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김지준,김진수,류관호,최정길,이진형,홍준표 ( Ji Joon Kim,Jin Soo Kim,Gwan Ho Ryu,Jeong Kil Choi,Zin Hyoung Lee,Chun Pyo Hong ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.3
N/A In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.
김지준,최정길,홍준표 ( Ji Joon Kim,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.1
N/A Prediction of shrinkage cavity in shaped castings considering solidification contraction has been considered to be one of the most important subjects in casting design. Several methods of prediction of the position and shape of shrinkage cavity in castings by computer simulation have been reported. However, most of them did not fully consider solidification contraction. Casting defects caused by volume contraction during solidification of molten metal are categorized into shrinkage cavity and porosity, depending on their generation mechanism. This paper describes in detail a method for predicting the shape and position of shrinkage cavities and porosities in shaped castings both for pure metals and alloys. A computer program was developed to calculate the shape and dimension of shrinkage cavities in shaped castings. The potential of the present method has been successfully demonstrated by comparing predicted cavity shapes with those obtained in a series of experimental castings.
주강품 압탕 설계에 체적 수축을 고려한 응고해석의 적용
김지준,김기영,최정길,홍준표 ( Ji Joon Kim,Ki Young Kim,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.5
N/A Test castings in plate, disc, and cubic shaped castings for 0.2wt.% carbon and stainless steel have been poured to examine the effects of the riser dimensions including riser neck on the casting soundness. Three empirical methods were chosen in risering of steel castings. A computer program of solidification analysis considering liquid and solidification contraction was developed to apply for riser-design calculated by using their methods in plate, disc, and cubic shaped castings, and to calculate the position and dimension of shrinkage cavity in complex shaped casting. The potential of present method has been successfully demonstrated by comparing predicted cavity shapes with those obtained in a series of experimental castings. Three empirical methods can be used in a practical way to make a rapid estimation of tie minimum riser diameter, but they can not provide a criterion of casting soundness with shape and material on all occasions. The shape and position of shrinkage cavity can be successfully predicted both using the present method and using risering calculated by their methods regardless of the shape and cast material.
그리스의 생산 균질도 파악을 위한 실시간 색추적 알고리즘 연구
김지준(Ji-Jun Kim),이진(Jin Lee) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.7
교반공정은 일반적으로 공정시간을 조절하고 공정시간이 길어짐에 따라서 균질성이 높아진다. 하지만 과도한 교반공정은 기포발생으로 인한 성능저하 및 생산량 감소로 이어진다. 그리스에 첨가제를 추가하는 경우 균질성과 기포정도에 따라서 성능이 결정된다. 그리스의 점도와 첨가제의 종류에 따라서 적합한 교반공정 시간은 예측하기 어렵고 실험을 통해 측정한다. 실험을 통해서도 그리스의 점도와 첨가제에 따라서 얼마나 교반공정이 진행 되었는지는 확인 할 수 있는 방법이 매우 제한적이다. 이러한 문제를 해결하기 위해서 이미지센서를 활용하여 그리스의 교반정도를 측정하는 방법을 제안한다. 제안하는 방법은 색공을 그리스위에 띄워서 색공의 움직임을 측정하는 방법이다. 제안된 방법을 이용하여 공의 움직임 정도를 그리스의 교반진행 정도로 표현 할 수 있다. 실제 산업현장에서 사용성을 높이기 위해서 실시간 성능을 구현하였다. 제안된 방법을 검증하기 위해 교반기의 교반 속도를 높여서 제안된 수식을 적용하여 교반정도를 나타내는 값이 상승하는 것을 확인하였다. 향후 그리스 생산뿐 아니라 다양한 교반공정에서 교반정도를 측정하는 수단으로 사용하여 다양한 환경변수에 따라 적합한 공정시간을 측정하는데 도움이 될 것으로 기대된다. Generally, the homogeneity of grease increases as the stirring time becomes longer. However, excessive stirring leads to a decrease in performance and production quantity due to the formation of bubbles. The performance of the product is determined by the homogeneity and the amount of foam generated when additives are added to grease. It is difficult to predict the appropriate stirring time, which depends on the viscosity of the grease and the type of additives, and it is measured through experiments. However, there are very limited ways to determine how much stirring has occurred depending on the viscosity and the type of additive. To solve this problem, we propose a method to measure the degree of stirring of grease using an image sensor. The proposed method involves floating a colored ball on the grease and measuring its movement. With the proposed method, the degree of movement of the ball can be used to represent the degree of stirring of the grease. Real-time performance was implemented to increase the methods usability. To verify the proposed method, we increased the speed of the stirrer and confirmed that the result indicates the degree of stirring of the grease increased when applying the proposed formula. This method could be useful for measuring the appropriate stirring time according to various environmental variables in grease production and other stirring processes.