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Ti-6A1-4V 티타늄 합금나사의 가공방법에 따른 절삭 특성
김형선,최종근,김동민 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
A screw is used to fasten the various parts of an assembly together and to transfer power from a driving part to passive one. Now a day, titanium is one of the most attractive materials due to their superior properties of high specific strength and excellent corrosion resistance. The applications in aerospace and medical industries demand machining process more frequently to obtain more precise products. In the thread cutting of titanium alloys, the key point for successful work is to select proper cutting methods and tool materials. This study suggests a guidance for selecting the cutting methods and the tool materials to improve thread quality and productivity. Some experiments investigate surface roughnesses, cutting forces and tool wear with change of various cutting parameters including tool materials, cutting methods, cutting speed. As the results, the P10 type insert tip was assured as the best for thread cutting of Ti-6A1-4V titanium alloy. Also the initial depth of infeed was desirable to use the value below 0.5mm as the uniform cutting area method is applied.
문석형,최호신,권석근,육종철 대한방사선 방어학회 1987 방사선방어학회지 Vol.12 No.1
X-선 발생장치 시설에 대한 방사선 차폐해석은 두가지 측면에서 고려된다. 먼저 1차 방사선과 누설방사선에 의한 영향을 고려하여야 하며 본 연구에서는 NCRP-49 및 51에 제시된 방법을 사용하였다. 둘째, 시설의 미로 출입구에서는 산란방사선에 의한 영향이 보다 중요한데, 본연구에서는 이 영향을 평가하기 위하여 Albedo개념을 근거로 한 단순한 방법이 제시되었고, 이를 토대로 계산된 결과를 컴퓨터 코-드(MORSE-CG)의 계산치 및 실측된 결과와 비교하였다. 본 연구에서 제시된 방법에 의한 결과는 미로출입구 안쪽의 경우에 대한 해석에서는 약간의 오차를 보이고 있으나 미로출입구 문바깥에서는 비교적 잘 일치한다. 여기서 출입문바깥의 경우에 대한 해석이 방사선방어 측면에서 보다 중요하다는 관점에서 볼 때 이 방법은 의료용 또는 산업용의 X-선 및 감마선시설의 차폐설계 및 해석이 응용될 수 있을 것이라고 판단된다. Radiation shielding analysis for a 6MeV X-ray facility was carried out. The primary and leakage radiation for the facility can be evaluated based on the methodology in NCRP No. 49 and 51. The present study deals with radiation scattering analysis for the outside and inside door of the facility based on the albedo concept. The calculated dose rates were compared with the results of MORSE-CG code calculation and the measured data, resulting in a good agreement, even though there existed some deviation for the inside door. These results can be utilized to the radiation shielding design of the medical and industrial X and gamma ray facilities, and to the safety evaluation of these facilities.
Study of a “wing-type” implant on stress distribution and bone resorption at the alveolar crest
Jong-Wook Park,Sin-Guen Kim,Dong-Won Choi,Mi-Ra Choi,Youn-Jin Yoon,Jun-Woo Park,Dong-Ju Choi 대한구강악안면외과학회 2012 대한구강악안면외과학회지 Vol.38 No.6
Objectives: Implants connect the internal body to its external structure, and is mainly supported by alveolar bone. Stable osseointegration is therefore required when implants are inserted into bone to retain structural integrity. In this paper, we present an implant with a “wing” design on its area. This type of implant improved stress distribution patterns and promoted changes in bone remodeling. Materials and Methods: Finite element analysis was performed on two types of implants. One implant was designed to have wings on its cervical area, and the other was a general root form type. On each implant, tensile and compressive forces (30 N/m 2 , 35 N/m 2 , 40 N/m 2 , and 45 N/m 2 ) were loaded in the vertical direction. Stress distribution and displacement were subsequently measured. Results: The maximum stresses measured for the compressive forces of the wing-type implant were 21.5979 N/m 2 , 25.1974 N/m 2 , 29.7971 N/m 2 , and 32.3967 N/m 2 when 30 N/m 2 , 35 N/m 2 , 40 N/m 2 , and 45 N/m 2 were loaded, respectively. The maximum stresses measured for the root form type were 23.0442 N/m 2 , 26.9950 N/m 2 , 30.7257 N/m 2 , and 34.5584 N/m 2 when 30 N/m 2 , 35 N/m 2 , 40 N/m 2 , and 45 N/m 2 were loaded, respectively. Thus, the maximum stresses measured for the tensile force of the root form implant were significantly higher (about three times greater) than the wing-type implant. The displacement of each implant showed no significant difference. Modifying the design of cervical implants improves the strength of bone structure surrounding these implants. In this study, we used the wing-type cervical design to reduce both compressive and tensile distribution forces loaded onto the surrounding structures. In future studies, we will optimize implant length and placement to improve results. Conclusion: 1. Changing the cervical design of implants improves stress distribution to the surrounding bone. 2. The wing-type implant yielded better results, in terms of stress distribution, than the former root-type implant.
최종근(Jong-Guen Choi),최현철(Hyeon-Cheol Choi),이응기(Eung-Ki Lee) 한국생산제조학회 2006 한국공작기계학회 춘계학술대회논문집 Vol.2006 No.-
The impurities of roller surface affect directly the surface quality of the products obtained by rolling processes. As a devices to eliminate impurities on roller surface, the Roll Cleaner composes a blade being contacted to the roller surface during operating. In order to remove these impurities effectively, it is necessity to keep proper pressure between the cleaner blade and the roll surface. The Nip Pressure means this one. It is the most important parameter which decides the performance of roll cleaner, and depends upon several parameters including the cleaner design and the mechanical properties of blades. This study, first, analyzes the pressure generation mechanism for a roll cleaner developed commercially. Second, it suggests a technique for the measurement of nip pressure, which is useful to verify the performance of roll cleaners and their proper setup at factory floor.
최종근(Jong-Guen Choi),김형선(Hyung-Sun Kim) 한국생산제조학회 2006 한국생산제조학회지 Vol.15 No.6
A slot cut in end milling processes is one of the laborious works because the cutting force is likely to deflect the tools excessively, then to make large errors or to fracture the tool. This difficulty is owing to the poor stiffness of slender shaped end mills. Though, in most cases, additional finish cuts are followed after rough cuts, the accuracy of rough cuts is still important because it affects the final accuracy after finish cuts and productivity. The accuracy in slot cuts depends on the tool stiffness and the cutting conditions including depth of cut and feed. In order to meet the desired accuracy, diameter of end mill and cutting allowance have to be selected carefully. This study suggests several guidances for selecting the end mill diameter and the slot cut allowance to improve machining accuracy and productivity in slot end millings. Some experiments were done with the various cutting parameters of tool diameter, depth of cut and feed.
엔드밀 가공의 정밀도 향상을 위한 최적정삭여유에 관한 연구
최종근(Jong-Guen Choi),김형선(Hyung-Sun Kim),김성초(Sung-Cho Kim) 한국생산제조학회 2004 한국생산제조학회지 Vol.13 No.3
A significant error in the end milling processes is generated due to using slender tools of which the strengths are not sufficient. In order to obtain the desired machining accuracy, therefore, it is general that at first the rough cut is implemented, then the finish cut is followed. The rough cut eliminates large volume and the finish cut does the remained part. This remaining portion after the rough cut is called as the finish allowance. Larger finish allowances make it hard to get precise dimensions at a following finish cut. Smaller finish allowances are helpful for good dimension, but it sometimes is responsible for inferior surface qualities and over cuts. This study suggests a guidance for the optimum finish allowance for machining accuracy improvement, in which the rough cuts are regulated to remain the desired margins without any over cuts. Some experiments were carried out with various cutting conditions including the change of tool strengths and depth of cuts, and also extended to up millings as well as down millings.
최종근(Jong-Guen Choi),김형선(Hyung-Sun Kim) 한국생산제조학회 2006 한국생산제조시스템학회 학술발표대회 논문집 Vol.2006 No.5
In the end milling processes, the feature of end mills, which is slender and poor strength, is responsible to the most of machining errors. The end milling process is frequently used to cut complicated parts having slots. The slot cut by end mill is one of the laborious task because the cutting force is likely to deflect the tools and to make the errors. In order to meet the desired accuracy, therefore, the diameter of end mill and rough cut allowance have to be selected carefully. This study suggests a guidance for selecting the end mill diameters and the slotting allowances to improve machining accuracy in slot end millings. The investigation was carried out with various cutting conditions including change of tool strengths, depth of cuts, and extended to slotting allowance.