Search Results (446)

To optimize the laser drilling process and reduce the processing time, this study investigates picosecond laser trepan drilling on the titanium alloy TC4, analyzing the effects of laser parameters on micro-hole diameter, taper, and roundness. Four independent variables were selected: laser power, defocusing distance, scanning speed, and the number of scans. An L₂₅ (5⁶) orthogonal array was employed for experimental design. The mean response and range analyses evaluated parameter impacts on micro-hole quality, revealing the influence mechanisms of these variables at different levels. The results indicate the following: (1) the scanning speed and laser power significantly affect entrance and exit micro-hole diameters; (2) the defocusing distance substantially influences micro-hole taper; (3) the laser power most critically impacts inlet roundness; (4) the defocusing distance, scanning speed, and laser power directly correlate with outlet roundness; (5) the number of scans exhibits weaker relationships with inlet/outlet diameters, taper, and roundness. A comprehensive balance method applied to orthogonal test results for process optimization yielded the following optimal parameters: 90% laser power (30 W total), −0.2 mm defocus, a 27 mm/s scanning speed, and 15 scans. Full article

In the present study, the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in C_f/SiC composites, coupled with nanosecond laser drilling in air for fabricating micro-holes with high aspect ratios, were investigated. The surface morphology, reaction products, and micro-hole shapes were thoroughly examined. The results reveal that, for the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in the C_f/SiC composite, the increasing of waterjet velocity enhances the material removal rate and micro-hole depth, but reduces the micro-hole diameter and taper angle. The coaxial waterjet isolates the laser-ablated region and cools down the corresponding region rapidly, leading to the formation of a mixture of SiC, SiO₂, and Si on the surface. As the coaxial waterjet velocity increases, the morphology of residual surface products changes from a net-like structure to individual spheres. Coaxial waterjet-assisted nanosecond laser drilling, with a waterjet velocity of 9.61 m/s, achieves micro-holes with a good balance between efficiency and quality. For the fabrication of micro-holes with a high aspect ratio in C_f/SiC composites, micro-holes fabricated by nanosecond laser drilling in air exhibit obvious taper features, which should be ascribed to the combined effects of spattering slag, plasma, and energy dissipation. The application of coaxial waterjet-assisted nanosecond laser drilling on micro-holes fabricated by laser drilling in air effectively expands the hole diameter. The fabricated micro-holes have very small taper angles, with clean wall surfaces and almost no reaction products. This approach, combining nanosecond laser drilling in air followed by coaxial waterjet-assisted nanosecond laser drilling, offers a promising technique for fabricating high-quality micro-holes with high aspect ratios in C_f/SiC composites. Full article

Aiming at the engineering problems of the severe wear and limited service life of mandrels during the hole extrusion strengthening of critical aerospace components, this study proposes a surface modification strategy for mandrels based on the anti-friction mechanism of micro-textures. Based on the Lame stress equation and the Mises yield criterion, a plastic strengthening stress distribution model of the hole wall was developed. Integrating Bowden’s adhesive friction theory, a parameterized numerical model was constructed to investigate the influence of micro-texture morphology on interfacial friction and wear behavior. An elastic–plastic contact model for micro-textured mandrels during hole extrusion strengthening was established using ANSYS. The effects of key parameters such as the micro-texture depth and area ratio on the contact pressure field, friction stress distribution, and strengthening performance were quantitatively analyzed. The results show that a circular micro-texture with a depth of 50 μm and an area ratio of 20% can reduce the fluctuation and peak value of the contact pressure by 41.0% and 29.7%, respectively, and decrease the average friction stress by 8.1%. The interfacial wear resistance and the uniformity of the residual compressive stress distribution on the hole wall are significantly enhanced, providing tribological insight and surface optimization guidance for improving the anti-wear performance and extending the service life of mandrels. Full article

Vegetable oil is regarded as a medium that can replace kerosene in electrical discharge machining (EDM) hole processing due to its renewability and environmental friendliness. Meanwhile, numerical simulation serves as an effective means to study the behavior of the gap flow field during EDM processing. Based on this, this study explored the influence of hole size and different vegetable oil dielectrics (sunflower seed oil, canola oil, and soybean oil) on the movement of electro-corrosion residues in the processing gap. The simulation results demonstrate that the viscosity of the oil affects the escape rate of the particles. In holes of 1 mm and 4 mm of size, the escape rate of canola oil at any time period is superior to that of sunflower seed oil and soybean oil. In a 1 mm hole, its average escape rate reached 19.683%, which was 0.24% and 0.19% higher than that of sunflower seed oil and soybean oil, respectively. Subsequently, experiments were conducted in combination with the simulation results to explore the influence of current, pulse width, and pulse interval on hole processing. This further confirmed the application potential of vegetable oil in electrical discharge micro-hole processing and provided theoretical support and experimental basis for optimizing the green manufacturing process. Full article

The disadvantages of traditional strip fertilization technology for corn planting in China include low fertilizer utilization rates, unstable operation quality, and environmental pollution. Therefore, in this study, a synchronous hole fertilization device for corn planting based on real-time intelligent control is designed, aiming to reduce fertilizer application and increase efficiency through the precise alignment technology of the seed and fertilizer. This device integrates an electric drive precision seeding unit, a slot wheel hole fertilization unit, and a multi-sensor coordinated closed-loop control system. An STM32 single-chip micro-computer is used to dynamically analyze the seed–fertilizer timing signal, and a double closed-loop control strategy (the position loop priority is higher than the speed loop) is used to correct the spatial phase difference between the seed and fertilizer in real time to ensure the precise control of the longitudinal distance (40~70 mm) and the lateral distance (50~80 mm) of the seed and fertilizer. Through the Box–Behnken response surface method, a field multi-factor test was carried out to analyze the mechanism of influence of the implemented forward speed (A), per-hole target fertilizing amount (B), and plant spacing (fertilizer hole interval) (C) on the seed–fertilizer alignment qualification rate (Y₁) and the coefficient of variation in the hole fertilizing amount (Y₂). The results showed that the order of primary and secondary factors affecting Y₁ was A > C > B, and that the order affecting Y₂ was C > B > A; the comprehensive performance of the device was best with the optimal parameter combination of A = 4.2 km/h, B = 4.4 g, and C = 30 cm, with Y₁ as high as 94.024 ± 0.694% and Y₂ as low as 3.147 ± 0.058%, which is significantly better than the traditional strip application method. The device realizes the precise regulation of 2~6 g/hole by optimizing the structural parameters of the outer groove wheel (arc center distance of 25 mm, cross-sectional area of 201.02 mm², effective filling length of 2.73~8.19 mm), which can meet the differentiated agronomic needs of ordinary corn, silage corn, and popcorn. Field verification shows that the device significantly improves the spatial distribution of the concentration of fertilizer, effectively reduces the amount of fertilizer applied, and improves operational stability and reliability in multiple environments. This provides technical support for the regional application of precision agricultural equipment. Full article

The burr removal and finishing of drilled hole walls typically require multiple post-processing steps. This experimental study introduces a novel single-step drilling approach using modified drill bits for simultaneous burr removal and surface finishing in aluminum 6061-T6. The odified-1 drill, equipped with a deburring micro-insert, achieved superior results, with a chamfer height of −2.829 mm, drilling temperature of 40.28 ◦C, and surface roughness of 0.082 µm under optimal conditions. Multi-objective optimization using the RSM and MOGA-ANN identified the optimal drilling parameters for the Modified-1 drill at 3000 rpm under water lubrication as compared to dry conditions and kerosene. Experimental validation confirmed the high prediction accuracy, with deviations under 6%. These results establish the Modified-1 twist drill bit with a deburring
 micro-insert as a highly effective tool for burr-free high-quality drilling in a single operation. This innovative drill design presents an efficient, single-step solution for burr elimination, chamfer formation, and surface finishing in drilling operations. Full article

This work presents an exhaustive parametric study of the multi-scale residual stress analysis on arbitrary substrate geometry based on a one-way-coupled thermo-mechanical model in an Atmospheric Plasma Spray process. It was carried out by modifying key process parameters, such as substrate surface geometry, substrate pre-heating temperature, and coating thickness, in an Al₂O₃ coating process on an aluminium substrate. The relationship of these parameters to the generation of quenching stress, thermal stress and residual stress was analysed at three different sub-modelling scales, from the macroscopic dimension of the substrate to the microscopic dimension of the splats. The thermo-mechanical phenomena occurring during the deposition process at the microscopic level were discussed in the proposed cases. Understanding these phenomena helps to optimise the parameters of the coating process by identifying the underlying mechanisms responsible for the generation of residual stresses. The simulated residual stresses of the 200 μm Al₂O₃ outer coated aluminium cylinder were experimental validated using the incremental high-speed micro-hole drilling and milling method. Full article

Femtosecond laser micromachining was utilized to build up a micro-through-hole array into a sacrificial film, which was coated onto a copper specimen. This micro-through hole was shaped in the paraboloidal profile, with its micro-dimple on the interface between the copper substrate and the film. This profile was simply in correspondence with the laser energy profile. The array was used as a nucleation and growth site for nickel cluster deposition during wet plating. The micro-pillared unit cells nucleated at the micro-dimple and grew on the inside of the micro-through hole. After removing the sacrificial film, cleansing, and polishing, the nickel micro-pillar array was obtained, standing on the copper substrate. These unit cells and their alignments were measured through scanning electron microscopy and laser microscopy. Thermographic microscopy with FT-IR was utilized to measure the IR emittance as a function of wavelength. The focused areas were varied by controlling the aperture to analyze the effects of arrayed microtextures on the IR emittance. Full article

In recent years, research on light-matter interactions in silicon-based micro/nano cavity optomechanical systems demonstrates high-resolution sensing capabilities (e.g., sub-fm-level displacement sensitivity). Conventional 2D photonic crystal (PhC) cavity optomechanical sensors face inherent limitations: thin silicon layers (200–300 nm) restrict both the mass block (critical for thermal noise suppression) and optical Q-factor. Enlarging the detection mass in such thin layers exacerbates in-plane height nonuniformity, severely limiting high-precision sensing. This study proposes a 500 nm thick silicon-based 2D slot-type PhC cavity design for advanced sensing applications, fabricated on a silicon-on-insulator (SOI) substrate with optimized air slot structures. Systematic parameter optimization via finite element simulations defines structural parameters for the 1550 nm band, followed by 6 × 6 × 6 combinatorial experiments on lattice constant, air hole radius, and line-defect waveguide width. Experimental results demonstrate a loaded Q-factor of 57,000 at 510 nm lattice constant, 175 nm air hole radius, and 883 nm line-defect waveguide width (measured sidewall angle: 88.4°). The thickened silicon layer delivers dual advantages: enhanced mass block for thermal noise reduction and high Q-factor for optomechanical coupling efficiency, alongside improved ridge waveguide compatibility. This work advances the practical development of CMOS-compatible micro-opto-electromechanical systems (MOEMS). Full article

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. Full article

Oil shale, an unconventional oil and gas resource, can generate the required hydrocarbons through high-temperature pyrolysis. In situ conversion extraction technology utilizes downhole heaters to directly inject high-temperature heat into the oil shale layer to achieve the effect of oil and gas recovery. For the metal material components of the combustion heaters, the uneven temperature fields experienced during the start of operations, processing, and end of operations can lead to fatigue conditions, such as high-temperature creep, micro-damage, and micro-deformation due to thermal effects. To prevent the occurrence of the aforementioned issues, it is necessary to conduct fatigue life analysis of downhole combustion heaters. By combining actual combustion heater operation experiments with finite element simulation, this paper analyzes the impact of temperature, structure, and stress amplitude on the fatigue life of heaters. The results indicate that the fatigue life of the heaters is most significantly influenced by the metal gaskets, and the higher the exhaust gas temperature, the lower the fatigue life of the heater. Heating operations significantly reduce the fatigue life of the heater, while cooling operations have almost no effect on the fatigue life. Circular-pore metal gaskets have a higher fatigue life than those with a square hole shape. Considering only the thickness of the metal gaskets, the thicker the gasket, the higher the fatigue life. Stress amplitude has the most significant impact on the fatigue life of the heater; when the stress amplitude is doubled, the metal gaskets quickly undergo fatigue damage. Full article

Anti-insect nets are characterized by a very low porosity that determines a variation in the microclimate below the protection in terms of an increase in the relative humidity, a reduction in air ventilation, and a temperature rise. The air permeability of the textile depends on numerous factors such as the thickness of the wires, the size of the holes, the porosity, and the air velocity. The knowledge of this relationship would make it possible to optimize the size of the holes in order to maintain the anti-insect function with the increase in air velocity. The air permeability coefficients of 10 anti-insect nets were evaluated by means of a micro wind tunnel. The results showed that the loss coefficient is linked to the porosity (ε) of the nets: as the porosity increases, the loss coefficient decreases. The parameter that demonstrated the strongest correlation with the loss coefficient was the function of porosity h(ε) = (1 − ε²)/ε². In the interval of porosity $0.10<\epsilon <0.60$, the linear regression correlation is quite high ($R^2=0.87$). Finally, the reduction factor RF(ε)—an estimation of the reduction in wind pressure acting perpendicularly on the surface of a textile due to its porosity—was calculated and compared with that proposed by the Australian standard, which, currently, is the only international standard that explicitly considers the effect of porosity on wind action. Full article

Micro-hole aerostatic bearings have emerged as critical components in ultra-precision machining systems, offering a superior load capacity, stiffness, and stability compared to traditional orifice-based designs. These enhancements are primarily attributed to the high-density configurations of micro-holes and the reduction in hole diameter. However, research on the design and analysis of micro-hole aerostatic bearings for high-rotational-speed applications remains limited. In this study, the finite element method (FEM) was employed to solve the Reynolds equation, thereby conducting a systematic evaluation of the static and high-speed performance characteristics of micro-hole aerostatic thrust bearings. The effects of restrictor types, micro-hole layouts, structural parameters, and centrifugal deformation under high-rotational-speed conditions on bearing performance have been comprehensively examined. The objective of this study is to provide a basis for the design of micro-hole high-speed aerostatic spindles. Full article

This study investigated the effects of water-based and underwater assistance methods on the quality of picosecond laser-drilled microholes in silicon nitride ceramics, analyzing the influence of laser power variations in air and aqueous environments on entrance/exit diameters, taper angles, internal wall morphology, surface roughness, and oxygen content. Water-based assistance involved submerging the workpiece’s lower surface while keeping the upper surface in the air, whereas underwater processing involved fully immersing the specimen. The experimental results demonstrated that both aqueous environments effectively improved microhole quality compared to air processing. The water-assisted methods significantly enhanced the entrance/exit morphology by reducing ablation traces and slag deposits. The aqueous medium increased the entrance/exit diameters while decreasing the taper angles and effectively removing debris, thereby reducing internal wall roughness. Underwater processing achieved lower roughness at the hole entrances and middle sections compared to water-based assistance. Both water-assisted methods produced superior internal wall morphology to air processing, with comparable performance. These findings provide valuable references for optimizing water-assisted picosecond laser drilling processes. Full article

Aiming at the key technology of defect detection in precision additive manufacturing of highly reflective metal materials, this study proposes an enhanced SCK-YOLOV5 framework, which combines polarization imaging and deep learning methods to significantly improve the intelligent identification ability of small metal micro and nano defects. This framework introduces the SNWD (Selective Network with attention for Defect and Weathering Degradation) Loss function, which combines the SIOU Angle Loss with the NWD distribution sensing characteristics. It is specially designed for automatic positioning and identification of micrometer hole defects. At the same time, we employ global space construction with a dual-attention mechanism and multi-scale feature refining technique with selection kernel convolution to extract multi-scale defect information from highly reflective surfaces stably. Combined with the polarization imaging preprocessing and the comparison of enhancement defects under high reflectivity, the experimental results show that the proposed method significantly improves the precision, recall rate, and mAP50 index compared with the YOLOv5 baseline (increased by 0.5%, 1.2%, and 1.8%, respectively). It is the first time that this improvement has been achieved among the existing methods based on the YOLO framework. It creates a new paradigm for intelligent defect detection in additive manufacturing of high-precision metal materials and provides more reliable technical support for quality control in industrial manufacturing. Full article