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朴鍾振,黃澣燮 弘益大學校 科學技術硏究所 2002 科學技術硏究論文集 Vol.13 No.-
In incremental forming of sheet metal, it has been known that the formability depends upon the type of tool to be used and its size. In the present study, two types of tools -- one is ball roller and the other is hemispherical head tool -- were used to assess the formability of fully annealed aluminum sheet of 0.3mm in thickness. In the latter, tools of four different sizes were compared. As a method to assess the formability, the straight groove test was proposed where biaxial tension occurs at the ends of the groove while plane-strain tension occurs along the groove. The test is simple, but quite reliable.
박종진,문영성 崇實大學校 生産技術硏究所 2002 論文集 Vol.32 No.-
IS-41 specifies the location management scheme for the PCS (Personal Communication System). However, it has an importanr shortcoming such that it becomes inefficient as the number of users increases. Thus it is necessary to augment the IS-41 scheme to achieve more efficient location management. The operations of location management are "location update" and "terminal paging". If MN (Mobile Node) enters a new RA(Registration Area), then corresponding VLR (Visitor Location Register) requests to update MN's location information to the HLR (Home Location Register). And if a call to the MN is arrived at VLR, then VLR requests to Know MN' location information to the HLR for connection. There are many approaches to increase efficiency for location update and terminal paging. In this paper, we proposed location management scheme with two timers for location update to reduce HLR's processing load. The results from the Performance evaluation confirms the efficiencies of the proposed scheme.
박종진 대한기계학회 1995 대한기계학회논문집 Vol.19 No.4
Titanium 6242(.alpha. + .betha.) alloy has a good strength/weight ratio and is used for aircraft components such as engine disks and compressor blades. When this material is forged at an elevated temperature, the process parameters should be carefully controlled because the process window of this material is quite narrow. In the present investigation, a rigid-thermoviscoplastic finite element method is used to predict the deformation behavior and temperature/strain distributions in an engine disk during near-net shape hot forging. The purpose of the investigation is to obtain a proper ram speed profile, assuming the hydraulic press used in the forging is capable of varying ram speed during loading. In result, it was found that the ram speed at constant strain-rate of 0.5/sec shows a sound deformation behavior, a relatively uniform deformation and a good temperature distribution. This information is also valuable in predicting resulting microstructures in the disk.
박종진 대한기계학회 1993 대한기계학회논문집 Vol.17 No.5
Several yield criteria for porous materials are compared with each other, defining the apparent yield stress as the yield stress of the porous material in simple compression. It was found that the plastic Poisson's ratio is the parameter needed to define the yield criterion, rather than the relative density. The plastic Poisson's ratio is regarded as a material characteristic that is obtained from a simple compression test. A new form of yield criterion was suggested, and it was applied to hydrostatic compression as well as uniaxial strain compression of sintered Al-2024 powder. The crossover point in the mean stress vs volume change curves of the processes was predicted. It is presented that the flow stress of the fully densed material can be obtained from that of the porous material using relations obtained from the yield criterion.