• Title/Summary/Keyword: Machined surface layer

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Characterization of Fiber Pull-out in Orthogonal Cutting of Glass fiber Reinforced Plastics

  • Park, Gi-Heung
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 2003.10a
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    • pp.113-117
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    • 2003
  • The reliability of machined fiber reinforced composites (FRC) in high strength applications and the safety in using these components are often critically dependent upon the quality of surface produced by machining since the surface layer may drastically affect the strength and chemical resistance of the material [1,2,3,4]. Current study will discuss the characterization of fiber pull-out in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized model composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The experimental correlation between the fiber pull-out and the AR coefficients is examined first and effects of fiber orientation, cutting parameters and tool geometry on the fiber pull-out are also discussed.

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The Effects of Heat-Affected Zone on Cold Forging Die Life (냉간단조용 금형의 열영향층 형성과 그 영향)

  • 이영선;이정환;정순철
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1998.06b
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    • pp.43-53
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    • 1998
  • Heat - affected zones degenerated in cold forging die have been investigated to improve the tool life. There are many cases of heat-affected zone which are degenerated in manufacturing die and using the cold forging process. In order to define amounts of grinding inmanufacturing the toolfor cold forging, we have investigated the hardness and microstructure of surface layer after EDM. Considering the results of T.R.S. and compression test, it is likely that mechanical properties of tool have been decreased sharply if the heat-affected zones degenerated by EDM were not machined properly. also analyzed the tool surfac which is fractured during the cold forging. According to the microstructures and hardness distribution, surface of many tools have been degenerated in cold forging and fractured due to the heat-affected zone.

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Comparative Study on the Failure of Polymer/Roughened Metal Interfaces under Mode-I Loading II: Adhesion Model (인장하중하에서의 고분자/거친금속 계면의 파손에 대한 비교연구 II: 접착모델)

  • Lee Ho-Young;Kim Sung-Ryong
    • Korean Journal of Materials Research
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    • v.15 no.1
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    • pp.6-13
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    • 2005
  • Copper based leadframe sheets were immersed in two kinds of hot alkaline solutions to form brown-oxide or blackoxide layer on the surface. The oxide-coated leadframe sheets were molded with epoxy molding compound (EMC). After post mold curing, the oxide-coated EMC-leadframe joints were machined to form sandwiched double-cantilever beam (SDCB) specimens. The SDCB specimens were used to measure the fracture toughness of the EMC/leadframe interfaces under quasi-Mode I loading conditions. After fracture toughness testing, the fracture surface were analyzed by various equipment to investigate failure path. An adhesion model was suggested to explain the failure path formation. The adhesion model is based on the strengthening mechanism of fiber-reinforced composite. The present paper deals with the introduction of the adhesion model. The explanation of the failure path with the proposed adhesion model was introduced in the companion paper.

High Speed Milling of Titanium Alloy (Ti 합금의 고속가공시 밀링특성에 관한 연구)

  • Chen, Ming;Lee, Young-Moon;Yang, Seung-Han;Jang, Seung-Il
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.5
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    • pp.34-39
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    • 2003
  • The paper will present chip formation mechanism and surface integrity generation mechanism based on the systematical experimental tests. Some basic factors such as the end milling cutter tooth number, cutting forces, cutting temperature, cutting vibration the chip status, the surface roughness, the hardness distribution and the metallographic texture of the machined surface layer are involved. The chip formation mechanism is typical thermal plastic shear localization at high cutting speed with less number of shear ribbons and bigger shear angle than that at low speed, which means lack of chip deformation. The high cutting speed with much more cutting teeth will be beneficial to the reduction of cutting forces, enlarge machining stability mot depression of temperature increment anti-fatigability as well as surface roughness. The burrs always exist both at low cutting speed and at high cutting speed. So the deburring process should be arranged for milling titanium alloy in my case.

Effect of Die Machining Method on the Surface of Die Steel STD11 (금형가공방법이 합금공구강 표면에 미치는 영향)

  • Kim Sei-Hwan;Chio Kye-Kwang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.6 no.5
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    • pp.391-395
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    • 2005
  • This paper has comparatively analyzed the characteristics of the machined surface of a specimen made by machining Die Steel STD11 and a specimen obtained by W-EDM steel. If a press die is manufactured through W-EDM, products of shapes that cannot easily be made through machining can be manufactured easily. However, the life of the press die is significantly reduced compared with the press die made through machining. This is believed to be caused by the deformed layer that has occurred on the surface of the press die that was made through W-EDM. The roughness of the 2 specimens was measured, and it was learned that the distribution of the roughness of the specimen made through the 1st W-EDM was rough. When the specimens were observed using a scanning-electron microscope, there was significant difference between the surface and the cross-section of the 2 specimens, while the cross section of the specimen obtained through W-EDM had the tempered and quenched surface structure which exists in the form of a deformed layer.

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Study on the Effect of Thermal Property of Metals in Ultrasonic-Assisted Laser Machining (초음파 원용 레이저 가공에서 재료의 열적 물성이 표면상태에 미치는 영향에 관한 연구)

  • Lee, Hu Seung;Kim, Gun Woo;Park, Jong Eun;Yang, Min Yang;Cho, Sung Hak;Park, Jong Kweon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.8
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    • pp.759-763
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    • 2015
  • The laser machining process has been proposed as an advanced process for the selective fabrication of electrodes without a mask. In this study, we adapt laser machining to metals that have different thermal properties. Based on the results, the metals exhibit a different surface morphology, heat-affected zone (HAZ), and a recast layer around the machined surface according to their thermal conductivity, boiling point, and thermal diffusivity. Then, we apply ultrasonic-assisted laser machining to remove the recast layer. The ultrasonic-assisted laser machining exhibits a better surface quality in metals with higher diffusivity than those having lower diffusivity.

RESPONSE OF OSTEOBLASI-LIKE CELLS ON TITANIUM SURFACE TREATMENT

  • Roh Hyun-Ki;Heo Seong-Joo;Chang Ik-Tae;Koak Jai-Young;Han Jong-Hyun;Kim Yong-Sik;Yim Soon-Ho
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.6
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    • pp.699-713
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    • 2003
  • Statement of problem. Titanium is the most important material for biomedical and dental implants because of their high corrosion resistance and good biocompatibility. These beneficial properties are due to a protective passive oxide film that spontaneously forms on the surface. Purpose. The purpose of this study was to evaluate the responses of osteoblast-like cells on different surface treatments on Ti discs. Material and Methods. Group 1 represented the machined surface with no treatment. Group 2 surfaces were sandblasted with $50{\mu}m\;Al_2O_3$ under $5kgf/cm^2$ of pressure. Groups 3 and 4 were sandblasted under the same conditions. The samples were treated on a titanium oxide surface with reactive sputter depositioning and thermal oxidation at $600^{\circ}C$ (Group 3) and $800^{\circ}C$ (Group 4) for one hour in an oxygen environment. The chemical composition and microtopography were analyzed by XRD, XPS, SEM and optical interferometer. The stability of $TiO_2$ layer was studied by petentiodynamic curve. To evaluate cell response, osteoblast extracted from femoral bone marrow of young adult rat were cultured for cell attachment, proliferation and morphology on each titanium discs. Results and Conclusion. The results were as follows : 1. Surface roughness values were, from the lowest to the highest, machined group, $800^{\circ}C$ thermal oxidation group, $600^{\circ}C$ thermal oxidation group and blasted group. The Ra value of blasted group was significantly higher than that of $800^{\circ}C$ thermal oxidation group (P=0.003), which was not different from that of $600^{\circ}C$ thermal oxidation group (P<0.05). 2. The degree of cell attachment was highest in the $600^{\circ}C$ thermal oxidation group after four and eight hours (P<0.05), but after 24 hours, there was no difference among the groups (P>0.05). 3. The level of cell proliferation showed no difference among the groups after one day, three days, and seven days (P>0.05). 4. The morphology and arrangement of the cells varied with surface roughness of the discs.

Failure Path of the Brown-oxide-coated Copper-based Leadframe/EMC Interface under Mixed-Mode Loading (혼합하중 조건하에서 갈색산화물이 입혀진 구리계 리드프레임/EMC 계면의 파손경로)

  • 이호영
    • Journal of the Korean institute of surface engineering
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    • v.36 no.6
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    • pp.491-499
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    • 2003
  • Copper-based leadframe sheets were oxidized in a hot alkaline solution to form brown-oxide layer on the surface and molded with epoxy molding compound (EMC). The brown-oxide-coated leadframe/EMC joints were machined to form sandwiched double-cantilever beam (SDCB) specimens and sandwiched Brazil-nut (SBN) specimens for the purpose of measuring the fracture toughness of leadframe/EMC interfaces. The SDCB and the SBN specimens were designed to measure the fracture toughness of the leadframe/EMC interfaces under nearly mode-I loading and mixed-mode (mode I + mode II) loading conditions, respectively. Fracture surfaces were analyzed by various equipment such as glancing-angle XRD, SEM, AES, EDS and AFM to elucidate failure path. Results showed that failure occurred irregularly in the SDCB specimens, and oxidation time of 2 minutes divided the types of irregular failures into two classes. The failure in the SBN specimens was quite different from that in the SDCB specimens. The failure path in the SBN specimens was not dependent on the phase angle as well as the distance from tips of pre-cracks.

Determination of Electrode Potential in Micro Electrochemical Machining of Stainless Steel (스테인리스강의 미세 전해 가공 시 전극 전위의 선정)

  • Park B.J.;Chu C.N.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.1281-1284
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    • 2005
  • In the micro electrochemical machining (ECM), unfavorable oxide/passive layer formation and overall corrosion of electrodes must be prevented. Generally, the stainless steel electrode corrodes, passivates or dissolves in the electrochemical cell according to the electrode potential. Therefore, the electrode must maintain stable potential. The stable electrode potentials of tool and workpiece were determined with the potentiodynamic polarization test and verified experimentally from the point of machining stability and machined surface quality.

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A Study on the Fabrication of Sub-Micro Mold for PDMS Replica Molding Process by Using Hyperfine Mechanochemical Machining Technique (기계화학적 극미세 가공기술을 이용한 PDMS 복제몰딩 공정용 서브마이크로 몰드 제작에 관한 연구)

  • 윤성원;강충길
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.351-354
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    • 2004
  • This work presents a simple and cost-effective approach for maskless fabrication of positive-tone silicon master for the replica molding of hyperfine elastomeric channel. Positive-tone silicon masters were fabricated by a maskless fabrication technique using the combination of nanoscratch by Nanoindenter ⓡ XP and XOH wet etching. Grooves were machined on a silicon surface coated with native oxide by ductile-regime nanoscratch, and they were etched in a 20 wt% KOH solution. After the KOH etching process, positive-tone structures resulted because of the etch-mask effect of the amorphous oxide layer generated by nanoscratch. The size and shape of the positive-tone structures were controlled by varying the etching time (5, 15, 18, 20, 25, 30 min) and the normal loads (1, 5 mN) during nanoscratch. Moreover, the effects of the Berkovich tip alignment (0, 45$^{\circ}$) on the deformation behavior and etching characteristic of silicon material were investigated.

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