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티타늄합금 주조용 치과매몰재의 조성에 따른 경화거동 및 용탕반응성에 관한 연구
여인동,정국진,심광보 한국주조공학회 1999 한국주조공학회지 Vol.19 No.5
Hardening behavior and metal-mold reaction of phosphate bonded investments for titanium and titanium alloys were investigated. Alumina and Y₂O₃-stabilized zirconia, which are thermodynamically more stable than Titania, were used as major filler materials. NH₄H₂PO₄ was used as binder, and MgO was used as hardening acceleration material. A different composition ratio of binder and hardening acceleration material had effected on general hardening behavior and castings. And adding Y₂O₃-stabilized zirconia to alumina, metal-mold reaction characteristics for castings was evaluated. Considering working conditions and effects on castings, the best composition ratio conditions were both 10:10 and 12:8(NH₄H₂PO₄ vs. MgO). On the other hand, increasing the contents of Y₂O-stabilized zirconia for filler material, metal-mold reaction layer of titanium castings was greatly decreased. (Received September 17, 1999)
용탕단조법으로 제조된 Al2O3 / AC4C 복합재료의 피로균열 전파거동에 관한 연구
여인동,이지환 ( In Dong Yeo,Chi Hwan Lee ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.4
N/A This study has been conducted with the purpose of examining the fatigue crack growth characteristics of Al₂O₃short fiber reinforced aluminum matrix composites made by squeeze casting process with different applied pressure and binder amount. Fatigue crack growth experiments have been performed under constant load amplitude method with a fixed load ratio. The rate of crack propagation was decreased with binder amount as well as applied pressure. Also fatigue crack growth path in matrix was changed from flat to rough mode with an increase of applied pressure. In the composites, fatigue crack was propagated to interface between matrix and reinforcement at 10㎫, but it was propagated to reinforcement at 20㎫. The major reason of thee result was considered that interfacial bonding force and microstructure of matrix were improved due to an increase of applied pressure. Localized ductile striation in the composites was observed at low growth rate region and such a phenominon was remarkable with an increase of applied pressure. At high growth rate region, the propensity of fracture appearance was changed from interfacial debonding to reinforcement fracture with an increase of applied pressure.
용탕단조법에 의한 δ-Alumina 단섬유강화 AC4C 기 복합재료의 계면반응에 관한 연구
여인동,이지환 ( In Dong Yeo,Chi Hwan Lee ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.4
N/A This paper has been examined for the interfacial reactions in δ-Al₂O₃short fiber-reinforced AC4C matrix composite materials after squeeze casting and thermal exposure. After squeeze casting, it was found that reaction products exist on the Al₂O₃short fiber surface in both composites with and without silica binder. After thermal exposure at 450℃ for 30min, the thickness of reaction zone was significantly increased; Al₂O₃short fiber morphology was observed to be rough due to interfacial reaction compared with squeeze cast specimen. STEM and XRD observation and analysis showed that reaction product appears to be MgAl₂O₄.
용탕단조법에 의한 Alumina 단섬유강화 AC4C 기 복합재료의 인장강도에 미치는 점결제 및 가압력의 영향
여인동,이지환 ( In Dong Yeo,Chi Hwan Lee ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.2
N/A The mechanical properties of Al/Al₂O₃composites have been investigated in relation with manufacturing factors such as applied pressure of casting and binder amount of preform. It was found that tensile strength increases with an increase of applied pressure, but decreases with binder amount. Increase of tensile strength is attributable to refinement of microstructure, improvement of intefacial bonding between Al₂O₃short fiber and matrix, decrease of porosity in the matrix. Due to the high thermal stability of alumina short fiber, tensile strength of composites at 150℃ was superior to matrix alloy at room temperature. To evaluate the strength of composites, modified Kelly-Tyson`s equation was introduced. Manufacturing factor M was obtained calculating from experimental data. M values were increased with applied pressure, but decreased with binder amount. The initiation of microcrack appeared to be at interface and reinforcement colony. Amount of micro-dimple was increased with applied pressure, and interfacial debonding phenomenon was remarkable with an increase of binder amount.
아동상담보호센터 거주 학대피해 남아의 또래갈등 해결을 위한 사회복지사의 심리사회적 개입 경험
여인동,오상은 대한질적연구학회 2021 대한질적연구학회지 Vol.6 No.2
Purpose: This qualitative research was conducted to explore the experiences of social workers encountering peer conflicts among abused boys living in child counseling protection center (center) and psychosocially intervening to resolve peer conflicts. Methods: The participants were four social workers who were caring for twenty abused boys at the center. Data were collected through participatory observation, in-depth interview, and field data. The collected data were analyzed by emic coding. Results: First, the experiences of social workers encountering peer conflict phenomena among abused boys were ‘psychological distortion from abuse trauma’, ‘manifestation of impulse or aggression to trivial stimuli’, and ‘lack of mutual respect among peers’. Second, the experiences of social workers intervening in resolving peer conflicts among abused boys were ‘stabilize offended feeling’, ‘maintain stability through verbal and non-verbal interventions’, ‘apply positive techniques to improve peer relations’, and ‘help abused children overcome trauma and grow’. Conclusion: Social workers confirmed that the role of social welfare experts was important to secure understanding and insight into peer conflicts between abused children and to convert the pain of abused children into positive energy. The results of this study will help social welfare professionals develop a family-centered abuse trauma recovery program for abused children.
석고주조한 (石膏鑄造) Al-8.6% Si-3.6% Cu 합금의 기계적 성질에 관한 연구
여인동,김동옥,강인찬 ( In Dong Yeo,Dong Ok Kim,In Chan Kang ) 한국주조공학회 1984 한국주조공학회지 Vol.4 No.4
This paper is presented for showing the effect of cooling rate on dendrite arm spacing, correlated with the chilling power of molding materials (conventional plaster, foamed plaster, silica sand) and section thickness, and also showing relationship between dendrite arm spacing and mechanical properties for an aluminum - 8.6 percent silicon - 3.6 percent copper alloy. Local solidification time (t_f) and secondary dendrite arm spacing (d) could be varied widely in accordance with the molding materials and casting thickness, and the following relationship is obtained: d=9.4t_f^(0.31) A good correlation between dendrite arm spacing and mechanical properties such as ultimate tensile strength, yield strength, hardness was found, that is, mechanical properties decreased in a linear manner with increase in log of secondary dendrite arm spacing. Ultimate tensile strength in conventional plaster mold casting decreased by 15 percent comparing with the sand casting, where as in foamed plaster mold casting, it decreased by 30 percent comparing with the sand casting. From those results, it has been verified that DAS might be the most representative parameter for predicting mechanical properties varing with the different cooling condition.
인산염계 매몰재에서 내화물 입도지수 변화에 따른 물리적 특성
양상욱,여인동,김교한 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.5
이전의 정밀주조에서는 주형재료로서 점토를 주로 이용하였으나, 석고(CaSO_4·1/2H_2O)가 정밀주형 재료로 개발되면서부터 치과분야와 귀금속공예 분야에서 석고매몰재가 널리 이용되어 왔다. 석고계매몰재는 현재 저융점 합금이나 귀금속 합금의 주조에 널리 사용되고 있으며, 주조체의 미려도 및 정밀한 부위의 재현성이 우수한 특성을 갖고 있다. 하지만 이러한 석고계 매몰재는 열분해온도가 낮아 고융점 합금이나 비귀금속 합금을 주조하면 석고는 SO_2를 발생시키면서 열분해 된다. 이러한 이유로 인하여 고온정밀 주조용으로 내열성이 우수한 에칠실리케이트(Ethyl Silicate), 콜로이달 실리카(Colloidial Silica) 및 인산염을 결합재로 사용하기 시작하였다.