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티타늄 합금판재(Ti-6Al-4V)의 온간 소성변형특성(2)
박진기(J. G. Park),박노광(N. K. Park),김영석(Y. S. Kim),J. H. Kim 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle However, due to the low formability and large spring back at room temperature, titanium alloy sheets were usually formed by slow forming or hot forming with heating die and specimen. In the sheet metal forming area, FE simulation technique to optimize forming process is widely used. To achieve high accuracy FE simulation results, Identification of material properties and deformation characteristic such as yield function are very important. In this study, uniaxial tensile of Ti-6Al-4V alloy sheet with thickness of 1.0㎜ were performed at elevated temperature of 400℃~600℃. Also, uniaxial compression tests with special jig were performed characterize the yield locus of Ti-6AI-4V alloy sheet at 600℃. The experimental results for yield locus are compared with new yield function which was proposed in this study. The new yield function can describe not only the anisotropic of material but also asymmetry behavior between tension and compression.
박재실(J. S. Park),석창성(C. S. Seok),구재민(J. M. Koo),김대진(D. J. Kim),신재호(J. H. Shin),구병춘(B. C. Goo) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
In this study, we compared the fatigue characteristics of weld metal with those of base metal. Also we examined the influence of heat treatment and weld bead profiles for the fatigue life of weld metals. From the experimental results, it was seen that the fatigue characteristics of welded specimens with a grinded toe of bead are slightly better than those are not grinded. Also the fatigue life is affected more by the stress concentration on the profile change in the weld toe rather than by residual stress influence, because the fatigue characteristic of weld metals was not influenced whether the heat treatment is conducted or not.
저주파 가진 시스템에 의해 성형된 마이크로 패턴의 특성 분석
박찬진(C. J. Park),최종필(J. P. Choi),박동영(D. Y. Park),홍남표(N. P. Hong),이혜진(H. J. Lee),이낙규(N. K. Lee),김성욱(S. O. Kim),주은덕(Andy Chu),김병희(B. H. Kim) 한국생산제조학회 2009 한국공작기계학회 추계학술대회논문집 Vol.2009 No.-
Many researchers have developed several micro-forming technologies such as micro deep drawnig, micro press forming, micro forging, extrusion etc. for forming of precise micro-patterns on a surface of metal substrate but the multi-step forming processes have been used to improve quality of the deformed patterns. The low frequency vibration forming system, which developed in the research, can not only easily deform the surface of metal substrates but also can remove the couple of steps of the conventional multi-step forming process. In order to find optimal process conditions, lots of experiments were carried out under varying the vibration frequency from 100㎐ to 500㎐. As a experimental results, The desktop micro forming system has obtained better results from low frequency vibrations than non-vibration.
S, J, K 주파수영역에서 MgFe₂O₄ 단결정의 강자성공명 연구
박만장(M. J. Park),김기현(K. H. Kim),이혜정(H. J. Lee),김영호(Y. H. Kim) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.5
We have manufactured FMR spectrometer over wide range(2-35 ㎓). In order to test FMR spectrometer, resonance absorption has been measured of the standard sample DPPH. The Q vaules of absorption line are 189-1096. As a result, We noticed that FMR spectrometer has been manufactured well. FMR studies of MgFe₂O₄ single crystal have been performed at S, J, K-band. The resonance lines have been observed for the each orientation of (100) plane at 300 K. The values of the magnetic anisotropy constant K₁ and the spectroscopic splitting g valule have been calculated from the ferromagnetic resonance curve, -2.9×10⁴erg/㎤, 2.02 at 23.89 ㎓, -2.2×10⁴erg/㎤, 1.89 at 5.3 ㎓ and -2.8×10⁴erg/㎤, 2.01 at 3.6 ㎓.