• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.592-600
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• 2007

Nowadays, researches for replacing material systems for cryotanks by composites have been being performed for the purpose of lightweight launch vehicle. In this paper, a type 3 propellant tank, which is composed of the composite developed for cryogenic use and an aluminum liner, was fabricated and tested considering actual operating environment, that is, cryogenic temperature and pressure. For this aim, liquid nitrogen (LN2) was injected into the fabricated tank and in turn, gaseous nitrogen (GN2) was used for pressurization. During this test procedure, strains and temperatures on the tank surface were measured. The delamination between hoop layer and helical one, was detected during the experiment. Several attempts were followed to investigate the cause analytically and experimentally. Thermo-elastic analysis in consideration of the progressive failure was done to evaluate the failure index. Experimental approach through a LN2 immersion test of composite/aluminum ring specimens suitable for simulating the Type 3 tank structure.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.63-68
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• 2017

Maintenance of sewer pipe process sewer pipe repairing process is necessary for deterioration of sewer pipe. In this research, analysis on performance (strength and twist strain) of eco-friendly and even expanded liner process using glass fiber and twist prevention band. As a results, tensile strength, bending strength and failure load is increased after the sewer pipe repairing process than advanced research results. And sewer pipe after the this process obtained advantage of prevention of twist strain and economic. After the this research, sewer pipe repairing process using glass fiber and twist prevention band could be suggest the eco-friendly and effective sewer pipe repairing process.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.355-361
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• 2004

Ceramic femoral heads in the total hip replacement have been developed to reduce the polyethylene liner wear, Alumina and zirconia (3Y-TZP) having the excellent tribological properties are coupled against acetabular cups of polyethylene and are used in clinical application worldwide. However, alumina has a risk of catastrophic failure, and zirconia has the low temperature degradation in spite of enhanced fracture toughness. Recently, novel zirconia/alumina composite is very attractive due to the low temperature degradation (LTD)-free character and high fracture toughness. In the present study, we focus on the wear of ceramic on ceramic, which are able to be used as femoral heads and acetabular cups. Therefore, LTD-free zirconia/alumina composites with three compositions are made in a form of disk and cylinder, and the wear of the composites is performed on pin-on-disk type wear tester. The wear is conducted with or without lubricant. All the composites fabricated with the different composition show the good wear resistance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.91-94
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• 2003

Ceramic femoral heads in the total hip replacement have been developed to reduce the polyethylene liner wear. Alumina and zirconia (3Y-TZP) are using in clinical application worldwide and there are many good test reports. However, alumina has a risk of catastrophic failure, and zirconia has the low temperature degradation in spite of enhanced fracture toughness. Recently, novel zirconia/alumina composite having low temperature degradation-free character and high fracture tough . was developed and it leads the lower wear 3f polyethylene than alumina and zirconia. In the present study, in order to optimise the microstructure of low temperature degradation (LTD)-free zirconia/alumina composite for the best wear resistance of polyethylene, various compositions of (LTD)-free zirconia/alumina composites were fabricated, and the sliding wear of UHMWPE against these novel composites were examined and compared with that against alumina and zirconia ceramics used for total hip joint heads.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.5
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• pp.255-264
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• 2017

Dynamic numerical simulation of pile-supported slab track system embedded in a soft soil and embankment was performed. 3D model was formulated in a time domain to consider the non-linearity of soil by utilizing FLAC 3D, which is a finite difference method program. Soil non-linearity was simulated by adopting the hysteric damping model and liner elements, which could consider soil-pile interface. The long period seismic loads, Hachinohe type strong motions, were applied for estimating seismic respose of the system, Parametric study was carried out by changing subsoil layer profile, embankment height and seismic loading conditions. The most of horizontal permanent displacement was initiated by slope failure. Increase of the embedded height and thickness of the soft soil layer leads increase of member forces of PHC piles; bending moment, and axial force. Finally, basic guidelines for designing pile-supported slab track system under seismic loading are recommended based on the analysis results.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.321-328
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• 2002

Various geosynthetics used as liners or the Protection layers are installed in the solid waste landfill. The interface shear strength between geosynthetics installed at the slope of the landfill is a very important variable for the safe design of bottom and cover systems in the solid waste landfill. The interface shear strengths between (1) Geomembrane(GM)/Geotexile(GT) and (2) Geomembrane(GM)/Geosynthetic Clay Liner(GCL) were estimated by a large direct shear test in this study and were evaluated by the Mohr-Coulomb failure criterion. Especially, this research is focused on the effect of water which exists between geosynthetics because interfaces become easily wet or hydrated by rain, leachate and groundwater beneath liners. The strength reduction at large displacement and the effects of the magnitude of normal stresses and GCL hydration methods also investigated. The test results showed that the interface shear strength and shear behavior varied depending upon the magnitude of normal stresses, water at the interface, and hydration methods. Summary of secant friction angles, which could be used as reference values at a site where similar geosynthetics are installed, together with normal stress and hydration condition are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.32-39
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• 2006

An acoustic emission technique was applied to the structural strength test for the structural integrity evaluation of the nozzle assembly. These AE results were compared with data from the strain gages and displacement transducer. NDT using X-ray technique was performed to improve the test reliability before and after each test. In this structural integrity evaluation of the nozzle assembly, the internal crack initiation in the structure could not be precisely revealed by the strain and displacement results but the location and load level of the initiated crack could be precisely evaluated by using AE technique. From this test, it was proven that some new cracks can be generated in composite liner of nozzle assembly under the unexpected load due to interference between obturator and nozzle and these can be a cause of the unexpected abnormal failure.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.243-248
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• 2000

Purpose: The aim of this study was to determine the relative radiopacities of cavity lining materials (Resin-modified Glass Ionomer cement, Compomer and Plowable resin) for posterior composite resin restoration. Material & Methods: Resin-modified glass ionomer cement (Fuji II LC, Vitrebond/sup TM/), Compomers (Dyract /sup (R)/ Compoglass, F2,000, Dyract/sup (R)/ flow Compoglass Flow) and Flowable resins (Tetric/sup (R)/ flow, Aeliteflo/sup TM/ Revolution/sup TM/) were used. Five specimens of 5 mm in diameter and 2 mm thick were fabricated with each material. Human molars were horizontally sectioned 2 mm thick to include both enamel and dentin. The radiopacities of enamel, dentin, cavity lining materials, aluminum step wedge were obtainded from conventional radiograph and NIH image program. Results: All the tested lining materials showed levels of radiopacity the same as or greater than that of dentin. All compomer tested (Dyract, Compoglass, F2,000, Dyract flow, Compoglass Flow) and Vitrebond/sup TM/, Tetric/sup (R)/ flow were more radiopaque than enamel. The radiopacities of Fuji II LC and Revolution/sup TM/ were between enamel and dentin and resin-modified glass ionomer cement, Compomer and Tetric/sup (R)/ flow were greater than those of Revolution/sup TM/, Aeliteflo/sup TM/ or dentin. The level of radiopacity of the tested materials was variable; those with low radiopacity should be avoided in class II restorations, where a clear determination of recurrent caries by the examining clinician could be compromised. Conclusion: Clinician should be able to distinguish these cavity lining materials radiographically from recurrent decay, voids, gaps, or other defects that lead to clinical failure. Utilization of materials ranked more radiopaque than enamel would enable clinicians to distinguish the lining material from tooth structure.

• Composites Research
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• v.17 no.5
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• pp.1-6
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• 2004

Composite pressure vessels with HDPE (high density polyethlyne) liner with metal boss at each end were developed by Filament Winding Process. The vessel is composed of a dome-shaped part at each end and a cylinder-shaped part at the middle of the vessel. The environmental tests carried out for possible vessel materials such as High Density Polyethlyn (HDPE), resins and reinforcing fibers up to a year showed no significant damages. The boss was designed to minimize the gas leak which was verified by FEM analysis. Most ideal fiber tension was obtained by experimental method and the fiber volume fraction, $\textrm{V}_{f}$, obtained by image analyzer were 55.4 % in cylinder and 55.6 % in dome parts, respectively. Winding pattern is programmed to control the composite thickness in the dome areas such that the failure of the vessel may occur in the cylinder. During the cure, the vessel was rotated and a constant internal pressure of 0.62 bar was applied. From this, the vessel's burst pressure is improved by 28 %. The burst and fatigue tests for under-wound and fully wound vessel showed satisfactory results.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.6
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• pp.809-818
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• 1999

This study was performed to evaluate the tensile bond strength and modulus of elasticity of three permanent soft denture liners (Molloplast $B^{(R)}$, Ufi Gel $C^{(R)},\;Tokuyama^{(R)}$) before and after thermocycling. And their water sorption were also evaluated. Each soft denture liner was bonded to PMMA denture base resin blocks and the tensile bond strength and modulus of elasticity were measured by using universal testing machine. For the water sorption, weight measured after immersion of sea denture liners in $37{\pm}1^{\circ}C$ water bath for 4 weeks. The results were as follows : 1. Molloplast $B^{(R)}$ had the highest tensile bond strength, while Tokuyama had the lowest tensile bond strength. There was no significant difference between $Tokuyama^{(R)}$ and Molloplast $B^{(R)}$ in the both nonthermocycling and thermocycling. There was significant difference in tensile strength of $Tokuyama^{(R)}$ before and after thermocycling(p<0.05). 2. For the modulus of elasticity, there was no significant difference between Ufi Gel $C^{(R)}\;and\;Tokuyama^{(R)}$ in the both nonthermocycling and thermocycling. There was significant difference in modulus of elasticity of $Tokuyama^{(R)}$ before and after thermocycling(p<0.05). 3 The failure modes of Molloplast $B^{(R)}$ and Ufi Gel $C^{(R)}$ were mainley adhesive type and that of $Tokuyama^{(R)}$ was mainly mixed type in case of nonthermocycling and cohesive type after thermocycling. 4. The water sorption of each soft liners was within ${\pm}2%$ in times (p<0.05) but. there was no significant difference among the soft liners in times.