• 한국세라믹학회지
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• 제38권9호
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• pp.860-865
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• 2001

본 논문은 출발물로서 2mol% CdO가 치환된 $0.05Pb(Mn_{1/3}Sb_{2/3})O_3-0.95Pb(Zr_{0.52}Ti_{0.48})O_3$ 분말을 제조 후, 닥터 블레이드 방법으로 green sheet를 제조하기 위한 slurry의 최적 공정첨가제 조성에 관한 연구를 수행하였다. 또한, 제조된 green sheet에 대하여 소결 특성과 두께 변환에 따른 유전 및 압전 특성을 관찰하였다. 공정첨가제의 첨가에 따른 점도거동을 통하여 slurry를 최적화하였고, TGA 분석으로 소결조건을 정하였으며, sheet의 특성에 미세구조와 XRD 등으로 측정하였다. 최적의 slurry는 고형분량 30vol%에 대해 분산제 3.0wt%에서 가장 안정화되었고, 이후 바인더/가소제(0.75/0.25) 3.0wt% 첨가시 점도는 7.55Pa${\cdot}$s이었다. Green sheet의 유전 및 압전 특성들은 각각 900$^{\circ}$C, 950$^{\circ}$C, 1000$^{\circ}$C로 소결온도를 증가함에 따라 다소 증가하였지만, 두께에 따른 특성들은 큰 변화가 관찰되지 않음을 확인하였다.

• 한국재료학회지
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• 제26권7호
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• pp.388-392
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• 2016

A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA1050 laminate complex sheet. Two AA1050 and one AA6061 sheets of 2 mm thickness, 40 mm width and 300 mm length were stacked up after surface treatment that included degreasing and wire brushing; material was then reduced to a thickness of 3 mm by one-pass cold rolling. The laminate sheet bonded by the rolling was further reduced to 1.2 mm in thickness by conventional rolling. The rolling was performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 210 mm. The rolling speed was 5.0 m/sec. The AA1050/AA6061/AA1050 laminate complex sheet fabricated by roll bonding was then hardened by natural aging T4) and artificial aging (T6) treatments. The microstructures of the as-roll bonded and the age hardened Al complex sheets were revealed by optical microscope observation; the mechanical properties were investigated by tensile testing and hardness testing. The strength of the as-roll bonded complex sheet was found to increase by 2.9 times compared to that value of the starting material. In addition, the hardness of the complex sheets increased with cold rolling for AA1050 and age-hardening treatment for AA6061, respectively. After heat treatment, both AA1050 and AA6061 showed typical recrystallization structures in which the grains were equiaxed; however, the grain size was smaller in AA6061 than in AA1050.

• 한국재료학회지
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• 제26권3호
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• pp.154-159
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• 2016

A roll-bonding process was applied to fabricate an AA1050/AZ91/AA1050 laminate complex sheet. Two AA1050 and one AZ91 magnesium sheets of 2 mm thickness, 30 mm width and 200 mm length were stacked up after surface treatment that included degreasing and wire brushing; material was then reduced to a thickness of 3 mm by one-pass cold rolling. The laminate sheet bonded by the rolling was further reduced to 2 mm in thickness by conventional rolling. The rolling was performed at 623K without lubricant using a 2-high mill with a roll diameter of 210 mm. The rolling speed was 15.9 m/min. The AA1050/AZ91/AA1050 laminate complex sheet fabricated by roll bonding was then annealed at 373~573K for 0.5h. The microstructure of the complex sheets was revealed by electron back scatter diffraction (EBSD) measurement; the mechanical properties were investigated by tensile testing and hardness testing. The strength of the complex sheet was found to increase by 11 % and the tensile elongation decreased by 7%, compared to those values of the starting material. In addition, the hardness of the AZ91 Mg region was slightly higher than those of the AA1050 regions. Both AA1050 and AZ91 showed a typical deformation structure in which the grains were elongated in the rolling direction; however, the mis-orientation distribution of grain boundaries varied greatly between the two materials.

• 소성∙가공
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• 제8권6호
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• pp.554-562
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• 1999

In this paper, the stress and strain behavior in near homogeneous isotropic matrix of metal like steel was studied during roll forming of thin steel sheet for cylindrical pipe. Analytical result reveals a body which is on the area of square thickness along and perpendicular to the width of thin steel sheet is in the state of plane strain during roll forming. As a result, construction of analytical method for calculating deformation load and stably deformed length along the width of strained steel sheet was established. Also, loads applied during roll forming were analyzed using two typical thin steel sheets. 12.3mm thick steel sheet with 42.5kg/㎟ yield strength of pipe and 5.3mm thick steel sheet with 32.5kg/㎟ yield strength of pipe. Through this analysis, applicability of the analytical method for deformation load during roll forming of cylindrical thin steel pipe was evaluated with a study of necessary production technology for roll forming and design technology for roll forming machine.

• 소성∙가공
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• 제3권3호
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• pp.335-346
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• 1994

The effect of sheet steel properties and lubrication on the optimal range of blank holding force (BHF) was investigated by means of the model die stamping of various sheet steels. The optimal range of blank holding force was expressed as the range between the lower BHF at flange wrinkling and the upper BHF at local necking. It showed that mechanical properties, thickness of sheet steel and lubrication condition were important factors affecting the optimal range of BHF in sheet steels. Especially, lubrication played an important role in the case of coasted sheet steels.

• 한국연초학회지
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• 제19권1호
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• pp.51-56
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• 1997

This experiment was conducted to reduce the cost of orient leaf using izmir, samsun and basma scraps in cigarettes manufacturing process. We manufactured rolled and paper sheet tobacco using orient scraps and substituted orient leaf in Pine tree to the rolled and paper sheet tobacco using orient scraps. Orient scraps were lower in total sugar, total sugar/nicotine and total nitrogen/nicotine, higher in nicotine and crude ash than those of orient leaves. Izmir and basma scraps were higher of 2-methyl butanoic, 3-methyl butanoic and 3-methyl pentanoic acid, but the chemical contents in samw scraps were lower than those of orient leaves. The specific gravity thickness, flness index, filling value were similar between orient scraps blended sheet tobacco and present sheet tobacco. The physical characteristics of orient scraps blended sheet tobacco were within Present sheet tobacco quality specification. The sheet tobacco using orient scraps was higher 2-metal butanoic, 3-methyl butanoic and 3-methyl pentanoic acid than those of present sheet tobacco. The rolled processed sheet tobacco using orient scraps was higher 2-methyl butanoic, 3-methyl butanoic and 3-methyl Pentanoic acid than those of paper sheet tobacco using orient scraps. The sample cigarettes using orient scraps sheet tobacco were lower 2-methyl butanoic, 3-mettwl butanoic and 3-mettwl Pentanoic acid than those of control cigarettes. The result of sensory test showed no great difference compared with sample of orient scraps and control cigarettes. This result shows that we can possible to substitute orient leaf to orient scraps to reduce the cost of orient leaf.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.62-65
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• 2001

The effects of the initial torture of workpiece as well as the process conditions such as punch speed and lubrication on the formablity of sheet stretching are investigated by experiments. Two types of the initial textures of aluminum sheet plane strain compression torture and recrystallization texture are chosen since those are the most common in practice. Punch loads vs depth and thickness strain distributions along radial directions having the slope of $0^{\circ},\;45^{\circ},\;90^{\circ}$ with rolling directions are reported for hemishperical punch stretchings under a variety of process conditions.

• 소성∙가공
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• 제7권5호
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• pp.459-464
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• 1998

Effect of the several initial textures such as random texture, rolling texture and cube texture, on the plane strain stretching was studied by interpretation of the finite element method. The calculation of yield locus indicated that the sheet oriented in the cube texture exhibits easy yielding on uniaxial stress state whereas the sheet having either a random or the rolling texture exhibits easy yielding on shear deformation. Upon stretching tests, the thickness strain at the center region contacting the punch was identical regardless of the initial textures while the dependence of the thickness strain on the initial texture was found in the other regions. In general punch loads required or the sheet with an initial cube texture was as expected from calculated yield locus, lower than those for the others.

• 소성∙가공
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• 제15권7호
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• pp.504-511
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• 2006

The drawability of AZ31B magnesium sheet is estimated at various temperatures($200,\;250,\;300,\;350\;and\;400^{\circ}C$), and forming speed(20, 50, 100mm/min), thickness(0.5, 0.8, 1.0, 1.4mm). The deep drawing process of circular cup and square cup were used in forming experiments. Experimental and FEM analysis are performed to investigate drawability and affection of controlled blank holding force. Through the controlled blank holding force, drawability was improved. Limit drawing ratio is increased from 2.1 to 3.0 in circular cup drawing and change of thickness is decreased from 16.3 to 6.9%. This result is verified by FEM analysis. Through the observation of microstructure, the main cause is investigated as a quantity of the dynamic recrystallization.

• 소성∙가공
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• 제24권4호
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• pp.241-247
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• 2015

In order to prevent shape defects such as fluting and stretcher strains during press forming of aged low carbon steel sheets, roller leveling conditions for reducing yield point elongation were studied. Yield point elongations of leveled sheets were determined as a function of leveling, which is defined as the plastic fraction or the ratio of plastically deformed part in sheet thickness section to the whole thickness of the sheet. By adjusting this plastic fraction during leveling to more than 78%, yield point elongation in the leveled sheets was reduced so no fluting occurred during subsequent tangential bending. Stretcher strains can be avoided by leveling the sheet to an 84% plastic fraction condition.