Search Results (331)

Tandem cylinders, widely used in heat exchangers, water storage units, and electronic cooling, require optimized flow and heat transfer to enhance engineering performance. However, the combined effects of various factors in tandem configurations remain insufficiently explored. This study proposes an innovative approach that integrates multiple parameters to systematically investigate the influence of surface pattern characteristics and rotational speed on the fluid dynamics and heat transfer performance of tandem cylinders. Numerical simulations are conducted to evaluate the effects of various pattern dimensions (w/D = 0.12–0.18), surface shapes (square, triangular, and dimpled grooves), rotational speeds (|Ω| ≤ 1), and frequencies (N = 2–10) on fluid flow and heat transfer efficiency at Re = 200. The study aims to establish the relationship between the complexity of the coupling effects of the considered parameters and the heat transfer behavior as well as fluid dynamic variations. The results demonstrate that, under stationary conditions, triangular grooves exhibit larger vortex structures compared to square grooves. When a positive rotation is applied, coupled with increases in w/D and N, square grooves develop a separation vortex at the front. Furthermore, the square and dimpled grooves exhibit significant phase control capabilities in the time evolution of lift and drag forces. Under conditions of w/D = 0.12 and w/D = 0.18, the C_L of the upstream cylinder decreases by 17.2% and 20.8%, respectively, compared to the standard smooth cylinder. Moreover, the drag coefficient C_D of the downstream cylinder is reduced to half of the initial value of the upstream cylinder. As the surface amplitude increases, the C_D of the smooth cylinder surpasses that of the other groove types, with an approximate increase of 8.8%. Notably, at Ω = −1, the downstream square-grooved cylinder’s C_L is approximately 12.9% lower than that of other groove types, with an additional 6.86% reduction in amplitude during counterclockwise rotation. When N increases to 10, the of the upstream square-grooved cylinder at w/D = 0.18 decreases sharply by 20.9%. Conversely, the upstream dimpled-groove cylinder significantly enhances at w/D = 0.14 and N = 4. However, the upstream triangular-groove cylinder achieves optimal stability at w/D ≥ 0.16. Moreover, at w/D = 0.18 and N = 6, square grooves show the most significant enhancement in vortex mixing, with an increase of approximately 42.7%. Simultaneously, the local recirculation zones in dimpled grooves at w/D = 0.14 and N = 6 induce complex and geometry-dependent heat transfer behaviors. Under rotational conditions, triangular and dimpled grooves exhibit superior heat transfer performance at N = 6 and w/D = 0.18, with TPI values exceeding those of square grooves by 33.8% and 28.4%, respectively. A potential underlying mechanism is revealed, where groove geometry enhances vortex effects and heat transfer. Interestingly, this study proposes a correlation that reveals the relationship between the averaged Nusselt number and groove area, rotational speed, and frequency. These findings provide theoretical insights for designing high-efficiency heat exchangers and open up new avenues for optimizing the performance of fluid dynamic systems. Full article

As a novel class of thin films, thin-film metallic glasses (TFMGs) hold broad application prospects in biomedicine, electronic components, etc. In this study, CuZr TFMGs were deposited at room temperature using a medium-frequency magnetron sputtering (MFMS) technique. The effects of bias voltage on the microstructure and properties of the films were systematically investigated. The results indicate that the CuZr system exhibits excellent glass-forming ability (GFA), with films possessing a smooth surface. As bias voltage increases, cross-sectional morphology transitions from a glassy morphology to a dimple-like structure. The high bias voltage induces reduced dimple size and significantly increased density. At a bias voltage of −50 V, the hardness of CuZr film reaches a maximum of 9.6 GPa. This hardness is approximately five times and twice that of pure Cu and Zr films, respectively. Compared with Zr film, CuZr TFMGs exhibit a significantly reduced friction coefficient while maintaining a low wear rate. All CuZr films demonstrate excellent electrical conductivity and hydrophobicity, providing the basis for future potential applications. Full article

Recently, considerable research has been conducted on wet shot peening (WSP), but a detailed investigation of this process is still lacking. For a systematic study, four three-dimensional models of WSP and shot peening (SP) were developed using the finite element method (FEM), based on the coupled Eulerian–Lagrangian (CEL) method. Micron-scaled water film is directly observed during WSP processing. Simulation results indicate that the water film has a significant impact on the dimple size and residual stress distribution. Compared with SP, WSP can produce (a) a dimple with a larger curvature radius, (b) greater compressive residual stress in the surface layer with a larger area, and (c) more uniformly distributed surface residual stress. This work reveals the mechanism underlying the changes mentioned above, which provides rationales for the promotional applications of WSP. Full article

Interest in textured surfaces for biomaterials and implants is increasing, with shot peening emerging as a promising method for surface modification. This study investigates the influence of conventional and fine shot peening on the surface morphology, topography, wettability, and antibacterial properties of biomedical-grade Ti6Al4V alloy. Peening was conducted using a custom-built, fully automated system, employing fine (100–200 µm) and coarse (700–1000 µm) shots using well-controlled sets of parameters. Both treatments introduced severe plastic deformation on the surface, resulting in increased roughness. Conventionally shot-peened samples exhibited deeper and wider dimples compared to finely peened ones. Surface wettability shifted from hydrophilic (contact angle: ~4°, untreated) to hydrophobic, reaching contact angles of ~91° and ~100° for fine and conventional shot peening, respectively. Antibacterial assays against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were evaluated by normalizing colony counts to the untreated Ti6Al4V surface. The inherent antibacterial response of Ti6Al4V against E. coli was preserved after both shot peening treatments, showing no notable increase in bacterial proliferation. In contrast, adhesion of S. aureus increased, more notably on fine shot-peened surfaces, indicating a strain-specific response influenced by surface roughness and wettability. In summary, both fine and conventional shot peening altered the surface morphology, topography, and wettability of Ti6Al4V. At the same time, their antibacterial influence was strain-dependent, underscoring the need for careful parameter selection in biomedical applications. Full article

The reduced ductility caused by the brittle needle-like α′ martensite limits the application of TC4 alloys produced by selective laser melting (SLM). Appropriate heat treatment can improve the microstructures and properties of SLM-fabricated TC4 alloys. In this work, SLM-fabricated TC4 alloys underwent stress relief annealing at 600 °C and high-temperature annealing at 800 °C. The effects of heat treatment temperature on phase composition, microstructural morphology, grain orientation, and mechanical properties were investigated. Meanwhile, the microstructural evolution and fracture mechanisms during the heat treatment process were analyzed. The results indicate that after annealing at 600 °C, the needle-like α′ phase transforms into elongated α, and nano-β phase increases. When annealed at 800 °C, the α′ phase completely transforms into a more stable lath-shaped α phase and a short rod-shaped β phase, with the nano-β phase disappearing. The texture orientation gradually shifts from <0001> towards <01-10>, where slip systems are more active. Additionally, heat treatment promotes the transition of grain boundaries to high-angle grain boundaries, thereby alleviating stress concentration and enhancing solid-solution strengthening. After heat treatment, the ultimate tensile strength of the material slightly decreases, but the elongation significantly increases. As the annealing temperature increased, the elongation (EL) improved from 5.22% to 11.43%. Following high-temperature annealing at 800 °C, necking and larger dimples appear on the fracture surface, and the fracture mechanism shifts from a mixed brittle–ductile fracture to a ductile fracture. This work provides a theoretical basis for improving the microstructures and properties of SLM-fabricated TC4 alloys through heat treatment. Full article

Surface texturing involves creating micro-channels, micro-dimples, micro-grooving, and other surface modifications. To do this, laser and micromachining are employed on the substrate surface in addition to other methods. The surface characteristics of the Arboblend V2 Nature biodegradable polymers with laser texturing, hexagonal and square patterns, and four and six passes are shown in this study. Regardless of the texture type, Arboblend V2 Nature’s hydrophilic surface (a contact angle of less than 90°) was demonstrated by the results of the wettability test. The underlying material’s wear behavior changed as a result of the LST surface modification. The COF values increased only after six passes with both textures. On the topographical side, Arboblend V2 Nature (square and hexagonal) shows a consistent X-axis expansion in the hexagonal geometry and a considerable amount of variability in the square geometry, especially at six passes, where the Y-axis (higher depths) is more compressed. According to the results, since textured surfaces are practicable, non-biodegradable polymers from a variety of industries can be substituted. Full article

Background: Inhaled delivery of cannabidiol (CBD) through dry powder inhalers is a promising approach for achieving optimal drug concentrations in the lungs. Spray drying is a commonly employed technique to prepare inhalable powders with particle sizes ideally ranging from 1 to 5 µm, for deep lung deposition. However, formulating aerosolizable CBD dry powders remains challenging due to the thermolabile nature of CBD and the cohesive behaviour of micron-sized particles, which affects powder dispersibility, reduces de-agglomeration during inhalation, and causes inefficient lung deposition. These challenges can be overcome by the inclusion of excipients that can stabilize CBD during processing and enhance the dispersion and aerosolization of the powder. Objectives and methods: This study investigates the role of different amino acids (lysine, cysteine, arginine, and phenylalanine) in combination with inulin, a sugar-based excipient, on the in vitro aerosolization performance, stability, and cytotoxicity of inhalable CBD dry powders. Results and conclusion: The prepared CBD dry powders exhibited a size range of 1–5 µm. Amino-acid-free CBD powder showed an irregular and flaky morphology, while in association with amino acids, CBD dry powder showed spherical morphology with a dimpled surface. The ATR-FTIR spectra confirmed no interactions between CBD and amino acids in the dry powder formulations. CBD dry powder formulations containing amino acids demonstrated a better aerosolization profile compared to amino-acid-free CBD powder, with the lysine-containing formulation achieving the highest fine particle fraction (FPF) of 56.6%. Additionally, all the formulations were stable under low and high humidity (<15% RH and 53% RH) conditions for 28 days. Cytotoxicity studies on A549 alveolar basal epithelial cells showed that the amino acids were non-toxic, while the CBD formulations with/without amino acids showed comparable levels of cytotoxicity. Full article

Micro-textures are crucial for enhancing surface performance in diverse applications, but traditional radial electrochemical micromachining (REMM) suffers from process complexity and workpiece damage. This study presents radial ultrasonic rolling electrochemical micromachining (RUREMM), an advanced technique integrating an ultrasonic field to improve electrolyte renewal, disrupt passivation layers, and optimize electrochemical reaction uniformity on SS304 surfaces. Aimed at overcoming challenges in precision machining, the research explores the synergistic effects of ultrasonic energy and flow field dynamics, offering novel insights for high-quality metal micromachining applications. The research establishes a mathematical model to analyze the interaction between the ultrasonic energy field and electrolytic machining and optimizes the flow field in the narrow electrolytic gap using Fluent software, revealing that an initial electrolyte velocity of 4 m/s and ultrasonic amplitude of 35 μm ensure optimal stability. High-speed photography is employed to capture bubble distribution and micro-pit formation dynamics, while SS304 surface experiments analyze the effects of machining parameters on micro-dimple localization and surface quality. The results show that optimized parameters significantly improve micro-texture quality, yielding micro-pits with a width of 223.4 μm, depth of 28.9 μm, aspect ratio of 0.129, and Ra of 0.205 μm, providing theoretical insights for high-precision metal micromachining. Full article

Cellulite, characterised by cutaneous dimpling, surface irregularities, and dermal atrophy skin texture, affects up to 90% of post-pubertal females. It is a multifactorial condition involving anatomical, hormonal, and metabolic components, primarily affecting the thighs and buttocks. Despite numerous available therapies, there remains a high demand for effective, non-invasive, and well-tolerated treatment options. This single-centre, in vivo, prospective study evaluated the efficacy of a non-pharmacological, thermogenic topical cream-gel combined with manual massage in women with symmetrical grade II or III cellulite (Nürnberger–Müller scale). A total of 56 female participants (aged 18–55 years) were enrolled and instructed to apply the product twice daily for eight weeks to the thighs and buttocks. Efficacy was assessed using instrumental skin profilometry (ANTERA^® 3D CS imaging system), dermatological clinical grading, and patient self-assessment questionnaires. Quantitative analysis showed a mean reduction of 23.5% in skin indentation volume (p < 0.01) and a mean decrease of 1.1 points on the cellulite severity scale by week 8. Patient-reported outcomes revealed 85.7% satisfaction with visible results and 91% satisfaction with product texture and ease of application. Dermatological evaluation confirmed no clinically significant adverse reactions, and only 3.5% of participants reported mild and transient skin sensitivity. These findings suggest that this topical cream-gel formulation, when used in conjunction with manual massage, represents a well-tolerated and non-invasive option for the cosmetic improvement of moderate to severe cellulite. Full article

The surface topography of the rolls used in skin-pass cold rolling determines the surface finish of rolled sheets. In this sense, work rolls can be intentionally textured to produce certain topographical features on the final sheet surface. The maskless electrochemical texturing method (MECT) is a potential candidate for industrial-scale application due to its reduced texturing cost and time when compared to traditional texturing methods. However, there are few studies in the literature that address the MECT method applied to the topography control of cold rolling work rolls. The present work aims to analyze the viability of surface texturing via MECT of work rolls used in skin-pass cold rolling. In this study, we first investigated how texturing occurs for tool steel using flat textured samples to facilitate the understanding of the dissolution mechanisms involved. In this case, a specially designed texturing chamber was built to texture flat samples extracted from an actual work roll. The results indicated that the anodic dissolution involved in tool steel texturing occurs preferentially in the metallic matrix around the primary carbides. Then, we textured a work roll used in pilot-scale rolling tests, which required the development of a special prototype to texture cylindrical surfaces. After texturing, the texture transfer from the work roll to the sheets was investigated. Rolling tests showed that the work roll surface textured with a dimple pattern generated a pillar-shaped texture pattern on the sheet surface, possibly due to a reverse extrusion mechanism. Full article

Wide-range electric submersible centrifugal pumps (ESPs) are critical for offshore oilfields but suffer from narrow high-efficiency ranges and frictional losses under dynamic reservoir conditions. This study introduces bio-inspired dimple-type non-smooth surfaces on impeller blades to enhance hydraulic performance. A combined numerical-experimental approach was employed: a 3D CFD model with the k-ω turbulence model analyzed oil–water flow (1:9 ratio) to identify optimal dimple placement, while parametric studies tested diameters (0.6–1.2 mm). Experimental validation used 3D-printed prototypes. Results revealed that dimples on the pressure surface trailing edge reduced boundary layer separation, achieving a 12.98% head gain and 8.55% efficiency improvement at 150 m³/d in simulations, with experimental tests showing an 11.5% head increase and 4.6% efficiency gain at 130 m³/d. The optimal dimple diameter (0.9 mm, 2% of blade chord) balanced performance and manufacturability, demonstrating that bio-inspired surfaces improve ESP efficiency. This work provides practical guidelines for deploying drag reduction technologies in petroleum engineering, with a future focus on wear resistance in abrasive flows. Full article

Silicon nitride (Si₃N₄) ceramic is widely used in the production of structural components. The surface wettability is closely related to the service life of materials. Laser surface texturing is considered an effective method for controlling surface wettability by processing specific patterns. This research focused on the laser surface texturing of a Si₃N₄ ceramic, employing rectangular patterns instead of the typical dimple designs, as these had promising applications in heat transfer and hydrodynamic lubrication. The effects of scanning speed and number of scans on the change of the morphologies and dimensions of the grooves were investigated. The results indicated that the higher scanning speed and fewer number of scans resulted in less damage to the textured surface. As the scanning speed increased, the width and depth of the grooves decreased significantly first, and then fluctuated. Conversely, increasing the number of scans led to an increase in the width and depth of the grooves, eventually stabilizing. The analysis of the elemental composition of different areas on the textured surface presented a notable increase in oxygen content at the grooves, while Si and N levels decreased. It was mainly caused by the chemical reaction between Si₃N₄ ceramic and oxygen during laser surface texturing in an air environment. This study also assessed the wettability of the textured surface, finding that the contact angle of the water droplet was significantly affected by the groove dimensions. After laser surface texturing, the contact angle increased from 35.51 ± 0.33° to 57.52 ± 1.83°. Improved wettability was associated with smaller groove volume, indicating better hydrophilicity at lower scanning speed and enhanced hydrophobicity with a fewer number of scans. Full article

This study presents a computational fluid dynamics (CFDs) investigation of the hydrodynamic behavior of surface-textured lateral bushings in external gear pumps (EGPs), emphasizing the effects of combined sliding and squeezing motions within the lubrication gap. A comprehensive numerical model was developed to analyze how surface texturing implemented through different dimple shapes and texture densities influences pressure distribution and load-carrying capacity under transient lubrication conditions. The analysis demonstrates that the interaction between shear-driven flow and squeeze-film compression significantly amplifies pressure, particularly when optimal dimple configurations are applied. Results indicate that dimple geometry, depth, and arrangement critically influence hydrodynamic performance, while excessive texturing reduces effectiveness due to increased average gap height. Cavitation was intentionally not modeled in the early single dimple evaluations to allow clear comparison between configurations. The findings offer a design guideline for employing surface textures to enhance tribological performance and efficiency in EGP applications under realistic dynamic conditions. Full article

During the service life of automotive panel stamping dies, the surface is often subjected to high loads and repeated friction, resulting in excessive wear. This leads to die failure, reduced machining accuracy, and decreased production efficiency. To enhance the anti-friction and wear-resistant performance of die steel surfaces, this study introduces the concept of biomimetic engineering in surface science. By mimicking microstructural configurations found in nature with outstanding wear resistance, biomimetic functional surfaces were designed and fabricated. Specifically, quadrilateral dimples inspired by the back of dung beetles, pentagonal scales from armadillo skin, and hexagonal scales from the belly of desert vipers were selected as biological prototypes. These surface textures were fabricated on Cr12MoV die steel using high-speed ball-end milling. Finite element simulations and dry sliding wear tests were conducted to systematically investigate the tribological behavior of surfaces with different dimple geometries. The results showed that the quadrilateral dimple surface derived from the dung beetle exhibited the best performance in reducing friction and wear. Furthermore, the milling parameters for this surface were optimized using response surface methodology. After optimization, the friction coefficient was reduced by 21.3%, and the wear volume decreased by 38.6% compared to a smooth surface. This study confirms the feasibility of fabricating biomimetic functional surfaces via high-speed ball-end milling and establishes an integrated surface engineering approach combining biomimetic design, efficient manufacturing, and parameter optimization. The results provide both theoretical and methodological support for improving the service life and surface performance of large automotive panel dies. Full article

Aluminum alloy, due to its low melting point and high thermal conductivity, deforms and contracts significantly during welding. To mitigate this and achieve full penetration in a single pass, this study uses GTAW (Gas Tungsten Arc Welding) additive manufacturing and optimizes welding groove parameters via the Box-Behnken Response Surface Methodology. The focus is on improving tensile strength and penetration depth by analyzing the effects of groove angle, root face width, and root gap. The results show that groove angle most significantly affects tensile strength and penetration depth. Hardness profiles exhibit a W-shape, with base material hardness decreasing and weld zone hardness increasing as groove angle rises. Root face width reduces hardness fluctuation in the weld zone, and an appropriate root gap compensates for thermal expansion, enhancing joint performance. The interaction between root face width and root gap most impacts tensile strength, while groove angle and root face width interaction most affects penetration depth. The optimal welding parameters for 7xxx aluminum alloy GTAW are a groove angle of 70.8°, root face width of 1.38 mm, and root gap of 0 mm. This results in a tensile strength of 297.95 MPa and penetration depth of 5 mm, a 90.38% increase in tensile strength compared to the RSM experimental worst group. Microstructural analysis reveals the presence of β-Mg₂Si and η-MgZn₂ strengthening phases, which contribute to the material’s enhanced mechanical properties. Fracture surface examination exhibits characteristic ductile fracture features, including dimples and shear lips, confirming the material’s high ductility. The coexistence of these strengthening phases and ductile fracture behavior indicates excellent overall mechanical performance, balancing strength and plasticity. Full article