Mg+A2Ca 첨가 ADC12 (Al-Si-Cu) 합금의 미세조직, 인장 및 고주기 피로 특성

김영균,김민종,김세광,윤영옥,이기안 한국소성∙가공학회 2017 소성가공 : 한국소성가공학회지 Vol.26 No.5

This study investigated the microstructure, tensile strength, and high cycle fatigue properties of ADC12 aluminum alloys with different Mg+Al2Ca contents manufactured using die casting process. Microstructural observation identified the presence of α-Al, eutectic Si, Al2Cu, and Fe-intermetallic phases. The increase of Mg+Al2Ca content resulted in finer pore size and decreased pore distribution. Room temperature tensile strength tests were conducted at strain rate of 110-3/sec. For 0.6%Mg ADC12, measured UTS, YS, and El were 305.2MPa, 157.0MPa, and 2.7%, respectively. For 0.8%Mg ADC12, measured UTS, YS, and El were 311.2 MPa, 159.4 MPa, and 2.4%, respectively. Therefore, 0.8% ADC12 alloy had higher strength and slightly decreased elongation compared to 0.6% Mg ADC12. High cycle fatigue tests revealed that 0.6% Mg ADC12 alloy had a fatigue limit of 150 MPa while 0.8% Mg ADC12 had a fatigue limit of 160MPa. It was confirmed that Mg+Al2Ca added ADC12 alloy achieved finer, spherical eutectic Si particles, and Al2Cu phases with greater mechanical and fatigue properties since size and distribution of pores and shrinkage cavities decreased as Mg+Al2Ca content increased.

BioOss와 Orthoblast II를 이용한 상악동 골이식술

김영균,김수관,임성철 대한치과이식임플란트학회 2006 The Korean Academy of Implant Dentistry Vol.25 No.2

We performed sinus bone graft using small amount of autogenous bone, Orthoblast?? II and BioOss?? and covered the sinus window with Ossix?? membrane in these case series. After 4.5 to 6 months after operation, histopathologic examinations of trephine core biopsy showed following results. 1. There was bone density of 43 to 87% and we could observe the favorable early new bone formation. 2. Active bony remodeling of woven and lamellar bone was observed during 4.5 to 6 months healing period.

Fe-14Cr계 페라이틱 산화물 분산 강화강의 고온 압축 및 크리프 특성에 미치는 열처리의 영향

김영균,주연아,박종관,김휘준,공만식,이기안 대한금속·재료학회 2017 대한금속·재료학회지 Vol.55 No.12

This study investigated the microstructure and the ambient-elevated temperature compression and elevated temperature creep properties of Fe-14Cr ferritic ODS steel manufactured by mechanical alloying (high energy ball milling) and hot extrusion processes. Initial microstructural observation of the as-extruded material identified elongated grains in the direction of extrusion; however, some recrystallization and grain growth were observed in the heat-treated material. The average grain sizes of the as-extruded material and heat-treated material were 0.4 and 1.1 μm, respectively. In addition, the heat treatment resulted in the increase in number density and the decrease in size of the nanocluster. A room temperature compression tests confirmed the heat-treated materials (1457 MPa) had relatively higher yield than the as-extruded material (1377 MPa), and a general tendency was observed that the difference in yield strength decreased as temperature increased. Furthermore, elevated temperature compressive creep tests confirmed that the heat-treated material had relatively greater creep resistance compared to the as-extruded material at all stress levels.

분말 사출 성형된 Fe-Cr-B/316L 스테인레스강 복합재료의 미세조직과 기계적 특성에 미치는 Fe-Cr-B의 영향

김영균,주연아,윤태식,이기안 대한금속·재료학회 2023 대한금속·재료학회지 Vol.61 No.1

Stainless steel-based composites (SMCs) mixed with 316L stainless steel powder and Fe-Cr-Bbased M alloys powder ed M) powder were manufactured using the powder injection molding (PIM) process,and their microstructure and mechanical properties were investigated. To examine the effect of M contenton the properties of SMCs, the M fraction was controlled to 30 vol.%, 50 vol.%, and 70 vol.%. It was observedthat PIM-processed Fe-Cr-B/316L SMCs (30 vol.%, 50 vol.%, 70 vol.%) had γ-austenite and minor α-ferriteas a matrix, and (Cr, Fe)2B was formed as a reinforced phase. In tensile tests at room temperature, theyield strengths of the 30 vol.%, 50 vol.%, 70 vol.% M SMCs were measured to be 519.9 MPa, 574.1 MPa,and 604.8 MPa (peak stress), respectively. From the fracture surface observation results, it was found thatthe deformation behavior changed from the intergranular fracture of boride to intergranular fracturebetween the matrix and boride, as the M fraction increased. Based on the above results, the deformationand fracture mechanisms of novel Fe-Cr-B/316L SMCs are also discussed.

CaO 첨가 AZ31 압출재의 개량된 미세조직이 인장, 고주기 피로 및 피로 균열 전파 특성에 미치는 영향

김영균,김민종,황유진,김세광,임현규,이기안 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.6

The effect of tailored microstructures in 0.5 wt% CaO added AZ31 on tensile, high-cycle fatigue, and fatigue crack growth properties was examined. By adding CaO, the average grain size (AGS) was significantly reduced from 4.25±2.32 μm (conventional AZ31) to 2.42±1.60 μm (CaO-AZ31). The fineprecipitates of CaO-AZ31 were more evenly distributed and their fraction was higher than those of conventional AZ31. The fine-precipitates were identified as Al8Mn4Ca and (Mg, Al)2Ca in CaO-AZ31, meanwhile, were identified as Al8Mn5 and Mg17Al11 in conventional AZ31. The tensile test results showed that the yield strengths of CaO-AZ31 and conventional AZ31 were 238.0 MPa and 206.7 MPa, respectively. The elongation-to-failure also increased when CaO was added. The improved tensile properties of CaO-AZ31 could be explained by grain refinement and precipitation hardening. The high-cycle fatigue limit also increased about 15% with added CaO. The fatigue limits as a function of the tensile strengths of CaO-AZ31 and conventional AZ31 were 0.508 and 0.457, respectively. The origin of the improved fatigue resistance was attributed to inhibition of the formation of DTs, which acted as the fatigue crack source, in CaO-AZ31. In contrast, the fatigue crack growth property did not change when CaO was added. Based on the above findings, the relationships between microstructure, mechanical properties and deformation mechanisms are also discussed.

초내식성 스테인리스강의 Hank 용액에서의 부식마모 거동에 관한 연구

김영균,박용수 한국표면공학회 1993 한국표면공학회 학술발표회 초록집 Vol.1993 No.-

Metal Injection Molding 공정으로 제조된 Fe-Cr-Ni계 HK30 합금의 미세조직 및 상·고온 인장 특성에 미치는 열간 등압 성형의 영향

김영균,윤태식,이기안 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.2

This study manufactured Fe-Cr-Ni-based alloy (HK30) using the metal injection molding (MIM) process and investigated the microstructure and room·high temperature mechanical properties of the material. The effect of hot isostatic pressing (HIP) on properties was also examined. The average grain sizes were 24.1 μm for an MIM specimen and 29.1 μm for an MIM+HIP specimen. Microstructure and phase analysis results confirmed that the matrix mainly consisted of γ-Fe, and Cr23C6 phase. To evaluate the mechanical properties of the material, tensile tests were performed at room temperature and 900 oC. The tensile tests at room temperature indicated that the MIM and MIMTHIP specimens showed tensile strength of 609.6 MPa and 645.0 MPa, and elongation of 32.7% and 43.7%, respectively. In both strength and elongation, the MIM+HIP sample had greater performance. The tensile results at 900 oC also showed that the HIP+MIM specimen had higher strength and elongation. This was attributed to fewer macro cracks, denser structures and finer distribution of Nb based carbide due to the additional HIP. This study also discussed the deformation behavior of MIM material at room·high temperatures.

주주총회에서 주주평등원칙의 적용

김영균,임춘환 한국상사판례학회 2017 상사판례연구 Vol.30 No.4

The breakdown of the general shareholders' meeting is a common phenomenon that corporations face today, which is an important factor threatening the nature of the corporation system. There are many reasons why the general meeting of shareholders can be broken down, but there may be a considerable cause in the operation of the general meeting of shareholders. Shareholders, especially the minority, can attend the general shareholders 'meeting, and shareholders who actively participate in the shareholders' meeting can act as shareholders to attend the general meeting. Shareholders may have difficulty attending the general meeting, or even if they attend, the seat or meeting room environment, where discussions and questions are limited, may be an obstacle to exercising shareholder rights. Even if they attend the meeting, the executives who hold the chairperson or the meeting should avoid the active role of the shareholders and deliberately terminate the shareholders' meeting without intentionally giving them the opportunity to ask questions and discussions. This may cause another shareholder meeting to be broken down. Therefore, management should give due consideration to the shareholders to facilitate their attendance at the shareholders' meeting, and to provide sufficient opportunity for shareholders to attend the meeting. If the general meeting of shareholders is held as a ceremony to pass as an annual event and the shareholders 'meeting is held in order to have the format of passing the shareholders' meeting, the function of the shareholders 'meeting will become meaningless, shareholders will turn away from the shareholders' meeting, will be. Shareholder equality must be realized from the attending general meeting of shareholders to the whole process of questioning, debating and resolving the shareholders in order for the general meeting of shareholders to be able to control and supervise management. 주주총회의 형해화는 오늘날 주식회사가 겪게 되는 공통된 현상으로서 주식회사제도의 본질을 위협하는 중요한 요인이 되고 있다. 주주총회가 형해화되는 원인은 여러 가지가 있을 수 있겟으나, 주주총회의 운영 그 자체에도 상당한 원인이 존재할 수 있다. 주주총회에 주주, 특히 소수들이 많이 참석할 수있고, 참석한 주주들이 적극적으로 주주로서의 역할을 할 수 있어야만 주주들이 총회에 참석하는 動因이 될 수 있다. 주주들이 총회에 참석 자체에 어려움이있거나, 참석한다하여도 토론과 질문이 제한되는 좌석 또는 회의장 환경이 주주권을 행사하는데 장애가 될 수 있다. 설령참석한다하여도 의장이나 회의를주최하는 경영진에서 주주들의 적극적인 역할을 기피하여 의도적으로 질문과토론의 기회를 주지 아니하고 오로지 주주총회를 조속히 종료하고자 한다면주주들은 주주총회에 참석한 의미를 찾지 못하게 되고 이것이 또 하나의 주주총회를 형해화하는 원인이 될 수 있다. 따라서 경영진들은주주들이 주주총회에 참석자체가 용이하도록 충분한 배려를 하여야 하고, 참석한 주주들로 하여금 질문과 토론을 할 수 있는 충분한 기회를 제공하여야 한다. 주주총회를 연례행사로서 통과의례로 생각하고 단지 주주총회의 통과라는 형식을 갖추기 위하여 주주총회를 운영한다면주주총회의 기능 자체가 무의미해지고, 주주들도주주총회를 외면하고 주주총회는 형해화되고 말것이다. 주주총회가 명실공히경영진을 견제하고 감독하는 기능을 감당하려면주주총회의 참석에서부터 주주의 질문과 토론, 의결의 전과정에서 주주평등이 실현되어야 한다.

<어린이연극> 5월

김영균 공연과이론을위한모임 2005 공연과 이론 Vol.- No.18

Guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate: case series

김영균,이지영,김수관,임성철 대한치과보철학회 2013 The Journal of Advanced Prosthodontics Vol.5 No.2

PURPOSE. The purpose of this case series was to evaluate the effect of guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate. MATERIALS AND METHODS. Guided bone regeneration using Demineralized Allogenic Bone Matrix with Calcium Sulfate (AlloMatrixTM, Wright. USA) was performed at the time of implant placement from February 2010 to April 2010. At the time of the second surgery, clinical evaluation of bone healing and histologic evaluation were performed. The study included 10 patients, and 23 implants were placed. The extent of bony defects around implants was determined by measuring the horizontal and vertical bone defects using a periodontal probe from the mesial, distal, buccal, and lingual sides and calculating the mean and standard deviation of these measurements. Wedge-shaped tissue samples were obtained from 3 patients and histologic examination was performed. RESULTS. In clinical evaluation, it was observed that horizontal bone defects were completely healed with new bones, and in the vertical bone defect area, 15.1% of the original defect area remained. In 3 patients, histological tests were performed, and 16.7- 41.7% new bone formation was confirmed. Bone graft materials slowly underwent resorption over time. CONCLUSION. AlloMatrixTM is an allograft material that can be readily manipulated. It does not require the use of barrier membranes, and good bone regeneration can be achieved with time.