論文 - 閻　紀旺

A novel calibration method for angular misalignment in independently controlled fast tool servo-based diamond turning

Tanikawa S., Sato Y., Yan J.

Precision Engineering （Precision Engineering）  83   216 - 227 2023年06月

ISSN  01416359

　概要を見る

With significant technological progress in optics fields, such as VR and 3D sensing technologies, the demand for optical components with complex shapes (e.g., freeform surfaces) has expanded significantly in recent years. Ultra-precision diamond turning is one of the common manufacturing methods used for freeform optics. There are two tool-motion mechanisms for freeform diamond turning: slow tool servo (STS), which moves the entire tool rest, and fast tool servo (FTS), which only drives the diamond tool. In particular, high-frequency and long-stroke FTS units driven by a separate control system from the machine tool controller have recently been developed as a new trend in FTS-based diamond turning. However, this type of independent FTS control system causes a time delay between the machine tool instruction and the FTS tool motion. Even a millisecond-scale time delay can cause a considerable angular misalignment owing to the high rotation rate of the spindle, resulting in a micron-scale form error on the workpiece surface. In this paper, a novel method for precisely measuring the time delay from the machined workpiece surface and compensating for the misalignment based on the measured time delay was proposed. To measure the time delay, spherical dimples were machined on the workpiece surface by using STS and FTS. Subsequently, the angular misalignment and time delay were obtained by comparing the measured surface profiles at specific positions of the spherical dimples. Thus, the time delay can be measured with microsecond-scale accuracy. Based on the measured time delay, the shifted tool position along the spindle axis by the time delay was compensated to the ideal tool position by considering the cutting velocity. Consequently, the angular misalignment was completely eliminated, and submicron-level form accuracy was achieved. This calibration method of angular misalignment for an independent FTS unit is expected to significantly improve the accuracy of ultra-precision machining of freeform optics.

• Access to Document (DOI)

Tailoring the surface characteristic of metallic glass for wettability control

Qian Y., Liu H., Zhang L., Jiang M., Huang H., Yan J.

Journal of Materials Research and Technology （Journal of Materials Research and Technology）  24   7040 - 7046 2023年05月

ISSN  22387854

　概要を見る

Bulk metallic glasses (BMGs) have attracted broad research interest in industrial and commercial fields due to their outstanding mechanical and physical properties. Achieving controlled manipulation of their surface wettability is expected to further improve their applicability. In this study, the functional MG surfaces with various wetting behaviors (including superhydrophilicity, superhydrophobicity, gradient wettability, coexistence of superhydrophilicity and superhydrophobicity) were fabricated by controlling the surface microstructure and chemical composition, which were achieved by laser processing and low-temperature heat treatment. The laser-patterned MG surface with hierarchical micro/nanostructures showed hydrophilicity, and it turned to hydrophobicity after heat treatment, which could be attributed to the adsorption of organic matter from the ambient air. The fabricated gradient wetting surface achieved directional transport of droplets, and the constructed extreme wetting contrast surface exhibited good ability in controlling the spreading of droplets.

• Access to Document (DOI)

The scratch characteristics of laser nitrided Zr-based metallic glass surface

Hong J., Wu H., Huang H., Zhang L., Zhang Z., Jiang M., Yan J.

Intermetallics （Intermetallics）  155 2023年04月

ISSN  09669795

　概要を見る

Improving the surface hardness and tribological characteristics of metallic glasses (MGs) is meaningful for their applications as surface contact materials. In this study, nanosecond laser nitriding was performed on Zr-based MG to improve its surface properties. Three types of laser nitrided surfaces with different hardness were prepared, and their tribological characteristics were systematically investigated by means of the scratch test. The experimental results indicated that compared with the as-cast MG, the hardness of these three laser nitrided surfaces was increased by 47.94%, 114.56%, and 171.99%, and their coefficients of friction were reduced by 29.12%, 65.05%, and 71.84%, respectively. Furthermore, the residual scratches and surrounding chips exhibited various features under different conditions, and the scratch damage mechanisms were analyzed accordingly.

• Access to Document (DOI)

Study on the non-free plastic shear removal of material and cutting-induced deformation of micron-submicron grooves

He Y., Zhou T., Kumar A.S., Wang X., Yan J.

Journal of Materials Processing Technology （Journal of Materials Processing Technology）  317 2023年04月

ISSN  09240136

　概要を見る

The shear interference and chip removal interference between different tool edges during non-free cutting are the main reasons for the deformation of micron-submicron grooves. To our best knowledge, the understanding of the non-free cutting of micron-submicron grooves is still not well established. This paper provides new insight into the material removal mechanism and cutting-induced deformation of micron-submicron grooves in non-free cutting. A novel variable shear angle removal model, revealing the difference of material shear at different positions of the tool edge, is established by infinitesimally segmenting the tool edge after analyzing the shear interference and chip removal interference mechanisms. An equation of the local shear angle enables the mathematical derivation of the topography of the shear surface and chip cross-section in the non-free cutting of micron-submicron grooves. The distribution of shear stress in the shear zone is calculated by establishing the relationship between the shear angle and shear stress based on the unequal division shear zone (UDSZ) theory and Johnson-Cook theory. Furthermore, a mechanics model of micron-submicron groove cutting, revealing the deformation mechanism of the micron-submicron grooves, is established using the differential cutting force method. Finite element simulations and high-speed cutting experiments are conducted to analyze the cutting microstate between the tool and the material and the dynamic deformation of the micron-submicron grooves during non-free cutting. The stress trend of the elastic nodes on the tool edge verifies the mechanics model, and the chip morphology verifies the formation of the shear surface and chips. The degree of non-free cutting is higher at the tool edge infinitesimal segments (TEISs) closer to the tool tip, resulting in a smaller shear angle, which makes the extrusion stress suffered by the groove increases nearly twice from top to bottom. The material flow due to dynamic deformation causes the relative cutting line of the rear-side tool edge to shift forward. The deformation of the micron-submicron grooves is related to the stiffness of the structure.

• Access to Document (DOI)

Generation of nanopore structures in yttria-stabilized zirconia by femtosecond pulsed laser irradiation

Yamamuro Yuka, Shimoyama Tomotaka, Yan Jiwang

Journal of Materials Research and Technology （Journal of Materials Research and Technology）  23   1155 - 1176 2023年03月

ISSN  2238-7854

　概要を見る

Femtosecond pulsed laser irradiation of yttria-stabilized zirconia (YSZ) was performed to investigate the feasibility and fundamental characteristics of nanopore structure fabrication. Numerous nanopores were successfully generated on the YSZ surface with only a single laser pulse shot by controlling laser power near the ablation threshold. The nanopore generation mechanism involves light focusing by the convex shape of a crystal grain and ablation inside the grain. By increasing laser power, the number of nanopores increased. Cross-sectional observation revealed that the depth of nanopores was about 500 nm, and nanopores were generated inside the YSZ grains of the top layer while keeping the grains' shapes unchanged. It was found that higher scanning speed and a small number of scans enabled nanopores fabrication without changing the original surface shape, avoiding the removal of the surface layer. Laser-irradiated surfaces of YSZ were characterized by Raman spectroscopy, and it was found that there was no significant phase change in the specimen after nanopore generation compared with the original YSZ surface, confirming that there was no thermal damage to the bulk material. The surface with nanopores showed an enhancement in surface hydrophilicity. These findings demonstrated the possibility of selectively generating nanopores in the top surface of YSZ for use in functional surfaces without serious thermal damage to the workpiece. It is expected that the nanopore generation will lead to new applications of YSZ.

• Access to Document (DOI)

Significant improvement in surface hardness of Zr-based metallic glass by nanosecond pulsed laser irradiation in graphite powder water suspension

Zhang H., Qian Y., Zhang L., Jiang M., Huang H., Yan J.

Surface and Coatings Technology （Surface and Coatings Technology）  454 2023年02月

ISSN  02578972

　概要を見る

Metallic glasses (MGs) have shown promising application prospects as structural materials due to their unique mechanical properties. While, for broadening their application as functional materials, significant improvement in surface hardness of MGs is required. Accordingly, in this study, laser carbonization of MGs was attempted by irradiating the Zr-based MG surface immersed in graphite powder water suspension using a nanosecond pulsed laser. Nanoindentation response and surface morphologies of the initial and irradiated surfaces were characterized in detail. The results indicated that the hardness of the laser-irradiated surfaces was increased by 130 %–200 % (from 6.407 GPa to 19.193 GPa), and as well, the serrated flows in load-depth curves and the surface shear bands around the residual indent disappeared, suggesting the change in micro-scale plastic deformation behaviors of the laser-irradiated surfaces. Furthermore, the chemical composition of the initial and irradiated surfaces was analyzed by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS), which showed that the irradiated surfaces were carbonized in the graphite powder water suspension. Accordingly, the increase in surface hardness was due to the formation of the hard crystalline phases.

• Access to Document (DOI)

Repairing surface defects of Zr-based metallic glass ribbons by nanosecond pulsed laser irradiation

Wang J., Zhang H., Zhang Z., Hong J., Qian Y., Huang H., Yan J.

Manufacturing Letters （Manufacturing Letters）  35   48 - 52 2023年01月

ISSN  22138463

　概要を見る

The metallic glass ribbons (MGRs) industrially produced by the single roller melt-spun method have many surface defects such as pits and scratches. In this study, it was attempted to repair the surface defects of Zr-based MGRs via nanosecond pulsed laser irradiation. The experimental results showed that the roughness of laser-repaired surfaces was significantly reduced compared to the melt-spun surface, and the surface topographies and morphologies were sensitive to the laser parameters. With optimal laser parameters, the smooth and defect-free surface could be achieved. This work offers a convenient and high-efficiency approach for repairing the surface defects of MGRs.

• Access to Document (DOI)

Life-cycle assessment of the laser sintered-silicon anode for lithium ion battery production

Hendrickx B., Yan J., Duflou J.

Procedia CIRP （Procedia CIRP）  116   594 - 599 2023年

ISSN  22128271

　概要を見る

As the global market for lithium-ion batteries continues to grow, sourcing alternative materials for battery cell production gains interest and has an ever increasing potential to reduce environmental impact during the production phase. Around 97% of the produced Li-ion batteries contain a graphite-based anode, coated on a copper foil. In this Life Cycle Assessment the potential reduction of environmental impact over various categories during the production of batteries when using an anode production method by laser sintering Si-waste powder in an innovative process is investigated. The study provides an indication of environmental feasibility of the suggested production process, comparing the technical innovative process to currently available anode production processes. The impact comparison is made on the level of anode production (cradle to gate) with the potential to zoom out to the full battery production process in future work. Current results indicate that the overall impact of production increases 27% when using the suggested anode production process, with the results being sensitive to the amount of energy required for sintering and the allocation of impact towards the Si-waste. The impact of this switch of anode production method for the full Li-ion battery production will depend on the affected charge capacity and lifetime duration of an assembled battery module.

• Access to Document (DOI)

Nanosecond Laser “Pulling” Patterning of Micro–Nano Structures on Zr-Based Metallic Glass

Cui M., Huang H., Zhang L., Yan J.

Small （Small）  19 （ 14 ）  2023年

ISSN  16136810

　概要を見る

Flexible and controllable fabrication of micro–nano structures on metallic glasses (MGs) endow them with more functional applications, but it is still challenging due to the unique mechanical, physical, and chemical properties of MGs. In this study, inspired by a new physical phenomenon observed in the nanosecond laser–MG interaction (i.e., the surface structure is transformed from the normally observed microgroove into the micro–nano bulge at a critical peak laser power intensity), a nanosecond laser “pulling” method is proposed to pattern the MG surface. The formation mechanism and evolution of the micro–nano bulge are investigated in detail, and accordingly, various micro–nano structures including the unidirectional stripe, pillar, cross-hatch patterns, “JLU”, circle, triangle, and square, are derived and created on the MG surface, which affects the surface optical diffraction. Overall, this study provides a highly flexible and controllable method to fabricate micro–nano structures on MGs.

• Access to Document (DOI)

Fabrication and functional characteristics of micro/nano structures on the RB-SiC surface through nanosecond pulsed laser irradiation

An H., Qian Y., Zhang L., Zhang Z., Huang H., Yan J.

Ceramics International （Ceramics International）  49 （ 22 ） 36276 - 36288 2023年

ISSN  02728842

　概要を見る

Reaction-bonded silicon carbide (RB-SiC) is gaining increasing attention due to its exceptional mechanical properties contributed by the dispersion of hard silicon carbide (SiC) and silicon (Si), which has been extensively applied in aerospace and automobile industries. Fabrication of micro/nano structures on the RB-SiC surface can endow it some specific functional properties, but conventional manufacturing procedures face challenges due to the intrinsic hard-brittle nature of RB-SiC. In the present study, various micro/nano structures, including dome-like particle structures, micro-cone structures and the spider web-like film, are fabricated on the RB-SiC surface by nanosecond pulsed laser irradiation under different experimental conditions. Comparative experiments are performed to explore the effects of laser power and scanning speed on the microscopic morphology and chemical composition. Consequently, the ablation mechanism is clarified. The formation of micro-cone structures covered by the spider web-like film can result in a wettability transition of the RB-SiC surface from hydrophilicity to superhydrophilicity. In addition, by introducing the spider web-like film, the reflectivity of the RB-SiC surface is increased by an impressive 83% or more in the wavelength range of 200 to 2500 nm. This study provides a method for improving the surface properties of RB-SiC substrates using a laser-based approach, which is anticipated to expand their application prospects as functional materials.

• Access to Document (DOI)

Effects of process parameters on cutting forces, material removal rate, and specific energy in trochoidal milling

Wagih M., Hassan M.A., El-Hofy H., Yan J., Maher I.

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）  238 （ 7 ） 2745 - 2757 2023年

ISSN  09544062

　概要を見る

Trochoidal milling has been developed to enhance tool life during slot machining. It is characterized by reduced cutting forces, cutting temperature, and tool wear as compared to conventional milling processes. It is effective in machining difficult-to-cut materials, high-speed machining, and groove corners. However, this process has not been deeply investigated enough to discover its advantages and optimize its parameters. A full factorial design of 144 experiments has been applied in this paper to investigate extensively the effects of axial depth of cut, feed rate, and trochoidal step on material removal rate, cutting forces, and specific energy in trochoidal milling. Trochoidal step and axial depth of cut almost have the same contributions on cutting forces by 32% and 31% respectively, followed by feed rate by 25%. Feed rate, trochoidal step, and axial depth of cut influence the material removal rate by 37%, 30%, and by 19% respectively. The contributions of feed rate, trochoidal step, and axial depth of cut on relative specific energy are 57%, 24%, and 8% respectively. The increase of axial depth of cut increases the maximum resultant force till a threshold value, then it stabilizes. This behavior occurred due to the increase of the maximum engagement angle to a certain limit, then it does not increase any more. Both feed rate and trochoidal step linear affect maximum resultant force and material removal rate, while the relationships are non-linear for specific energy. It is recommended to machine slots in full depth with the highest possible trochoidal step and feed rate, considering the increase of tool wear and surface roughness. It is preferred to use a cutting tool of a large helix angle and small diameter to reduce the threshold axial depth of cut. Overall, this study is significant in characterizing, designing, and optimizing of trochoidal milling through experimental work.

• Access to Document (DOI)

Effect of tool geometry on ultraprecision machining of soft-brittle materials: A comprehensive review

Huang W., Yan J.

International Journal of Extreme Manufacturing （International Journal of Extreme Manufacturing）  5 （ 1 ）  2022年12月

ISSN  26318644

　概要を見る

Highlights Effects of tool geometry on machining characteristics of soft-brittle materials are reviewed. The differences in material behaviors between soft- and hard-brittle materials are identified. The surface formation mechanisms for various processing methods are compared. The optimal tool geometries and parameters for different machining methods are analyzed. Challenges, feasibility, and future perspectives in this area are outlined.

• Access to Document (DOI)

What micro-mechanical testing can reveal about machining processes

Axinte D., Huang H., Yan J., Liao Z.

International Journal of Machine Tools and Manufacture （International Journal of Machine Tools and Manufacture）  183 2022年12月

ISSN  08906955

　概要を見る

For many years, the machining community has dedicated significant efforts to investigate the microscopic scale level phenomena during the material removal process. On one hand much research has been carried out in relation to workpiece surface integrity after machining and the methods for its study. On the other hand, many studies have been dedicated to replicate machining conditions at microscopic scales using high resolution setups. Although these two topics seem to be little related, there is an opportunity of the machining community to take the advantage of the advanced testing/investigation setups that enable these two strands of research to be performed at very high resolution and repeatability, thus giving new pathways for research in this field. Here we are flagging up to the community the research opportunities offered by micro-mechanical testing that can be performed using in-situ scanning electron microscopes (SEM) or other high-resolution imaging instruments. As such, this review paper discusses the recent research advances in using in-situ micro-mechanical testing for: (i) understanding the phenomena occurring in the workpiece (sub) surfaces after machining operation by performing very high resolution micro-mechanical testing (e.g. compression/bending of micro-pillars/beams) within particular zones of machined superficial layers; (ii) studying the material removal mechanisms at micrometric level using common indenters or dedicated edges to understand how the workpiece materials (e.g. groups/single grains) react to cutting conditions. Finally, we comment on possible future research topics using micro-mechanical testing in-situ in high resolution imaging instruments and how this could help to advance the understanding of machining processes.

• Access to Document (DOI)

Design and fabrication of micro and nano surface structures for enhancing metal–polymer adhesion using femtosecond laser treatment

Omiya M., Nakajima A., Yan J.

Materials and Design （Materials and Design）  224 2022年12月

ISSN  02641275

　概要を見る

This study investigated the effects of micro- and nanostructures on the adhesion strength between copper and an encapsulating mold compound (EMC). The shape of the microgrooves was designed based on fracture mechanics theory, and the effect of laser-induced periodic structure surface (LIPSS) formation on the microgroove was investigated using numerical simulations. The designed surface profiles were fabricated using femtosecond laser treatments, and the adhesion strength between copper and the EMC was evaluated. The results show that deep microgrooves improved the adhesion strength owing to the anchor effect. However, the aspect ratio between the pitch and depth of the microgroove had a limitation in enhancing the adhesion strength. The formation of LIPSSs on the mountaintop of the microgroove was very effective; however, an LIPSS on the valley of the microgroove was ineffective. Numerical analyses revealed that LIPSSs suppressed the shear deformation of the EMC and worked as resistance to interface delamination. Based on the findings obtained in this study, combining micro- and nano-scale surface structure formation with femtosecond laser treatments is an effective and eco-friendly method for improving adhesion strength.

• Access to Document (DOI)

Investigating the Combined Effect of Multiple Dent and Bump Faults on the Vibrational Behavior of Ball Bearings

Atef Mahmoud M., Khair-Eldeen Wael, Yan Jiwang, Nassef Mohamed G. A.

Machines （Machines）  10 （ 11 ）  2022年11月

　概要を見る

The rolling element bearing is a fundamental component of any rotating machinery. During operation, wear debris and lubricant impurities create dents and bumps on the bearing raceway surfaces. Such localized defects produce transient vibration impulses at one of the bearing characteristic frequencies. Having a combination of multiple types of point defects on the raceway results in superimposed vibration patterns, which reduce the ability to recognize these defects’ effects. In this paper, a 6-DOF dynamic model is developed to accurately investigate the vibration characteristic of a ball bearing with a multipoint defect comprising a dent and bump on its raceway surface. The model considers the effects of time-varying contact force produced due to defects, lubricant film damping, bearing preload, and the inertia effect of rolling elements. The simulation results reveal the vibration behavior of multipoint defect bearings. In addition, bearing vibration response is affected by the number of defects, the angle between them, and the type and size of each defect. Furthermore, it is challenging to predict bearing defects parameters such as the numbers, types, sizes, and angles between adjacent defects from acceleration signal analysis without jerk signal analysis. The validation of the model is proved using signals from the Case Western University test setup.

• Access to Document (DOI)

Surface hardening of Zr-based metallic glass via laser surface alloying with silicon powder

Zhang D., Qian Y., Zhang L., Huang H., Yan J.

Scripta Materialia （Scripta Materialia）  220 2022年11月

ISSN  13596462

　概要を見る

Increasing the hardness and wear resistance of metallic glasses (MGs) is beneficial to prolong their service life in highly aggressive environments. For the purpose of achieving surface hardening, in this work, laser surface alloying technology was employed to modify Zr-based MG with silicon powder as the pre-placed powder. The experimental results showed that the laser alloyed layer with thickness of several tens of micrometers was generated on the MG substrate. The surface hardness of the laser alloyed layers ranged from 11.34 to 17.97 GPa, which was significantly higher than that of the as-cast MG surface (6.36 GPa). Furthermore, the scratch resistance of the laser alloyed layer was improved compared to the as-cast sample. The chemical composition analysis indicated that the laser alloyed layer was mainly composed of in-situ formed ZrSi2 phase and residual Si, and these hard phases were responsible for the high hardness of the laser alloyed layer.

• Access to Document (DOI)

Formation, evolution and characterization of nanoporous structures on the Ti6Al4V surface induced by nanosecond pulse laser irradiation

Wang C., Huang H., Zhang Z., Zhang L., Yan J., Ren L.

Materials and Design （Materials and Design）  223 2022年11月

ISSN  02641275

　概要を見る

Manipulating materials at nanoscale is challenging but rewarding. Nanostructures exhibit some unique properties distinguished from macroscopic bulk materials, so fabrication of nanostructures on the material surface is beneficial to broaden their functional applications. In this study, by nanosecond pulse laser irradiation in nitrogen atmosphere, it was found that unique nanoporous structures could be formed on the Ti6Al4V surface. The effects of laser parameters including the laser power, overlap rate, scanning speed, and repetition frequency on the formation and evolution of the nanoporous structures were systematically investigated. By changing the laser parameters, the nanoporous structures with various porosities could be easily achieved on the Ti6Al4V surface. According to the structural evolution and chemical composition, the formation mechanism of the nanoporous structures was discussed. Furthermore, by characterizing the micro-mechanical properties and wettability, it was found that the surface with nanoporous structures exhibited similar surface hardness but improved tribological performances compared to the original Ti6Al4V surface, and the surface wettability could be tuned. This study provides a simple method for fabricating nanoporous structures on the Ti6Al4V surface, which would broaden its functional applications.

• Access to Document (DOI)

Study on nano-graphitic carbon coating on Si mold insert for precision glass molding

Zhang L., Yan J.

Surface and Coatings Technology （Surface and Coatings Technology）  448 2022年10月

ISSN  02578972

　概要を見る

Precision glass molding is an efficient and promising technique for large-volume micro-optical manufacturing. Even though significant progress in precision glass molding has been achieved on the anti-adhesive coating, technical challenges and barriers still exist towards tailoring the coating layer to ensure durability and long-term processing consistency in numerous molding cycles. This manuscript presents a novel molding technique utilizing micro-patterned Si mold inserts coated with a newly developed nano-graphitic carbon coating as an isolation layer in high-precision glass molding. The coating is prepared by atmospheric pressure chemical vapor deposition (APCVD), in which the liquid benzene and silicone rubber are used as the carbon source and silicon oxycarbide (SiOC) source, respectively. The nano-morphologies of the nano-graphitic carbon coating with different conditions are characterized and analyzed, illustrating notable differences in surface features with the addition of silicone rubber and various growth durations. In the demonstration, the nano-graphitic carbon-coated Si mold inserts exhibit unique properties, including anti-adhesive and hydrophobic at elevated temperatures. Two kinds of micro-patterned Si mold inserts, a micro-pillar matrix and a micro-lens array, generated by UV lithography and diamond turning, are utilized to demonstrate the feasibility of the anti-adhesive coating in precision glass molding. The obtained results indicate that the micro-optical features on the coated Si mold inserts are successfully transferred to glass substrates with high replication fidelity without notable signs of adhesion or contamination in repetitive molding cycles. This emerging technology makes Si an alternative mold material with low surface adhesion, enhances micro-optical machining efficiency, and replicates high-precision, low-cost micro-optics on large scales that were previously unavailable.

• Access to Document (DOI)

On the conversion of point-to-linear hierarchical micro/nano-structures on the glassy carbon surface by nanosecond pulsed laser irradiation

Wang C., Zhang H., Huang H., Zhang Z., Zhang L., Yan J.

Applied Surface Science （Applied Surface Science）  599 2022年10月

ISSN  01694332

　概要を見る

Fabrication of microstructures on the glassy carbon (GC) surface is crucial for its functional applications. However, due to its intrinsic mechanical, physical, and chemical properties, it is still challenging to fabricate hierarchical micro/nano-structures on the GC surface. In this study, by tuning the interval between adjacent points as well as the irradiation time, the conversion from the point to linear hierarchical micro/nano-structures was successfully achieved on the GC surface by nanosecond pulsed laser irradiation. The detailed conversion process and mechanism were explored and discussed. On this basis, the linear hierarchical micro/nano-structures were fabricated by direct line scanning, and the internal nanostructures were always parallel to the laser scanning direction. By repeated line scanning with relatively low laser fluence, the method of direct line scanning was further improved, and well-defined and uniform hierarchical micro/nano-structures were fabricated.

• Access to Document (DOI)

Towards understanding the mechanism of vibration-assisted cutting of monocrystalline silicon by cyclic nanoindentation

Huang W., Yan J.

Journal of Materials Processing Technology （Journal of Materials Processing Technology）  311 2022年10月

ISSN  09240136

　概要を見る

Ultrasonic vibration cutting (UVC) is a promising technology that can promote the processing of hard-brittle materials in ductile mode. The feature of intermittent cutting in UVC is considered to promote the ductile responses of brittle materials. However, the effect of cyclic loading/impact on microscopic deformation behavior of the workpiece material in UVC is not clearly understood. This study used cyclic nanoindentation to reveal the UVC mechanism in monocrystalline silicon (Si). The surface morphology and subsurface microstructure of the residual indents were characterized and compared with those of the UVC-machined grooves. This work attempted to correlate the tool-workpiece contacts for cyclic nanoindentation and vibration cutting. Cyclic nanoindentation results show that cyclic loading promotes the extent of silicon amorphization and decreases the threshold for transitioning the β–Sn phase to the bc8 and r8 phases. As the number of indentation cycles increases, the subsurface microstructure changes from the amorphous phase to the bc8 and r8 phases. In UVC, both the critical cutting depth for brittle-to-ductile transition and the degree of amorphization in cutting chips increase in comparison to conventional cutting, which matches the trend of cyclic nanoindentation results. The findings inform the chip formation and subsurface deformation mechanisms of brittle materials during UVC.

• Access to Document (DOI)