• Journal of Industrial Technology
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• v.24 no.A
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• pp.3-8
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• 2004

This study was performed to investigate the effect of two step austenitized treatment on the mechanical properties and fracture characteristic of the ductile cast iron and austempered ductile cast iron(ADI). The obtained results of this study were as follows. The matrix structures of specimens were changed differently by austenitizing heat treatment. Microstructure of austempered ductile cast iron obtained by two step austenitized treatment was bainitic ferrite and retained austenite. With two step austenitized treatment, vield strength, tensile strength and hardness decreased, while the elongation increased.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.56-64
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• 1997

Macrostructural characteristic of the transverse cracks and fatigue behavior were studied for EH 32 TMCP 50mm thick plate welded with FACW under the variation in preheat and interpass temperatures. Transverse cracks were detected in specimen welded with preheat and interpass temperature below $30^{\circ}C$, but cracks were not detected in the specimens welded with preheat and interpass temperatures at the range of $100~120^{\circ}C$.C. The location of crack formation was found to strongly depend upon the thickness of weld layers as regard to the plate thickness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1583-1589
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• 2001

Metal matrix composites with whisker reinforcements have significant potentials for demanding mechanical applications including defense, aerospace, and automotive industries. Especially metal matrix composites, which are reinforced with aluminum borate whisker, have been used leer the part of piston head in automobile because of good specific strength and wear resistance. In this study, AC4CH-based metal matrix composites with $Al_{18}$B$_{4}$ $O_{33}$ reinforcement have been produced using squeeze casting method, after T6 heat treatment, we evaluated fatigue life property of matrix and MMC composite and investigated fracture mechanism.m.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.155-158
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• 2002

Eu-doped lead zirconium titanate $Pb_{1.1}(Zr_{0.3}Ti_{0.7})O_{3}$ thin films on the Pt/Ti/$SiO_2$/Si substrates prepared by a metalorganic decomposition (MOD) method. The effect on the structural and electrical properties of the films measured according to Eu content. Eu-doping altered significantly the dielectric and ferroelectric properties. The remanent polarization and coercive field decreased with increasing the concentration of Eu content. The dielectric constant and dielectric loss of the film decreased with increasing Eu contents. The 3 mol% of Eu-doped PZT thin film showed large remanent polarization and the fatigue characteristic of the film did not change up to $10^9$ switching cycles.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.1
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• pp.21-32
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• 1988

An experimental study was carried out to identify the fatigue fracture behavior of steel for merchant ships. The bending and shear loads were applied simultaneously on the specimens to simulate of real load condition for a ship. The effects of the stress intensity factor under mode I with mode II loading condition on the initiation and the propagation of a crack were investigated, with particular emphasis on mode II. When the $K_{II}$ stress intensity factor in mode II was applied under mode I loading condition, the propagation behavior of a crack is to be affected mainly by the anisotropic characteristic of materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.7
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• pp.611-615
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• 2003

Eu-doped lead zirconate titanate(Pb$\sub$1.1/(Zr$\sub$0.6/Ti$\sub$0.4/)O$_3$; PZT) thin films on the Pt/Ti/SiO$_2$/Si substrates prepared by a sol-gel method. The effect on structural and electrical properties of PZT thin films measured according to the Eu content. Eu-doping altered significantly dielectric and ferroelectric properties. The remanent polarization and the coercive field decreased with the increasing Eu content. The dielectric constant and the dielectric loss of PZT thin films decreased with the increasing Eu content. The 0.5 mol% of Eu-doped PZT thin film showed improved fatigue characteristic comparing to the undoped PZT thin film.

• Journal of the Korea Convergence Society
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• v.7 no.3
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• pp.167-175
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• 2016

This study was conducted to understand Fatigue and CPR-related stress level anddob Job satisfaction of long-term Care Hospital nurses. The participants were 220 Care Hospital nurses in Gwang Ju and Chonnam region. Data were collected from November 17 to 30, 2014. and analyzed with SPSS 20.0 version program. The mean value for CPR-related stress was $3.29{\pm}0.64$point, $3.37{\pm}0.56$point for Fatigue and $3.06{\pm}0.44$point for Job satisfaction. Depending on subjects' characteristic, CPR-related stress and fatigue showed significant difference due to gender and manpower, however, Job satisfaction showed no difference. CPR-related stress was positively correlated with fatigue. CPR-related stress accounted for 27.8% of the cause of fatigue. Results of the study suggested seeking countermeasure to diminish the stress level for flexible nursing resources management and putting efforts to provide comfortable hospital environment. in consideration of the convergent relationship between CPR-related stress, Fatigue and Job satisfaction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.24-33
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• 2000

Switching behaviour of the ferroelectric thin film and device characteristics of the MFSFET(Metal-Ferroelectric-Semiconductor FET) are simulated with taking into account the accumulation of oxygen vacancies near interface between the ferroelectric thin film and the bottom electrode caused by the progress of fatigue. In our switching model, relative switched charge is 0.74 nC before fatigue, but after the progress of fatigue it reduces to 0.15 nC with the generation of oxygen vacancies. It indicates that the generation of oxygen vacancies strongly suppresses polarization reversal. $C-V_G\;and\;I_D-V_G$ curves in our MFSFET device model exhibit the memory window of 2 V and show the accumulation, the depletion and the inversion regions in capacitance characteristic clearly. The difference of saturation drain current of the device before fatigue in shown by the dual threshold voltages in $I_D-V_G$ curve as 6nA/$cm^2$ and decreases as much as 50% after fatigue. Decrease of the difference of saturation drain currents by fatigue implies that the accumulation of oxygen vacancies with the fatigue should be avoided in the device application. Our simulation model is expected to play an important role in estimation of the behavior of MFSFET device with various ferroelectric thin films.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5684-5688
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• 2012

This paper aims to design the leaf spring of high fatigue life which guides the moving part of the horizontal linear vibrating actuator. The vertical linear vibrating actuator has been used as the vibration device for haptic and alarm function on smart phone. However, the vibrating actuator has a major cause on the limitation to make smart phone slim because of its own characteristic of vertical direction vibration. The horizontally linear vibrating actuator for smart phone slimness has been developed in recent years. One of the most significant parts of horizontal vibrating linear actuator is the guide spring which supports moving part of actuator and enables actuator to vibrate elastically. Various types of leaf springs were designed and analyzed to get the required stiffness with high fatigue life through the stress analysis using commercial structural analysis program, ANSYS. The experiments were performed with prototypes to measure vibration acceleration and life time of leaf spring.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.555-559
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• 2011

Oil hydraulic piston pumps are extensively used worldwide because of their simple design, light weight, and cost effectiveness. However, an oil hydraulic pump is likely to have high leakage, friction, and low energy efficiency after long-term use. In oil hydraulic piston pumps the clearance between the valve block and the piston plays an important role in the volumetric and overall efficiency. We studied the wear property of the SACM645 material used in hydraulic piston pumps via experiments with different heat treatments. We prepared three different specimens. The maximum tensile strengths of the QT and QT-nitration specimens are similar (about 820 MPa), but the strains are significantly different. However, the fatigue characteristic depended on the heat treatment.