Microstructure and High Temperature Mechanical Property of Fe–Cr–B Based Metal/Ceramic Composite Manufactured by Metal Injection Molding Process

Kee‑Ahn Lee,Jin‑Han Gwon,윤태식 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2

This study investigated the microstructure and the room and high temperature mechanical properties of Fe–Cr–B alloy manufacturedby metal injection molding. In addition, hot isostatic pressing was performed to increase the density of the material,and a comparison of properties was made. Microstructural observation confirmed a bi-continuous structure composedof a three-dimensional network of α-Fe phase and (Cr,Fe)2B phase. The HIPed specimen featured a well-formed adhesionbetween the α-Fe phase and boride, and the number of fine pores was significantly reduced. The tensile results confirmed thatthe HIPed specimen (RT to 900 °C) had higher strengths compared to the as-sintered specimen, and the change of elongationstarting from 700 °C was significantly greater in the HIPed specimen. Fractography suggested that cracks propagatedmostly along the interface between the α-Fe matrix and boride in the as-sintered specimen, while direct fracture of boridewas observed in addition to interface separation in the HIPed specimen.

외상성 횡격막 손상

안성국,이상목,이기형,고석환,김용호,박호철,고영관,조규석 대한응급의학회 1995 대한응급의학회지 Vol.6 No.1

Fifty two cases of traumatic diaphragmatic injuries that we have experienced from Jan. 1973 to Oct. 1994 were evaluated. The following results were obtained. The age of the patient was ranged from 1 to 74 years. Male was 38 and female was 14 in number with a ratio of 2.7 : 1. The traumatic diaphragmatic injuries were due to blunt trauma in 35 cases(motor vehicle accident 25, fall down 8, press 1, kick by fight 1) and penetrating trauma in 17 cases(stab wound 15, shot wound 1, explosion 1). In the blunt trauma, the preoperative diagnosis of the diaphragmatic injury was possible in 25 out of 35 cases(71%) and in the penetrating trauma, 15 out of 17 cases(88%). In the blunt trauma, the repture site was located in the left in 22 cases(63%) and in the right in 13 cases(31%). In the penetrating trauma, the rupture site was located in the left in 9 cases(53%) and in the right in 8 cases(47%). In the blunt trauma, 20 cases(63%) were treated within 24 hours and in the penetrating, 15 cases(88%) within 24 hours. In the blunt trauma, the herniated organs into the thorax were stomach(7), omentum(6), spleen(6), liver(5), colon(4), small bowel(2) and in the penetrating, stomach(7), colon(6), omentum(3), liver(2), and spleen(1) were herniated. Injury severity score(ISS) of 35-blunt trauma ranged from 11 to 66 with mean value of 30.6. Mean ISS of survivors and nonsurvivors was 27.6 and 52.7 respectively. The diaphragmatic repair of 49 cases was performed with thoracic approach in 23 cases, thoracoabdominal approach in 7 cases and abdominal approach in 19 cases, and 3 cases were not operated. The postoperative complication and mortality were developed in 16 out of 49 cases(33%) and in 5 cases(9.6%) respectively, and the causes of death were hypovolemic shock(1), combined head injury(2), asphyxia(1), and pulomnary edema and renal failure(1). In conclusion, the injuries of the diaphragm should be suspected in all patients with severe blunt trauma or penetrating injuries at thorax and upper abdominal area near the diaphragm. All of the cases had associated injury and most of deaths were related to the severity of associated injuries.

외상 후 속발된 주관절 변형에 있어서 운반각의 변화가 척골 근위부 성장에 미치는 영향

안상로,이광진,박원,오기영 충남대학교 의과대학 지역사회의학연구소 1994 충남의대잡지 Vol.21 No.2

The posttraumatic cubitus varus and valgus deformity is generally caused by malunion of supracondylar and condylar fracture of humerus in growing children. Generally it is known that carrying angle change is benign deformity causing no specific functional disabilities and the correction of the carrying angle change is performed for cosmetic reason. But after corrective osteotomy, there remained some Lasy S deformity on elbow joint. We invesgated the cause of this Lasy S deformity and found that most of deformity is caused by improper osteotomy, but we also found there developed some bowing deformity of the proximal ulnar metaphysic. So we measure the proximal ulnar bowing of 12 cases of cubitus varus and 4 cases of cubitus valgus which were operated on from 1984 to 1994. We also study the correlation between the amount and duration of the carrying angle change which the amount of the proximal ulnar bowing. The amount of carrying angle and carrying angle change correlate with the change of proximal ulnar bowing significantly. There is some correlation with duration of carrying angle change from proximal ulnar bowing.

價格差別과 社會厚生에 관한 小考

金安浩,奇聖來 조선대학교 경영경제연구소 1995 經營經濟硏究 = Management and economics research Vol.18 No.2

β-CuZn 합금의 인장 및 파괴 거동에 미치는 변형률 속도와 온도의 영향

이기안,이종수 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

A series of tensile tests were carried out on a B2-type b-CuZn alloy in the temperature range, room temperature to 400oC at three different strain rates (10^(-5) sec^(-1), 10^(-4) sec^(-1), 5.2x10^(-2) sec^(-1)). The stress-strain curves could be divided into three types. Type I indicates a remarkably linear sustained work hardening to fracture, type II work hardening and subsequent necking, type III yield drop behavior and stress saturation, respectively; corresponding to the insensitive yield stress region, anomalous yield stress region, and yield stress decreasing region, in the yield strength vs. temperature graph. The ultimate tensile strength basically decreased as temperature increased, only showing characterized strength hump-up region just below T_(p). The fracture mode was changed mainly from transgranular at room temperature to intergranular at high temperatures. The elongation increases with increasing temperature in region I, and then slightly decreases in region II (anomalous yield stress region). When the specimens were tensile-fractured at high temperatures (region III, above Tp), the elongation drastically increased with decreasing strain rate, for instance from 12% at 5.2x10^(-2) sec^(-1) to 87% at 10^(-5) sec^(-1). The dependence of ductility on strain rate was mainly attributed to the thermally activated <100> dislocation climb, inducing stress relief at the grain boundaries, as evidenced by microvoids at grain facets.

β-CuZn 합금의 항복강도 이상거동에 미치는 변형률 속도와 온도의 영향

이기안,장영원,이종수 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.3

A series of tensile and load relaxation behaviors in B2 type β-CuZn alloy have been examined to clarify the strain rate & the temperature dependence of yield stress anomaly. It has been found in tensile tests that the region showing anomalous peak of yield stress moves to a higher stress and higher temperature region with increasing strain rate. The anomalous yielding region below peak temperature(T_p) revealed slightly positive strain rate dependence, while the region above T_p showed considerably positive strain rate dependence. The slip lines formed below peak temperatures (T_P) were clearly visible with naked eye(coarse slip lines), and became finer near T_p(fine slip lines), while they disappeared completely above T_p. Based on the different tendency of temperature and strain rate dependence of anomalous yielding as the above-mentioned results, two types of deformation modes were suggested and incorporated into the flow curve analysis, which was in accord well with the experimental results. The slightly positive strain rate dependence of yield stress anomaly indicated that the yield stress anomaly in β-CuZn alloy mainly seemed to be attributed to the vacancy hardening.

Fe-29%Ni-17%Co 코바 합금의 고온 내산화성 및 열간 가공성에 미치는 Mo 첨가의 영향

이기안,조창완,성병근,김병문,김문철 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.3

Fe-Ni-Co 저열팽창성 합금의 고온 변형 특성 및 열간가공에 따른 열팽창 거동 연구

이기안,박종혁,조봉현,남궁정,김문철 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9

The high temperature deformation behavior and the effect of hot compression on the thermal expansion behavior of Fe-29Ni-17Co low thermal expansion Kovar alloy were investigated in the compressive temperature range of 900~1300℃ at the strain rate range of 25~0.01 sec.^(-1). The temperature (T) and strain rate (ε˙) dependence of the flow stress (σ_(0.7)) could be well described by hyperbolic sine law as ε˙= A [sinh(0.0084 σ)^(5.2018)] exp(-330.41/RT). Surface hot cracking and significant voids around grain boundary could be found at low temperature below 1000℃ and low strain rate (0.01 sec.^(-1)). Thermal expansion coefficient α_(30~400) generally increased with increasing compressive temperature. Moreover, α_(30~400) remarkably increased as strain rate decreased at high temperature above 1100℃. However the thermal expansion coefficient α_(30~400) of low compressive temperatures (900℃ and 1000℃) anomalously increased especially at high strain rates. Experimental results indicated that not only α phase appearance but also grain size had definite influence on the thermal expansion behavior with hot deformation. The correlation between microstructure and thermal expansion behavior of Kovar alloy were also discussed.

고속 ATM 네트워크를 위한 통신 프로토콜에 관한 연구

박기현,안기중,이상배,강문식 연세대학교 산업기술연구소 1992 논문집 Vol.24 No.1

In this paper, a new network protocol, AD²R(ATM Distributed queue Dual Ring), is proposed for high-speed communication. This protocol is a slotted using ATM scheme. With the mathematical analysis and computer simulation, it is shown that proposed protocol is appropriate for the high-speed communication. Also, it is verified that the AD²R network performance is enhanced by using the ring topology, the destination release and the distributed queue scheme.

수정체의 노화에 따른 단백성분의 산화 : 수정체의 Nucleoschlerosis에 따른 변화

최기오,정영도,양성렬,황태익,안봉한,이민화 한국노화학회 1991 한국노화학회지 Vol.1 No.1