• 한국세라믹학회지
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• 제31권11호
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• pp.1307-1314
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• 1994

The aim of this work is to show the way of manufacturing the SiC mechanical seal at the low temperature of 130$0^{\circ}C$ using clay and frit as source of secondary phase. $\alpha$-SiC and $\beta$-SiC powder which showed different distribution of particle were used as starting materials, i.e. average particle size of $\alpha$-SiC was larger than that of $\beta$-SiC. The mechanical and tribological properties of two groups of specimen, i.e. one contained mainly larger $\alpha$-SiC powder and the other mainly fine particle $\beta$-SiC, were measured. The specimen consisted of larger $\alpha$-SiC exhibited lower density flexural strength and wear resistance is comparison with these of sample containning mainly $\beta$-SiC . This difference could be originated from the dependence of capillary force on the particle size. For the larger SiC particle, the liquid phase may not fill the whole pores during sintering, due to low capillary force, whereas the liquid phase can infiltrate into the small ores surrounded small $\beta$-SiC particle. Thus, the course of high flexural strength and high wear resistance of specimen prepared using small particles can be explaced from the easy infiltration of liquid phase.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.55-60
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• 2001

The automobile is made up of thousands of parts. Some parts are formed by pressing and combined by spot welding. To find weldability conditions of spot welding, clearance between two welding plates was made and after spot welding, weldability is evaluated by means of tensile shear load, nugget size and shape. Specimen used in this study was a steel plate of 1.2mm thickness and electrode was Cu-Cr alloy of 6mm diameter. When spot welding started, the clearance of two specimens was changed 0mm, 3mm and 5mm and distance from vise to measure influence of bending moment 25mm, 45mm, 65mm step by step. The fractured surface of specimen after this test was observed by Optical Microscope to measure microstructure and nugget shape. When clearance of two specimen was 3mm and 5mm, strength and nugget size was decreased and nugget shape was not clear. The much bending moment and crosshead speed are the much tensile shear load is.

• 한국재료학회지
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• 제23권4호
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• pp.250-254
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• 2013

In order to increase the toughness of ZTA(zirconia toughened alumina) ceramics, the present study focused on rearrangement and densification of particles according to the particle size of the parent material. When rough alumina was used for production of ZTA, densification behavior was observed in the specimen sintered at a temperature over $1550^{\circ}C$. However, it was found that the densification behavior was occurred in the specimen sintered at $1450^{\circ}C$ when fine alumina powder was used. High relative density exceeding 98% was obtained when fine alumina powder was mixed with 15 wt% of 3Y-TZP and sintered at $1600^{\circ}C$. Also, a hardness of 1820.2 Hv was obtained when a specimen containing 10 wt% of 3Y-TZP was sintered at $1600^{\circ}C$. In the case of 3Y-TZP containing rough alumina powder that had been sintered the hardness value was around 1720.3 Hv. It was predicted that an improved toughening effect in ZTA could be achieved by using finer alumina powder as the parent material.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.960-965
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• 2014

Transmission loss of specimen is calculated by measuring energy of incident and transmission and using reverberant room of large size. But normal measurement of transmission loss has trouble because it is actually demanded that large area and specimen of certain size is satisfied with condition of diffused sound field. Especially, in case of mechanical component, interested frequency band is mid-frequency band between 500 ~ 2k Hz, and it is used to be available to minimize a reverberation chamber under conditions satisfying acoustic one because production of specimen for transmission loss measurement has limit. But, as in semi-reverberation room, it is difficult to satisfy condition of diffuse sound field and modification factor is applied to complement that. Correction factor when measuring transmission loss using semi-reverberation chamber is required accuracy because it works as main factor determining reliability of reuslts on transmission loss. In this study, it is analyzed that an effect on correction factor based on varying materials and sizes of specimens in order to deduction of it. Also It is confirmed that applied by elicited correction factor with actual railway vehicle's floor has reliability.

• 한국추진공학회지
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• 제18권4호
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• pp.61-66
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• 2014

본 연구의 흑연은 로켓 노즐목 재료로 많이 사용되는 것으로써 온도, 가공성 및 무게 측면에서 유리하다. 하지만 고온 및 고압상태에서 고속으로 취성파괴 되므로 설계 시 구조적 안정성을 충분히 확보해야 한다. 본 연구에서는 로켓 노즐목에 이용되는 ATJ 흑연의 압축 파괴 거동에 대해 연구했다. 상온 및 고온에서 ASTM C 695에 준하여 일축 압축 시험을 수행하였다. 또한 시편의 단면적 변화에 의한 압축강도 및 파단특성을 분석하였다.

• 한국자기학회지
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• 제8권3호
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• pp.125-130
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• 1998

13Cr-1.5Nb-Fe합금분말이 수분사법으로 제조되엇다. 제조된 합금뷴말을 압축기를 이용하여 ring현상으로 성형한후, 진공중에서 소결하였다. as-prepared 분말의 현상, 입도분포, 성분분석 및 포화자화물 조사하였으며, 소결된 시편의 투자율, 교류자기이력손실이 조사되었다. as-prepared 13Cr-1.5Nb-Fe합금분말의 포화자화는 160emu/g이었으며, 산소함유량은 약 600ppm이었다. 입도분포는 약 70$\mu$m에서 50%vol.을 나타낸다. 교류투자율은 소결온도 및 성형온도가 증가할수록 증가한다. 주파수 20KHz에서 교류자기이력손실은 12ton/cm2성령압력 및 120$0^{\circ}C$ 소결온도 조건에서 107W/cc로 가장우수하다.

• 한국산업융합학회 논문집
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• 제5권4호
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• pp.367-372
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• 2002

Experimental study was conducted for lapping process after WEDMed specimen. In order to decide the lapping depth of the specimen, the number of the grain size was increased from 400, 600 to 800 to obtain the better surface. Observation of scanning electron microscope, hardness test, surface roughness test and energy dispersive spectrum(EDS) analysis were used for this experimental study. From the comparison and analyses of the results of between the wire-cut electrical discharge machining and the lapping, the following results were obtained. The surface roughness after lapping was found to be improved as increasing the number of lapping process like 1st, 2nd, 3rd lapping and the number of grain size such as 400, 600, 800. The surface hardness after increasing the lapping depth of the specimen was slowly increased. It was found that after 3rd lapping process the hardness was reached the hardness of original base material. It was found that the small amount of coating components within 3% was remained after the 1st lapping process, compared to that approximately 16% after WEDM process.

• 대한기계학회논문집
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• 제11권6호
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• pp.867-876
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• 1987

본 연구에서는 보통강재인 SS 41 강을 열처리하여 얻은 M.E.F.복합조직강의 모상입경변화와 3.5% NaCl수용액의 pH변화 조건하에서 반복굽힘피로실험을 하여 부식 피로파괴에 미치는 영향에 대해 고찰하였다.

• 한국분말재료학회지
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• 제9권5호
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• pp.352-358
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• 2002

The effects of boron or manganese added as $B_4C$, Mn, $TiB_2$, B on TiC-30vo1.%$Ni_3Al$ cermet sintered at 1380 and $1400^{\circ}C$ for 1 hour, were examined in relation with shrinkage, relative density, microstructure, lattice parameter, hardness and fracture toughness ($K_{IC}$). The results are summarized as follows: 1) The highest shrink-age showed about 30.5% in the specimen added B$_4$C and the maximum relative density was about 99% in the specimen added $TiB_2$; 2) The grains of TiC were grown during sintering and made the surrounding structure by adding boron and manganese. The largest grain size showed about $2.8\mutextrm{m}$ in the specimen with boron sintered at $1400^{\circ}C$;3) The lattice parameter of TiC was about $4.325\AA$ and $Ni_3Al$ about $3.592\AA$ by adding other elements; 4) The highest hardness was about $1100kgf/\textrm{mm}^2$ in the specimen with B4C; 5) The fracture toughness ($K_{IC}$) showed about $15MNm^{-3/2}$ in the specimen added $TiB_2$.

• 대한조선학회논문집
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• 제43권4호
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• pp.494-503
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• 2006

Inherent damage zone model is presented to explain the fatigue properties near the fatigue limit and the crack growth threshold consistently Inherent damage zone model assumes that the stress at a point which is located at a small distance, $r_0$, an inherent length of the material that represents the size of effective damage zone, from the crack initiation position governs the fatigue characteristics regardless of the geometric configuration of the specimen; smooth specimen, notched specimen or cracked specimens with short and long crack length. A special feature of the paper is using the exact stress distributions of notched and cracked specimens at the strength evaluations. Analytical elastic solutions by Neuber and Westergaard are employed for this purpose Relationship between fatigue limit of smooth specimen and threshold stress of cracked specimen, occurrence condition of non-propagating crack at the root of elliptic notch and circular hole and relationship between stress concentration factor and fatigue notch factor are discussed quantitatively based on the proposed model.