Search Results (2,067)

Beech (Fagus sylvatica L.) is a widely used hardwood species whose limited natural durability and dimensional instability under moisture restrict its outdoor applications. This study investigated the effect of vacuum impregnation with corn oil (Zea mays L.), a low-cost and underexplored vegetable oil, on the surface and hygroscopic properties of beech wood. Specimens were impregnated for 30 or 60 min and characterized, together with non-impregnated controls, for weight percentage gain (WPG), dimensional change, FTIR spectra, color, hardness, surface roughness, and contact angle, before and after accelerated artificial weathering in a Xenon chamber; hygroscopic behavior was further assessed through water absorption and dimensional swelling during 24 h of water immersion. FTIR analysis confirmed effective oil penetration into the wood structure through characteristic triglyceride absorption bands. Impregnation resulted in high oil uptake (WPG > 45%) at both durations without inducing substantial dimensional change and significantly increased the contact angle and reduced water absorption (by 65%–66%) and radial and tangential swelling relative to the controls (p < 0.05), while surface hardness remained unaffected (p = 0.263). Color difference (ΔE*) after artificial weathering was significantly higher in impregnated specimens than in the controls (p < 0.001), reflecting the natural yellowish hue of the oil rather than material degradation. Overall, corn oil impregnation, applied for as little as 30 min, improved the hydrophobicity and dimensional stability of beech wood without compromising its hardness, supporting its potential as a sustainable, bio-based wood modification medium. Full article

This paper presents the design, kinematic modeling, and dynamic simulation of a novel conical-slider-based transformable wheel with five deployable wheel-leg elements for mobile robotic systems. The proposed wheel can operate in a closed-wheel configuration for regular terrain and in an open wheel-leg configuration for enhanced interaction with rough terrain and obstacle profiles. The transformation motion is generated through a central linear actuation input transmitted by a conical slider mechanism integrated into the wheel hub. A CAD-supported mechanical design was developed to examine the geometric feasibility of the proposed wheel structure and to verify the radial deployment motion of the wheel-leg elements. The kinematic formulation was revised in a compact indexed form by consistently considering the angular offsets of all five wheel-leg elements. In addition, a dynamic model including the six-wheel vehicle body, suspension elements, wheel–ground contact, wheel-leg–ground contact, and wheel driving inputs was formulated. A unilateral contact model was used to represent contact, loss of contact, and re-contact events while preventing non-physical tensile normal forces. The proposed wheel concept was evaluated using a MATLAB-based representative mixed-terrain simulation scenario that combines rough-terrain locomotion and traversal of a 0.35 m single obstacle. The simulation results show that the fully deployed wheel-leg configuration successfully traverses the tested 0.35 m obstacle, whereas the closed-wheel configuration fails under the same terrain condition. Because the conical slider is continuously adjustable, an intermediate deployment state was also evaluated: it traverses a 0.30 m obstacle that the closed configuration cannot, yet fails against the 0.35 m obstacle, so that the traversal threshold varies monotonically with the deployment stroke. The comparison demonstrates that the deployed wheel-leg elements improve obstacle traversal capability by increasing the effective contact geometry and providing additional interaction with the obstacle surface. The results indicate that the proposed conical-slider-based transformable wheel has the potential to improve the terrain adaptability and obstacle traversal performance of six-wheel mobile robotic systems. Since the present study is limited to CAD-supported design verification and MATLAB-based dynamic simulation, future work will focus on prototype manufacturing, actuator design, structural analysis, and experimental validation under real terrain conditions. Full article

Interfaces at multiple scales within rocks critically control the mechanical properties of rock masses. However, the mechanisms by which interface roughness characteristics affect non-plastic deformation remain incompletely understood. In this study, particle-flow simulations were used to conduct loading–unloading tests on rough interfaces. The results show that contact surfaces inclined relative to the overall interface provide additional resistance during unloading and recovery, thereby increasing both the magnitude and likelihood of interfacial hysteresis. This mechanism explains why hysteresis can occur under loading normal to the interface. Differences between the static and dynamic friction coefficients, together with dynamic changes in the normal vectors of the contact surfaces, further intensify the hysteretic response. When deformation of the surrounding material is considered, the “lateral compression–expansion effect” caused by asperity extrusion and interlocking under compression, as well as the slip-induced “dilatancy effect,” also contributes substantially to rough-interface hysteresis. In addition, initial stress on crack surfaces can enhance the degree of hysteresis. The grain-based rock model incorporating interface roughness and in situ stress effectively reproduces the non-plastic hysteretic behavior of rocks. Full article

In the field of flexible electronics, traditional composite copper foils generally suffer from weak interfacial adhesion between the copper layer and polymer substrate, poor corrosion resistance, insufficient surface uniformity, and limited functional adaptability. To address these issues, Cu/Cu-CeO₂ composite coatings were deposited on polyimide (PI) substrates via PVD magnetron sputtering using argon as the working gas, aiming to enhance the comprehensive properties of composite copper foils, including interfacial bonding strength and corrosion resistance. Initially, pure Cu coatings were deposited on polyimide (PI), polyethylene terephthalate (PET), and polypropylene (PP) substrates. The deposition parameters were optimized through orthogonal and single-factor experiments, and the optimal process combination was determined as follows: PI substrate, sputtering time of 20 min, sputtering power of 60 W, and argon flow rate of 90 sccm, which achieved a balance between mechanical and electrical properties. Subsequently, comparative studies of Ar plasma treatment (100 s, 200 s, 300 s, and 400 s) and NaOH chemical etching (0 mol/L, 1 mol/L, 2 mol/L, and 3 mol/L) were conducted on the three polymer substrates. Comprehensive analyses of water contact angle, surface energy, bonding strength, and surface roughness demonstrated that the PI substrate treated with Ar plasma for 300 s exhibited superior overall performance, with a water contact angle of 48.5°, surface energy of 61.78 × 10⁻³ J/m², bonding strength of 4.56 N, and surface roughness of 0.89 μm. On this basis, the performance of pure Cu coatings and Cu/Cu-CeO₂ composite coatings prepared under different CeO₂ sputtering powers (20 W, 30 W, 40 W, and 50 W) was further investigated. Combined analyses of SEM, EDS, and XPS characterizations, together with bonding strength, resistivity, electrochemical impedance spectroscopy, polarization curves, and corrosion morphology tests, revealed that the Cu/Cu-CeO₂ composite coating prepared at a sputtering power of 50 W exhibited superior overall performance in terms of interfacial bonding strength and corrosion resistance. Full article

Compacted graphite iron (CGI) is widely used in thermomechanically demanding engineering applications owing to its high thermal conductivity, vibration-damping capacity, and machinability. However, its surface performance can be limited under the simultaneous effects of elevated temperature, sliding contact, and corrosive environments. In this study, CGI surfaces were subjected to pack boriding using a silica-free B₄C–NaBF₄ powder mixture at 800, 900, and 1000 °C for 4 h, and the microstructural characteristics of the resulting boride layers, together with their wear behavior at room temperature and 500 °C and their electrochemical corrosion resistance, were systematically investigated. Cross-sectional SEM/EDS analyses revealed the formation of boride layers exhibiting a saw-tooth interface morphology, with thickness increasing from 44 ± 4 µm to 108 ± 9 µm with increasing boriding temperature. XRD results indicated the formation of a dual-phase FeB/Fe₂B structure in all borided specimens, with the Fe₂B phase dominant at 800 °C and the FeB phase becoming dominant at 1000 °C. Boriding increased the surface hardness from approximately 470–480 HV to a range of 2122–2550 HV. In room-temperature wear tests, specimens B1 and B2 exhibited specific wear rates approximately 13-fold lower than that of the untreated CGI, whereas B3 showed a higher wear loss attributable to the brittle character of the FeB phase. At 500 °C, B1 maintained the most balanced tribological performance, with the lowest volumetric wear loss and coefficient of friction, while microcracking and three-body abrasion effects became more pronounced in B2 and B3. In electrochemical tests conducted in 3.5 wt.% NaCl solution, B1 exhibited more stable open-circuit potential behavior, whereas B3 showed the highest resistance in terms of Tafel kinetics, with the lowest corrosion current density and corrosion rate. Overall, the results demonstrate that the Fe₂B-dominant boride layer obtained at 800 °C provides the most balanced performance among hardness, wear, and corrosion behavior, whereas the thick, FeB-dominant layer formed at 1000 °C, despite offering high hardness and favorable corrosion kinetics, may compromise tribological reliability owing to its brittleness, increased surface roughness, and tendency toward microcracking. Full article

Bamboo is a renewable and mechanically robust bio-based material with potential for sand-barrier construction; however, its long-term outdoor use is limited by ultraviolet-induced photoaging, moisture uptake, wind-sand abrasion, and biological colonization. In this study, a fluorine-free EP/TiO₂/ODTMS superhydrophobic coating was deposited on moso bamboo using a simple spraying process. Rutile TiO₂ was incorporated as a roughness-building and ultraviolet-shielding filler, waterborne epoxy resin served as a film-forming binder to improve particle anchoring and coating cohesion, and octadecyltrimethoxysilane was used to reduce the surface energy. The formulation containing 50–100 nm rutile TiO₂ and 2 wt.% epoxy resin provided the best overall balance between surface wettability and mechanical durability, with a water contact angle of 156.4° and a sliding angle of 6.9°. SEM observations revealed a hierarchical surface composed of TiO₂ particles and microscale agglomerates immobilized within the epoxy matrix. EDS and FTIR results supported the incorporation of TiO₂- and ODTMS-derived components, while UV–Vis–NIR diffuse-reflectance measurements showed an improved optical response in the ultraviolet region. The coating retained superhydrophobicity after sandpaper abrasion, gravel impact, and tape-peeling tests. After 672 h of xenon-lamp aging, the coated bamboo maintained a water contact angle above 150°, exhibited a total color difference of approximately 7.65, and retained 91.1% of its initial flexural strength. In addition, qualitatively reduced visible mildew colonization was observed during 45 days of high-humidity exposure. These results demonstrate that the spray-deposited coating provides a fluorine-free and potentially scalable approach for improving the water repellency, mechanical durability, and accelerated-weathering resistance of bamboo sand-barrier materials. Full article

Industrial heritage sites have predominantly been examined through visual, material, and conservation-oriented frameworks, while the haptic and embodied ways in which contemporary users experience reused industrial heritage environments remain comparatively underexplored. Focusing on Tophane-i Amire Culture and Art Centre, a historically significant Ottoman industrial heritage site repurposed as a contemporary cultural and artistic centre, this study examines how material contact, bodily movement, and tactile encounters contribute to the sensory heritage experience. Rather than proposing haptic sensewalking as a new method, the study uses an existing sensewalking approach in a haptic-centred way within the specific context of an Ottoman industrial heritage site undergoing adaptive reuse. Sensory data were generated through in situ walking observations, embodied sensory narratives, tactile descriptions, researcher field notes, and post-walk reflective accounts. The findings suggest that, within this haptic-focused protocol, participants did not describe the site merely as a visual-historical object. Instead, they articulated Tophane-i Amire as an embodied haptic environment in which rough stone textures, participant-perceived coldness and material heaviness, spatial thresholds, uneven walking surfaces, and movement-based encounters made architectural space bodily noticeable. The study does not claim that ordinary visitors naturally prioritise haptic experience; rather, it examines what participants articulated when their sensory attention was deliberately oriented toward tactile, thermal, kinaesthetic, and embodied aspects of the reused industrial heritage environment. The article makes two main contributions. Empirically, it shows how participants described haptic experience at Tophane-i Amire through encounters with rough stone surfaces, participant-perceived thermal qualities, thresholds, floors, and bodily movement. Conceptually, it interprets industrial heritage not only as a visual or material object but also as an embodied haptic environment in which historical meaning is sensed through touch, temperature, movement, and spatial negotiation. Full article

This study focuses on how modulating the electrical pulse frequency alters both the topographic features and corrosion resistance of ceramic coatings produced via micro-arc oxidation (MAO) on an AZ31B magnesium substrate. In a silicate-based electrolyte, MAO treatments were executed utilizing four distinct frequencies: 300, 500, 800, and 1000 Hz. Phase configurations, microstructural features, and surface patterns were thoroughly evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM) integrated with energy dispersive spectroscopy (EDS), and an ultra-depth-of-field microscope. Furthermore, the fabricated coatings underwent rigorous assessments for their porosity, contact angle, Vickers hardness, and electrochemical attributes. The outcomes demonstrate that the surface appearance, phase structure, defect state, and density of the MAO coatings are highly sensitive to variations in pulse frequency. Notably, although the coating prepared at 800 Hz exhibited elevated surface roughness (Ra), it achieved a highly consolidated microstructure and the lowest porosity level, underscoring that roughness alone is not a definitive quality indicator. This structural refinement was driven by the presence of well-crystallized Mg₂SiO₄ and MgO phases. This group recorded a peak inner barrier layer resistance (R_b) of 1.62 × 10⁴ Ω·cm² alongside a minimum corrosion current density (I_corr) of 3.38 × 10⁻⁷ A·cm⁻², confirming its exceptional protective capacity. Consequently, the structural quality and corrosion resistance of MAO coatings can be strategically enhanced by tuning the electrical frequency, offering valuable engineering guidelines for utilizing AZ31B alloy parts under aggressive environmental conditions. Full article

Additive manufacturing (AM) enables rapid, near-net-shape fabrication with high material efficiency, but the resulting components often exhibit surface roughness, microstructural heterogeneity, and tensile residual stresses that reduce their performance. Machine hammer peening (MHP) is a mechanical surface treatment capable of modifying the surface integrity of AM components. It can be applied either as a conventional post-processing step after fabrication or as a hybrid interlayer treatment integrated into the build process. In this study, the effects of MHP process parameters and treatment strategies on wire-based laser metal deposition (LMD-w) Inconel 718 components were investigated, including the implementation of hybrid interlayer MHP. Surface topography, hardness, microstructure, and residual stresses were examined experimentally, while numerical simulations were developed to support the measurements and to characterize local contact conditions and plastic strain evolution during peening. The results show that MHP significantly reduces surface waviness and roughness, increases near-surface hardness, refines the microstructure, and introduces deep compressive residual stresses. Furthermore, hybrid interlayer MHP enhances the depth and uniformity of the modified layer by influencing the evolving microstructure during deposition. Standard forged Inconel 718 samples were also treated with MHP as a reference, showing comparable characteristics between the forged and AM components. These findings demonstrate that MHP is a versatile and effective modification technique for improving the performance and reliability of AM components, particularly when implemented as a hybrid interlayer treatment during the AM process. Full article

Contactless gas-phase boriding is suitable for strengthening the surface of precision steel components because it avoids direct contact between the workpiece and the boriding medium, thereby helping to maintain dimensional accuracy and surface roughness. To address the toxicity, corrosiveness, flammability, and strict gas-handling requirements associated with externally supplied boron-containing gaseous precursors in conventional gas-phase boriding, this study proposes a novel sealed-container structure for contactless gas-phase boriding, in which powder-filled pockets are distributed along the inner wall of the sealed container, and conducts experimental investigations on gas-phase boriding. Compared with the conventional structure, the modified container places the powder charge in wall-mounted pockets close to the heated container wall, thereby accelerating powder heating. This arrangement also reduced the powder-heating time from approximately 1.1 h to 0.85 h and promoted the earlier generation of an active boron-containing atmosphere, shortening the boriding holding time from 3 h to 1.5 h. Meanwhile, the average boride-layer thickness increased from approximately 54 μm to 117 μm, and the maximum surface microhardness reached 3500 HV. These results indicate that improving the sealed-container structure and optimizing the arrangement of the powder boron source can effectively intensify the contactless gas-phase boriding process. A thick boride diffusion layer can be rapidly formed while maintaining limited dimensional change and acceptable surface roughness. Full article

Contact-angle prediction from literature data is vulnerable to target leakage when solid surface-free-energy descriptors are reconstructed using the liquid, which is later treated as the target. We developed a target-masked workflow that removes the target liquid before fitting nonnegative Owens-Wendt-Rabel-Kaelble components by nonnegative least squares and uses that physical prediction to anchor residual learning. A row-level revision audit re-extracted or excluded mismatched legacy sources before all models were retrained. Development used nested source-group cross-validation; the fixed cross-source external confirmation set was excluded from selection. The revised residual model achieved mean absolute errors of 15.5 degrees in nested validation and 13.2 degrees on that confirmation set. Surface-cluster bootstrap supported improvement over physics, whereas source-cluster uncertainty remained substantial. Diagnostics showed source dependence, sparse roughness, and limited strict unseen-liquid support. The method is therefore positioned as an auditable, risk-aware and reproducible materials-screening tool for surfaces with at least two non-target probes, with explicit out-of-distribution risk and refusal conditions rather than universal transfer claims. Full article

The non-Gaussian height distribution and power spectral density (PSD) characteristics of rough surfaces have significant effects on the real contact area, local pressure distribution, oil-film formation, and friction and wear behavior of lubricated contact interfaces in mechanical components. Conventional methods for generating non-Gaussian rough surfaces commonly rely on iterative correction under explicit statistical constraints, which limits their computational efficiency in large-scale sample generation. To address this issue, this study proposes a PSD-amplitude-constrained phase conditional variational autoencoder (phase C-VAE) for generating non-Gaussian rough surfaces. Unlike conventional constructive methods that repeatedly correct surface samples under explicit statistical constraints, the proposed method learns the conditional distribution of the Fourier phase, while the spectral amplitude used for reconstruction is directly determined from the prescribed PSD. By taking the target skewness, kurtosis, and PSD as conditional inputs, the proposed method achieves joint control of higher-order statistical characteristics and spectral characteristics within a unified generative framework. Under target conditions derived from measured surfaces, the generated non-Gaussian rough surface samples achieved mean absolute relative errors of $0.056\%$ and $0.044\%$ for skewness and kurtosis, respectively, with a generation time of $24.62\mathrm{s}$. These results indicate that the proposed method can effectively match the target skewness and kurtosis while maintaining good consistency between the generated surfaces and the target PSD. The proposed method alleviates the efficiency limitation of conventional constructive methods in the large-scale generation of non-Gaussian rough surface samples and provides an effective machine-learning-based generative approach for rapid batch modeling of rough surfaces in lubrication, friction, and contact analyses. Full article

This study investigates the tribological behavior of the attachment force between bio-inspired claw–spines and rough surfaces and conducts theoretical and model-based analyses of the corresponding attachment mechanism. Based on critical interfacial tribological theory, a frictional mechanics model for a single claw–spine interacting with an arbitrary rough surface was developed. Furthermore, a stiffness-matrix-based mechanical model of bio-inspired claw–spine attachment to arbitrary surfaces was established, together with a contact interaction model between the claw–spine and the contact surface. The force distribution during the contact and attachment of the claw–spine to arbitrary surfaces was analyzed in detail. Criteria for determining stable claw–spine attachment were formulated, and the safe range of frame displacement variation under the corresponding conditions was identified. Based on these analytical results, a test platform for the bio-inspired claw–spine attachment structure was designed. In the experiments, the developed attachment-force measurement system was used to measure and analyze the frictional attachment forces generated by the claw–spine foot on different rough surfaces. After the claw–spine entered the stable attachment stage, the maximum claw–spine attachment forces measured on 60-grit, 80-grit, and 120-grit sandpaper surfaces were 0.62 N, 0.54 N, and 0.61 N, respectively. The corresponding maximum attachment forces measured on horizontal and vertical brick surfaces were 0.92 and 0.99 N, respectively. The results provide a basis for the mechanical analysis and force sensing of bio-inspired claw–spine attachment states and establish theoretical and experimental foundations for subsequent research on attachment-state recognition and motion control based on attachment-force feedback. Full article

Contact fatigue, bending fatigue, and wear failures in gears are governed by the stress state, hardening gradient, microstructural stability, and surface topography within the near-surface and subsurface regions. For tooth flanks, rolling–sliding contact, asperity interaction, lubricant-film disturbance, and subsurface shear stress control micropitting, pitting, and spalling. For tooth-root fillets, local stress concentration and surface or near-surface defects dominate bending-fatigue crack initiation. Laser shock peening (LSP) introduces deep compressive residual stress, gradient hardening, and microstructural refinement, and is therefore relevant to gears when these effects are matched to the critical damage zones. This review examines LSP of gear steels and related load-bearing steels from the viewpoint of tooth-flank and tooth-root damage control. It links laser parameters, shock-induced plastic deformation, residual-stress depth, hardening response, surface roughness, and profile accuracy to bending fatigue, rolling contact fatigue, and wear behavior. LSP is most effective when the compressive residual-stress layer and hardened layer reach the contact- or bending-damage depth while lubrication compatibility, flank form accuracy, and subsequent finishing are preserved. Excessive pulse energy, overlap, or unstable absorbing/confining conditions may increase roughness, produce ablation or micropitting-sensitive defects, and compromise tooth profile accuracy. Thus, LSP for gears should be evaluated together with carburizing, nitriding, shot peening, surface rolling, polishing, coatings, and laser texturing rather than as an isolated treatment. The central task is to define gear-specific process windows that balance residual-stress depth, surface integrity, dimensional accuracy, and manufacturing repeatability. Full article

Antimicrobial resistance is a critical global challenge that necessitates the development of durable, material-based strategies to limit pathogen survival and transmission. Conventional cleaning and disinfection methods only provide transient protection due to rapid surface re-contamination. This study investigates the fabrication of polyethylene terephthalate (PET) surfaces designed for antibacterial applications via femtosecond laser-induced micro- and nanostructuring. Surface texturing was performed using a Ti:sapphire femtosecond laser (wavelength λ = 800 nm, pulse duration τ = 70 fs) at peak laser fluences (F) of 2.04 J/cm² and 4.08 J/cm², generating hierarchical surface textures with controlled morphology, spacing, and geometry through ultrafast, non-contact laser processing while preserving the bulk properties of PET. The resulting patterns, including parallel and intersecting microchannels decorated with laser-induced nanostructures, enabled tunable surface roughness and wettability, with water contact angles ranging from 33.21° to 118.2°. Comprehensive surface characterization, including morphological, topographical, and wettability analyses, was performed to establish structure–property relationships associated with previously reported antibacterial surface design principles. However, direct antibacterial performance was not evaluated in the present study and will be the subject of future investigations. In addition, the durability of the laser-structured PET was evaluated under simulated real-life conditions, including thermal cycling, ultraviolet exposure, abrasion, chemical resistance, and dust contamination. The structured surfaces demonstrated high structural and functional stability following environmental testing. The results indicate that the laser-induced surface modifications remain stable under conditions representative of prolonged practical use, supporting their potential long-term applicability for antibacterial and self-cleaning PET surfaces. Full article