. The bonding status could be judged whether the bonding status is perfect or contact condition by the data correlation study with AE signals and strain data measured from air pressure test. And, to classify the bonding status of motor case and rubber layer among bonding layers, UT method was also applied. From this study, the bonding status could be classified and detected into fourth types for all bonding layers as follows: (1) initial un-bonding, (2) perfect do-bonding during an air pressure test, (3) partially de-bonding during an air pressure test, and (4) perfect bonding.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.646-654
• /
• 2005

The crossing construction under railroad have two methods which are cut and cover and trenchless method. First, cut and cover method is an extremely limited method concerning non-running time. Whereas, trenchless method is free from restriction such as train speed and running time, and has the strong points of safe and rapid construction. Front Jacking method, one of the trenchless methods, is frequently applied recently due to its stability during construction and vantage of assuring schedule reliability. The procedure is that after minimizing interlocking friction with structure and earth pressure due to jacking the small steel tube, pulling the precast box manufactured at the field in the ground using PC strand and hydraulic Jack. This method is able to be applied regardless of section size and length of box and condition of soil. And that is also pro-environmental. This paper presents the case of Daejeon E. W. perforate Road Project applied with the Front Jacking method.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.1
• /
• pp.14-20
• /
• 2003

Piezoelectric ultrasonic transducers for high temperature contact measurement were developed. These high temperature ultrasonic transducers (HTUT) consisted of bismuth titanate piezoceramic element whose Curie temperature is higher than $600^{\circ}C$, a backing material of the mixture of tungsten powder and inorganic binder, an inner alumina tube, a wear Plate and a housing. The operational frequencies or the HTUT were 1.04 and 2.08 MHz, respectively. Various commercially available couplants for high temperature were evaluated and compared. As a couplant for high temperature ultrasonic testing between HTUT and test specimen, gold epoxy was selected. The peak amplitude of pulse-echo signals from steel test specimen decreased with increasing temperature. The operational temperature of the HTUT reached up to $500^{\circ}C$ at which the continuous contact measurement was possible.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.43-46
• /
• 2010

As the nuclear power plant has been constructed continuously for several decades in Korea, the welding technology for components manufacturing and installation has been improved largely. Standardization for weld test and qualification was also established systematically according to the concerned code. The welding for the main components requires the high reliability to keep the constant quality level, which means the repeatability of weld quality. Therefore the weld process qualified by thorough test and evaluation is able to be applied for manufacturing. Narrow gap SAW and GTAW process are usually applied for girth seam welding of pressure vessel like Reactor vessel, steam generator, and etc. For the surface cladding with stainless steel and Inconel material, strip welding process is mainly used. Inside cladding of nozzles is additionally applied with Hot wire GTAW and semi-auto welding process. Especially the weld joint having elliptical weld line on curved surface needs a specialized weld system which is automatically rotating with adjusting position of the head torch. The small sized pipe, tube, and internal parts of reactor vessel requests precise weld processes like an automatic GTAW and electron beam welding. Welding of dissimilar materials including Inconel690 material has high possibility of weld defects like a lack of fusion, various types of crack. To avoid these kinds of problem, optimum weld parameters and sequence should be set up through the many tests. As the life extension of nuclear power plant is general trend, weld technologies having higher reliability is required gradually. More development of specialized welding systems, weld part analysis and evaluation, and life prediction for main components should be taken into a consideration extensively.

• Journal of the Korean Society of Safety
• /
• v.31 no.6
• /
• pp.1-5
• /
• 2016

A bicycle is one of the most popular sporting goods in view of a sport activity and a human health. Metallic materials such as steel, aluminum, etc. were mainly used to the bicycle fork in the past. Nowadays, the carbon fiber reinforced composite materials are widely used to the manufacturing of a bicycle fork to reduce the weight and to increase the efficiency. Safety is a most important design parameter of a bicycle fork even if the weight and cost reduction are important. Bicycle failure may happen at the critical spot of a bicycle fork and cause the accident. In this paper, the composite bicycle fork will be analyzed to secure the safety and detect a critical spot by using the finite element method with Tsai-Wu failure criterion. The stress data were obtained for the laminated composites with various number of plies and fiber orientation under the bending load. Thus, design concept of a bicycle fork was proposed to secure the safety of a bicycle. The finite element analysis results show that the connection area between a steer tube and a fork blade is critical spot, and 75 or more layers of 0 degree are needed to secure the safety of a bicycle fork.