• 한국재료학회지
• /
• 제25권1호
• /
• pp.9-15
• /
• 2015

The effect of retained and reversed austenite on the damping capacity in high manganese stainless steel with two phases of martensite and austenite was studied. The two phase structure of martensite and retained austenite was obtained by deformation for various degrees of deformation, and a two phase structure of martensite and reverse austenite was obtained by reverse annealing treatment for various temperatures after 70 % cold rolling. With the increase in the degree of deformation, the retained austenite and damping capacity rapidly decreased, with an increase in the reverse annealing temperature, the reversed austenite and damping capacity rapidly increased. With the volume fraction of the retained and reverse austenite, the damping capacity increased rapidly. At same volume of retained and reversed austenite, the damping capacity of the reversed austenite was higher than the retained austenite. Thus, the damping capacity was affected greatly by the reversed austenite.

• 열처리공학회지
• /
• 제3권4호
• /
• pp.41-52
• /
• 1990

This research has been performed in order to investigate the effect of prior deformation on the Ms temperature and reversed As of Fe-Ni alloy. The Ms temperature rose with increment of strain to 30% but lowered over 50%. It can be analysed that martensitic transformation was promoted by partial dislocation in low strain, but suppressed by dislocation cell structures in high strain. The As temperature was substantially increased with higher deformation to 20% but slowly above 50%. It may be caused that as the transition bands formed by deformation constrained shear strain, therefore austenitic transformation was hindered.

• 한국주조공학회지
• /
• 제28권1호
• /
• pp.37-40
• /
• 2008

본 연구는 ADI의 기계적 성질을 개선하고자 오스테나이트화 과정에서 초기 변태온도를 $900^{\circ}C$ (${\gamma}$ 구역)에서 시작하여 $800^{\circ}C$까지(${\alpha}+{\gamma}$ 구역) 일정한 냉각제어에 의해 오스템퍼링을 한다. 여기서 Full ADI에서 생성되는 고탄소 오스테나이트 조직을 저탄소 오스테나이트로 유도하고 미세한 침상의 Full ADI조직을 연성이 높은 조대한 아공석 페라이트 조직이 생성되도록 하여 Semi ADI를 만든다. Full ADI와 Semi ADI의 기계적 성질 및 피로강도를 연구한 결과 Full ADI와 Semi ADI의 정적강도는 유사하지만, 피로강도는 Semi ADI의 기지조직의 변화에 기인하여 Full ADI보다 피로강도가 높게 나타났다. 이러한 현상은 Semi ADI의 조대한 페라이트가 균열개구 저항력이 낮아 초기에는 쉽게 개구되지만, 균열개구와 동시에 균열선단에서 큰 소성역이 발생되어 균열성장이 지연하는 효과로 판단된다.

• 환경생물
• /
• 제30권1호
• /
• pp.26-30
• /
• 2012

본 연구는 금강하구둑과 관련하여 금강에 서식하는 참게($Eriocheir$ $sinensis$)의 이동과 산란을 알아보기 위해 2007년 5월부터 2009년 1월까지 금강 수계에서 조사하였다. 참게의 유생은 5월에 기수역에서 채집되었으나, 이후 치해로 변태하여 소상하는 개체들은 채집되지 않았다. 산란을 위해 참게들이 금강하구에 도달하는 시기는 9월 초순이었고, 3월부터 4월 사이에 산란을 하는 것으로 확인되었다. 연구 결과 기수에서 부화한 참게의 유생이 치해로 변태하여 담수로 이동하는 통로를 만들어 준다면, 금강 수계의 자연산 참게 복원이 제한적이나마 가능할 것으로 판단된다.

• 대한기계학회논문집A
• /
• 제21권3호
• /
• pp.405-413
• /
• 1997

In the present paper, it is attempted to reconfirm the "Intelligent" material properties using both the sintered TiNi/Al(1100) matrix composite made by powder metallurgy method and the squeeze-casted TiNi/Al6061 specimens. A metal matrix composite is, its fault has been considered to deteriorate a strength of composite by heating residual stress of the matrix. Therefore, it is necessary to remove a tensile residual stress, to produce the strength of a composite better. On the contrary, if compressive residual stress happens in matrix of composite in place of tensile residual stress, it will make the strength of composite better. So that, this paper introduce the development of a high strength of composite, by using compressive residual stress well, on the study. By using these specimens, shape memory strengthening effects in tensile strength and fatigue crack propagation above inverse transformation temperature of TiNi fiber were investigated. We occurs the prestrain and volume fraction for to discuss the effects of a composite strength. Moreover, by SEM observation, the effect of the residual stress at the interface between Al matrix and TiNi fiber and some brittle precipitation layers such as inter metallic compounds on fracture mechanisms was discussed metallurgically.urgically.

• 한국재료학회지
• /
• 제13권7호
• /
• pp.453-459
• /
• 2003

In this paper the effect of interstitial heat treatment on the microstructure and mechanical properties was examined both in the 0.15C-6Mn steels and 0.15C-6Mn steels added with Nb or Ti. This result will be applied into the development of a steel which has the properties of high strength and high ductility resulted from the transformation induced plasticity. The strength-elongation combination was increased as the holding time was increased when the temperature is at $625^{\circ}C$. However, the strength-elongation combination was decreased sharply as the holding time was increased when the temperature is at $675^{\circ}C$. The tensile strength and elongation of a reverse transformed steels added with Ti or Nb was 93 kg/$\textrm{mm}^2$ and 40%, respectively. This steel shows higher strength more than 10% of the 0.15C-6Mn steel without loss of ductility. The autenite formed from the reverse transformed treatment has a fine lath type, which has the width size of 0.1-0.3 $\mu\textrm{m}$. The TRIP sequence normally transforms the austenite to martensite, however, some of the sequence will produce retained austenite \longrightarrow deformation twin \longrightarrow martensite

• 한국산업융합학회 논문집
• /
• 제25권6_2호
• /
• pp.1055-1062
• /
• 2022

In this study, the mechanical properties of 80% cold-rolled austenitic 316L stainless steel were evaluated using specimens subjected to reverse transformation at 500-750℃ for 20 minutes and reverse transformation at 700℃ for 2-60 minutes. Also, for the elastic wave obtained from the tensile test, the dominant frequency according to the reverse transformation condition was investigated by time-frequency analysis. The SEM image of the 80% cold-rolled material was transformed into martensite and showed line and cross shapes. The TEM image showed that line shapes were shown at the grain, and grain boundary of martensite. The higher the heat treatment temperature and the longer time, the larger the grain. Tensile strength decreased as the heat treatment temperature and time increased, but elongation increased. Hardness was proportional to tensile strength. This is because the grain with different directions showed the same direction due to reverse transformation. The dominant frequency was decreased and then increased as the temperature and time increased. This is because the direction of the grain is different at a low temperature and the same direction is shown at a high temperature.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
• /
• pp.356-365
• /
• 1999

The present study is aimed at developing the TRIP(transformation induced plasticity) aided high strength low carbon steel using reversion process. An excellent combination of elongation over 40% and tensile strength abut 100kgf/$\textrm{mm}^2$ achieved in processing of 0.15C-0.5 Si-6Mn steel by slow heating to intercritial temperature region and accelerated cooling into room temperature. This good combination is caused by TRIP phenomena of retained austenite in steels during deformation. The stability of retained austenite is very important for the good ductility and it depends on the diffusion of carbon and manganeses during heat treatment. The accelerated cooling after holding at annealing temperature retards the formation of pearlite and provides the carbon enrichment in retained austenite in steel, resulting in the increase in elongation of the cold-rolled TRIP steel. On the other hand, heat treating the steel at 600$^{\circ}C$ for 5 hour before cold rolling increases elongation but reduces the amount of retained austenite after reversion processing. It is accounted that the heat treating is effective for the increase in the stability of retained austenite.

• 대한금속재료학회지
• /
• 제50권6호
• /
• pp.413-418
• /
• 2012

This study was carried out to investigate the effect of reverse transformation on the mechanical properties in high manganese austenitic stainless steel. Over 95% of the austenite was transformed to deformation-induced martensite by 70% cold rolling. Reverse transformation became rapid above an annealing temperature of $550^{\circ}C$, but there was no significant transformation above $700^{\circ}C$. In addition, with an increasing annealing time at $700^{\circ}C$, reverse transformation was induced rapidly, but the transformation was almost completed at 10 min. There was a rapid decrese in strength and hardness with annealing at temperature above $550^{\circ}C$, while elongation increased rapidly above $600^{\circ}C$. At $700^{\circ}C$, hardness and strength decreased rapidly, and elongation increased steeply with an increasing reverse treatment time up to 10 min, whereas there were no significant change with a treatment time after 10 min. The reverse-transformed austenite showed an ultra-fine grain size less than $0.2{\mu}m$, which made it possible to strengthen the high manganese austenitic stainless steel.

• 한국산업정보학회논문지
• /
• 제15권2호
• /
• pp.23-30
• /
• 2010

본 논문은 WCDMA, HSDPA 및 WiBro와 같은 광역무선통신망 기반의 V2I2V 차량통신시스템을 구현하여 차량통신시스템의 실제 도로주행 실험을 통해 이동차량과 위치관리서버 사이의 다양한 성능인자에 대한 실험적 성능을 측정하였다. GPS가 탑재된 이동차량 내 클라이언트와 각 이동차량의 위치 추적을 위한 위치 관리 서버 사이의 RTT, 종단간 전달지연 및 기타 성능인자들을 측정하였다. 이동차량이 도심지에서의 운행 시 차량의 이동속도별, 광대역통신망의 종류별 성능인자들을 측정하고 분석하였다. 본 연구 결과는 광역무선통신망 기반의 차량통신시스템을 이용한 서비스 지원 시, 차량통신을 이용한 교통 안전정보 서비스의 지원 가능성을 판단할 수 있는 기초 자료로 활용할 수 있을 것이다.