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Papers - Yan, Jiwang

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Laser nitriding enables robust wear resistance in Zr-4 alloy across multiple typical service environments

Huang H., Xu P., Qian Y., Yan J.

Tribology International 217 2026.05

ISSN 0301679X

Due to its low thermal neutron absorption cross-section and adequate irradiation stability, Zr-4 alloys are widely used in nuclear reactors for critical components such as fuel rod cladding and cooling tubes. These components operate under diverse conditions, including high and ambient temperatures, as well as aqueous environments, where they are exposed to mechanical wear and corrosive media. However, the inherently limited surface hardness of Zr-4 alloy leads to poor wear resistance, potentially compromising component integrity. In this study, laser nitriding is employed to enhance the surface properties of Zr-4 alloy across multiple operating environments. Laser irradiation with a power level of 23 W in a nitrogen atmosphere increases the surface hardness to 8.75 GPa, representing a 495 % improvement over the as-received material. The laser-nitrided surfaces exhibit exceptional wear resistance, achieving maximum reductions in cross-sectional wear area of 90.8 % in room temperature air, 98.6 % in room temperature ultrapure water, and 52.1 % in air at 300 °C, compared to the as-received surface. This enhancement arises from the formation of hard nitride phases and a transformation in the dominant wear regime. Electrochemical tests reveal that the polarization resistance of the laser-nitrided surface processed at a relatively high laser power of 19 W is approximately 34 times higher than that of the as-received surface, demonstrating significantly improved corrosion resistance. These findings highlight laser nitriding as a highly effective surface engineering approach for improving the durability of Zr-4 alloy components in nuclear reactors, with important implications for enhancing the reliability of nuclear energy systems.

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A novel approach for reducing thermal damage in laser processing of CFRP through synergistic cryogenic cooling and lateral gas blowing: Mechanism analysis and parameter optimization

Composites Part A: Applied Science and Manufacturing 2026.01

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Micromachining of Carbon Fiber Reinforced Plastics Using Femtosecond Pulsed Laser

Konishi, Y; Yan, JW

NANOMANUFACTURING AND METROLOGY 8 ( 1 ) 2025.12

ISSN 2520-811X

Microscale grooves and holes were fabricated in carbon fiber reinforced plastics (CFRPs) using femtosecond pulsed laser irradiation, and the characteristics and mechanisms of laser processing were investigated. The relationship between laser fluence and ablation depth was established by measuring the cross-sectional profiles of the microgrooves produced at different laser fluences. Furthermore, the effect of the angle between the edge of the micro holes and the carbon fibers was examined by analyzing the edges and wall surfaces of circular and rectangular holes. Experimental results revealed that the laser processing mechanism was strongly dependent on fiber orientation due to significant heat conduction along carbon fibers. The findings of this study contribute to a deeper understanding of the ultrashort pulsed laser processing characteristics and mechanisms for creating small holes in CFRPs and emphasize the possibility of drilling high-precision holes that can be used in the direct bonding of sensors/IC chips to CFRPs.

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Effect of System Dynamics on Surface Topography in Fast Tool Servo-Based Diamond Turning of Microlens Arrays

Hashimoto T., Yan J.

Nanomanufacturing and Metrology 8 ( 1 ) 2025.12

ISSN 2520811X

A lens array is often used for optical components of sensing devices, requiring high surface quality and form accuracy. Fast tool servo (FTS)-based diamond turning is one of the technologies for manufacturing complicated shapes, such as freeform optics, structured surfaces, and microlens arrays, with high machining efficiency. In this study, lens array machining was performed on copper using an FTS on a diamond turning machine. For evaluating the lens array surface topography, the focus was on surface waviness formation. As a dominating factor of surface waviness, the system dynamics behavior was investigated by capturing and analyzing the position signal. It was found that a specific waviness pattern could be formed on the surface due to the servo response. By considering the dynamics of the FTS system from the captured signals, the FTS system behavior was identified, and optimal machining parameters for the lens array were proposed. A machining test under the optimized cutting conditions reduced the average Sdq used to quantify the waviness amount from 93 to 50 µrad and the standard deviation from 33 to 3 µrad, which greatly improved the consistency in accuracy for all lens arrays. This study will contribute to the appropriate utilization of FTS systems in the ultraprecision machining of various advanced optics, such as microlens arrays.

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Fabrication of Groove-with-Protrusion Surface Structures on Oxygen-Free Copper Using a Laser-Engineered Burnishing Tool

Otani A., Yan J.

Nanomanufacturing and Metrology 8 ( 1 ) 2025.12

ISSN 2520811X

Microtextured surfaces, such as those with groove, hole, or protrusion structures, are widely used in various industries for bonding dissimilar materials because of their anchor effect, which enhances adhesion and penetration with other materials. Although surfaces with grooves and protrusions are expected to show higher bonding strength, it is difficult to fabricate such hybrid structures using a material removal process or additive manufacturing. This study established a new burnishing method using a tool with preformed microgrooves at the tip to fabricate groove-with-protrusion structures on metal surfaces by plastic deformation. The tip of a ball-shaped polycrystalline diamond (PCD) tool was irradiated with a femtosecond pulsed laser to generate multiple trapezoid ten-micron scale grooves. Burnishing was then conducted on an oxygen-free copper surface to investigate the characteristics and mechanism of the burnishing-induced plastic deformation behaviors. The results showed that protrusions and grooves, which were several tens of micrometers in height and depth, were simultaneously produced along the tool path on the material surface. Tool sliding on the workpiece induced shear stress, which mainly triggered dislocation movement and plastic deformation enhancement. Cross-sectional observation revealed that grain elongation and refinement remarkably increased with the burnishing depth, indicating that the shear stress from burnishing produced refined grains that flowed and formed the protrusions. This research demonstrates the feasibility of a highly efficient method for simultaneously generating groove-with-protrusion structures with enhanced surface properties.

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Laser masking enabled replication of latent fingerprints from transparent substrates

Guo H., Qian Y., Wang X., Zhang Z., Jiang M., Huang H., Yan J.

Vacuum 242 2025.12

ISSN 0042207X

Latent fingerprints (LFPs), though critical in forensic investigations, are often invisible and difficult to detect, especially on transparent material surfaces. Here, we present a novel nanosecond pulsed laser printing technique to replicate LFPs from transparent substrates onto metal surfaces. By placing a metal plate beneath the transparent material with the fingerprint side up, the components of the fingerprint selectively block the laser, enabling the transparent substrate to act as a photomask. This results in controlled ablation of the metal surface, replicating the fingerprint with high fidelity. Additionally, laser-induced backside etching produces a mirrored copy of the fingerprint pattern on the underside of the transparent material. Grayscale analysis confirms enhanced clarity of the printed fingerprints compared to the original LFPs. Importantly, the method is effective on curved, colored, and flexible transparent substrates and allows multiple high-quality replications from a single sample, offering a promising tool for forensic applications.

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Feedforward Compensation of Dynamics-Induced Form Errors in High-Speed Diamond Turning of Freeform Surfaces Using a Long-Stroke Fast Tool Servo

Hashimoto, T; Yan, JW

NANOMANUFACTURING AND METROLOGY 8 ( 1 ) 2025.11

ISSN 2520-811X

The fabrication of freeform optical components is increasingly demanded in emerging technologies such as augmented reality, imaging systems, and compact spectrometers. Fast-tool-servo (FTS) diamond turning has become a promising solution for high-speed, high-precision machining of such surfaces. However, achieving nanometric form accuracy remains challenging due to servo-induced dynamic errors, particularly overshoot and control delay. This study proposes a feedforward methodology to predict and compensate for dynamics-induced form errors in long-stroke FTS systems. By capturing FTS position signals and applying normalized cross-correlation (NCC) analysis, a repeatable motion error referred to as the time-shifted following error (TSFE) was identified through time delay compensation of the servo. The three-dimensional map of TSFE was constructed and integrated into the tool path to compensate for the error before machining. Experimental machining test of a dual-sinewave freeform shape achieved peak-to-valley (PV) form error of 0.26 µm, which was a 56% reduction compared to without measurement compensation. The repeatability of the three-dimensional map of TSFE showed a standard deviation of 0.007 µm on the PV, which confirmed that the TSFE map has enough repeatability to be used as a pre-compensation dataset. Additionally, the FTS system had latent TSFE error regardless the spindle rotation rates. In this study the TSFE map derivation of system indicated approximately 0.5 µm PV. These findings establish a fundamental and broadly applicable framework for improving form accuracy in high-speed freeform optics manufacturing using FTS, contributing to the advancement of ultra-precision machining technologies.

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Simultaneous laser nitriding and biomimetic texturing: A synergistic strategy for enhancing mechanical properties and corrosion resistance of Ti6Al4V alloy

Zhang H., Huang H., Yan J.

Journal of Materials Processing Technology 345 2025.11

ISSN 09240136

The service reliability and lifespan of Ti6Al4V in high-end equipment application are limited by its poor wear resistance and susceptibility to pitting corrosion. Pulsed laser nitriding and simultaneous microtexturing can improve surface hardness and wear resistance. However, this method faces a mutual constraint between modified layer thickness and structural regularity. In this study, composite microtextures comprising periodic ripples and uniform vein-like structures are fabricated on Ti6Al4V by CW laser nitriding. Inspired by biological surfaces, various biomimetic textures are created, among which the biomimetic fish scale surface (BFS) exhibits remarkable performance enhancement. Its cross-section consists of a dendritic TiN layer on the surface and a dense acicular α'-Ti phase within the molten pool, with the modified layer thickness increasing to nearly 20 μm. Compared with the substrate, the cross-sectional hardness increases by 117 %, while the wear rate decreases by 10 % and 96 % under dry friction and starved lubrication, respectively. Moreover, the corrosion potential shifts positively from −579.84 mV to −299.47 mV, and the corrosion current density decreases by three orders of magnitude. The formation mechanisms of the microtextures are elucidated based on the evolution of microscopic morphologies and finite element simulations. The hardness enhancement is interpreted through analysis of the cross-sectional microstructure, whereas the improvement in corrosion resistance is revealed through impedance spectroscopy and passive film composition. This work provides a new strategy for the integrated construction of nitrided layers and functional microtextures on titanium alloy surfaces.

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Generation of high-aspect-ratio 3C-SiC nanowires and evaluation of their potential as battery materials

Minami K., Shimazu K., Hattori Y., Yan J.

Materials & Design 259 2025.11

ISSN 02641275

Waste Silicon (Si) powder generated during semiconductor manufacturing has attracted attention as a potential anode material for lithium-ion batteries. This study proposes a novel method to fabricate high-aspect-ratio cubic silicon carbide (3C-SiC) nanowires using a mixture of waste Si and graphite powders through laser processing. The mixture is placed between two plates to sandwich the laser-induced plume. This confinement promotes nanowire growth, increases the aspect ratio, shortens the lithium-ion diffusion length, and enables the fabrication of flexible electrodes. High-speed camera observations confirmed that the sandwiched plume was compressed and remained in air for nearly 10 s. Consequently, nanowires approximately 100–1200 nm in length and 15–60 nm in diameter (aspect ratio greater than 25) were generated. Electron diffraction and XRD analyses revealed that the nanostructures mainly comprised 3C-SiC. Battery performance evaluation tests of the generated nanowires showed that after 10 charge–discharge cycles at a current density of 50 mA/g, the SiC nanowires exhibited a specific capacity of 455 mAh/g, significantly higher than that of Si nanoparticles (291 mAh/g) and comparable to that of C-coated SiC nanoparticles (477 mAh/g). The SiC nanowires outperformed both Si nanoparticles and graphite anodes, demonstrating the potential of the proposed method in next-generation lithium-ion battery (LIB) anode fabrication.

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Fabrication of convex and concave microstructures on Ti6Al4V via nanosecond laser texturing and their distinct effects on surface wettability

Wang C., Li L., Huang H., Yan J.

Journal of Manufacturing Processes 152 616 - 630 2025.10

ISSN 15266125

Precise control of surface microstructures is crucial for the functional design of advanced materials, particularly in applications such as superhydrophobic surfaces. However, current laser micro/nano fabrication techniques still face a persistent “easy-concave, hard-convex” challenge, where concave structures (e.g., microcraters and grooves) are readily produced but the fabrication of convex structures (e.g., micropillars, bulges) remains difficult. Consequently, the underlying mechanisms governing the functional difference between convex and concave structures are still not clear. In this study, both convex and concave microstructures were successfully fabricated on Ti6Al4V surfaces by optimizing the parameter window of nanosecond laser irradiation. The evolution of surface morphology under various laser parameters was systematically explored, and the formation mechanisms were clarified through the coupling effects of Marangoni convection and recoil pressure. Convex and concave arrays with varying hatch distances were fabricated and subjected to annealing treatment for comparatively studying their difference in wettability. After annealing, concave structures consistently exhibited superhydrophobicity, whereas convex structures demonstrated hydrophobicity or superhydrophobicity depending on the hatch distance. The mechanism underlying the difference in wettability was further revealed by analyzing the surface morphology and chemical composition. Furthermore, lossless liquid transportation was successfully realized by utilizing the adhesion difference between the convex and concave structures. This study not only offers a novel approach for constructing microstructures on titanium alloy surfaces but also provides new insights into the functional difference between convex and concave structures.

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Study on the cutting-caused deformation of sloping-arranged nano-grooves in amorphous nickel phosphorus with nanoscale superior plasticity

He Y., Yang X., Zeng Z., Zhou T., Yu D., Zhang P., Liu J., Yan J.

Journal of Manufacturing Processes 152 1166 - 1178 2025.10

ISSN 15266125

Creating nanoscale grooves along sloping and curved path is significant for achieving multi-scale structured surfaces with superior surface properties. Attributed to the excellent ability to fabricate micro/nanoscale surface structures, ultra-precision diamond cutting technology is an effective method to engrave sloping-arranged nano-grooves. However, due to the tool-edge extrusion effect, the material removal behavior becomes very complicated when the tool is fed along the sloping path, consequently nano-grooves with weak stiffness are extremely prone to irregular deformation. This paper investigates the formation and cutting-caused deformation of sloping-arranged nano-grooves on amorphous nickel‑phosphorus (a-Ni-P) through mechanism analyzation, simulation, and experiments. The mechanism of nano-grooves deformation and materials residue under the non-free cutting condition is revealed. The influence of the size of the stress zone by the extrusion of the tool edge on the deformation is analyzed. What's more, the influence mechanism of direction of the sloping feed path and its slope on the deformation are investigated. Compared to extruding the long bevels of nano-grooves in the downward feed path, the tool edge extrudes the short bevels of nano-grooves in the upward feed path, making the stress zone smaller and deformation suppressed. To suppress the deformation of undulating sloping-arranged nano-grooves in the full feed path, a novel intermittent-upward feed path is proposed for fly cutting of sloping-arranged nano-grooves on a side-mounted workpiece. The proposed tool feed strategy was demonstrated to be able to improve the machining quality of the undulating sloping-arranged nano-grooves.

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Towards understanding the ultrasonic vibration-assisted diamond cutting of ZnO crystals: Surface integrity and tool wear mechanism

Huang W., Hashimoto T., Yan J.

Journal of Materials Processing Technology 344 2025.10

ISSN 09240136

Zinc oxide (ZnO) is a promising material for optics and optoelectronics. However, its machining methods are limited, with polishing being virtually the only available technique, which restricts the fabrication of complex shapes. In this study, for the first time, ultraprecision diamond cutting of single-crystal ZnO was explored. Conventional cutting (CC) and ultrasonic vibration-assisted cutting (UVC) experiments were performed in dry and oil mist lubrication environments. It was found that under dry conditions, both CC and UVC resulted in surface fractures owing to the oxidation-induced chemical tool wear. Using oil mist lubrication significantly reduced tool wear, particularly for UVC. As a result, surface roughness was reduced to 1.9 nm Sa. Cutting in the [11−20] direction was more likely to achieve crack-free surfaces on ZnO than cutting in the [1−100] direction under CC; however, the machinability in cutting in the [1−100] direction was improved by applying UVC. Both CC and UVC processes activated basal and pyramidal slip systems in the subsurface region, accompanied by a high density of dislocations located immediately beneath the surface. UVC further promotes polycrystallization and pyramidal slip activity in the subsurface. A microlens array was fabricated with a surface form error of less than 49 nm peak-to-valley and a surface roughness of less than 2.2 nm Sq by integrating slow tool servo diamond turning with ultrasonic vibration assistance under oil mist lubrication. This study reveals the fundamental cutting characteristics of ZnO, provides guidance for ultraprecision cutting of brittle oxide crystals, and validates a potential solution for fabricating micro-structures on ZnO surfaces.

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Amorphization of pure aluminium in ultraprecision cutting process: experimental observation and theoretical analysis

He C., Wang S., Yan J.

CIRP Journal of Manufacturing Science and Technology 60 76 - 87 2025.09

ISSN 17555817

Preparing amorphous pure metals has long been significantly challenging because of their stringent transformation requirements. Here, we report a surprising discovery: the preparation of a layer of amorphous aluminium by ultraprecision cutting a polycrystalline bulk material. The findings indicated that under specific cutting conditions, polycrystalline aluminium was transformed into a completely amorphous phase on the surface layer. Additionally, the material matrix exhibited shear bands, including an amorphous phase, a 9 R phase, and high-density SFs. The modification resulted in a significant increase in surface micro-hardness, with the average value increasing from 0.93 ± 0.13 GPa to 2.21 ± 0.92 GPa. The amorphization in the ultraprecision cutting process is attributed to the high shear strain and strain rate, as confirmed by molecular dynamics simulation and theoretical calculation. This study provides a novel approach for preparing an amorphous layer on a crystalline aluminium bulk material to enhance its surface properties.

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Revealing the mechanism of crystal orientation-dependent surface morphology and topography evolution in single-crystal ZnO using nanoindentation

Huang W., Yan J.

Materials and Design 257 2025.09

ISSN 02641275

Single-crystal zinc oxide (ZnO) is an important optoelectronic material, but its micro/nanoscale mechanical behavior is poorly understood. In this study, nanoindentation tests were performed on various crystalline planes of ZnO crystals using a Berkovich indenter at different indenter orientations. The surface and subsurface characteristics of the different crystal planes were analyzed and compared. It was found that indentation on the (0001) plane activated both basal and pyramidal slip systems, which suppressed pile-up. Dislocation pinning caused pop-in events during loading and promoted edge crack formation during unloading due to high elastic recovery. Indentation on the (1−100) and (11−20) planes activated basal and prismatic slip systems. As these systems cannot accommodate dislocation glide along the [0001] direction, corner cracks easily initiated. Meanwhile, dislocations glided toward the surface with minimal resistance, thereby facilitating outward material flow and pile-up formation along the [11−20] and [1−100] directions. Indenter orientation variation did not alter slip system activation for any plane and had minimal impact on plastic flow trends. No phase transformation was detected on the indented surfaces, while dislocation-induced luminescence quenching was observed. This study reveals how crystal orientation governs surface evolution in ZnO, offering guidance for machining method development and processing parameter optimization.

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On-machine measurement and Zernike-based compensation cutting for large-aperture additive metal mirrors with ultra-high lightweight ratio

Wang C., Xu K., Sun X., Bian X., Zhong H., Zhang Z., Deng W., Zhang X., Yan J.

Optics Express 33 ( 17 ) 36930 - 36942 2025.08

ISSN 1094-4087

In recent years, large-aperture additively-manufactured metal mirrors have been widely used in optics, astronomy, and aerospace. However, achieving precision diamond cutting of these mirrors remains challenging due to their intrinsic non-uniform lightweight structures. On-machine measurement of surface errors and compensation cutting offer promising solutions; however, current techniques for large-aperture metal mirrors remain insufficiently mature. Furthermore, compensation cutting is hindered by the coupling of multiple error factors, including inherent equipment errors, measurement uncertainties, and surface fitting deviations. To address these challenges, this study developed an on-machine measurement system combined with a compensation cutting method based on Zernike polynomials. Unlike compensating for the entire surface error, the first 36 Zernike terms of the entire surface error were extracted for compensation. In the experiment, an additively-manufactured AlSi10Mg mirror with a diameter of 510 mm and a lightweight ratio of 86% was fabricated. To the best of our knowledge, an additively-manufactured mirror of such a diameter with such a high lightweight ratio has never been reported in the literature. Using the proposed on-machine measurement system, a repeatability of 50 nm root-mean-square (RMS) was achieved. Furthermore, comparative validation with coordinate measuring machine results confirmed the reliability of the on-machine measurement system. Subsequently, Zernike polynomials were employed to reconstruct the surface errors. After a single compensation cutting process, the surface error decreased from 0.636 µm to 0.30 µm (RMS), achieving a convergence rate of 52%. The experimental results demonstrate that the proposed on-machine measurement methodology, combined with an error compensation strategy, significantly improves both precision and efficiency of ultra-precision machining.

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Using fast Fourier transform analysis for the rapid evaluation of the diffraction fringes of optical components produced through ultraprecision single-point diamond turning

Tang K.E., Yan J., Kwan S.Y., Zhen M.Y., Liu C.W.

Mechanical Systems and Signal Processing 237 2025.08

ISSN 08883270

High-end optical molds are essential for mass-producing precision optical components used in biomedical, defense, and automotive manufacturing applications. These components are often produced through single-point diamond turning (SPDT), and their optical performance depends on their surface quality and shape accuracy. On mirror-grade surfaces, periodic microstructures caused by feed rate variations and tool wear can induce diffraction, leading to visible rainbow diffraction fringes that degrade optical performance. In traditional surface metrology, inspections of diffraction fringes require visual or laser-based methods, which are labor-intensive, time-consuming, and heavily reliant on human judgment and experience. To improve the efficiency of quality inspection, this study developed a fast Fourier transform (FFT)-based method to assess diffraction intensity. A full-factorial experiment was performed to analyze the effects of feed rate and tool wear on diffraction intensity, with the FFT employed to extract surface periodic features. The experimental results indicated that greater tool wear led to higher diffraction intensity, with the second harmonic of the FFT response being strongly correlated with diffraction intensity (K > 0.89) under 650-nm laser illumination. Analysis of the theoretical diffraction angle confirmed that the second harmonic was the main cause of diffraction, with the positional accuracy of theoretical diffraction spots exceeding 90 %. When the second harmonic response exceeded the surface roughness threshold, imaging quality was negatively affected. The proposed innovative FFT-based approach enabled rapid diffraction assessment, assists in tool wear monitoring and reducing quality inspection time by 65 % compared with traditional laser-based inspection methods. Thus, this method has high potential for application in quality inspections in SPDT.

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Micro-convex structure-assisted laser-induced backside dry etching for high-efficiency fabrication of micro-groove array on fused silica toward manipulation of wetting characteristics

Huang H., An H., Qian Y., Zhang Z., Jiang M., Yan J.

Journal of Manufacturing Processes 145 236 - 251 2025.07

ISSN 15266125

Fused silica has garnered significant attention in various industrial applications. The creation of surface micro/nanostructures on fused silica can impart specialized functional properties, such as extreme wettability, ultra-high transmittance, and excellent antimicrobial characteristics. Nonetheless, existing technologies for achieving surface micro/nanopatterning of fused silica, including wire electrical discharge machining, chemical etching, and electrochemical deposition, generally suffer from long processing cycles and high energy consumption, which are inconsistent with the development concept of the low-carbon economy. In this study, a novel approach termed micro-convex structure-assisted laser-induced backside dry etching (MCSALIBDE) is proposed for high-efficiency fabrication of micro-groove array on fused silica surfaces. The synergistic effect of enhanced heat conduction and plasma explosion in a confined space facilitates material ablation. The impact of processing parameters including scanning pitch and peak laser power intensity on the morphological and topographical features of the MCSALIBDE-processed fused silica surfaces is studied. Notably, the micro-groove structures with a depth-to-width ratio of 1.19 is fabricated. Furthermore, the wetting behaviors of the MCSALIBDE-processed fused silica surfaces before and after annealing treatment are studied. Experimental findings reveal that the MCSALIBDE-processed fused silica surfaces exhibit enhanced hydrophilicity compared to the untreated one. After annealing treatment, a transformation from hydrophilicity to superhydrophobicity is observed. The superhydrophobic surfaces produced under different laser parameters exhibit distinct adhesion and droplet bouncing behaviors. This work offers an in-depth understanding of the high-efficiency fabrication of micro/nanostructures on fused silica surfaces and as well the modulation of their wetting characteristics, heralding innovations in surface engineering for diverse applications.

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Micro-amplitude vibration-assisted scratching: a new method for one step and controllable fabrication of the microscale V-groove and nanoscale ripples

Wu H., Huang H., Zhang Z., Yan J.

International Journal of Extreme Manufacturing 7 ( 3 ) 2025.06

ISSN 26318644

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Unveiling the effects of laser scanning direction and processing parameters on heat transfer and ablation behavior of CFRP

An H., Qian Y., Jiang M., Huang H., Yan J.

Composites Part B: Engineering 298 2025.06

ISSN 13598368

Carbon fiber reinforced plastic (CFRP) has found extensive applications in aerospace, automotive, and biomedical fields owing to its exceptional mechanical properties. Nanosecond pulsed laser processing offers a promising avenue for treating CFRP laminates; however, the inevitable thermal damage during processing may significantly degrade the surface integrity. An in-depth analysis of the correlation between ablation characteristics of CFRP and laser processing conditions is essential for understanding the complex heat transfer and ablation mechanisms during laser processing of CFRP and is a prerequisite for improved control of thermal damage. This study examines the thermal transfer and ablation behavior of CFRP subjected to nanosecond laser ablation, focusing on how laser scanning direction and processing parameters influence the surface characteristics of the laser-ablated regions. The results indicate that the width of the heat-affected zone (HAZ) increases with increasing laser power, decreasing scanning speed, and decreasing scanning pitch. Moreover, the scanning direction plays a crucial role in determining the HAZ characteristics and material removal rate. Processing CFRP along the 0° direction relative to the carbon fiber orientation yields higher efficiency and less thermal damage compared to the 90° direction. Chemical composition analysis reveals that laser ablation induces a structural transformation in carbon fibers, shifting from sp2 graphite-like lattice orbitals to sp3 hybird orbitals. Numerical simulations further elucidate the heat transfer and ablation mechanisms under various experimental conditions. This study contributes to a deeper understanding of the laser-CFRP interaction, facilitating the development of high-integrity CFRP surfaces and broadening their practical applications across multiple industries.

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Investigation of the Effect of Tool Rotation Rate in EDM Drilling of Ultrafine Grain Tungsten Carbide Using Predictive Machine Learning

Gattu S.D., Bernardi L.P., Yan J.

Journal of Manufacturing and Materials Processing 9 ( 6 ) 2025.06

Electric discharge machining (EDM) is widely employed for machining hard, conductive materials. Tool rotation has emerged as an effective strategy to enhance debris flushing and improve stability during deep-hole EDM drilling. This study proposes a machine learning-based approach to evaluate the influence of tool rotation and predict the unstable machining conditions in EDM of ultrafine grained tungsten carbide. A structured analytical workflow, combining Taguchi–Grey optimization, regression analysis, and classification models, was designed to capture discharge dynamics across macro- and micro-timescales. Classification models trained on raw and processed electrical signal features achieved over 88% accuracy and 90% recall. SHAP analysis revealed that the relationship between key discharge events such as sparks and short circuits varied significantly across stable and unstable machining phases, underscoring the importance of phase-specific modeling. While correlation analysis showed weak global associations, phase-dependent SHAP values revealed opposing feature effects, allowing the context-informed interpretation of model behavior. Phase segmentation revealed that, compared to 1000 RPM, short circuits were reduced by about 40% during stable machining at 8000–9000 RPM. Conversely, during unstable phases, spark effectiveness dropped by nearly 45%, and secondary discharges increased throughout this range. These insights support the design of adaptive control strategies that adjust the rotation rate in response to detected phase changes, aiming to sustain machining stability. The findings support the development of dynamic control frameworks to improve EDM performance, particularly for mold fabrication using tungsten carbide.

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