• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.164-169
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• 2006

A systematic methodology has been proposed to establish a reliable design of water pump system. A simplified steady-state dynamic model of water pump system has been developed to study the response of water pump system to the dynamic load mainly due to the run-out and unbalance. Design modifications are needed to strengthen the structural integrity of existing designs. Increasing the natural frequency of system is pursued to prevent a resonance from occurring in the engine excitation range. A computational reliability methodology combined with finite element analysis is used to identify the most significant factor affecting the system performance. This method considered influence of design control parameters for the performance of design. By including control factors to the system model in a systematic way, more reliable design is expected.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.610-616
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• 2004

The aim of this study was to investigate the hydride embrittlement when the LBB evaluation was carried out for the integrity of PHWR Pressure Tubes. The transverse tensile and CCT toughness tests were performed at three hydrogen concentrations while the test temperatures were changed (RT to 30$0^{\circ}C$). Both the transverse tensile and the fracture toughness tests showed the hydrogen embitterment clearly at RT but this phenomenon was disappeared while the test temperature arrived at 25$0^{\circ}C$. Using the DHC test results, the CCL and LBB time were calculated and compared. The hydride embrittlement at the LBB evaluation made the LBB time short definedly. If the operating temperature, DHCV and LBB deterministic parameters such as A and m were known, LBB time could be estimated without the calculation of CCL.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.9-19
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• 2011

Most real world design evaluation and risk-based decision support combine quantitative and qualitative (linguistic) variables. Decision making based on conventional mathematics that combines qualitative and quantitative concepts always exhibit difficulty in modelling actual problems. The successful selection process for choosing a design/procurement proposal is based on a high degree of technical integrity, safety levels and low costs in construction, corrective measures, maintenance, operation, inspection and preventive measures. In this paper, a design decision support framework using a composite structure methodology grounded in approximate reasoning approach and evidential reasoning method is suggested for design evaluation of machinery space of a ship engine room at the initial stages. An illustrative example is used to demonstrate the application of the proposed framework.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.753-760
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• 2013

The hydrogen embrittlement of metallic materials is an important issue from the viewpoint of structural integrity. In this regard, the estimation of mechanical properties and fracture toughness under hydrogen conditions provides very important data. This study provides an experimental validation of the approach for simulating the small punch of Inconel 617 using finite element damage analysis, as recently proposed by the authors, and applies an inverse method for the determination of the constitutive tensile behavior of materials. The mechanical properties obtained from the inverse method are compared with those obtained from the tensile test and validated. The mechanical properties and fracture toughness are predicted by using the inverse method and finite element damage analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.447-451
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• 2015

The objective of this study is to predict the structural characteristics of a heat exchanger mounted on an aircraft engine using finite element analysis. The plastic fracture and life of the heat exchanger were estimated by a thermo-mechanical analysis. Tensile tests were conducted under high temperature conditions (700, 800, 900, 1000 K) using five specimens to obtain the mechanical properties of the Inconel 625 tubes. To assess the structural characteristics of the heat exchanger, the full and partial models were applied under the operating conditions given by the thermo-mechanical and inertial load. As a result, the case, tubesheet, flange, and mounting components have a reasonable safety margin to the allowable stress assuming a fatigue strength of Inconel 625 of 10000 cycles under 1000 K.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.38-46
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• 2020

The purpose is to evaluate the structural characteristics of 750 mm diameter injection spiral blades under various operating conditions. A fiber-glass reinforced polypropylene material was employed to the injection blades, and mechanical tests on two kinds of glass-reinforced polypropylene were performed to evaluate the mechanical properties and to select a suitable candidate material. Also, three kinds of spiral blade geometries were studied to observe the influence of fixing rods between blades. For this, structural analyses were conducted to understand the role of fixing rods under a range of rotating speed. In addition, modal analysis was performed to confirm the resonance in the operating speed range. One-way fluid-structure interaction (FSI) analysis was carried out to know its mechanical integrity under dangerous wind speed conditions. Through this work, the structural characteristics of the proposed spiral blade geometries were studied under various operating conditions, and the requirements of mechanical properties of blades were determined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1535-1542
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• 2012

A Heat Recovery Steam Generator(HRSG) is the main component of a Combined Cycle Power Plant(CCPP). It is a very large structure that is made from relatively thin metal sheets. Therefore, the structural integrity of an HRSG is very important to ensure safe operation during plant lifetime. In particular, thermal deformation and thermal fatigue have been revealed as the main causes of the mechanical degradation of an HRSG. In order to prevent unexpected damage, safety evaluation based on a large-scale analysis is necessary. Therefore, this study aims to improve the safety of HRSG by using Finite Element Analysis(FEA) results derived from large-scale analysis. Furthermore, the modified design is verified by comparing it with the original one. This result will be used as basic data for improving the safety of a vertical-type HRSG.

• Tribology and Lubricants
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• v.34 no.6
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• pp.270-278
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• 2018

STS 316L prepared by additive manufacturing (AM) exhibits deterioration of mechanical properties and wear resistance due to the presence of defects such as black-of-fusion defects, internal porosity, residual stress, and anisotropy. In addition, high surface roughness (integrity) of AM products remains an issue. This study aimed to apply ultrasonic nanocrystal surface modification (UNSM) technology to STS 316L prepared by AM to increase the surface hardness, to reduce the surface roughness, and to improve the friction and wear behavior to the level achieved by bulk material manufactured using traditional processes. Herein, the as-received and polished specimens were treated by UNSM technology and their resulting properties were compared and discussed. The results showed that UNSM technology increased the surface hardness and reduced the surface roughness of the as-received and polished specimens. These results can be attributed to grain size refinement and pore elimination from the surface. Moreover, the friction of the as-received and polished specimens after UNSM technology was lower compared to those of the as-received and polished specimens, but no significant differences in wear resistance were found.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.1
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• pp.11-16
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• 2014

A Satellite Based Augmentation System (SBAS) is a representative differential GNSS system, which is used for the navigation performance improvement of Global Navigation Satellite System (GNSS) users. SBAS has been developed focusing on the securement of user integrity so that it can be used for the navigation in aviation fields. Accordingly, the development of SBAS has been completed, and it has been actively used in the United States, Europe, and Japan. As the new satellite of Global Positioning System (GPS) recently started to broadcast new civil signals (L5 frequency), the methods for improving user navigation performance in SBAS using this signal have also been studied. In Korea, to keep pace with these circumstances, full-scale SBAS development is expected to start in 2014, and studies on dual-frequency SBAS using L1/L5 frequencies will also be performed. In this study, before the full-scale development of dual-frequency SBAS in Korea, a simulation was performed to predict the performance and analyze the expected effects.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.17-24
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• 2020

As an interconnect scaling faces a technical bottleneck, the device stacking technologies have been developed for miniaturization, low cost and high performance. To manufacture a stacked device structure, a vertical interconnect becomes a key process to enable signal and power integrities. Most bonding materials used in stacked structures are currently solder or Cu pillar with Sn cap, but copper is emerging as the most important bonding material due to fine-pitch patternability and high electrical performance. Copper bonding has advantages such as CMOS compatible process, high electrical and thermal conductivities, and excellent mechanical integrity, but it has major disadvantages of high bonding temperature, quick oxidation, and planarization requirement. There are many copper bonding processes such as dielectric bonding, copper direct bonding, copper-oxide hybrid bonding, copper-polymer hybrid bonding, etc.. As copper bonding evolves, copper-oxide hybrid bonding is considered as the most promising bonding process for vertically stacked device structure. This paper reviews current research trends of copper bonding focusing on the key process of Cu-SiO₂ hybrid bonding.