• Title/Summary/Keyword: Die steel

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Microscale Analysis of the Anisotropic Sintering of Metal Powder Compacts

  • Vagnon, Alexandre;Kapelski, Georges;Bouvard, Didier.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.260-261
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    • 2006
  • The behaviour of steel powder compacts during sintering has been investigated by dilatometry and X-ray computed microtomography. Dilatometry measurements showed that the anisotropic deformation results from various phenomena arising at different moments of the cycle including the delubrication stage. Microtomography provided 3D images of the microstructure induced by prior die pressing and its changes throughout sintering. Finally a schematic description of the main phenomena responsible for the deformation of metal powder compacts during sintering is proposed.

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THE EFFECT OF CYCLIC LOADING ON THE RETENTIVE STRENGTH OF FULL VENEER CROWNS (반복 하중이 Full veneer crown의 유지력에 미치는 영향에 관한 연구)

  • Kim, Ki-Youn;Lee, Sun-Hyung;Chung, Hun-Young;Yang, Jae-Ho;Heo, Seong-Joo
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.5
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    • pp.583-594
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    • 2000
  • Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with $8^{\circ}\;or\;16^{\circ}$ convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 2 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 3 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 4 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 5 : $16^{\circ}$ taper die, cementation with Panavia 21, without loading Group 6 : $16^{\circ}$ taper die, cementation with Panavia 21, with loading Group 7 : $8^{\circ}$ taper die, cementation with Panavia 21 without loading Group 8 : $8^{\circ}$ taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed according to the manufacturer's recommendations. A static load of 5kg was then applied for 10 minutes with static loading device. Twenty-four hours later, group 1, 3, 5, 7 were only thermocycled, group 2, 4, 6, 8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From the finding of this study, the following conclusions were obtained 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups (p<0.05). 2. There was a significant difference in the retentive strength between $8^{\circ}\;and\;16^{\circ}$ taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21 (p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups(p<0.05). 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the $16^{\circ}$ taper die, 25% in the $8^{\circ}$ taper die, and for Panavia 21, 21% in the $16^{\circ}$ taper die, 18% in the $8^{\circ}$ taper die.

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The analysis and optimization of dual armor plate considering EQPS (EQPS를 이용한 복합장갑의 해석 및 최적설계)

  • 박명수;유정훈;정동택
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2004.04a
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    • pp.111-118
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    • 2004
  • For the precise analysis of high velocity impact problem though FEM with element erosive method, the adequate mesh size and critical equivalent plastic strain(EQPS) is chosen prior to the simulation. In this research, it is strongly required from a standpoint that critical EQPS is used to decide whether perforation occurs or not. The optimization of dual armor plate consisting of 4340 steel and 2024 aluminium against a die steel sphere with high-velocity has been suggested using Lagrangian explicit time-integration code, NET2D. The response surface method based on the design of experiment is utilized for the size optimization. The optimized thickness of each layer, in which perforation does not occur, the strength of multi-layer is maximized and total weight is minimized, is obtained at a constant velocity of a pellet with a designated total thickness.

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Experimental study on the severe deep drawing for complex cylindrical housing of STS 305 stainless steel (스테인리스 강 STS305의 디프 드로잉 가공에 관한 실험적 연구)

  • Kim, Doo-Hwan
    • Transactions of Materials Processing
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    • v.7 no.5
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    • pp.439-444
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    • 1998
  • Recently many automotive parts have been made with stainless steels by deep drawing processes, But there are various problems occurred in deep drawing works of stainless steels compared with low carbon steels. For the severe deep drawing of complex cylindrical housing optimum process planning is required to eliminate intermediate annealing improve shape accuracy and maintain surface integrity without drawing defects such as tears wrinkles and scratches or galling. Therefore in this study a sample process planning of the severe of the severe deep drawing process is applied to a complex cylindrical housing needed for a 6 multi-stepped deep drawing of type STS 305 . A series of experiments are performed to investigate optimum process variables such as drawing rate radius and clearance. Through experiments the variations of the thickness strain distribution and hardness distribution in each drawing step are observed. Also the effects of other factors on formability such as drawing oil, blank holding force and die geometry are examined and discussed.

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Heat Treatment of Stator Core in Permanent Magnet Type Motor for Reduction of Friction Torque and Analysis of Their Cause (영구자석형 모터의 프릭션 토크 저감을 위한 고정자 철심의 열처리 및 발생원 분석)

  • Ha, Kyung-Ho;Lim, Yang-Su;Kwon, Oh-Yeoul;Kim, Ji-Hyun;Kim, Jae-Kwan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.10
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    • pp.1752-1758
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    • 2008
  • This paper deals with the reduction of friction torque in permanent magnet motors by using the heat treatment of stator core. The stator core is made of electrical steel sheared by the punching die. From the punching process, large mechanical stress acting on the edge of stator tooth induces significant plastic and elastic deformation and then cause the change of magnetization properties. Then, the mechanical and magnetic unbalance in the sheared region of stator tooth produced by material cutting has influence on the friction torque. This paper investigated the effect of the punching process on the magnetization process and the mechanical deformation, and then proposed the stress relief annealing method for the reduction of friction torque among one of motor characteristics.

The Effect of Deformation Heat Compensation in the Hot Forging Analysis of SAF 2507 Stainless Steel (SAF 2507 스텐레스강의 열간단조해석에서 가공열 보정의 효과)

  • 방원규;정재영;장영원
    • Transactions of Materials Processing
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    • v.10 no.3
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    • pp.206-213
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    • 2001
  • Dynamic deformation of metallic materials mostly accompanies substantial amounts of deformation heat. Since the flow stress of deformation is sensitive to temperature, implication of heat due to plastic work is essential to the evaluation of constitutive relations. In this study, a series of compression tests were conducted for SAF 2507 super duplex stainless steel at various temperatures and strain rates. The accumulation of plastic work was calculated through numerical integration and converted into the elevation of temperature. Subsequent logarithmic interpolation deduced isothermal flow surfaces, which were primary input data of finite element analysis. Simple closed die forging process was analyzed and optimized with commercial FEM code applying both raw and calibrated material database. The effect of accounting deformation heat was more noticeable in high-speed forming process.

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A study of frictional characteristics of galvanized sheet steels for automobiles (자동차용 표면처리강판의 마찰특성에 관한 연구)

  • 김영석;남재복;최원집
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.6
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    • pp.1474-1486
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    • 1990
  • The frictional characteristics of galvanized sheet steels(GA, EG, EGF, EGN) for automobiles were studied and compared with that of cold rolled sheet steel. A draw bead tester which simulates metal flow through a draw bead in stamping die face was used to measure coefficients of friction of galvanized sheet steels for four kinds of lubricants. Stamping formability of galvanized sheet steels for quarter outer panel was examined. The results show that stamping formability and friction characteristics were mainly influenced by the nature of zinc coating, surface roughness and micro hardness of coated layer, and proved to be very sensitive to the lubricant used.

Evaluation of machining characteristics according to cutting condition of hardened steel in high speed machining (고경도 금형강(SKD61)의 고속가공에서 절삭조건 변화에 따른 가공성 평가)

  • 김득현;강명창;이득우;김정석;김광호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.05a
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    • pp.878-881
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    • 2000
  • Recently high speed machining is being studied actively to reduce machining time and to improve machining precision. To perform efficient high speed machining, evaluation of high speed machinability must be studied preferentially and it can be identified by investigation of cutting force, tool wear and surface roughness. In this study. the cutting force and tool wear and surface roughness are investigated in case of various cutting conditions for hardened die steel.

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Effect of Cold Forming Method on Drawability Trunk Floor Panel (냉각성형공법이 트렁크 플로어 드로잉성에 미치는 영향)

  • 최치수;최이천;오영근;이정우;이항수
    • Transactions of Materials Processing
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    • v.10 no.2
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    • pp.123-129
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    • 2001
  • This study is to investigate the effects of cold forming method with steel sheet of SCP3C to improve continuous productivity. Experiments were carried out in various working conditions, such as the number of stamping and the punch temperature. The effects of the punch temperature and the number of stamping on drawability of steel sheet of SCP3C as well as clearance and draw-in in the number of stamping were examined and discussed. More improvement of continuous productivity in case of cold stamping rather than by conventional stamping at room temperature is obtained. The optimum forming condition for drawing trunk floor panel of SCP3C is shown as the punch is cooled by coolant of $-5^{\circ}C$ and at the same time both the die and the blankholder are heated by stamping and frictional heat.

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