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추연근(Qiu Yuangen),조해용(Hae Young Cho) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.5
A split-die design for the cold forging of symmetric parts such as those having a hexagonal cross-section is presented in this paper. Parts with a hexagonal cross-section, such as bolt heads and nuts, should be forged with a die that has a hexagonal-shaped hole. A split type die is required to mitigate the buildup of stress concentrations located at the corners of the hexagonal hole. Generally, the insert of a hexagonal die is made by cutting each corner of a cylinder using a hexagonal hole and then combined with the die and shrink-fitted. However, split dies face problems when extruding material at the corners of the hexagonal split die. To address this problem, two types of split dies were evaluated: rounded hexagonal dies and angular hexagonal dies. The effects of the pre-stress ring on the dies were compared and analyzed and results show that using the angular split hexagonal die can extend the lifetime of forging dies.
김동범,추연근,조해용,Kim, Dongbum,Qiu, Yuangen,Cho, Hae-Yong 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.3
Self-piercing riveting is an joining method of advanced high strength steels (AHSS) and other dissimilar materials. It has attracted considerable interest from the automotive industry. The SPR has become an interesting alternative joining technique for difficult to weld materials such as steels and aluminium alloys. In this paper, self-piercing rivet and anvil for SPR were designed for the joining conditions with AHSS and aluminium alloy. Various conditions of SPR were simulated for the design of rivets and anvils. The simulated results were in good agreement with experimental ones. As a result, over HV500 rivet is desirable to joint SPFC780 AHSS and aluminum alloy.
A Study on the Backward Extrusion of Internal Spline
YongIl Cho(조용일),JongUng Choi(최종웅),Yuangen Qiu(추연근),Heayong Cho(조해용) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.9
Spline is a machine component using transmits rotating energy with grooves on internal of boss and external periphery of shaft. Internal spline is generally produced by machining process. However, to reduce manufacturing cost and save time, plastic deformation process such as backward extrusion is gradually adapted for spline production. In plastic deformation process, forming load, stress on tools and flow flaws should be taken into account to have sound products. For this purpose, kinematically admissible velocity fields for Upper Bound Method in backward extrusion of internal spline has been suggested, then forming load and relative pressure have been calculated. Internal spline forming experiments have been con-ucted under hydraulic press and the calculated forming load well predicts the load of experiment.
조용일(Yong-Il Cho),김승환(Seung-Hwan Kim),추연근(Yuan-gen Qiu),조해용(Hae-Yong Cho) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.5
Pipe expansion involves various methods to enlarge the diameter of the pipes with the use of a mandrel or punch placed inside the pipe. In this study, the upper bound method was used to analyze the pipe expanding process as well as design a die. A kinematically admissible velocity field was derived for the upper bound analysis with the occurrence of pipe thinning during the expansion factored in. The analysis confirms that a semi-cone angle of the punch between 15ween pip is most advantageous for pipe expansion. The results of the upper bound analysis, which were also consistent with those of the FEM, can be useful for the design of a pipe expansion die.