Huang, Weihai

写真a

Affiliation

Graduate School of Science and Technology （Yagami）

Position

Researcher (Non-tenured) / Project Researcher(Non-tenured)
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Papers 【 Display / hide 】

  • Investigation of failure modes and material structural responses of nanographite coatings on single-crystal silicon by nanoscratching

    Brüssel F., Huang W., Yan J.

    Tribology International 193 2024.05

    ISSN  0301679X

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    The failure modes of a nanographite-on-silicon system and the effects of the coating on the load-induced phase transformation of the silicon substrate were investigated using a series of nanoscratching tests with a spherical diamond indenter. The critical normal load for the failure of the nanographite coating was determined based on the thickness of the coating. When the load increased beyond the critical point, cracks, press spallation, and lift spallation were observed, and the silicon substrate underwent a phase transformation from the original crystalline phase to a mixture of amorphous, Si-III and Si-XII phases. For a thin coating, the silicon substrate was free of phase transformation owing to the coating protection. These findings provide guidance for glass molding and other applications.

  • Surface conditioning of zirconia ceramic by enhanced ultrasonic vibration-assisted burnishing

    Tsuchida T., Huang W., Yan J.

    Production Engineering 18 （ 2 ） 353 - 366 2024.04

    ISSN  09446524

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    Yttria-stabilized zirconia (YSZ) ceramic is a widely used material in mechanical and biomedical engineering, such as machine parts and dental implants. For most applications, surface conditioning methods are required to produce smooth and reinforced surfaces with compressive residual stress. This paper investigates the processing characteristics of YSZ under ultrasonic vibration-assisted burnishing (UVB) enhanced by flexible stage and tool rotation techniques, respectively. For the use of flexible stage-enhanced UVB, the fluctuation of burnishing force was greatly reduced. As results, a smooth surface with a roughness of 164 nm Ra was obtained, which shows 39.7% surface roughness reduction from the original surface, and 9.4% surface roughness reduction from the surface burnished with conventional UVB. The burnished surface yielded strong residual compressive stresses of 401 MPa in the burnishing direction and 695 MPa in the step-feed direction. For the use of tool rotation-enhanced UVB, tool rotation-induced arc-shaped surface textures were formed on the burnished surface, and the textures became more distinct and denser as the rotation speed increased. The surface roughness was reduced by 58.9% from the original surface with the tool rotation-enhanced UVB. Stress-induced phase transformation of YSZ was identified in all burnished surfaces. This study demonstrates the feasibility of one-step manufacturing of a smooth surface with high residual compressive stress, which expands the applications of YSZ.

  • Influences of tool tip geometry on surface/subsurface damage formation in nanoscratching of single-crystal 4H-SiC

    Huang W., Yan J.

    Procedia CIRP 123   185 - 190 2024

    ISSN  22128271

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    Creating a smooth surface finish with nanometer-scale roughness on SiC is extremely difficult due to its hard, brittle properties and crystal anisotropy. In this study, nanoscratching tests were performed on single-crystal 4H-SiC along various crystal directions by using a sharp Berkovich tip (radius ~150 nm) and a blunt spherical tip (radius ~1 μm), respectively, to reveal the effects of tool geometry on its surface integrity. Results indicate that, under the same load conditions, the Berkovich face-forward tip produced the greatest penetration depth, followed by the Berkovich edge-forward tip and the spherical tip. The extent of surface and subsurface damage caused by the three tips follows the same trend as the penetration depth. Phase transformation did not occur in the scratched surface with the three tips, while it was occurred in the chips generated with Berkovich face-forward tip. The critical load for surface crack formation was larger when scratching along <01−10> directions compared to scratching along <11−20> directions, independent of tool geometry. Microcrack-like defects may form in the subsurface even the surface is free of damage. The microcracks were caused by {01−11} pyramidal <a> and <a+c> slip and by {11−22} pyramidal <c+a> slip when scratching along <11−20> and <01−10> directions, respectively.

  • Fabrication of microlens arrays on single-crystal CaF<inf>2</inf> by ultraprecision diamond turning

    Huang W., Nagayama K., Yan J.

    Journal of Materials Processing Technology 321 2023.12

    ISSN  09240136

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    Single-crystal calcium fluoride (CaF2) is considered a superior optical material with good transmittance in a wide transmitted wavelength region. However, the production of high surface quality freeform surfaces on CaF2 is difficult owing to its soft, brittle, and anisotropic properties. This study attempted to fabricate spherical and hexagonal microlens arrays on CaF2 using diamond turning with a slow tool servo. In addition, the machining characteristics of CaF2 were systematically investigated. It was found that microcracks tended to be generated in the cut-in and cut-out regions of the lenses. When cutting along the [− 211] and [11 − 2] directions, the machined surfaces were very prone to cracking. When reducing the maximum undeformed chip thickness to less than approximately 60 nm, continuous ribbon-like chips were formed throughout the cutting process, and all lenses were machined in ductile mode without surface cracking. In addition, a spherical microlens array was successfully fabricated in ductile mode with a surface roughness of approximately 2 nm Sa. Consequently, a hexagonal microlens array with sharp edges and crack-free surfaces was achieved using the proposed depth-offsetting segment cutting method. The surface roughness was approximately 4.1 nm Sa with a form error of approximately 147 nm P-V (peak to valley). Tool wear was insignificant until a machining distance of approximately 50 m; however, with further increase in the machining distance, crater wear and microchipping were observed. This study demonstrated the feasibility of fabricating high-quality freeform microstructured surfaces on CaF2 and other soft-brittle materials via diamond turning.

  • Mechanisms of tool-workpiece interaction in ultraprecision diamond turning of single-crystal SiC for curved microstructures

    Huang W., Yan J.

    International Journal of Machine Tools and Manufacture 191 2023.10

    ISSN  08906955

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    Single-crystal silicon carbide (SiC) is one of the most attractive materials for electronics and optics but extremely difficult to cut owing to its hard and brittle properties. While in previous studies, the focus has been placed on machining flat surfaces, in this study, the mechanisms of tool-workpiece interaction in cutting curved microstructures on 4H–SiC (0001) were explored through the ultraprecision diamond turning of micro-dimples. The surface/subsurface of both machined workpieces and used diamond tools were characterized, and the machining characteristics, such as chip formation and cutting forces, were also investigated. It was found that microcracks occurred easily in the feed-in/cut-in area of the dimples, which is caused by a large friction-induced tensile stress due to a large thrust force. The dimples located on the secondary cleavage directions <10−10> (S-dimples) were easy to produce crack-free surfaces, while the dimples located on the primary cleavage directions <−12−10> (P-dimples) were very prone to cause cracks on surfaces, even though the chips were formed in a ductile mode. The dimples located on the in-between direction (I-dimples) were moderately prone to surface cracking. It was also found that although the S-dimple has a crack-free surface, it has the thickest subsurface damage (SSD) layer containing a disordered layer, dislocations, and stacking faults; the SSD layer of the P- and I-dimples do not contain stacking faults; and the SSD layer of the I-dimple is the thinnest. Flank wear with nanoscale grooves on the diamond tool was significant without edge chipping and diamond graphitization detected. By optimizing the cutting conditions, a crack-free micro-dimple array was fabricated with nanometric surface roughness. The findings from this study provide guidance for the manufacture of curved SiC parts with high surface integrity, such as molds for replicating microlens arrays and other freeform surfaces on glass.

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Awards 【 Display / hide 】

  • FUJIWARA Award

    2022.03, Keio Univeristy Faculty of Science and Technology

    Type of Award： Keio commendation etc.

  • HEIDENHAIN Scholarships

    2021.06, European Society for Precision Engineering and Nanotechnology

    Type of Award： Award from international society, conference, symposium, etc.

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