The Experts below are selected from a list of 212685 Experts worldwide ranked by ideXlab platform

Inhyu Choi - One of the best experts on this subject based on the ideXlab platform.

  • Micro Surface phenomenon of ductile cutting in the ultrasonic vibration cutting of optical plastics
    Journal of Materials Processing Technology, 1997
    Co-Authors: Jeongdu Kim, Inhyu Choi
    Abstract:

    Abstract Mirror-Surface machining is a very important technology in the manufacturing of precision parts, especially optical parts. At the present time these are parts produced by multi-processes, i.e. grinding and polishing, which are inefficient. In this study, ultrasonic vibration cutting as a substitute for such processes in the precision machining of optical plastics (CR-39) which have been used for optical lenses is suggested and experimented upon. To analyze the characteristics of Surfaces machined by ultrasonic vibration cutting in the ductile mode, wavelength spectrum analysis is carried out and the Micro-structure is compared with that of conventional cutting. As a result, in Micro cutting by ultrasonic vibration, it was confirmed that Surfaces of ductile cutting are obtained, for depths of cut of less than 2.7 μm.

Lijun Yang - One of the best experts on this subject based on the ideXlab platform.

  • a comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil
    European Transactions on Electrical Power, 2009
    Co-Authors: Ruijin Liao, Shuaiwei Liang, Lijun Yang
    Abstract:

    Aging of two kinds of transformer insulation paper in natural ester is compared to that in conventional transformer oil (mineral oil). Sealed aging vessels containing copper, insulation paper (Kraft paper and thermally upgraded paper), and dielectric fluid (mineral oil and natural ester) were aged at 90, 110, and 130°C for 399, 371, and 329 days. Under the same aging condition, both the degree of polymerization (DP) and the leveling-off degree of polymerization (LODP) for natural ester aged paper were higher than the ones for mineral oil aged paper, and the Micro Surface of natural ester aged paper was destroyed less seriously than that of the mineral oil aged paper. The aging time to reach LODP for natural ester aged paper was only 1/4 to 2/3 of that for mineral oil aged paper. When water content in natural ester for natural ester aged Kraft paper samples reached the maximum, acids concentration in natural ester increased abruptly. Water content in natural ester decreased in the whole aging process for natural ester aged thermally upgraded paper samples. Six physical and chemical mechanisms for the slower aging rate of natural ester aged paper are proposed. Evidence for transesterification between natural ester and paper was presented with infrared spectra instrument. Although the acids in natural ester were far more than in mineral oil, the natural ester can significantly slow the thermal aging of the paper. Three mechanisms of this abnormal phenomenon were presented. Copyright © 2009 John Wiley & Sons, Ltd.

  • a comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil
    European Transactions on Electrical Power, 2009
    Co-Authors: Ruijin Liao, Shuaiwei Liang, Lijun Yang
    Abstract:

    Aging of two kinds of transformer insulation paper in natural ester is compared to that in conventional transformer oil (mineral oil). Sealed aging vessels containing copper, insulation paper (Kraft paper and thermally upgraded paper), and dielectric fluid (mineral oil and natural ester) were aged at 90, 110, and 130°C for 399, 371, and 329 days. Under the same aging condition, both the degree of polymerization (DP) and the leveling-off degree of polymerization (LODP) for natural ester aged paper were higher than the ones for mineral oil aged paper, and the Micro Surface of natural ester aged paper was destroyed less seriously than that of the mineral oil aged paper. The aging time to reach LODP for natural ester aged paper was only 1/4 to 2/3 of that for mineral oil aged paper. When water content in natural ester for natural ester aged Kraft paper samples reached the maximum, acids concentration in natural ester increased abruptly. Water content in natural ester decreased in the whole aging process for natural ester aged thermally upgraded paper samples. Six physical and chemical mechanisms for the slower aging rate of natural ester aged paper are proposed. Evidence for transesterification between natural ester and paper was presented with infrared spectra instrument. Although the acids in natural ester were far more than in mineral oil, the natural ester can significantly slow the thermal aging of the paper. Three mechanisms of this abnormal phenomenon were presented. Copyright © 2009 John Wiley & Sons, Ltd.

  • thermal aging Micro scale analysis of power transformer pressboard
    IEEE Transactions on Dielectrics and Electrical Insulation, 2008
    Co-Authors: Ruijin Liao, Lijun Yang, Chao Tang, S Grzybowski
    Abstract:

    In order to analyze the thermal aging mechanism of the insulation paper inside the power transformer, a series of accelerated thermal aging tests were performed on pressboard. Subsequently, the atomic force Microscope (AFM) together with scanning electron Microscope (SEM) and X-ray diffraction (X-RD) were utilized to observe the Micro Surface of the thermal-aged pressboard. The experiments and analysis indicate that either the links among the D-glucopyranose units or the hexagonal mesh structures of the D-glucopyranose units were broken under thermal stress; the number of D-glucopyranose units after 6 weeks of aging was 0.8-1 per nm2, only about one third of un-aged value. The wall of a cellulose cell was deteriorated and thinned by thermal stress. At the same time, the cracks expanded gradually on the Surface of the cellulose, which shortened the average width of cellulose fiber from about 40 mu of un-aged sample to about 25 mu after 6 weeks of aging. Meanwhile, the relative crystallinity and the size of the crystallite in the pressboard decreased nonlinearly with the thermal aging time.

R W Schultz - One of the best experts on this subject based on the ideXlab platform.

  • macro and Micro Surface engineering to improve hot roll bonding of aluminum plate and sheet
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
    Co-Authors: Jiantao Liu, Simon Sheu, M E Karabin, R W Schultz
    Abstract:

    Abstract Hot roll bonding of aluminum plate and sheet currently is the primary manufacturing method of fuselage skin sheet for aircraft and brazing sheet for automotive applications. Tremendous challenges and opportunities exist to improve quality and productivity of these products. This work explored the effects of macro- and Micro-Surface engineering on hot roll bonding process. It was found that Micro-Surface engineering yielded better bonding quality than macro-Surface engineering did. The critical Surface roughness of the core was about 0.58 μm below which bonding quality in terms of area contact and bonding energy can be significantly improved. However, no marked improvement was observed when the Surface roughness was reduced further to 0.03 μm. Also, the oxide layer on the Surface of the core and local deformation on the Surface of liner played a very important role. Ultrasonic test and roller peel test were employed to assess the bonding strength and quality. The quantitative ultrasonic test results are in good agreement with the roller peel test results.

Izhak Etsion - One of the best experts on this subject based on the ideXlab platform.

  • Improving Tribological Performance of Mechanical Components by Laser Surface Texturing
    Tribology Letters, 2004
    Co-Authors: Izhak Etsion
    Abstract:

    Significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components can be obtained by forming regular Micro-Surface structure in the form of Micro-dimples on their Surfaces. A feasibility study was performed both theoretically and experimentally using the Laser Surface Texturing (LST) technique to produce the Micro-dimples. Each Micro-dimple can serve either as a Micro-hydrodynamic bearing in cases of full or mixed lubrication or as a Micro-reservoir for lubricant in cases of starved lubrication conditions. Theoretical models were developed, and laboratory tests were performed, to investigate the potential of LST in tribological components like mechanical seals, piston rings and thrust bearings. In the entire laboratory tests, friction was substantially reduced with LST compared to the non-textured components.

  • experimental investigation of laser Surface texturing for reciprocating automotive components
    Tribology Transactions, 2002
    Co-Authors: Grigory Ryk, Yuri Kligerman, Izhak Etsion
    Abstract:

    An experimental study is presented to evaluate the effectiveness of Micro-Surface structure, produced by laser texturing, to improve tribological properties of reciprocating automotive components. The test rig and test specimens are described and some test results are presented. Good correlation is found with theoretical prediction of friction reduction on a simple, yet representative, test specimen. Potential benefit of the laser Surface texturing under conditions of lubricant starvation is also presented. Finally, friction reduction with actual production piston rings and cylinder liner segments is demonstrated. Presented at the 57th Annual Meeting in Houston, Texas May 19–23, 2002

  • friction reducing Surface texturing in reciprocating automotive components
    Tribology Transactions, 2001
    Co-Authors: Aviram Ronen, Izhak Etsion, Yuri Kligerman
    Abstract:

    A model is presented to study the potential use of Micro-Surface structure in the form of Micro pores to improve tribological properties of reciprocating automotive components. The Reynolds equation and the equation of motion are solved simultaneously for a simplified “piston/cylinder” system with Surface texturing. The solution provides the time behavior of both the clearance and the friction force between the “piston ring” and “cylinder liner” Surfaces. It is shown that Surface texturing can efficiently be used to maintain hydrodynamic effects even with nominally parallel Surfaces. It is also shown that optimum Surface texturing may substantially reduce the friction losses in reciprocating automotive components. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001

Ruijin Liao - One of the best experts on this subject based on the ideXlab platform.

  • a comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil
    European Transactions on Electrical Power, 2009
    Co-Authors: Ruijin Liao, Shuaiwei Liang, Lijun Yang
    Abstract:

    Aging of two kinds of transformer insulation paper in natural ester is compared to that in conventional transformer oil (mineral oil). Sealed aging vessels containing copper, insulation paper (Kraft paper and thermally upgraded paper), and dielectric fluid (mineral oil and natural ester) were aged at 90, 110, and 130°C for 399, 371, and 329 days. Under the same aging condition, both the degree of polymerization (DP) and the leveling-off degree of polymerization (LODP) for natural ester aged paper were higher than the ones for mineral oil aged paper, and the Micro Surface of natural ester aged paper was destroyed less seriously than that of the mineral oil aged paper. The aging time to reach LODP for natural ester aged paper was only 1/4 to 2/3 of that for mineral oil aged paper. When water content in natural ester for natural ester aged Kraft paper samples reached the maximum, acids concentration in natural ester increased abruptly. Water content in natural ester decreased in the whole aging process for natural ester aged thermally upgraded paper samples. Six physical and chemical mechanisms for the slower aging rate of natural ester aged paper are proposed. Evidence for transesterification between natural ester and paper was presented with infrared spectra instrument. Although the acids in natural ester were far more than in mineral oil, the natural ester can significantly slow the thermal aging of the paper. Three mechanisms of this abnormal phenomenon were presented. Copyright © 2009 John Wiley & Sons, Ltd.

  • a comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil
    European Transactions on Electrical Power, 2009
    Co-Authors: Ruijin Liao, Shuaiwei Liang, Lijun Yang
    Abstract:

    Aging of two kinds of transformer insulation paper in natural ester is compared to that in conventional transformer oil (mineral oil). Sealed aging vessels containing copper, insulation paper (Kraft paper and thermally upgraded paper), and dielectric fluid (mineral oil and natural ester) were aged at 90, 110, and 130°C for 399, 371, and 329 days. Under the same aging condition, both the degree of polymerization (DP) and the leveling-off degree of polymerization (LODP) for natural ester aged paper were higher than the ones for mineral oil aged paper, and the Micro Surface of natural ester aged paper was destroyed less seriously than that of the mineral oil aged paper. The aging time to reach LODP for natural ester aged paper was only 1/4 to 2/3 of that for mineral oil aged paper. When water content in natural ester for natural ester aged Kraft paper samples reached the maximum, acids concentration in natural ester increased abruptly. Water content in natural ester decreased in the whole aging process for natural ester aged thermally upgraded paper samples. Six physical and chemical mechanisms for the slower aging rate of natural ester aged paper are proposed. Evidence for transesterification between natural ester and paper was presented with infrared spectra instrument. Although the acids in natural ester were far more than in mineral oil, the natural ester can significantly slow the thermal aging of the paper. Three mechanisms of this abnormal phenomenon were presented. Copyright © 2009 John Wiley & Sons, Ltd.

  • thermal aging Micro scale analysis of power transformer pressboard
    IEEE Transactions on Dielectrics and Electrical Insulation, 2008
    Co-Authors: Ruijin Liao, Lijun Yang, Chao Tang, S Grzybowski
    Abstract:

    In order to analyze the thermal aging mechanism of the insulation paper inside the power transformer, a series of accelerated thermal aging tests were performed on pressboard. Subsequently, the atomic force Microscope (AFM) together with scanning electron Microscope (SEM) and X-ray diffraction (X-RD) were utilized to observe the Micro Surface of the thermal-aged pressboard. The experiments and analysis indicate that either the links among the D-glucopyranose units or the hexagonal mesh structures of the D-glucopyranose units were broken under thermal stress; the number of D-glucopyranose units after 6 weeks of aging was 0.8-1 per nm2, only about one third of un-aged value. The wall of a cellulose cell was deteriorated and thinned by thermal stress. At the same time, the cracks expanded gradually on the Surface of the cellulose, which shortened the average width of cellulose fiber from about 40 mu of un-aged sample to about 25 mu after 6 weeks of aging. Meanwhile, the relative crystallinity and the size of the crystallite in the pressboard decreased nonlinearly with the thermal aging time.