The Experts below are selected from a list of 366 Experts worldwide ranked by ideXlab platform
Changseon Bang - One of the best experts on this subject based on the ideXlab platform.
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effect of the blowing agent on the low temperature mechanical properties of co2 and hfc 245fa blown glass fiber reinforced polyurethane foams
Composites Part B-engineering, 2016Co-Authors: Seongbo Park, Sungwoong Choi, Changseon BangAbstract:Abstract Glass-fiber-reinforced polyurethane foams, one of the most widely used insulation materials in liquefied-natural-gas Cargo-Containment systems, is generally blown by various blowing agents that exist in the gaseous state in closed cells. Hydrofluorocarbon-245fa, also known as HFC-245fa, is one of the most environmentally friendly blowing agents, but it has a high potential to contribute to global warming that is about 1000 times that of CO 2 . As a result, CO 2 has received much attention as an ideal eco-friendly blowing agent. Therefore, a study was carried out to compare the low-temperature compression characteristics of CO 2 - and HFC-245fa-blown glass-fiber-reinforced polyurethane foams at various temperatures and strain rates. It was confirmed that the blowing agent affected the microscopic and mechanical characteristics of the glass-fiber-reinforced polyurethane foams. It also revealed for the first time that the compressive stress decreased as the strain rate increased when the test temperature was below the freezing point of the blowing agent, contrary to the tendency above the freezing point.
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optimum glass fiber volume fraction in the adhesive for the al sus adhesively bonded joints at cryogenic temperatures
Composite Structures, 2014Co-Authors: Changseon Bang, Choongheum Park, Dai Gil LeeAbstract:Abstract The tight control of adhesive thickness in large bonding areas such as the secondary barrier of CCS (Cargo Containment system) for LNG (Liquefied Natural Gas) carriers or floaters is difficult and expensive although the adhesive thickness is a dominant parameter to determine the bonding performance of adhesively bonded joint, especially at cryogenic temperatures. Therefore, the method for improving bonding strength and fracture toughness for thick adhesive layer was investigated by reinforcing the adhesive layer with glass fiber mat for the robust and sustainable system design for the secondary barrier. Randomly oriented E-glass fiber mat was used as reinforcement for the film type epoxy adhesive. The lap shear strength and fracture behavior were investigated with respect to fiber volume fraction, and compared to those of the adhesive without reinforcement. The effects of repeated thermal shocks on adhesive bonding performances of adhesive joints with reinforced adhesive were also studied. The experimental results revealed that the randomly oriented glass fiber reinforcement improved much the bonding strength and fracture toughness of adhesive even with 1.0 mm thickness at the cryogenic temperature. Also it was found that the enhancement of bonding performances strongly depended on the CTE (Coefficient of Thermal Expansion) differences between the stainless steel foil and reinforced adhesive. Finally an optimum volume fraction of the glass fiber reinforcement was proposed for the newly developed Al-SUS adhesively bonded joint.
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glass composite vibration isolating structure for the lng Cargo Containment system
Composite Structures, 2014Co-Authors: Jaeheon Choe, Changseon BangAbstract:Abstract The primary barrier of the Cargo Containment system (CCS) for the liquefied natural gas (LNG) carriers is subjected to large impact loads due to the cavitation of LNG. Therefore, the impact loads should be reduced to protect the insulation foam from cracking because the foam has very low fracture toughness at the operating temperature of −163 °C. In this study, a corrugated-plate type vibration isolating structure (VIS) has been developed using glass fiber reinforced composites to reduce the load transmissibility from the primary barrier to the insulation foam of the CCS at cryogenic temperature. The uniform spring constant characteristic was achieved by optimizing the stacking sequence of the composite laminate and the wavelength of the corrugation. The crack resistance of the VIS against the impact load was measured by the drop weight impact test with respect to the stacking sequence of the glass composite laminate. The specifications of the VIS were obtained by the finite element analysis and experiments. Also, the durability against repetitive impacts on the VIS was investigated.
Dai Gil Lee - One of the best experts on this subject based on the ideXlab platform.
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optimum glass fiber volume fraction in the adhesive for the al sus adhesively bonded joints at cryogenic temperatures
Composite Structures, 2014Co-Authors: Changseon Bang, Choongheum Park, Dai Gil LeeAbstract:Abstract The tight control of adhesive thickness in large bonding areas such as the secondary barrier of CCS (Cargo Containment system) for LNG (Liquefied Natural Gas) carriers or floaters is difficult and expensive although the adhesive thickness is a dominant parameter to determine the bonding performance of adhesively bonded joint, especially at cryogenic temperatures. Therefore, the method for improving bonding strength and fracture toughness for thick adhesive layer was investigated by reinforcing the adhesive layer with glass fiber mat for the robust and sustainable system design for the secondary barrier. Randomly oriented E-glass fiber mat was used as reinforcement for the film type epoxy adhesive. The lap shear strength and fracture behavior were investigated with respect to fiber volume fraction, and compared to those of the adhesive without reinforcement. The effects of repeated thermal shocks on adhesive bonding performances of adhesive joints with reinforced adhesive were also studied. The experimental results revealed that the randomly oriented glass fiber reinforcement improved much the bonding strength and fracture toughness of adhesive even with 1.0 mm thickness at the cryogenic temperature. Also it was found that the enhancement of bonding performances strongly depended on the CTE (Coefficient of Thermal Expansion) differences between the stainless steel foil and reinforced adhesive. Finally an optimum volume fraction of the glass fiber reinforcement was proposed for the newly developed Al-SUS adhesively bonded joint.
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cryogenic characteristics of chopped glass fiber reinforced polyurethane foam
Composite Structures, 2014Co-Authors: Ilbeom Choi, Soohyun Nam, Dai Gil LeeAbstract:Abstract Liquefied natural gas (LNG) is mainly carried by membrane type LNG ships, whose Cargo Containment system is composed of dual tightness barriers and two insulation boards. The insulation board should have not only cryogenic reliability against thermal load, but also high thermal insulation performance for safe and efficient transportation of LNG. Although polyurethane foam (PUF) has been widely used for the insulation board due to its low production cost and relatively good thermal and mechanical properties, the cryogenic reliability of PUF is a remaining concern in marine fields due to its brittleness at cryogenic temperatures. In this work, the PUF was reinforced with chopped E-glass fiber because of its good dispersion and distribution characteristics. The compression, tension and the fracture toughness test were conducted with respect to the amount of the chopped E-glass fiber both at the room (25 °C) and cryogenic (−150 °C) temperatures. From the experimental results, it was found that the chopped E-glass fiber reinforcement increased the fracture toughness of the PUF much, especially at the cryogenic temperature. Therefore, the PUF reinforced with chopped glass fibers will improve much the reliability of the LNG cryogenic Containment system during the voyage of LNG ships.
Jae-myung Lee - One of the best experts on this subject based on the ideXlab platform.
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Experimental Investigation of Structural Response of Corrugated Steel Sheet Subjected to Repeated Impact Loading: Performance of LNG Cargo Containment System
MDPI AG, 2019Co-Authors: Myung-sung Kim, Jeong-hyeon Kim, Seul-kee Kim, Jae-myung LeeAbstract:The primary barrier in contact with LNG (Liquefied natural gas) Cargo is manufactured from stainless steel, and has a corrugated membrane structure due to thermal deformation caused by extreme temperature differences. Because the primary barrier is tailored to be LNG watertight, the structural integrity of the primary barrier must be maintained despite the increase in LNG sloshing load. Among the various types of fluid impacts in a Cargo hold, jet flow runs up along the wall of the Cargo hold and extreme impact load is exerted on the side of the corrugation of the primary barrier. However, the impact behavior of the primary barrier under the prevailing environment has not been investigated due to the limitation of test methods. Thus, in the present study, the inelastic structural behavior of thin-walled and curved-shaped structures for liquefied natural gas Cargo Containment systems under repeated impact loading was investigated experimentally. Custom-built structural impact test equipment with large-scale weight drop test facilities was fabricated, and a series of structural impact tests were carried out. The impact energy and the number of repetitions were taken into account in order to investigate the characteristics of the inelastic structural behavior, such as plastic deformation and reaction force time history according to impact energy
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numerical model to predict deformation of corrugated austenitic stainless steel sheet under cryogenic temperatures for design of liquefied natural gas insulation system
Materials & Design, 2014Co-Authors: Jeong-hyeon Kim, Myung-hyun Kim, Seul-kee Kim, Jae-myung LeeAbstract:Abstract Austenitic stainless steel exhibits nonlinear hardening behavior at low temperature and under various strain rate conditions caused by the phenomenon of transformation-induced plasticity (TRIP). In this study, a uniaxial tensile test for 304L austenitic stainless steel was performed below ambient temperature (−163, −140, −120, −50, and 20 °C) and at strain rates (10−4, 10−3, and 10−2 s−1) to identify nonlinear mechanical characteristics. In addition, a viscoplastic damage model was proposed and implemented in a user-defined material subroutine to provide a theoretical explanation of the nonlinear hardening features. The verification was conducted not only by a material-based comparative study involving experimental investigations, but also by a structural application to the corrugated steel membrane of a Mark-III-type Cargo Containment system for liquefied natural gas. In addition, an accumulated damage contour was represented to predict the failure location by using a continuum damage mechanics approach.
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fatigue strength assessment of mark iii type lng Cargo Containment system
Ocean Engineering, 2010Co-Authors: Myung-hyun Kim, Jae-myung Lee, Sangmin Lee, Byung Jae Noh, Wha Soo KimAbstract:The aim of this paper is to investigate the fatigue strength of the GTT Mark-III type LNG insulation system. The LNG insulation system consists of several composite layers with various connections; plywood, triplex, reinforced polyurethane foam and mastic. Consequently, the LNG insulation system may include mechanical failures such as cracks as well as delaminations within the layers due to sloshing impact loads and fatigue loadings. In addition, these failures may cause a significant decrease of structural integrity. In this study, a series of fatigue tests have been carried out for Mark-III type LNGC insulation systems at room temperature considering the effect of sloshing impact. The load levels have been determined based on the ultimate strength of reinforced polyurethane foam. The aim of the study is to investigate the typical failure characteristics of the MARK-III LNG insulation system and to obtain the S–N data under fatigue loading. A consolidated single S–N curve is obtained based on a systematic finite element procedure. Future use of the S–N data in fatigue analysis requires that the response analysis is carried out using a finite element model with the same mesh density and material properties. This study can be used as a fundamental study for the fatigue assessment of the LNGC insulation system as well as a design guideline.
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experimental investigation on the impact behavior of membrane type lng carrier insulation system
Journal of Loss Prevention in The Process Industries, 2009Co-Authors: Min Sung Chun, Myung-hyun Kim, Wha Soo Kim, Sanghyun Kim, Jae-myung LeeAbstract:The aim of present paper was to experimentally investigate the dynamic strength characteristics of LNG Cargo Containment system under impact loads. A series of impact tests for full-scale membrane-type LNG insulation system has been undertaken using a custom-built drop test facility as varying height and weight of the drop object. Based on a series of repeated drop tests, displacement recovery was measured for the assessment of damping characteristic of insulation system. Crack initiation was also measured during the cyclic drop test.
Myung-hyun Kim - One of the best experts on this subject based on the ideXlab platform.
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Damping Effect of Reinforced Polyurethane Foam under Various Temperatures†
2016Co-Authors: Tak Kee Lee, Myung-hyun Kim, Min Sung Chun, Chae Whan Rim, Yong Suk SuhAbstract:Reinforced polyurethane foam (RPUF) is one of the important materials of Mark III type insulation systems used in liquefied natural gas (LNG) Cargo Containment systems. However, RPUF is the most difficult material to use with regard to its safety assessment, because there is little public and reliable data on its mechanical proper-ties, and even some public data show relatively large differences. In this study, to investigate the structural response of the system under compressive loads such as sloshing ac-tion, time-dependent characteristics of RPUF were examined. A series of compressive load tests of the insulation system including RPUF under various temperature conditions was carried out using specimens with rectangular section. As a result, the relationship between deformation of RPUF and time is linear and dependent on the load-ing rate, so the concept of strain rate could be applied to the analysis of the insulation system. Also, we found that the spring constant tends to converge to a value as the loading rate increases and that the convergence level is dependent on temperature
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numerical model to predict deformation of corrugated austenitic stainless steel sheet under cryogenic temperatures for design of liquefied natural gas insulation system
Materials & Design, 2014Co-Authors: Jeong-hyeon Kim, Myung-hyun Kim, Seul-kee Kim, Jae-myung LeeAbstract:Abstract Austenitic stainless steel exhibits nonlinear hardening behavior at low temperature and under various strain rate conditions caused by the phenomenon of transformation-induced plasticity (TRIP). In this study, a uniaxial tensile test for 304L austenitic stainless steel was performed below ambient temperature (−163, −140, −120, −50, and 20 °C) and at strain rates (10−4, 10−3, and 10−2 s−1) to identify nonlinear mechanical characteristics. In addition, a viscoplastic damage model was proposed and implemented in a user-defined material subroutine to provide a theoretical explanation of the nonlinear hardening features. The verification was conducted not only by a material-based comparative study involving experimental investigations, but also by a structural application to the corrugated steel membrane of a Mark-III-type Cargo Containment system for liquefied natural gas. In addition, an accumulated damage contour was represented to predict the failure location by using a continuum damage mechanics approach.
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fatigue strength assessment of mark iii type lng Cargo Containment system
Ocean Engineering, 2010Co-Authors: Myung-hyun Kim, Jae-myung Lee, Sangmin Lee, Byung Jae Noh, Wha Soo KimAbstract:The aim of this paper is to investigate the fatigue strength of the GTT Mark-III type LNG insulation system. The LNG insulation system consists of several composite layers with various connections; plywood, triplex, reinforced polyurethane foam and mastic. Consequently, the LNG insulation system may include mechanical failures such as cracks as well as delaminations within the layers due to sloshing impact loads and fatigue loadings. In addition, these failures may cause a significant decrease of structural integrity. In this study, a series of fatigue tests have been carried out for Mark-III type LNGC insulation systems at room temperature considering the effect of sloshing impact. The load levels have been determined based on the ultimate strength of reinforced polyurethane foam. The aim of the study is to investigate the typical failure characteristics of the MARK-III LNG insulation system and to obtain the S–N data under fatigue loading. A consolidated single S–N curve is obtained based on a systematic finite element procedure. Future use of the S–N data in fatigue analysis requires that the response analysis is carried out using a finite element model with the same mesh density and material properties. This study can be used as a fundamental study for the fatigue assessment of the LNGC insulation system as well as a design guideline.
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experimental investigation on the impact behavior of membrane type lng carrier insulation system
Journal of Loss Prevention in The Process Industries, 2009Co-Authors: Min Sung Chun, Myung-hyun Kim, Wha Soo Kim, Sanghyun Kim, Jae-myung LeeAbstract:The aim of present paper was to experimentally investigate the dynamic strength characteristics of LNG Cargo Containment system under impact loads. A series of impact tests for full-scale membrane-type LNG insulation system has been undertaken using a custom-built drop test facility as varying height and weight of the drop object. Based on a series of repeated drop tests, displacement recovery was measured for the assessment of damping characteristic of insulation system. Crack initiation was also measured during the cyclic drop test.
Seongbo Park - One of the best experts on this subject based on the ideXlab platform.
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effect of the blowing agent on the low temperature mechanical properties of co2 and hfc 245fa blown glass fiber reinforced polyurethane foams
Composites Part B-engineering, 2016Co-Authors: Seongbo Park, Sungwoong Choi, Changseon BangAbstract:Abstract Glass-fiber-reinforced polyurethane foams, one of the most widely used insulation materials in liquefied-natural-gas Cargo-Containment systems, is generally blown by various blowing agents that exist in the gaseous state in closed cells. Hydrofluorocarbon-245fa, also known as HFC-245fa, is one of the most environmentally friendly blowing agents, but it has a high potential to contribute to global warming that is about 1000 times that of CO 2 . As a result, CO 2 has received much attention as an ideal eco-friendly blowing agent. Therefore, a study was carried out to compare the low-temperature compression characteristics of CO 2 - and HFC-245fa-blown glass-fiber-reinforced polyurethane foams at various temperatures and strain rates. It was confirmed that the blowing agent affected the microscopic and mechanical characteristics of the glass-fiber-reinforced polyurethane foams. It also revealed for the first time that the compressive stress decreased as the strain rate increased when the test temperature was below the freezing point of the blowing agent, contrary to the tendency above the freezing point.