• Carbon letters
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• 제8권3호
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• pp.207-213
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• 2007

The properties and electrochemical characteristics of anode material using pitch-coated graphite residue compounds by heat-treatment at $600^{\circ}C$ for 1 hour were investigated. The distance of layers of pitch-coated graphite residual compounds was 3.3539 ${\AA}$, which was as same as that of graphite. Its electrochemical and charge discharge characteristics were tested according to different four types of carbon material, natural graphite, pitch-coated graphite, amorphous graphite and pitch-coated graphite residual compounds, respectively. So it was shown the best charge-discharge characteristics in all of the samples. For the electrochemical and charge-discharge characteristics, although pitch-coated graphite residual compounds had different carbon contents 70% and 80%, these two samples were shown good electrochemical and charge-discharge characteristics.

• Composites Research
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• 제28권4호
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• pp.182-190
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• 2015

The phenomenological evolution laws of damage can be defined either based on residual life or residual strength. The failure of a specimen can be defined immediately after or before fracture. The former is called in this paper by "failure defined by approach I" and the latter "failure defined by approach II." Usually at failure there is a discontinuity of loading variables and, because of this, damage at failure is discontinuous. Therefore the values of damage at failure by two different approaches are not the same. Based on this idea the sequence effects of the phenomenological evolution law of damage given by $dD/dN=g(D)f({\Phi})$ were studied. Thin-walled graphite/epoxy tubes consisting of four of $[{\pm}45]_s$ laminates were used for the experimental study of sequence effects and the effects of mean stress on fatigue life. It was found that the sequence effects in two step uniaxial fatigue for $[{\pm}45]_s$ graphite/epoxy tubular specimen showed that a high-low block loading sequence was less damaging than a low-high one.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1452-1460
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• 2001

A new method of parameter determination in the fatigue residual strength degradation model is proposed. The new method and minimization technique is compared experimentally to account for the effect of tension-compression fatigue loading of spheroidal graphite cast iron and graphite/epoxy laminate. It is shown that the correlation between the experimental results and the theoretical prediction on the fatigue life and residual strength distribution using the proposed method is very reasonable. Therefore, the proposed method is more adjustable in the determination of the parameter than minimization technique for the prediction of the fatigue characteristics.

• 한국주조공학회지
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• 제29권5호
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• pp.204-212
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• 2009

The effects of addition of magnesium only and the simultaneous addition of magnesium and aluminum on the graphite morphology of the cast iron with the composition of 3.6wt.% and 2.5wt.%Si poured into shell stack mold were investigated. The nodularity and mechanical properties of the specimen with smaller cross-section were higher than those with langer one, when copper was not added. When the magnesium only was added, the nodularity was decreased with decreased residual magnesium content and the C. V, graphite was obtained with the magnesium content in the range of 0.010~0.015wt.%. When the magnesium and aluminum were added together, the nodularity was decreased with decreased residual magnesium and increased aluminum contents. When copper was added, the volume fraction of pearlite in the matrix, strength and hardness were higher and elongation was lower for specimen with smaller cross-section. The volume fraction of pearlite, strength and hardness were increased and the elongation was decreased with increased copper content for the specimen with C, V, graphite.

• 한국주조공학회지
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• 제9권5호
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• pp.389-395
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• 1989

The effects of phosphorus and boron additions and isothermal holding time on the residual magnesium and sulfur content, and on the resultant graphite structure of cast irons were investigated. The effective recovery ratio of magnesium showed that adding phosphorus to the melt retarded the fading rate of magnesium but adding boron accelerated it. However, the residual sulfur content was found to be decreased with isothermal holding time at the begining, and then to be increased again with holding time by resulfurization. The Mg-Equivalent for producing compacted vermicular graphite structure was found to be increased with the addition of phosphorus, whereas to be decreased with the addition of boron.

• 산업기술연구
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• 제19권
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• pp.25-29
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• 1999

Rotary bending fatigue tests were carried out to investigate the fatigue behavior of high performance ductile cast iron experienced super rapid induction heat treatment. The effect of super rapid induction treatment on fatigue limit was experimentally examined with the special focus on the variation surface microstructure and the fatigue crack initiation and propagation through fractography. Main results obtained are as follows. By super rapid induction treatment in FCD500, the martensite structure obtained through conventional quenching heat treatment was confirmed on the specimen surface. The fatigue crack initiation in the hardened surface layer was restricted by the martensite structure and compressive residual stress. Thus, it could be interpreted that the initiation stress would be increased by the improvement of surface structure. The fatigue crack propagation in the hardened layer was retarded by the presence of the globular shape martensite around the graphite nodule and compressive residual stress. The crack propagation path has shown zigzag pattern in the hardened surface layer.

• 대한기계학회논문집A
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• 제26권4호
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• pp.596-601
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• 2002

Rotary bending fatigue tests were carried out to investigate the fatigue characteristics of high performance ductile cast iron experienced super rapid induction treatment. The influence of super rapid induction treatment on fatigue limit was experimentally examined with the special focus on the variation of surface microstructure and the fatigue crack initiation and propagation through fractography. Main results obtained are as follows. By super rapid induction treatment in FCD500, the martensite structure obtained through conventional heat treatment was confirmed on the specimen surface. The fatigue crack initiation in the hardened surface layer was restricted by the martensite structure and compressive residual stress. Thus, it could be interpreted that the initiation stress would be increased by improved structure in the surface. The fatigue crack propagation in the hardened layer was retarded by the presence of the globular shape martensite around the graphite nodule and compressive residual stress and the crack propagation behavior has zigzag pattern in the hardened surface layer.

• 한국주조공학회지
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• 제14권6호
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• pp.520-529
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• 1994

This study describes the influence of the trace amount of sulphur on the nucleation behavior of graphite crystals in high purity Fe-C-Si alloys prepared by levitation melting method. Detailed microstructural analyses of high purity(HP) and sulphur added(HP＋S) samples showed that the nucleation of graphite crystals was prevented by sulphur. With decreasing the sulphur content, the shape of graphite crystals tended to spherulitic, and below 2ppm S, that of graphite crystals was only nodular. The critical cooling rate for the nucleation of griphite crystals was calculated as $1.5{\times}10^3k/s$. It is obvious from this work that residual C-C clusters act as an effective nucleation site for graphite crystals and one of the important role of nodularizing elements is to act as scavenger which removes harmful impurities from the solution.

• 한국주조공학회지
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• 제11권3호
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• pp.236-244
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• 1991

This paper describes a study of the nucleation and growth of graphite crystal of levitation melted high purity Fe-C-Si alloys with emphasis on hypereutectic composition. Spherulitic graphite was observed to form at high purity alloy and converted to compacted by changing the starting iron from ultra-pure zone refined iron to 99.95 pct electrolitic iron. Residual C-C clusters might be acting as an effective nucleation site for graphite, and sulphur was the element to prevent graphite from nucleating. The graphite morphology changed from compacted to spherulitic as the sulphur content decreased.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.134-137
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• 1992