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Min-Suk Oh,Sang-Heon Kim,Jong-Sang Kim,Jae-Won Lee,Je-Ha Shon,Young-Sool Jin 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.1
The effects of Mg and Al content on the microstructure and corrosion resistance of hot-dip Zn-Mg-Al alloycoated steel sheets were investigated. Pure Zn and Zn-based alloy coatings containing Mg (0-5 wt%) and Al (0.2-55 wt%) were produced by a hot-dip galvanizing method. Mg and Al addition induced formation of intermetallic microstructures, like primary Zn, Zn/MgZn2 binary eutectic, dendric Zn/Al eutectoid, and Zn/Al/MgZn2/ternary eutectic structures in the coating layer. MgZn2-related structures (Zn/MgZn2, Zn/Al/ MgZn2, MgZn2) played an important role in increasing the corrosion resistance of Zn-Mg-Al alloy-coated steel sheets. Zn-3%Mg-2.5%Al coating layer containing a large volume of lamellar-shaped Zn/MgZn2 binary eutectic structures showed the best cut-edge corrosion resistance. The analysis indicated that Mg dissolved from MgZn2 in the early stage of corrosion and migrated to the cathodic region of steel-exposed cut-edge area to form dense and ordered protective corrosion products, leading to prolonged cathodic protection of Zn- Mg-Al alloy-coated steel sheets.
Flow Stress Equations of Ti-6Al-4V Titanium Alloy Sheet at Elevated Temperatures
Duc-Toan Nguyen,김영석,정동원 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
In this study, to achieve constitutive equations of Ti-6Al-4V alloy sheet, uni-axial tensile tests of Ti-6Al-4V alloy sheet with thickness of 1.0mm were performed at elevated temperature of 400oC ~ 700oC. Equations of stress-strain curves are established for Ti-6Al-4V alloy sheet at elevated temperatures describing both work-hardening and softening stage of Ti-6Al-4V alloy sheet. Least square fitting method is used to determine material parameters. The parameters of fitting curves are utilized to determine them as a function of temperature using polynomial models. New mathematical models are used to calculate and predict the stress-strain curves at elevated temperatures. The calculated flow stress curves are in good agreement with experimental data and shown better than that of previous equation.
Flow Stress Equations of Ti-6Al-4V Titanium Alloy Sheet at Elevated Temperatures
Nguyen, Duc-Toan,Kim, Young-Suk,Jung, Dong-Won 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.5
In this study, to achieve constitutive equations of Ti-6Al-4V alloy sheet, uni-axial tensile tests of Ti-6Al-4V alloy sheet with thickness of 1.0mm were performed at elevated temperature of $400^{\circ}C{\sim}700^{\circ}C$. Equations of stress-strain curves are established for Ti-6Al-4V alloy sheet at elevated temperatures describing both work-hardening and softening stage of Ti-6Al-4V alloy sheet. Least square fitting method is used to determine material parameters. The parameters of fitting curves are utilized to determine them as a function of temperature using polynomial models. New mathematical models are used to calculate and predict the stress-strain curves at elevated temperatures. The calculated flow stress curves are in good agreement with experimental data and shown better than that of previous equation.
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.
이충안(Chung An Lee),서오석(Oh Suk Seo),이명규(Myoung Guy Lee),김지훈(Ji Hoon kim),김대용(Dae Young Kim),김헌용(Heon Young Kim) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3
Recently, lightweight material has been used widely in the field of automotive and electronic industries. However, some difficults exists in characterizing the material, poor formability and abnormal stress-strain behavior such as Mg alloy sheet. In this paper, a new cyclid load tester, which can measure the stress-strain curves of thin sheet metals under non-monotonous condition such as tension /compression or compression /tension, was debeloped. Material tests including tension / compression / tension or compression/tension/compression test are performed to aluminum and magnesium alloy sheets and construct a database of its material properties.
김경진,윤종헌 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
In this work, half channel angular extrusion, a recently developed severe plastic deformation (SPD) process, applied to AZ31 Mg alloy. Effects of the initial microstructure of AZ31 alloy on the microstructural development such as the grain refinement and texture evolution during the half channel angular extrusion (HCAE) has been studied. It was found that the grains of the AZ31 alloys can be refined remarkably by single pass of HCAE than other SPD techniques and not only the grain refinement but also the deformation induced textures result in a noticeable enhancement of mechanical properties.
서오석(Oh Suk Seo),김헌영(Heon Young Kim),이명규(Myoung-Gyu Lee),김지훈(Ji Hoon Kim),김대용(Dae Yong Kim) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Recently, lightweight material has been used widely in the field of automotive and electronic industries. However, some difficulties exists in characterizing the material, poor formability and abnormal stress-strain behavior such as Mg alloy sheet. In this paper, a new cyclic load tester, which can measure the stress-strain curves of thin sheet metals under non-monotonous condition such as tension /compression or compression /tension, was developed. Material tests including tension / compression/ tension or compression/tension/compression test are performed to aluminum and magnesium alloy sheets and construct a database of its material properties.
자동차용강판과 알루미늄합금의 저항점용접부에 대한 인장전단강도 특성
유덕생(Duk Saeng Ryu),이종호(Jong Ho Lee),윤한기(Han Ki Yoon) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Optimal welding condition on resistance spot welding of 0.8 ㎜ thick aluminum alloy sheet(Al5052-H32) and automatic borrowing galvanized sheet(SGARC35) were investigated by tension shear strength test. The tension shear tests were carried out at cross-head speeds of 0.1 ㎜/min in accordance with the KS B0851. The resistance spot welding conditions of welding current were three kinds of 7.5 ㎄, 9.5 ㎄ and 11.5 ㎄ and welding time were 2 cycle, 3 cycle and 4 cycle. The results, in SGARC35/SGARC35, the tensile-shear strength gradually increases with increase welding current 7.5 ㎄, 9.5 ㎄ and 11.5 ㎄ at electrode force of 270 ㎫ and welding time of 12cycle. The tensile-shear strengths are high as welding current is 11.5 ㎄. The tensile-shear strength of Al5052-H32/SGARC35 are 0.1 kN, 0.6 kN and 0.6 kN when welding current are 8.0 ㎄, 8.5 ㎄ and 9.0 ㎄ at welding time is 10 cycle and electrode force is 210 ㎫, respectively.