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탄소강의 담금질 처리과정에서 변형율이력을 고려한 탄소성열응력의 유한요소 해석(1) - 온도분포의 해석 -
김옥삼,조의일,구본권 ( Ok Sam Kim,Eui Il Cho,Bon Kwon Koo ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.3
Temperature distribution, transformation and residual stresses generated during the quenching process of carbon steel. It follows many difficulties in the analytical considerations on those quenching process because of the coupling effects on temperature and metallic structures. In this paper one of the basic study on the quenching stresses was carried out for the case of the round steel bar specimen(SM45C) with 40㎜ both in its diameter and length. The temperature distributions considering strain hysteresis were numerically calculated by finite element technique. In calculating the transient temperature field, the heat flux between water and rod surface was determined from the heat transfer coefficient. The gradient of temperature is almost same to geometric of specimen. At early stage of the quenching process, the abrupt temperature gradient has been shown in the surface of the specimen.
탄소강의 Quenching처리 과정에서 변형율이력을 고려한 탄소성열응력의 유한요소 해석 (2) -탄점소성 열응력 해석-
김옥삼,구본권 ( Ok Sam Kim,Bon Kwon Koo ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.2
The aero-industry in union industry which includes a research development type, a knowledge accumulation type and a developed country type. The aero-industry of Korea is in semi-developed type stage but departed later than that of other country such as Taiwan, Indonesia etc. Therefore, the necessity of domestic airplane material is required. This study on 7050Al extruded alloy aims to suggest an adequate heat treatment conditions of T73, T74 and T76. The results of this study show that: 1. The optimum conditions of T7x heat treatment in extruded 7050Al alloy show this; T73 : 121℃×7hr+177℃×14hr T74 : 121℃×7hr+177℃×10hr T76 : 121℃×7hr+163℃×21hr 2. The 2nd step aging heat treatment such as T73, T74 and T76 etc. is effective in 7050Al alloy but the variation otf microstructure and mechanical property with dispersive inclusions produced for extrusion process causes some troubles. Accordingly, in order to produce a good 7050Al alloy, a careful attention is needed in manufacturing process.
탄소강의 Quenching과정에서 유한요소법을 이용한 온도해석
김옥삼,조의일,신영우 ( Ok Sam Kim,Eui Il Cho,Ypung Woo Shin ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.2
It is well-known that the analysis of temperature distribution is substantilly important in optimal design of quenching process. The unsteady state temperature gradients generated during the quenching process were numerically calculated by the Finite Element Method(F. E. M.). Formulations of F. E. M. based weighted residural method were presented for the analysis of the two dimensional heat conduction problem. In the process of calculation, the temperature dependency of physical properties of the material was in consideration. At early stage of the quenching process, the abrupt temperature gradient has been shown in the surface of the carbon steel(SM45C).
선박용 TEMA 열교환기의 전열관 확관시 탄소성 응력 해석
김옥삼,박종대,Kim, Ok-Sam,Park, Jong-Dai 해양환경안전학회 2011 해양환경안전학회지 Vol.17 No.2
선박에 사용되는 TEMA 열교환기 전열관의 확관 공정에서 발생되는 탄소성 응력과 변형량의 거동을 유한요소법으로 해석하였다. 열교환기의 관판 구명의 홈 깊이와 롤러 익스팬더의 작용압력을 변화시켜 해석한 결과, 전열관의 관판 구멍의 홈 깊이가 커지면 탄소성 압축응력은 감소하였고, 롤러 익스팬더 압력이 높을수록 관판 구멍의 홈 모서리 부분의 탄소성 응력이 증가되었다. Marine TEMA heat exchanger is the equipment to transfer the heat energy through both fluids that are enclosed separately by applying conduction and convection phenomena for a large vessels, Especially for heat exchanger working under the high temperature and high pressure, the expansion ratio should be taken into account other than under the low temperature and low pressure. This study was tried to find out the ideal expansion ratio through analyzing the elasto-plastic stress behavior of deformation while tubes are expanded with the finite element methods.
Quenching시 나트륨계 수용액의 냉각성능에 관한 연구
김옥삼,최은순,민수홍 ( Ok Sam Kim,Eun Soon Choi,Soo Hong Min ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.4
Coolingability of coolants is important factor in cooling processor heat treatment of steel, Using standard apparatus and method defined in the Korean Industrial Standard three different shapes of probe were designed, ie, cylinderical, spherical and square on shape with same volume of standard probe. Distilled water and sodium aquious solutions with different concentration of NaOH, NaCl and Na₂CO₃were examined. Estimation of coolingability of each quenchants for the probes of cylinderical, spherical or square shape, the cooling rate is greater square, cylinder and sphere in order. Coolingability of sodium aquious solution of NaCl, Na₂CO₃and NaOH is found generally greater then that of distilled water. Effectiveness of ingredients is in the order of Na₂CO₃, NaOH and NaCl. In both solutions coolingability increases in 20%, 5%, and 10% in order. Analytical results obtained from Finite Element Method were compared with experimental ones and found as practically satisfactional.
FEM 을 이용한 주조금형의 (鑄造金型) 탄소성 (彈塑性) 열응력 (熱應力) 및 열변형 해석
김옥삼,구본권,민수홍 ( Ok Sam Kim,Bon Kwon Koo,Soo Hong Min ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.1
N/A It is well-known that the analysis of elasto-plastic thermal stress and deformation are substantially important in optimal design of metal casting mould. The unsteady state thermal stress and deformation generated during the solidification process of ingot and mould have been analyzed by two dimensional thermal elasto-plastic theories. Distributions of temperature, stress and relative displacement of the mould are calculated by the finite element method and compared with experimental results. In the elasto-plastic thermal stress analysis, compressive stress occurred at the inside wall of the mould whereas tensile stress occurred at outside wall. A coincidence between the analytical and experimental results is found to be fairly good, showing that the proposed analytical method is reliable.
Quenching과정에서 상변태를 고려한 탄소성 열으역의 유한요소해석(1) - 오스테나이트에서 퍼얼라이트의 변태 -
김옥삼,구본권 ( Ok Sam Kim,Bon Kwon Koo ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.4
Constitutive relation of thermoelasto-plastic material undergoing phase transformation during quenching process were developed on the basic of continuum thermodynamics. The metallic structure, temperature and residual stresses distributions were numerically calculated by the finite element technique. The metallic structure were defined by transformation from austenite to pearlite and characterized as a fuction of thermal history and mixture rule of phase. On the distribution of thermal stress along the radial direction, axial and tangential stresses are compressive in the surface, and tential in the inner part. Radial stress is tensile in the whole body. The reversion of residual stress takes plase at 11.5∼15.5㎜ from the center.
김옥삼(Ok Sam Kim),김일수(Il Soo Kim),손준식(Joon Sik Son),서주환(Joo Hwan Seo),문채주(Chae Joo Moon) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.2
In this research work attempts were made to study the bonding of thermo-plastics with adhesives using solar radiation. In order to study the curing behaviour necessary experiments were conducted under varying conditions of temperature, exposure time and power of solar energy. The cured samples were then studied under the optical microscope before subjecting to tensile testing in order to study their mechanical properties of thermo-plastics. The fracture surfaces were further studied under the Scanning Electron Microscopy(SEM) in order to research the microstructural changes that are taken place during curing. In order to measure the performance of solar energy cured joints the parameters such as; bond strength, surface morphology, the microstructual changes, variation in properties of adhesives bonded joints are compared to that of specimen cured at ambient conditions and specimen cured using microwave techniques.
김옥삼 ( Ok-sam Kim ),민은비 ( Eun-bi Min ),황두진 ( Doo-jin Hwang ) 한국수산해양기술학회 2021 수산해양기술연구 Vol.57 No.4
By applying super-high pressure (150-250 MPa) to a sealed pressure vessel, it is possible to make oyster shucking machine that automatically opens two-sheet shellfish or oysters. Possibility of developing a shucking machine was confirmed by identifying the working pressure for meat of oysters produced in the southern coast and conducting sensory evaluation of meat oysters. As a result of confirming the shucked oysters under super-high pressure of 150 MPa in the pressure vessel, the number of type A with separated shells and well-separated meat was 22 and type B with both shells and internal meat and shells not separated. For the oysters that were treated at 175 MPa, there were 58 type As with shell separated and meat well separated and 42 type Bs without oyster shells and insides. When looking at the oysters shucked at 200 MPa in the pressure vessel, the number of type A was 86 and type B was 14 accounting for 86% of oysters with good marketability. As a result of shucking oysters by applying 250 MPa, 96% type A oysters and 4% type B oysters were obtained from the total specimen. The total specimen oyster weight used in the conducted experiment was 6 kg, the average oyster shell weight was 3.99 kg and the average oyster meat weight was 1.25 kg. Therefore, the fatness of oyster meat, which measures the added value of oysters, is 20.8%. Sensory evaluation was conducted on thinned oysters by hand and type A oysters shelled by machine with an operating pressure of 200 MPa. The hand-worked oyster sample scored 4.7 points only in salty taste, and scored 5.0 or higher in color, shape, smell, fishy taste, texture and preference.