http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Counter Flow 방식의 랙 다이를 이용한 고정밀도 Worm 전조기술 개발
고대철(Dae-Cheol Ko),이정민(Jung-Min Lee),김병민(Byung-Min Kim) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.10
The objective of this study is to suggest the form rolling technology to produce high precision worm on the base of three dimensional finite element simulation and experiment. It is important to determine the initial workpiece diameter in form rolling because it affects the quality of tooth profile. The calculation method of the initial workpiece diameter in form rolling is suggested and it is verified by finite element simulation. The form rolling processes of worm shaft used as automotive part using both the rack dies of counter flow type and the roll dies are considered and simulated with the same numerical model as actual process by the commercial finite element code, DEFORM-3D. Deformation modes of workpiece between the form rolling by the rack dies of counter flow type and the roll dies are investigated from the result of simulation. The experiments using rack dies and roll dies are performed under the same conditions as those of simulation. The surface roughness, the straightness and the profile of worm are measured precisely using the worm shafts obtained from experiment. The results of simulation and experiment in this study show that the form rolling process of worm shaft using the rack dies is decidedly superior to that using roll dies from the aspect of the precision of worm such as the surface roughness, the straightness and the profile of worm.
신선 시 선재의 잔류응력 완화 방법에 관한 연구 및 나노 압입 시험을 이용한 잔류응력 평가
고대철(Dae Cheol Ko),황원호(Won Ho Hwang),이상곤(Sang Kon Lee),김병민(Byung Min Kim) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.5
Steel cord which is used as reinforcement in car tires is produced by wet-drawing process. Recently the quality improvement of the steel cord product is demanded by the tire market. After cold drawing process, produced residual stresses have a harmful effect on the durability of the wire and become the cause which decreases the quality of the product. Therefore, to improve the quality of the steel cord product, the research regarding the method of residual stress relaxation is necessary. To evaluate the quality of the cold drawn wire, it is very important to measure the residual stress, because the residual stress decides a variety of the quality level which is demanded in the cold drawn wire. The aim of this study is to propose residual stress relaxation method in the drawn wire using FE-analysis. The validity of the analysis results was verified by Nano indentation test.
고대철(Dae-Cheol Ko),이상곤(Sang-Kon Lee),김민안(Min-An Kim),김병민(Byung-Min Kim) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.1
Wire drawing process of the high carbon steel with a high speed is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In the multi-pass drawing process, temperature rise in each pass affects the mechanical properties of the final product such as bending, torsion, and tensile property, etc. This temperature rise during the deformation promotes the occurrence of delamination, and deteriorates the torsion property and durability of wire. This study investigates the occurrence of delamination in the wire through the torsion test and the evaluation of wire temperature. The excessive wire temperature leads to the occurrence of the delamination. Based on the calculation of the wire temperature, a new pass schedule, which can prevent the delamination due to the excessive wire temperature rise, is designed through the isothermal pass schedule.
고대철(Dae-Cheol Ko),이인수(In-Soo Lee),김병민(Byung-Min Kim),안병환(Byung-Hwan Ahn) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.9
The lead frame manufactured by stamping process plays an important role in connecting semiconductor to PCB board. As a result of the miniaturization of semiconductor, its corresponding lead frame punch has been narrow. In case of the punch with high slenderness ratio such as lead frame punch, the punch can be broken suddenly due to buckling. To prevent the fracture of lead frame punch, some manufacturers have experientially attached stiffeners to weak parts of punch. The purpose of this study, therefore, is to suggest the guideline for design of stiffened punch. The optimal position and the number of stiffeners to be attached to punch are investigated by elastic buckling analysis. The elastic buckling analysis consists of the eigenvalue buckling analysis and nonlinear buckling analysis. The critical buckling load of elastic buckling analysis is compared with that of buckling test. Finally, the guideline for attaching stiffeners is suggested through analysis of cross section of lead frame punch such as moment of inertia and eccentricity.