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Papers - Yan, Jiwang

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Direct observation of discharging phenomena in vibration-assisted micro-electrical discharge machining

Shitara T., Fujita K., Yan J.

International Journal of Advanced Manufacturing Technology (International Journal of Advanced Manufacturing Technology) 108 ( 4 ) 1125 - 1138 2020

ISSN 02683768

© 2020, Springer-Verlag London Ltd., part of Springer Nature. It has been previously reported that electrical discharge machining (EDM) performance can be improved by tool electrode vibration. However, the mechanism of vibration-assisted EDM has not been clarified and the optimal vibration condition remains unknown due to the difficulty in direct process observation. In this study, direct observation of the EDM gap by using a high-speed video camera through a transparent workpiece electrode made of single-crystal 4H-SiC was attempted. It was found that tool vibration caused discharge dispersion and discharge frequency increase, and this tendency was more significant at higher amplitudes and higher frequencies. In addition, tool vibration-induced periodic discharge was observed, which prevented concentrated discharge and short-circuiting. Accordingly, the machining speed was improved and surface roughness was reduced. This study succeeded for the first time in observing the discharge behaviors in vibration-assisted EDM, thus revealed the effects of key parameters for process optimization.

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Surface formation behaviors in wavy microgroove cutting on various workpiece materials

Terabayashi T., Yan J.

International Journal of Automation Technology (International Journal of Automation Technology) 14 ( 2 ) 245 - 252 2020

ISSN 18817629

© 2020, Fuji Technology Press. All rights reserved. Functional films with multi-directional wavy microgrooves can be applied to reduce fluid drag in turbulent flow applications. For high-efficiency mass production of functional films through polymer imprinting, it is necessary to machine wavy microgrooves on the surfaces of metal roll molds. When wavy grooves are cut, to reduce the follow-up errors of machine tools, a very low cutting speed is normally used, but the mechanism of this cutting is still unclear. In this study, microgrooving experiments were conducted on three different workpiece materials: brass, oxygen free copper, and aluminum alloy, and their cutting mechanisms were investigated. Distinct differences in chip formation behavior and machined surface integrity were identified among these materials. Aluminum alloy was chosen as the most suitable material for roll mold fabrication. Two-directional wavy microgrooves with form accuracy on 1 µm level and surface roughness of less than 10 nm Ra were obtained.

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Influence of Wax Lubrication on Cutting Performance of Single-Crystal Silicon in Ultraprecision Microgrooving

Ameli Kalkhoran S.N., Vahdati M., Zhang Z., Yan J.

International Journal of Precision Engineering and Manufacturing - Green Technology (International Journal of Precision Engineering and Manufacturing - Green Technology) 8 ( 2 ) 611 - 624 2020

ISSN 22886206

© 2020, Korean Society for Precision Engineering. Lubrication can improve the tool-workpiece interface condition in ultraprecision machining, especially in microgrooving processes. The aim of this study was to compare the effects of dry, liquid (cutting oil), solid (wax) and hybrid (cutting oil and wax) lubrication conditions, on the creation of arc-sectioned microgrooves on single-crystal silicon wafers using a single-crystal diamond tool. Micro cutting forces, chip morphology, and surface quality at different locations of the grooves were investigated. Rose-shaped continuous chips were observed in dry cutting, indicating stable ductile mode material removal. The entrance side of the groove was always smoother than the exit side with a higher degree of phase transformation. Chip adhesions on the tool edge were found in dry and oil lubricated cutting, whereas wax coating could prevent the adhesion. Wax coating played the dual roles of a chip breaker as well as a high-performance lubricant, thus improved the surface integrity. This study demonstrated the capability of using wax coating as an environmentally friendly solid lubricant for microgrooving of single-crystal silicon and possibly for other hard brittle materials.

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Manufacturing of multiscale structured surfaces

Brinksmeier E., Karpuschewski B., Yan J., Schönemann L.

CIRP Annals (CIRP Annals) 69 ( 2 ) 717 - 739 2020

ISSN 00078506

© 2020 Multiscale structured surfaces are a way to provide advanced, otherwise not attainable functionality on a technical part. Applications of such parts can be manifold, and numerous works have already covered the transfer of natural examples into bio-inspired surfaces or the geometrical and functional metrology of such surfaces. After briefly presenting typical functionalities of multiscale structured surfaces, this keynote paper will focus on the available manufacturing processes and review their capabilities to generate multiscale structured surfaces. To compare such processes, the so-called “multiscality” is defined that characterizes the structured surfaces according to the lateral and vertical extent of the individual stacked elements and is used as a first indicator to assess the difficulty of their manufacture. As the boundaries of what is considered a multiscale structure are diffuse, ranges of low, medium and high multiscality are defined instead. After presenting the state of the art of manufacturing processes currently utilized for the manufacture of (not only multiscale) structured surfaces, this keynote paper summarizes the capabilities of single-step and multi-step/multi-physics approaches for their applicability across different scales and gives an outlook on which processes could potentially become relevant in the future.

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Measurement and compensation of tool contour error using white light interferometry for ultra-precision diamond turning of freeform surfaces

Nagayama K., Yan J.

International Journal of Automation Technology (International Journal of Automation Technology) 14 ( 4 ) 654 - 664 2020

ISSN 18817629

© 2020, Fuji Technology Press. All rights reserved. In ultra-precision diamond turning of freeform optics, it is necessary to obtain submicron-level form accuracy with high efficiency. In this study, we proposed a new method for the quick measurement and compensation of tool contour errors to improve the form accuracy of the workpiece. In this method, the nanometer-scale contour error of a diamond tool is quickly and precisely measured using a white light interferometer and then compensated for, before machining. Results showed that the contour of a diamond tool was measured with an error less than 0.05 μm peak-to-valley (P-V) and the feasibility of error compensation was verified through cutting experiments to create a paraboloid mirror and a microlens array. The form error decreased to 0.2 μm P-V regardless of the contour error of the diamond tools when cutting the paraboloid mirror, and that of the microlens array was reduced to 0.15 μm P-V during a single machining step.

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Surface modification of tungsten carbide cobalt by electrical discharge coating with quarry dust suspension

Yap C.Y., Liew P.J., Yan J.

International Journal of Advanced Manufacturing Technology (International Journal of Advanced Manufacturing Technology) 111 ( 7-8 ) 2105 - 2116 2020

ISSN 02683768

© 2020, Springer-Verlag London Ltd., part of Springer Nature. This study explores the feasibility of reusing waste quarry dust as a coating material for surface modification of tungsten carbide cobalt (WC-Co) using electrical discharge coating (EDC). The main objective is to investigate the effect of quarry dust suspension with different concentrations (0–40 g/l) on the characteristics of coated surface such as coating layer thickness, coating element composition and chemical compound, surface morphology, surface roughness and Vickers micro-hardness. Before the EDC process, characterisation of the raw quarry dust was conducted through scanning electron microscopy, X-ray fluorescence and particle size analyser. The results showed that the coating layer thickness was strongly affected by the quarry dust concentration. The formation of hard carbides (SiC, Mg2C3, Fe2C and CaC2) and oxide phases (SiO2, Al2O3, Fe2O3, CaO, CoO and ZnO) in the coated layer due to material migration was confirmed through X-ray diffraction analysis. Vickers micro-hardness of the coated surface was improved significantly with the addition of quarry dust. The best surface finish without micropores and microcracks was obtained using a quarry dust concentration of 10 g/l. These results demonstrated the capability of recycling quarry dust as an environmentally friendly coating material for surface modification.

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New evidences for understanding the serrated flow and shear band behavior in nanoindentation of metallic glasses

Huang H., Jiang M., Yan J.

Journal of Alloys and Compounds (Journal of Alloys and Compounds) 857 2020

ISSN 09258388

© 2020 Elsevier B.V. Nanoindentation of a Zr-based metallic glass was performed under various loading rates by using a cube-corner indenter. Experimental results showed that increasing the loading rate from 2 to 20 mN/s, the size of serrated flow was greatly weakened, but the number of serrated flow kept very stable, together with very similar shear band features around the residual indents. These results challenge the current understanding derived from the results obtained by using the Berkovich indenter, and can be well explained by the shear-band propagation dynamics model, i.e., loading rate impeded the propagation of shear band rather than its nucleation.

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Effects of cyclic loading on subsurface microstructural changes of zirconia polycrystals in nanoscale mechanical processing

Kosai K., Yan J.

International Journal of Machine Tools and Manufacture (International Journal of Machine Tools and Manufacture) 159 2020

ISSN 08906955

© 2020 Elsevier Ltd Yttria stabilized zirconia (YSZ) is an attractive biomaterial with excellent properties, but its deformation mechanism under repetitive loads is still unclear. In this study, the subsurface microstructural changes of YSZ polycrystals under repetitive loading/unloading were investigated by multi-cyclic nanoindentation. Raman spectroscopy analysis revealed that a tetragonal-to-monoclinic (t-m) phase transformation occurred, and multi-cyclic indentation promoted this transformation significantly. Cross-sectional scanning transmission electron microscopy showed that monoclinic variants were extensively generated beneath the free surfaces outside the indent planes, whereas grain refinement was dominant beneath the indenter tip. In addition, load-displacement curve analysis demonstrated that the t-m phase transformation occurred during unloading rather than loading, and that the phase transformation-induced volume expansion caused an incremental change of residual indent depth. The extension of monoclinic variants was promoted by repetitive shear deformation, resulting in significant pileups, as detected by atomic force microscopy. The effect of sample surface preprocessing on indentation behaviors was also investigated. Microcracking and surface spalling were confirmed around the multi-cyclic indents made on a diamond-turned YSZ sample. Based on the experimental results, a model of subsurface microstructure distribution and evolution was established. The findings from this study help clarify the historical effects in subsurface damaging mechanism of brittle polycrystalline materials caused by cyclic tool-workpiece interactions in nanoscale mechanical processing.

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Softening and hardening on a Zr-based bulk metallic glass induced by nanosecond laser surface melting

Jiao Y., Brousseau E., Kosai K., Lunt A.J.G., Yan J., Han Q., Zhu H., Bigot S., He W.

Materials Science and Engineering A (Materials Science and Engineering A) 803 2020

ISSN 09215093

© 2020 Elsevier B.V. The study reported here confirms that laser surface melting (LSM) can be employed to modify the hardness and the shear banding behaviour of bulk metallic glasses (BMGs). More specifically, by conducting LSM operations on the Zr-based Vitreloy 105 BMG in ambient atmosphere using a nanosecond laser, it was found that surface hardening can be achieved, in addition to the well-known surface softening effect. Besides, it was found that the presence of compressive residual stress and an increased introduction of crystalline precipitates accompanied LSM-induced surface hardening. On the contrary, tensile residual stress and a reduced fraction of crystalline precipitates were observed for a softened surface post-LSM. Finally, differences in shear-banding mechanisms were detected near the surface of the laser irradiated regions. More specifically, overall reduced serrated flow but important surface shear bands events were observed following the LSM-based introduction of compressive residual stress. In contrast, more pronounced serrated flows and the likely distribution of shear banding activity well beneath the irradiated BMG surface was promoted when LSM resulted in the introduction of tensile residual stress.

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Laser induced micro-cracking of Zr-based metallic glass using 1011 W/m2 nano-pulses

H Huang, Y Qian, C Wang, J Yan

Materials Today Communications 25, 101554 2020

Distortion measurement of optical system using phase diffractive beam splitter

Wang F., Zhang Z., Wang R., Zeng X., Yang X., Lv S., Zhang F., Xue D., Yan J., Zhang X.

Optics Express (Optics Express) 27 ( 21 ) 29803 - 29816 2019.10

© 2019 Optical Society of America Traditional methods for distortion measurement of large-aperture optical systems are time-consuming and ineffective because they require each field of view to be individually measured using a high-precision rotating platform. In this study, a new method that uses a phase diffractive beam splitter (DBS) is proposed to measure the distortion of optical systems, which has great potential application for the large-aperture optical system. The proposed method has a very high degree of accuracy and is extremely economical. A high-precision calibration method is proposed to measure the angular distribution of the DBS. The uncertainty analysis of the factors involved in the measurement process has been performed to highlight the low level of errors in the measurement methodology. Results show that high-precision measurements of the focal length and distortion were successfully achieved with high efficiency. The proposed method can be used for large-aperture wide-angle optical systems such as those used for aerial mapping applications.

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Effect of the pillar size on the electrochemical performance of laser-induced silicon micropillars as anodes for lithium-ion batteries

Yang X., Tachikawa N., Katayama Y., Li L., Yan J.

Applied Sciences (Switzerland) (Applied Sciences (Switzerland)) 9 ( 17 ) 2019.09

© 2019 by the authors. Silicon micropillars with tunable sizes are successfully fabricated on copper foils by using nanosecond-pulsed laser irradiation and then used as anodes for lithium-ion batteries. The size of the silicon micropillars is manipulated by using different slurry layer thicknesses ranging from a few microns to tens of microns. The effects of the pillar size on electrochemical properties are thoroughly investigated. The smaller the pillars, the better the electrochemical performance. A capacity of 1647 mAh g-1 at 0.1 C current rate is achieved in the anode with the smallest pillars, with 1215, 892, and 582 mAh g-1 at 0.2, 0.5, and 1.0 C, respectively. Although a significant difference in discharge capacity is observed in the early period of cycling among micropillars of different sizes, this discrepancy becomes smaller as a function of the cycle number. Morphological studies reveal that the expansion of micropillars occurred during long-term cycling, which finally led to the formation of island-like structures. Also, the formation of a solid electrolyte interphase film obstructs Li+ diffusion into Si for lithiation, resulting in capacity decay. This study demonstrates the importance of minimizing the pillar size and optimizing the pillar density during anode fabrication.

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Improving the surface integrity of additive-manufactured metal parts by ultrasonic vibration-assisted burnishing

Teramachi A., Yan J.

Journal of Micro and Nano-Manufacturing (Journal of Micro and Nano-Manufacturing) 7 ( 2 ) 2019.06

ISSN 21660468

Copyright © 2019 by ASME. Metal additive manufacturing (AM) has been attracting attention as a new manufacturing method, but a surface finishing process is usually needed to improve the surface quality. As a new surface finishing process, ultrasonic vibration-assisted burnishing (UVAB) is promising. In this study, UVAB was performed on an additive-manufactured AlSi10Mg workpiece to improve its surface/subsurface integrity. The effects of ultrasonic vibration (UV) and lateral tool pass width on the burnishing performance were investigated. It was observed that the surface roughness, filling ratio, and hardness of the surface layer were simultaneously improved after burnishing. This study shows the effectiveness of applying UVAB to improve the surface quality of additivemanufactured products for various industrial uses.

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Manufacturing technologies toward extreme precision

Zhang Z., Yan J., Kuriyagawa T.

International Journal of Extreme Manufacturing (International Journal of Extreme Manufacturing) 1 ( 2 ) 2019.06

ISSN 26318644

© 2019 The Author(s). Published by IOP Publishing Ltd on behalf of the IMMT Precision is one of the most important aspects of manufacturing. High precision creates high quality, high performance, exchangeability, reliability, and added value for industrial products. Over the past decades, remarkable advances have been achieved in the area of high-precision manufacturing technologies, where the form accuracy approaches the nanometer level and surface roughness the atomic level. These extremely high precision manufacturing technologies enable the development of high-performance optical elements, semiconductor substrates, biomedical parts, and so on, thereby enhancing the ability of human beings to explore the macro- and microscopic mysteries and potentialities of the natural world. In this paper, state-of-the-art high-precision material removal manufacturing technologies, especially ultraprecision cutting, grinding, deterministic form correction polishing, and supersmooth polishing, are reviewed and compared with insights into their principles, methodologies, and applications. The key issues in extreme precision manufacturing that should be considered for future R&D are discussed.

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Ultra-precision cutting of roll molds having two-directional wavy microstructures

T. Terabayashi, J. Yan

Transactions of the JSME 85 ( 874 ) 1-18 2019.06

Research paper (scientific journal), Joint Work, Accepted

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Formation behavior of laser-induced periodic surface structures on stainless tool steel in various media

Kobayashi T., Wakabayashi T., Takushima Y., Yan J.

Precision Engineering (Precision Engineering) 57 244 - 252 2019.05

ISSN 01416359

© 2019 Elsevier Inc. The formation of laser-induced periodic surface structure (LIPSS) has been observed on various materials. As LIPSS can be used for modifying various surface properties such as wettability, tribology and optical performance, the control of the period and topography of LIPSS is an important issue. In this study, picosecond pulsed laser irradiation was performed on a stainless tool steel in various types of media including the air, water, sugar syrup (water and sucrose (C 12 H 22 O 11 )), decane (C 10 H 22 ), and ethanol (C 2 H 5 OH). Different surface morphologies were observed on the steel surface after laser irradiation, depending on the types of media. A strong relationship was identified between the period of LIPSS and the refractive index of liquid. In addition to the change of LIPSS period, complicated mesh patterns were formed on the surface irradiated in decane and ethanol, indicating the significant effect of thermal conductivity of the liquids on surface formation mechanisms. This study demonstrated the possibility of controlling the period and topography of LIPSS by using different media.

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Direct observations of multi-cyclic nanoindentation-induced phase transformations in single-crystal Ge

Kosai K., Yan J.

Materials Research Express (Materials Research Express) 6 ( 7 ) 2019.04

© 2019 IOP Publishing Ltd. Multi-cyclic nanoindentation experiments with various holding loads were carried out on single-crystal Ge to investigate pressure-induced phase transformation behaviors. Cross-sectional transmission electron microscopic observation and laser micro-Raman spectroscopy of the indents revealed various phase transformation behaviors at different holding loads. Distinctive phase transformation behaviors were observed under various loading and unloading conditions. With a low holding load, a broad phase transformed region containing r8-Ge phase and dislocations was generated. A middle holding load promoted twinning but limited phase transformations. On the other hand, a densely transformed region containing dc-Ge, a-Ge, r8-Ge and st12-Ge was widely formed at a high holding load. In addition, the calculation results of the average contact pressure in the last unloading step verified the occurrence of these phase transformations. By integrating these results, a path diagram for phase transformations of single-crystal Ge during multi-cyclic nanoindentation was established, which is useful for understanding the subsurface damage formation in mechanical processing of the material.

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Investigation on wear modes and mechanisms of abrasive belts in grinding of U71Mn steel

Z. He, J. Li, Y. Liu, J. Yan

The International Journal of Advanced Manufacturing Technology (International Journal of Advanced Manufacturing Technology) 101 ( 5-8 ) 1821 - 1835 2019.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 02683768

© 2018, Springer-Verlag London Ltd., part of Springer Nature. We investigated the wear modes and mechanisms of alumina grits during abrasive belt grinding of U71Mn steel under various normal forces and grinding speeds. Our approach consisted of an experimental procedure that produced sufficient wear followed by a resin-embedding method for observing the cross sections and topographies of grits. Statistics of wear modes and protrusion heights were calculated to visualize and quantify abrasive belt wear. The results demonstrated that different subsurface structures emerged inside the worn grits, and these structures were sensitive to process parameters. Transitions between abrasion and fracture wear modes were frequently observed. The effects of abrasive belt wear and process parameters on wear modes were clarified. The critical protrusion height of the abrasive belts for each wear mode of abrasive grits was experimentally determined.

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Fabrication of polycrystalline diamond three-dimensional structures by sinking EDM using carbon diffusion reaction

S. Kasai, T. Sodetai, J. Yan

Journal of the Japan Society of Electrical-machining Engineers 53 ( 132 ) 5 - 11 2019.03

Research paper (scientific journal), Joint Work, Accepted

Ultrasonic vibration-assisted microgrinding of glassy carbon

P. Beiring, J. Yan

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science) 233 ( 12 ) 1 - 11 2019.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 09544062

© IMechE 2019. Glassy carbon is an amorphous material which, due to its unique material properties, has recently been introduced to micro/nanoimprinting as mold substrates. However, since glassy carbon is a hard, brittle, and highly elastic material, the precision machining of micro/nanostructures on it remains a challenging task. In this research, ultrasonic vibration-assisted microgrinding was proposed for ductile machining of glassy carbon. To find suitable conditions, the effects of ultrasonic vibration assistance and tool inclination were investigated. The results showed that by utilizing ultrasonic vibration assistance and tool inclination, a ductile response was achieved with improved surface roughness. In addition, the periodical waviness of the groove edge due to material elastic recovery was successfully prevented. This study provided an insight into the kinematics in ultrasonic vibration-assisted grinding of a highly elastic, hard, and brittle material.

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