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대형유도전동기용 단락고리 제조를 위한 구리의 냉간 링롤링 공정설계 연구
이성원(S. W. Lee),조재완(J. W. Jo),강민영(M. Y. Kang),이정민(J. M. Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
The large end rings for generators have been mostly manufactured by bending in a circle, welding and machining of a long copper square bar in order. However, these welded parts can not only occasionally contain various welding defects that are hydrogen embrittlement, residual stresses, cracks and inclusions but also lead to electrical discontinuity within the end ring. To solve these problems, this study proposed the new manufacturing method which contains a ring rolling process to make an initial material into a ring preform. The initial material is produced into ring shape by a centrifugal casting method and a subsequent machining. The ring preform is machined into final desired dimensions. The typical defects of the ring rolling process are the uniform deformations of ring shape and the fishtail of its section. They are very sensitive to the process variables like an initial and a desired ring geometry, a ring-growth-rate, an axial stand and a rolling curve (ratio between height reduction rate in axial gap and mandrel feed rate). Thus, this paper was design to investigate the effect of the different process parameters on the dimensions of the ring preform during ring rolling process using Finite element analysis.
유한요소해석을 이용한 타이타늄 합금(Ti-6Al-4V) 판재의 고온 성형성 평가
이성원(S. W. Lee),조재완(J. W. Jo),이정민(J. M. Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
Recently, titanium alloy parts have been actively studied as hot-forming processes in a temperature range where α case is not formed as an alternative to SPF(super plastic forming). This process provides shorter forming time and lower costs than SPF because it is no chemical milling required to remove alpha case in substance. In particular, the formability of Ti-6Al-4V sheet in hot forming process is very sensitivity to forming temperature. Thus, it is very important to clearly define the forming behavior of Ti-6Al-4V sheet at high temperature. This paper was designed to evaluate the high temperature formability of Ti-6Al-4V sheet. First, the behaviors of the material was defined through tensile and anisotropy tests for different temperatures (600 ~ 800°C) and strain rates (0.01 ~ 1.0). Also, the failure criterion of the sheet was judged as FLC(Forming Limit Curve) for various temperatures (600 ~ 800°C). Finally, these characteristics were used for FE simulations of deep drawing and U-bending processes to determine the spring back and drawability of Ti-6Al-4V sheet for different temperature.