• Title/Summary/Keyword: strength, surface roughness

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A Study on the Characteristics of High-Tension Bolted Joints' Behavior due to Surface Condition (표면상태에 따른 고장력볼트 마찰이음부의 거동특성에 관한 연구)

  • Cho, Sun Kyu;Hong, Sung Wook
    • Journal of Korean Society of Steel Construction
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    • v.9 no.3 s.32
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    • pp.421-430
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    • 1997
  • In this study, the static and the fatigue tests were performed with high tension bolted joints, of which the surfaces were spread with inorganic zinc-primer after shot-blast, and milling surface, and steel-natural surface, difference of friction surface condition were examined by comparing the esults of tests. From the result of synthetical investigation of this study. it is proper that using the torque management method in order to introduce design axial force to blots, and the provision of specifications that initial axial forces must be 110% of design axial forces is proper. Decreasing ratio of axial forces to initial force is proportional to common lorgarithms of time progress, it converge constant value after 20 hours, and decreasing ratio is little related to the roughness of friction surface. Sliding coefficient of milling, spreading inorganic zinc-primer, just producting is great in order and sliding forces are dependent on the applied axial forces, but if the applied axial forces are great, sliding coefficient become small by a loss of roughness. So it is confirmed that relation between the applied axial forces and the sliding forces are not proportional linearly. From the result of estimation on fatigue strength, all specimens satisfy the specifications with B-grade and milling surface is lower than the others about 14% in fatigue strength because in milling surface lose the function of friction-types joints at lower number of cycles. From the result of eximination for the distribution area of compressive force, friction area near to inside bolt is wider in the direction of stress than near to outside. It is guessed that this situation occurs because outside bolts firstly change from the friction connection to the bearing connection.

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Al2O3 Coating on Transparent Polycarbonate Substrates for the Hard-coating Application (투명 폴리카보네이트 보호코팅을 위한 산화알루미늄 박막)

  • Kim, Hun;Nam, Kyoung-Hee;Jang, Dong-Su;Lee, Jung-Joong
    • Journal of Surface Science and Engineering
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    • v.40 no.4
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    • pp.159-164
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    • 2007
  • Transparent aluminum oxide films were deposited on polycarbonate (PC) substrates by inductively coupled plasma (ICP) assisted reactive sputtering. the oxygen flow rate was regulated by controlling the target voltage with a proportional integrate derivative controller. The PC substrate was treated with plasma prior to the deposition in order to the enhance the adhesive strength of the $Al_2O_3$ film. The characteristics of hardness, structure, density, transmittance, deposition rate, surface roughness and residual stress were investigated to estimate the possibility for the hard coating.

Analysis of the High Formability of Automotive Steel Sheets by the Surface Texturing Effect (자동차용 강판의 표면 텍스처링 효과에 따른 고성형성 연구)

  • Yoon, Seung-Chae;Lyo, In-Woong;Cho, Min-Haeng
    • Korean Journal of Metals and Materials
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    • v.50 no.1
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    • pp.8-12
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    • 2012
  • This study aims to analyze the formability property of surface texturing processed automotive steel sheet for improving the sheet forming property. In the paper, the effect of cavities fabricated using the laser surface texturing technique on automotive high strength steel sheets was studied. The frictional behavior of the sheet drawing is a function of interface parameters such as sheet surface roughness, holding force, contact pressure, etc. For these reasons, automotive steel researchers want to optimize the surface topography of automotive steel sheets in order to enhance the formability. Therefore, this study presents the behavior of deformation of a laser surface texturing steel sheet by considering the frictional operation during the deep drawing process.

Durability Evaluation of ER Fluids in Hydraulic Control Systems (유압제어시스템 적용을 위한 ER 밸브의 내구성 평가)

  • Kim, Do-Tae;Jang, Sung-Cheol
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.2
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    • pp.100-105
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    • 2007
  • Electro-rheological(ER) fluid and valve are fabricated and evaluated experimentally in its durability to utilize the hydraulic control systems for long term operation. The two-ports ER valve used in the experiment consist of twelve parallel multi-layer electrodes and provide a restriction to the passage of ER fluid because of the viscous pressure drop and a component induced by the electric field. The durability test of ER valve are performed by measuring the surface roughness of electrodes with variation of an electric field strength and test time(1000 or 1800min.). Also, the shear stress and shear rate are measured to evaluate the durability of ER fluid as function of time. After durability test, ER shear stress increases approximately proportional to the shear rate with applied electric field intensity, In the ER valve, the center line average height roughness(Ra) of copper electrode increases about 1.56 times and ten-point median height roughness(Rz) increases about 2.2 times after the durability test. An understanding of these durability is essential to predicting the service life of ER fluid and valves.

Effect of Intermediate Layer Coated Diamond Particles on Performance of Diamond Tool (다이아몬드 입자에 형성된 중간층이 다이아몬드 공구 성능에 미치는 영향)

  • Son, Kyung-Sik;Lee, Jung-Hoon;Choi, Yong-Je;Jung, Uoo-Chang;Chung, Won-Sub
    • Journal of Surface Science and Engineering
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    • v.46 no.5
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    • pp.216-222
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    • 2013
  • In order to improve the performance of electrodeposited diamond-nickel composite, surface modification of diamond particles was carried out using powder immersion reaction assisted coating (PIRAC). Titanium and chromium were selected as coating elements, which are known as carbide former. With respect to the powder elements, various phases were formed on diamond; metallic Ti and TiC for Ti powder, $Cr_3C_2$ for Cr powder, and TiC and $Cr_3C_2$ for Ti-Cr mixed powder. Surface modified diamond particle showed higher specific surface area, especially Ti coating induced considerable increase of specific surface area. The increase of specific surface area suggests increase of surface roughness, and that was confirmed by surface observation using FE-SEM. In addition, wear properties of diamond-nickel composite including surface modified diamonds were improved, and Ti coated diamond showed the highest performance. The wear property of diamond-nickel composite is dependent on adhesion strength between diamond particle and nickel layer. Therefore, surface modification of diamond particle by PIRAC increasing surface roughness is effective to improve the properties of diamond-nickel composite.

Evaluation of Shear Strength of Concrete Layers with Different Strength considering Interfacial Indentation (이종강도 부재간 연결면 조건에 따른 전단강도 평가)

  • Kang, Jae-Yoon;Park, Jong-Sup;Jung, Woo-Tai;Keum, Moon-Seoung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.8
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    • pp.449-455
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    • 2016
  • This study is a part of research to develop a steel-concrete hybrid girder using ultra high-performance concrete with a compressive strength of 80 MPa. To this end, the Eurocode design formula for the shear resistance developed in a concrete-to-concrete interface was examined for the interface between concrete layers of different strengths. To examine the effect of the surface roughness on the shear resistance, a push-out test was conducted on specimens while considering the parameters of the Eurocode design equation. The actual behavior was evaluated with respect to the compressive strength of the concrete, the reinforcement ratio of the shear rebar, and the interfacial surface condition. The specimen with a rough interface shows 20-50% higher shear strength than that estimated by the design equation. In the case of failure mode, abrupt failure tends to occur at the interface of the concrete layer for the specimen with a low reinforcement ratio. It is expected that the shear strength of the concrete layer will increase according to the strength differential in the concrete layers.

A Study on Mechanical Properties and Microstructure of Local-Hardening Heat-Treated Automotive Panel (국부 경화 열처리된 차체 부품의 기계적 성질과 미세조직에 관한 연구)

  • Lee, Jae Ho;Jeong, Woo Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.23 no.6
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    • pp.301-308
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    • 2010
  • A steel with chemical composition, 0.22% C, 0.25% Si, 1.26% Mn, 0.22% Cr, 0.04% Ti, 0.0042% B, and a microstructure of ferrite and spheroidized cementite has been press-formed to automotive center pillar followed by local-hardening heat-treatment. Hardness, tensile properties, fractography, microstructure and surface roughness of local-hardening heat-treated automotive center pillar have been examined. The directly heated and quenched area had fully martensitic structure with Vickers hardenss in the range of 500 to 510. The heat affected area close to the directly heated area showed dual-phase structure of ferrite and martensite. The width of the heat-treated and heat-affected areas after the local-hardening heat treatment was ranging from 32 mm to 50 mm. The surface of the local-hardening heat-treated center pillar revealed some temper color as a consequence of the oxidation during the heat treatment, but the surface roughness was not affected by the local-hardening heat treatment.

A Study on the Comparison Mechanical Properties of 3D Printing Prototypes with Laminating Direction (3D 프린팅 방식의 적층방향에 따른 시제품의 기계적 특성 비교에 관한 연구)

  • Park, Chan;Kim, Myung Hun;Hong, Sung Moo;Go, Jeung Sang;Shin, Bo Sung
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.24 no.3
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    • pp.334-341
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    • 2015
  • This paper summarizes the results of an investigation into the environmental factors that have an indirect impact on parts quality, as well as those process variables and modeling information that have a direct impact. The effects of strength, surface hardness, roughness, and accuracy of shape, that is, qualities that users generally need to know, were evaluated with laminating direction experimentally. The 3D printing methods used in this experiment were fused deposition modeling (FDM), stereolithography apparatus (SLA), selective laser sintering (SLS), 3D printing (3DP) and laminated object manufacturing (LOM). The goal was to achieve a high standard of quality control and product quality by optimizing the fabrication process.

Evaluation of Micro End-Milling Characteristics of AlN-hBN Composites Sintered by Hot-Pressing (열간가압소결에 의해 제조된 AlN-hBN 복합재료의 마이크로 엔드밀링 가공특성 평가)

  • Baek, Si-Young;Cho, Myeong-Woo;Seo, Tae-Il
    • Korean Journal of Metals and Materials
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    • v.46 no.6
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    • pp.390-401
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    • 2008
  • The objective of this study is to evaluate various machining characteristics of AlN-hBN machinable ceramics in micro end-milling process for its further application. First, AlN based machinable ceramics with hBN contents in the range of 10 to 20vol% were prepared by hot-pressing. Material properties of the composites, such as relative density, Vickers hardness, flexural strength, Young's modulus and fracture toughness were measured and compared. Then, micro end-milling experiments were performed to fabricate micro channels using prepared system. During the process, cutting forces, vibrations and AE signals were measured and analyzed using applied sensor system. Machined micro channel shapes and surface roughness were measured using 3D non-contact type surface profiler. From the experimental results, it can be observed that the cutting forces, vibrations and AE signal amplitudes decreased with increasing hBN contents. Also, measured surface roughness and profiles were improved with increasing hBN contents. As a result of this study, optimum machining conditions can be determined to fabricate desired products with AlN-hBN machinable ceramics based on the experimental results of this research.

Die-sinking Electrical Discharge Machining with Ultrasonic Emission for Ceramic Matrix Composite (초음파 진동 부가에 의한 세라믹 복합체의 형조방전가공)

  • Wang, Duck-Hyun;Woo, Jeong-Yun;Yun, Jon-Do
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.8
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    • pp.9-15
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    • 1999
  • Die-sinking electrical discharge machining(EDM) for conductive ceramic matrix composite(CMC) of Tic/$Al_2O_3$ was experienced with addition of ultrasonic emission, and the results were compared with ones obtained by the EDM only. From this experimental study, the values of material removal rate(MRR) and surface roughness($R_{max}$), scanning electron microscope(SEM) micrographs, and weibull probability distribution of bending strength for the specimens were obtained and compared. The trend of MRR was found to be increased slightly with the current and the duty factor for both EDM only and EDM with ultrasonic emission. The MRR values were found to be increased for EDM with ultrasonic emission. The SEM micrographs of EDMed surface by under various operating conditions showed less micro cracks in various places. Although smaller bending strength value was obtained by EDMed surface with ultrasonic emission by weibull probability distribution analysis of bending strength.

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