• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.189-192
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• 2004

In this study, mode II interlaminar fracture phenomena of carbon fabric/epoxy composite for tilting train were investigated. The end notched flexural specimen containing an artificial crack with the thickness of 12.5fl11l was used. The mode II interlaminar fracture toughness was evaluated through a three point bending test and the fractured surfaces were examined through a scanning electron microscope. The experimental results obtained in this study would be applicable in the design and structural analysis of the composite structures.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.256-259
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• 2005

Mixed-mode interlaminar fracture toughness of carbon fabric/epoxy composites, which are applicable to tilting train carbody, was evaluated through the MMB (Mixed-mode bending) test. Specimens were made of CF3327 plain woven fabric with epoxy and a starter delamination at one end was made by inserting Teflon film with the thickness of 12.5 μ m. Mixed-mode interlaminar fracture test was conducted for 6 types of specimens with the mode II ratio of 20 ,35, 50, 65, 80, 90%. Also crack propagating behaviors and fractured surfaces were examined through an optical travelling scope and a scanning electron microscope, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1720-1729
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• 2001

Wear characteristics of Nylon and acetal pinions against steel gears for different pitch line velocities was studied with a power circulating gear test rig under unlubricated condition. Specific wear rate was measured as a function of tooth number, module, tooth width and total revolution. The worn tooth surfaces were examined with a profile projector. The Nylon pinion showed lower specific wear rate than the acetal pinion. However, the Nylon pinion was fractured at high tooth loads, whereas the acetal pinion exhibited a steady wear behavior. The wear characteristics of Nylon pinion varied significantly with the Pitch line velocity. Wear occurred most severely at the tooth tip and the region immediately below the pitch line of pinion. The dominant wear mechanisms were adhesion and abrasion.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.369-372
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• 2008

An experimental study is carried out to study two-phase vertically upward hydraulic transport of solid particles by water in a vertical and inclined (0${\sim}$60 degree) concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in shear-thinning fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, and so on. Annular fluid velocities varied from 0.2 m/s to 1.5 m/s for the actual drilling operational condition. Macroscopic behavior of solid particles, averaged flow rate, and particle rising velocity are observed. Main parameters considered in this study were radius ratio, inner-pipe rotary speed, fluid flow regime, and particle injection rate. For both water and CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become

• Journal of Welding and Joining
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• v.17 no.1
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• pp.77-81
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• 1999

Through-hole PCB(Printed Circuit Board) was soldered by flow soldering process using cleaning or noncleaning fluxes. Preheating temperature and conveyor speed were changed in the range of 323∼413K and 0.3∼2m/min respectively. The soldered joints were tensile tested in order to evaluated bonding strength. As experimental results, relatively high tensile fracture load, 120∼140N, were obtained in case of preheating temperature of 383K, and conveyor speed was 0.6∼1.0 m/min. Fractured surfaces of higher tensile strength show some dimple area, while those of lower tensile fracture load show brittle fracture.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.255-263
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• 2005

Migration experiments of THO and 237Np have performed through a sampled granite core in Chemlab2 probe at the Aspo hard Rock laboratory. The elution curves of THO were analysed to determine hydraulic properties such as the extent of dispersion effect according to flow rates. The retardation phenomena of the solutes were observed and described with elution curves and migration plumes. After migration test, the rock core was opened, and the remaining radioactivities on the rock fracture surfaces were measured. The transport process was simulated with a two-dimensional channel model. The mass transport process was described with three types of basic processes ; advection, sorption and matrix diffusion. By the combination of these processes, effects of each process on transport were described in terms of elution curves and migration plumes. By comparing the simulation results to the experimental one, it was possible to analyse the retardation effect quantitatively.

• Transactions of Materials Processing
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• v.25 no.5
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• pp.306-312
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• 2016

Effects of manufacturing conditions, such as austenitizing temperature, patenting temperature and carbon content in steels, on mechanical properties, especially on reduction of area (RA), of hyper-eutectoid steel wires were investigated. RA increased and then decreased with transformation temperature. This was attributed to the presence of abnormal structures in steels transformed at low transformation temperatures and the occurrence of shear cracking during tensile testing of steels transformed at high transformation temperatures. The increase of austenitizing temperature resulted in the increased austenite grain size and consequently the decrease of RA. The decrease of RA with increasing the carbon content in steels was attributed to the increased fraction of cleavage fracture in tensile fractured surfaces.

• Journal of Welding and Joining
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• v.12 no.1
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• pp.80-93
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• 1994

The microstructure and fractography of the friction welded joint of Al to Cu have been investigated in order to understand the formation of intermetallic compounds and their effects on the failure in tensile test of the joint. The variation of welding pressure did not affect significantly the tensile strength of joint. However, the tensile strength of joint decreaed as welding time increased. The thickness of reaction layers of welded joints was several micro-meters and mainly composed of intermetallic compounds of $CuAl_2$, $Cu_9Al_4$ and Al+$CuAl_2$. The thickness of $CuAl_2$, $Cu_9Al_4$ was increased with welding time. However, $CuAl_2$ was gradually changed to $Cu_9Al_4$ which caused the decrease of tensile strength . Even though the morphology of fractured surfaces depended upon the welding time, the failure occurred along $CuAl_2$ intermetallic compound itself or between $CuAl_2$ and $Cu_9Al_4$ in most cases.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.47-53
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• 2013

SCMH2 steel is widely used in the industrial members of car and tractor. This study focused on material properties and evaluation technology of the SCMH2 steel regarding the surface treatment followed by carburizing and nitriding, by means of impact test, hardness test. and fatigue test including HCF (high cycle fatigue) and VHCF (very high cycle fatigue). Drop weight impact tester (Instron, 9250 Hv) and Cantilever type rotating-bending fatigue tester (YRB200, 3150 rpm) were used to characterize the SCMH2 standard specimen before and after carburizing/nitriding. In order to understand those effects on fatigue characteristics and material properties, the fractured surfaces were carefully observed and analyzed by SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectroscopy).

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.698-703
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• 2004

In this study, mode I interlaminar fracture phenomena of carbon fabric/epoxy composite for tilting train were investigated. Specimens were 25mm $\times$ 180mm $\times$ 4.7mm with an initial artificial delamination of 65mm at one end. This delamination with the thickness of 12.5$\mu$m and 25$\mu$m (teflon film) was used. Mode I interlaminar fracture toughness was measured using the double cantilever beam and the fractured surfaces were examined through a scanning electron microscope. The experimental results obtained in this study would be applicable in the design and structural analysis of the composite structures.