• 한국정밀공학회지
• /
• 제3권4호
• /
• pp.43-52
• /
• 1986

Experimental results on plastic strain induced in truning operation are presented in this paper. The plastic strain is computed by lagrangian strain using grid method, and metal cutting phenomena are also illustrated by micrograph and distribution figures of plastic strain and microvickers hardness of the machining surface. In the cutting of ductile materials, such as carbon steel, generally, the plastic strain is found to be concentrated near the surface. The amount of plastic strain increases with increasing cutting speed and feed rate. The dustribution of microvickers hardness is greater near the cutting surface and decreases from the machining surface under which its hardness returns to the normal hardness of the material.

• 한국표면공학회지
• /
• 제46권3호
• /
• pp.126-132
• /
• 2013

It was investigated that the effects of hydrogen charging on the properties of 590 MPa Dual Phase(DP) steels at the surface layers. The hydrogen-charging time was changed from 5 to 50 hours and current densities from 100, 150, and 200 $mA/cm^2$, respectively. It was found that the hydrogen content in the specimen was increased with as the charging time and the current density. The microvickers hardness of the subsurface zone was increased from 215.3 HV to 239.5 HV due to the increase in current density and charging time. The comparison of the absorbed energies tested by a small-punch (SP) test showed that the absorbed energy of the specimen was greatly reduced from 436 to 283 $kgf-mm^2$ because of hydrogen embrittlement. It was confirmed that bulb aspects of fracture surface became more brittle with increasing hydrogen content.

• 한국주조공학회지
• /
• 제14권5호
• /
• pp.419-428
• /
• 1994

The microvickers hardness and microstructure of Fe/Al composite fabricated by squeeze casting method were investigated. Pure Al and A356 Alloy were chosen for the matrix composition and Fe preform was fabricated with sintered Fe powder at $1000^{\circ}C$ for 30min. under hydrogen atmosphere. Experimental variables were included preheating temperature, melt temperature and applied pressure. Analysing the experimental result concerning microstructure of fabricated composites, Fe/A356 composite showed improved microstructure at $600^{\circ}C$ melt temperature and $350^{\circ}C$ preform preheating temperature in Fe distribution and Infiltrated distance. The results of EDX and XRD showed that the interfacial zones of Fe/Al composite were composed of non-equilibrium intermetallic layers[$(Al_5Fe_2)_x$, $Al_{13}Fe_4m\;Fe_3Al$, FeAl]. The microvickers hardness of Fe/Al composite showed higher value than Fe/A356 composite in interface.

• 소성∙가공
• /
• 제10권5호
• /
• pp.418-424
• /
• 2001

In this study, a relationship between hardness and electrical conductivity for an Al-Si aluminum alloy, forged after extruded, is investigated. Microvickers hardness is measured and compared with its corresponding electrical conductivity obtained by the eddy current test. It is found that a distinct relationship between the hardness and the electrical conductivity exists for the material. Using the relationship, the hardness of forging is predicted from the electrical conductivity obtained by eddy current test and the result is used to evaluate the condition of heat treatment.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
• /
• pp.34-37
• /
• 1996

The expanding method of tube to tubesheet joint part on neclear steam generators are classified into three classes of roller expanding, explosive expanding and hydraulic expanding. After the expanded Mock-Up specimen are made by the three expanding method. The general properties, microstructure/microvickers hardness, pull-out strength, hydraulic leak pressure, of tube to tubesheet joint part were inspected. and We evaluated the operation efficiency of expansion, reproduction of expanded joint about three expanding method. Through the overall evaluation of tube to tubesheet joint part, The hydraukic expanding and explosive expanding could be certificated more useful expanding method.

• 한국정밀공학회지
• /
• 제5권1호
• /
• pp.29-39
• /
• 1988

Plastically deformed layer beneath metal surface machined by orthogonal cutting was evaluated in terms of residual stress, microvickers hardness, side spread, and the side strain. An attempt was made to predict the depth of layer according to machining conditions particularly tool geometry and the shear plane angle. In this paper, we employed two models concerning the sliplines. The exact model was validated by comparision of computed and measured tool force and its angle, and the model offers an upper boundary of the deformed layer to be in good agreement with the experiment.

• 한국주조공학회지
• /
• 제19권5호
• /
• pp.403-409
• /
• 1999

Mg-Zn-Zr ternary alloys containing 6wt% Zn and (0, 0.4, 0.6)wt% Zr, which is added for grain refinement, can be cast into complex shape by squeeze casting. The influence of Zn and Zr as additional elements on microstructure and mechanical characteristics is investigated by OM, SEM, WDX, XRD and microvickers hardness measurement. The microstructure of Mg-Zn-Zr alloys consists of primary ${\alpha}-Mg$ and MgZn eutectic compound between dendrites. The grain size is decreased from $136{\mu}m$ to $97\;{\mu}m$ by Zr addition, resulting in that the hardness is increased from 42Hv to 59Hv. Furthermore, the grain size is changed to $83{\beta}$ and the hardness is increased to 65Hv by additional infiltration pressure. These results indicate that the Zr addition and additional infiltration pressure are effective for grain refinement acting as an important factor to increase the hardness. The increment in hardness by the Zr addition is slightly larger than that by the additional infiltration pressure.

• 연구논문집
• /
• 통권28호
• /
• pp.193-207
• /
• 1998

Fully dense THCN) based carbonitride ceramics were fabricated by pressureless sintering. During sintering, solid solutions were formed from the ceramic ingredients. The ceramics exhibited microvickers hardness of 1560-2050kgf/mm2, fracture toughness of 3.0-5.4 MPa $m^(1/2)$, and three point flexural strength of 645-1072 MPa. Some of the ceramics were shaped in a cutting tool, and the cutting performance was evaluated. In case of cutting SCM440 alloy steel, the ceramics showed better performance than the commercially available alumina-titanium carbide ceramic cutting tool. Considering the excellent productivity of pressureless sintering compared with other densification methods and their cutting performance, this new class of ceramics are very promising for wear resistant applications.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.899-903
• /
• 2009

Recently, research and development of the linear compressor are being active. The reason is that the one has not only higher efficiency than reciprocating type, but also lower noise. But because the dicharge valve of linear compressor is operated in high pressure and temperature circumstance, it is important to prevent leakeage. In this paper three other plastic reinforced composite materials were used. Those are TPI, PEEK and PEK which were containing other volume and kind of carbon fibers. First, for assessing mechanical properties, we measured the hardness and the heating property of the trst sepecimen by the microvickers hardness tester and the differential scanning calorimeter respectively. Finally, through FALEX tester, we could know the characteristics of the wear proving the results of before-conducted experiments.

• 열처리공학회지
• /
• 제6권4호
• /
• pp.213-222
• /
• 1993

This research was performed to investigate the transformation behavior and shape memory effect of Cu-13.5Al-4.5Ni(wt%) alloy with various aging temperature and time. The results obtained in this study are as follows: Transformation temperature was very increased when aging temperature is at $250^{\circ}C$. The variation of transformation temperature in first reverse transformation cycle and second was very significant, but there was little difference in case of 2nd and 3rd. Transformation temperature at various aging temperature was increased with increasing of aging temperature and time. Microvickers hardness was increased with increasing of aging temperature and time. It was found that ${\alpha}$ and ${\gamma}_2$ phase were created by aging of long time at high temperature.