Search Results (616)

This study investigates the influence of surface texturing on temperature distribution in lubricated sliding contacts using infrared thermography. The work addresses the broader challenge of understanding thermal effects in conformal hydrodynamic contacts, where localized heating and viscosity variations can significantly affect tribological performance. A pin-on-disc configuration was employed, featuring steel pins with laser-etched micro-dimples that slid against a sapphire disc, allowing for thermal imaging of the contact zone. A dual-bandpass filter infrared thermography technique was developed and rigorously calibrated to distinguish between the temperatures of the steel surface and the lubricant film. Friction measurements and laser-induced fluorescence were used in parallel to assess contact conditions and the behavior of the lubricant film. The results show that surface textures can alter local frictional heating and contribute to non-uniform temperature distributions, particularly in parallel contact geometries. Lubricant temperature was consistently higher than the surface temperature, highlighting the role of shear heating within the fluid film. However, within the tested parameter range, no unambiguous viscosity-wedge signature was identified beyond the dominant temperature-driven viscosity reduction captured by the in situ correction. The method provides a novel means of experimentally resolving temperature fields in sliding textured contacts, offering a valuable foundation for validating thermo-hydrodynamic models in lubricated tribological systems. Full article

In this work, we demonstrate precise control over laser-induced periodic surface structures (LIPSS) on stainless steel (SS) using femtosecond (fs) laser processing to suppress bacterial adhesion. We systematically compare the antifouling behavior of laser-textured surfaces with distinct pattern directionalities—linear and circular. Fs laser irradiation with linear polarization produces directional and anisotropic LIPSS, which progressively evolve into more complex hierarchical surface textures as processing conditions vary. In contrast, fs laser irradiation with circular polarization yields isotropic surface morphologies. Despite these morphological differences, the surface wettability remains nearly constant, with contact angles confined to a narrow range of 32.6–36.9°. Bacterial adhesion tests using Escherichia coli reveal that surfaces patterned with anisotropic features generated by linear polarization—particularly at an incident power of 30 mW—exhibit enhanced antifouling performance compared to isotropic counterparts. These results indicate that antifouling efficacy is governed not only by surface wettability but also by the spatial organization and anisotropy of the LIPSS. This study highlights the critical role of polarization-controlled fs laser processing in tailoring surface architectures and provides a rational strategy for designing bio-resistant metallic surfaces. Full article

This study evaluated the influence of various surface treatments on the bonding performance and mechanical behavior of zirconia, with particular emphasis on the effect of laser surface texturing (LST) compared with conventional 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and airborne particle abrasion (APA) methods. Two zirconia compositions, 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 5 mol% partially stabilized zirconia (5Y-PSZ), were subjected to four surface treatment protocols: as-milled, 10-MDP, APA, and LST (n = 12). Shear bond strength (SBS) to titanium and biaxial flexural strength (BFS) of zirconia were measured. Surface morphology, failure mode, and phase composition were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Data were analyzed with two-way ANOVA and Tukey’s post hoc test (α = 0.05), and the reliability of flexural strength was assessed using Weibull analysis. Surface treatment significantly affected SBS (p < 0.05). The LST groups exhibited the highest SBS values and a higher proportion of mixed failures, whereas other groups predominantly showed adhesive failures. However, LST-treated specimens, particularly 5Y-PSZ, showed reduced BFS. XRD confirmed phase stability, although localized microstructural changes were observed after LST. LST enhanced the zirconia–titanium interfacial bond strength and promoted mixed failure modes; however, this improvement was accompanied by a reduction in flexural strength, particularly in 5Y-PSZ. Full article

Surface finish plays a critical role in the tribological performance of additively manufactured engineering components. In exploring part characteristics in laser powder-bed fusion (L-PBF), this study investigates the effect of contouring strategies on the upskin surface of inclined specimens (30°, 45°, and 60°) made with L-PBF, using post- and pre-contouring strategies with various levels of process parameters. The surface data of fabricated inclined specimens were acquired by white-light interferometry, followed by a quantitative analysis using surface images. The results show that post-contouring leads to better surface finishes, with the lowest S_a of 8.68 µm attained at the highest laser power (195 W) and the slowest scan speed (500 mm/s) on 30°-inclined specimens, likely due to increased remelting and less step-edges. In contrast, pre-contouring produces distinct surface textures on the upskin of L-PBF specimens, resulting in a rougher surface morphology, with a maximum S_a of 33.39 µm also from 30°-inclined specimens at the lowest power (100 W) and the highest speed (2000 mm/s), suggesting an insufficient remelting of surface defects. In comparative analysis, in general, post-contouring yields smoother upskin surfaces, with a 17%–30% reduction in S_a, than those from equivalent pre-contouring conditions, highlighting the potential of scan sequences for optimizing L-PBF to improve the surface finish of inclined structures. Full article

Fiber laser surface texturing was applied to AA1050 aluminum to improve friction and wear performance of PTFE coatings. A Taguchi L16 design varied texture geometry (square, diamond, hexagon, circle), scanned area ratio (20% to 80%), and laser power (40 to 100 W) prior to primer plus PTFE topcoat deposition (25 to 35 µm). Dry reciprocating sliding against a 6 mm 100Cr6 ball was conducted at 20 N, 1 Hz, and 50 m, and wear track geometry was measured by non-contact profilometry. The non-textured reference exhibited an average COF of 0.143, whereas the lowest mean COF was achieved with diamond 60% and 40 W (0.095) and the highest with hexagon 60% and 100 W (0.156); hexagon 20% and 60 W matched the reference. ANOVA indicated scanned area ratio as the dominant contributor to COF (39.72%), followed by geometry (35.07%) and power (25.21%). Profilometry confirmed reduced coating penetration for optimized textures: the reference wear track was approximately 1240 µm wide and 82 µm deep, compared with 930 µm and 34 µm for square 80% and 40 W, 997 µm and 39 µm for diamond 60% and 40 W, and 965 µm and 36 µm for hexagon 40% and 40 W. Full article

CO₂ laser processing has emerged as an efficient dry-finishing technique capable of inducing controlled chemical and morphological transformations in cotton and denim textiles. The strong mid-infrared absorption of cellulose enables localised photothermal heating, leading to selective dye decomposition, surface oxidation, and micro-scale ablation while largely preserving the bulk fabric structure. These laser-driven mechanisms modify colour, surface chemistry, and topography in a predictable, parameter-dependent manner. Low-fluence conditions predominantly produce uniform fading through fragmentation and oxidation of indigo dye; in comparison, moderate thermal loads promote the formation of carbonyl and carboxyl groups that increase surface energy and enhance wettability. Higher fluence regimes generate micro-textured regions with increased roughness and anchoring capacity, enabling improved adhesion of dyes, coatings, and nanoparticles. Compared with conventional wet processes, CO₂ laser treatment eliminates chemical effluents, strongly reduces water consumption and supports digitally controlled, Industry 4.0-compatible manufacturing workflows. Despite its advantages, challenges remain in standardising processing parameters, quantifying oxidation depth, modelling thermal behaviour, and assessing the long-term stability of functionalised surfaces under real usage conditions. In this review, we consolidate current knowledge on the mechanistic pathways, processing windows, and functional potential of CO₂ laser-modified cotton substrates. By integrating findings from recent studies and identifying critical research gaps, the review supports the development of predictable, scalable, and sustainable laser-based cotton textile processing technologies. Full article

The operational ability of a unit or mechanism depends mainly on the quality of the mechanically produced working surfaces. Many materials can be assigned to a group of hard-to-cut materials that includes titanium- and aluminum-based alloys, a new class of heat-resistant alloys, SiCp/Al composites, hard alloys, and other alloys. The difficulties in their machining are related not only to the high temperatures achieved on the contact pads under mechanical load and the extreme cutting conditions but also to the properties of those materials, which affect the adhesion of the chip to the tool faces, hindering chip flow. One of the possible solutions to reduce those effects and improve the operational life of the tool, and as a consequence, the final quality of the working surface of the unit, is texturing the rake face of the tool with microgrooves or nanogrooves, microholes or nanoholes (pits, dimples), micronodes, cross-chevron textures, and other microtextures, the depth of which is in the range of 3.0–200.0 µm. This review is addressed at systematizing the data obtained on micro- and nanotexturing of PCD tools for cutting hard-to-cut materials by different techniques (fiber laser graving, femto- and nanosecond laser, electrical discharge machining, fused ion beam), additionally subjected to fluorination and dip- and drop-based coatings, and the effect created by the use of the textured PCD tool on the machined surface. Full article

This paper presents an experimental study on the influence of surface texturing on friction and film thickness in the hydrodynamic lubrication regime. Using a pin-on-disk tribometer equipped with light-induced fluorescence microscopy, simultaneous measurements were conducted on smooth and textured samples under parallel and inclined surface conditions. The circular faces of the pins were partially or fully covered by circular laser-machined textures consisting of dimples with depths of 5 or 10 µm, diameters of 50 or 100 µm, and coverage density of 20%. The results demonstrate that while texturing significantly reduces friction and increases film thickness in parallel gaps, with partial inlet coverage being the most effective, its impact is minimal in inclined wedge gaps. The study further reveals that the global geometric wedge dominates over texture effects in inclined contacts and that in-texture cavitation, prevalent in parallel conditions, is suppressed by surface inclination. Three distinct contributions of the textures were discussed: a global hydrodynamic effect, a local hydrodynamic effect, and the influence of surface non-flatness (waviness). The findings suggest that texturing is primarily beneficial for acting as a pseudo-wedge or as surface roughness in contacts where a physical wedge is absent. Full article

Pavement macrotexture, quantified by mean texture depth (MTD) and mean profile depth (MPD), is a critical parameter for road safety and performance. The traditional sand patch test is labor-intensive and slow, creating a bottleneck for modern pavement management systems. Accurately translating the rich point cloud data into reliable MTD values using the 3D scanning method remains a challenge, with current methods often relying on oversimplified correlations. This research addresses this gap by developing and validating a novel machine learning framework to predict MTD and MPD directly from high-resolution 3D laser scans. A comprehensive dataset of 127 pavement samples was created, combining traditional sand patch measurements with detailed 3D point clouds. From these point clouds, 27 distinct surface features spanning statistical, spatial, spectral, and geometric domains were developed. Six machine learning algorithms, consisting of Random Forest, Gradient Boosting, Support Vector Regression, k-Nearest Neighbor, Artificial Neural Networks, and Linear Regression, were implemented. The results demonstrate that the ensemble-based Random Forest model achieved superior performance, predicting MTD with an R² of 0.941 and a mean absolute error (MAE) of 0.067 mm, representing a 56% improvement in accuracy over traditional digital correlation methods. Model interpretation via SHAP analysis identified root mean square height (Sq) and surface skewness (Ssk) as the most influential features. Full article

The article addresses the issue of panoramic photogrammetry for the reconstruction of interior spaces. Such environments often present challenges, including poor lighting conditions and surfaces with variable texture for photogrammetric scanning. In this case study, we reconstruct the interior spaces of the historical house of Samuel Mikovíni, which represents these unfavorable conditions. The 3D reconstruction of interior spaces is performed using the Ricoh Theta Z1 spherical camera (Ricoh Company, Ltd.; Tokyo, Japan) in six variants, each employing a different number of images and different camera networks. Scale is introduced into the reconstructions based on significant dimensions measured with a measuring tape. A comparison is carried out using a point cloud obtained from terrestrial laser scanning and difference point clouds are generated for each variant. Based on the results, reconstructions produced from a reduced number of spherical images can serve as a basic source for simple documentation with accuracy up to 0.15 m. When the number of spherical images is increased and images from different height levels are included, the reconstruction accuracy improves markedly, achieving positional accuracy of up to 0.05 m, even in areas affected by poor lighting conditions or low-texture surfaces. The results confirm that for interior reconstruction, a higher number of images not only increases the density of the reconstructed point cloud but also enhances its positional accuracy. Full article

We explore the wettability modulation induced on alumina (Al₂O₃) targets by femtosecond laser texturing to demonstrate the stable and durable hydrophilic character of the surface. Specifically, we identify a suitable operational regime to tailor micro-nanostructures onto Al₂O₃ plates and accurately assess the ablation threshold in our experimental conditions. A periodic geometry with triangular patterns of various groove depths, ranging from 3.2 ± 0.1 to 17.1 ± 0.1 µm, was optimized for establishing a long-term wetting response. The latter was monitored on daily basis over a time interval exceeding 40 days by collecting the contact angle measurements of samples with and without a post-process thermal annealing, adopted to stabilize the surface wettability soon after the laser treatment. The results show that deeper grooves significantly enhance and maintain the hydrophilic character, particularly in samples without post-process thermal annealing, where superhydrophilicity (θ < 5°) is demonstrated to persist the entire time throughout the test. These findings disclose the potential for an effective fine-tuning of the alumina wettability, thus opening up the possibility of specific applications requiring long-term control of surface–liquid interactions, such as biomedical implants, and orthopedic and dental prostheses. Full article

Laser surface texturing (LST) is an effective method for enhancing surface functionality, but its effect on corrosion resistance highly depends on texture design and processing parameters. This study investigates the influence of two LST patterns—orthogonal ellipses and concentric octo-donuts—applied with 1 to 20 repetitions on the corrosion resistance of AISI 430 ferritic stainless steel. Corrosion behavior was evaluated using potentiodynamic polarization in a 3.5 wt.% NaCl solution at room temperature, complemented by SEM and EDS analysis. The results indicate that while a single laser pass can maintain good corrosion resistance, increasing the number of repetitions significantly degrades performance. This is attributed to the disruption of the protective oxide layer, the introduction of residual stress, and the creation of localized sites for galvanic corrosion. Consequently, the study concludes that a low number of laser repetitions is crucial for preserving the corrosion resistance of LST-processed AISI 430 steel. Full article

Machining of medium-carbon steels, such as AISI 1050, poses a significant challenge in terms of achieving stable cutting conditions, controlled chip evacuation and high surface integrity, in particular when full-face milling is performed under elevated material removal rates. The tool surface engineering approach, particularly laser-induced micro-texturing, comprises a promising route toward modifying the tribological conditions at the tool–chip interface, thus affecting friction, heat generation, chip formation and the resultant surface finish. This study investigates the combined effects of cutting speed, axial depth of cut and tool micro-texture orientation (parallel versus orthogonal to the chip flow direction) on machining performance under wet conditions. In addition to the experimental analysis of cutting forces, chip morphology and surface roughness, this work integrates a full factorial Design of Experiments, regression modeling, and ANOVA to quantify the statistical significance of each factor and to identify dominant interactions. The regression models show strong predictive capability across all measured responses, while the ANOVA confirms the axial depth of cut and tool texture orientation as the most influential parameters. Multi-objective optimization by Pareto analysis further underlines the superiority of orthogonal micro-texturing, which consistently reduces the cutting forces and improves surface quality while promoting controlled chip segmentation. The results provide quantitative and statistically validated evidence of the enhancement of lubrication effectiveness, reduction in interface friction, and stabilization in chip formation provided by the micro-textured tools. Overall, the findings contribute to the development of data-driven machining strategies and surface-engineered cutting tools in view of improved productivity, energy efficiency and surface integrity in advanced manufacturing applications. Full article

Background/Objectives: Non-ablative fractional lasers are widely used for scar remodeling, yet treatment parameters are often selected empirically, and thermal thresholds for consistent outcomes remain undefined. This study explored whether forward-looking infrared (FLIR) thermography can estimate laser-induced surface temperature changes during 1550 nm Er:Glass laser therapy and examined the association between post-treatment temperature elevation and early clinical improvement. Methods: A retrospective analysis was conducted on patients treated with fractional Er:Glass laser for post-surgical or traumatic scars. Skin temperature was recorded using FLIR C5 imaging at baseline (T₀), after topical anesthesia (T₁), and immediately post-treatment (T₂). The temperature change (ΔT₂) was calculated as T₂ − T₀. Clinical outcomes were assessed one month after treatment using standardized digital photographs and Vancouver Scar Scale (VSS) scores. Safety data were collected from post-procedure observations and patient reports. Results: Mean surface temperature increased from 32.4 ± 0.9 °C at T₀ to 33.7 ± 0.7 °C at T₂ (ΔT₂ = +1.3 ± 0.6 °C, p < 0.001). Hypertrophic scars showed higher ΔT₂ values than linear scars (p = 0.02). A moderate temperature elevation was modestly associated with early VSS improvement (r = 0.42, p = 0.003). Representative cases with ΔT₂ values around 1.5–2.5 °C exhibited favorable short-term changes in texture and pigmentation. No adverse events were observed during follow-up. Conclusions: Real-time FLIR thermography may provide a non-invasive method to indirectly assess surface thermal response during non-ablative fractional treatment. A moderate temperature increase may be associated with an exploratory thermal response range linked to early clinical improvement, but the findings are preliminary. Further prospective, controlled studies with standardized treatment parameters and longer follow-up are required to clarify whether ΔT₂ has clinical relevance as a physiologic parameter for temperature-based assessment in scar management. Full article

Poly(ether ether ketone)/carbon-fiber (PEEK/CF) composites possess excellent mechanical and thermal stability but exhibit inadequate friction and wear resistance for demanding tribological applications. In this study, femtosecond laser texturing was used to generate sinusoidal–circular hybrid microtextures on PEEK/CF surfaces, and the effects of laser power and geometric parameters were systematically evaluated through a Taguchi L9 design. The optimal laser power of 0.85 W produced the highest machining quality factor (MQF = 0.968). The textures caused a hydrophilic-to-hydrophobic transition, increasing the static contact angle from 43° to 96.2°. Under boundary lubrication, all textured specimens exhibited reduced steady-state friction compared with the untreated surface. Among them, specimen L7—corresponding to the largest amplitude (A) and wavelength (B) levels in the orthogonal design—achieved the lowest average coefficient of friction (≈0.12) and generated the narrowest wear track. These results demonstrate that femtosecond-laser-fabricated hybrid microtextures effectively enhance lubricant retention and improve the tribological performance of PEEK/CF composites. Full article