Search Results (129)

The structural units with different characteristic scales in gradient nanostructured (GS) 316L stainless steel act synergistically to achieve the matching of strength and plasticity, and the intrinsic plasticity of nanoscale and ultrafine grains is fully demonstrated. The macroscopic stress–strain responses of each material unit in the GS surface layer can be measured directly by tension or compression tests on microspecimens. However, the experimental results based on microspecimens do not reflect either the extraordinary strengthening effect caused by non-uniform deformation or the intrinsic plasticity of nanoscale and ultrafine grains. In this paper, a method for constructing depth-dependent constitutive relationships of GS materials was proposed, which combines strain hardening parameter (hardness) with physics-informed neural networks (PINNs). First, the microhardness distribution on the specimen cross-sections was measured after stretching to different strains, and the hardness–strain–force test data were used to construct the depth-dependent PINNs model for the true strain–hardness relationship (PINNs_εH). Hardness–strain–force test data from specimens with uniform coarse grains were used to pre-train the PINNs model for hardness and true stress (PINNs_Hσ), on the basis of which the depth-dependent PINNs_Hσ model for GS materials was constructed by transfer learning. The PINNs_εσ model, which characterizes the depth-dependent constitutive relationships of GS materials, was then constructed using hardness as an intermediate variable. Finally, the accuracy and validation of the PINNs_εσ model were verified by a three-point flexure test and finite element simulation. The modeling method proposed in this study can be used to determine the position-dependent constitutive relationships of heterogeneous materials. Full article

Janus nanoparticles (JNPs) extend the concept of amphiphilicity beyond classical molecular surfactants into the nanoscale. Amphiphilic behavior is defined by the presence of hydrophobic and hydrophilic moieties within a single molecular structure. Traditionally, such molecular structures are known as surfactants or amphiphiles and are capable of reducing interfacial tension, adsorbing spontaneously at interfaces, stabilizing emulsions and foams, and forming micelles, bilayers, or vesicles. Recent experimental, theoretical, and computational studies demonstrate that these behaviors are scalable to nanostructured colloids such as JNPs. Amphiphilic JNPs, defined by anisotropic surface chemistry on distinct hemispheres, display interfacial activity driven by directional wetting, variable interfacial immersion depth, and strong interfacial anchoring. They can stabilize liquid/liquid and liquid/gas interfaces, and enable templated or spontaneous self-assembly into supra-structures, such as monolayer sheets, vesicles, capsules, etc., both in bulk and at interfaces. Their behavior mimics the “soft” molecular amphiphiles but also includes additional particularities given by their “hard” structure, as well as contributions from capillary, van der Waals, hydrophobic, and shape-dependent forces. This review focuses on compiling the evidence supporting amphiphilicity as a scalable property, discussing how JNPs function as colloidal amphiphiles and how geometry, polarity contrast, interfacial interactions, and environmental parameters influence their behavior. By comparing surfactant behavior and JNP assembly, this work aims to clarify the transferable principles, the knowledge gap, as well as the emergent properties associated with amphiphilic Janus colloids. Full article

Optical coherence tomography (OCT) is a non-invasive imaging technique that provides high-resolution, real-time visualization of soft and hard periodontal tissues. It offers micrometer-level resolution (typically ~10–15 μm) and a scan depth ranging from approximately 0.5 to 2 mm, depending on tissue type and system configuration. The field of view generally spans a few millimeters, which is sufficient for imaging gingiva, sulcus, and superficial bone contours. Over the past two decades, its application in periodontology has gained increasing attention due to its ability to detect structural changes in gingival and alveolar tissues without the need for ionizing radiation. Various OCT modalities, including time-domain, Fourier-domain, and swept-source OCT, have been explored for periodontal assessment, offering valuable insights into tissue morphology, disease progression, and treatment outcomes. Recent innovations include the development of three-dimensional (3D) OCT imaging and OCT angiography (OCTA), enabling the volumetric visualization of periodontal structures and microvascular patterns in vivo. Compared to conventional imaging techniques, such as radiography and cone beam computed tomography (CBCT), OCT offers superior soft tissue contrast and the potential for dynamic in vivo monitoring of periodontal conditions. Recent advancements, including the integration of artificial intelligence (AI) and the development of portable OCT systems, have further expanded its diagnostic capabilities. However, challenges, such as limited penetration depth, high costs, and the need for standardized clinical protocols, must be addressed before widespread clinical implementation. This narrative review provides an updated overview of the principles, applications, and technological advancements of OCT in periodontology. The current limitations and future perspectives of this technology are also discussed, with a focus on its potential role in improving periodontal diagnostics and personalized treatment approaches. Full article

Monocular 3D object detection is a challenging task in autonomous systems due to the lack of explicit depth information in single-view images. Existing methods often depend on external depth estimators or expensive sensors, which increase computational complexity and complicate integration into existing systems. To overcome these limitations, we propose AuxDepthNet, an efficient framework for real-time monocular 3D object detection that eliminates the reliance on external depth maps or pre-trained depth models. AuxDepthNet introduces two key components: the Auxiliary Depth Feature (ADF) module, which implicitly learns depth-sensitive features to improve spatial reasoning and computational efficiency, and the Depth Position Mapping (DPM) module, which embeds depth positional information directly into the detection process to enable accurate object localization and 3D bounding box regression. Leveraging the DepthFusion Transformer (DFT) architecture, AuxDepthNet globally integrates visual and depth-sensitive features through depth-guided interactions, ensuring robust and efficient detection. Extensive experiments on the KITTI dataset show that AuxDepthNet achieves state-of-the-art performance, with ${AP}_{3D}$ scores of 24.72% (Easy), 18.63% (Moderate), and 15.31% (Hard), and ${AP}_{BEV}$ scores of 34.11% (Easy), 25.18% (Moderate), and 21.90% (Hard) at an IoU threshold of 0.7. Full article

In this paper, we propose the use of burnishing internal cylindrical surfaces with a hard tool in a mandrel shape. The burnishing force is exerted mainly by the press slide, which has pushing properties, moving the burnisher through the hollow tube. The burnishing of hollow surfaces is used as the finishing step for elements such as tubes. The purpose of using the burnishing method may be, for example, to increase the smoothness and accuracy of the object, for the improvement of its functional and operational properties, for economic reasons, or to increase its resistance to corrosion and fatigue. The depth of plastic deformation and the accuracy of processing are the main differences in the machining effects for individual burnishing methods. The selection of the burnishing conditions depends on the method of exerting pressure from the burnishing elements on the machined surface, which can be elastic or rigid. Computer simulations of the burnishing process were performed in FORGE^® NxT 2.1 software. A numerical analysis was performed using a three-dimensional triangular mesh. The theoretical and experimental research was determined to have very good compatibility, as determined by the numerically calculated results and by the mean deviation of residual stress method. This research analyzed the stress and strain state after the burnishing process, and a depth of deformation of approximately 20 μm to 30 μm in the material was determined. Full article

Considering the greater contact stress of turnout rails during wear and the development of heavy-haul railways, twin-disc sliding–rolling wear tests were performed on U75VH heat-treated rail steels applied for turnouts under high contact stress ranging from 1980 MPa to 2270 MPa. The microstructure of the worn surfaces was analyzed using optical microscope (OM), scanning electron microscope (SEM), 3D microscope, electron backscatter diffraction (EBSD), and hardness tests. The results indicated that after 10 h of wear, the weight loss was 63 mg at a contact stress of 1980 MPa, while it reached 95 mg at a contact stress of 2270 MPa. At a given contact stress, the wear rate increased with increasing wear time, while a nearly linear increase in wear rate was observed with increasing contact stress. As wear time and contact stress increased, the worn surface showed more pronounced wear morphology, leading to greater surface roughness. Crack length significantly increased with wear time, and higher contact stress facilitated crack propagation, resulting in longer, deeper cracks. After 10 h of wear under a contact stress of 2270 MPa, large-scale cracks with a maximum length of 128.29 μm and a maximum depth of 31.10 μm were formed, indicating severe fatigue wear. Additionally, the thickness of the plastic deformation layer increased with the wear time and contact stress. The surface hardness was dependent on the thickness of this layer. After 10 h of wear under the minimum and maximum contact stresses, hardening rates of 0.39 and 0.48 were achieved, respectively. Full article

This study investigates the elevated-temperature mechanical and viscoelastic properties of a PDMS–silica-based superhydrophobic nanocomposite coating using nanoindentation and a nano-dynamic mechanical analysis over a temperature range of 24 °C to 160 °C. The nanoindentation load–displacement curves exhibited consistent hysteresis, indicating a stable energy dissipation across the temperature range. Creep tests revealed an increased displacement and accelerated deformation at elevated temperatures, displaying a two-stage creep profile characterized by rapid primary and steady-state secondary creep. The hardness decreased with the creep time, while the strain rate sensitivity remained relatively stable, suggesting consistent deformation mechanisms. A time-dependent creep model incorporating linear and logarithmic terms accurately captured the experimental data. The nano-dynamic mechanical analysis results showed a decrease in the storage modulus with depth, while the loss modulus and tan δ peaked at shallow depths. These findings are crucial for the evaluation and design of superhydrophobic nanocomposite coatings. Full article

TiAlSiN/AlSiN coatings, with 3 and 30 periods, were successfully deposited by cathodic-arc evaporation technology. The composition, structure, mechanical, and tribological properties were studied at thermal treatment from 700 °C to 900 °C. The SEM observation and EDS analysis verified the dense structure and stable element composition in the coating depth at increased temperatures. A limited surface oxidation was identified at 800 °C, which increased moderately at a higher temperature of 900 °C. The coating period displays a nanocomposite structure of TiAl(Si)N and AlN nanograins incorporated in an amorphous Si₃N₄ matrix obtained by XRD and XPS analyses. The coatings exhibit high hardness of 41.1 GPa and 36.4 GPa for the 3- and 30-period coatings, respectively. The coatings with higher modulation periods demonstrate an excellent high temperature hardness and resistance to elastic and plastic deformations up to 900 °C. The hardness of the coatings with a smaller modulation period reduces to 29.7 GPa at the same temperature, causing a decrease in the H/E and H³/E^*2 ratios. The tribological tests found that the high-temperature wear resistance depends strongly on the coating composition and architecture. An oxidation wear mechanism dominates the coatings with a large modulation period, and the wear rate decreases with a temperature increase. Abrasive wear is predominant in coatings with a lower modulation period, leading to an increasing wear rate. Wear rate values of 7.27 × 10⁻⁶ mm³/N·m and 8.53 × 10⁻⁶ mm³/N·m were determined after annealing at 900 °C for the 3- and 30-period coatings, respectively. Full article

In this study, the methods of tangential magnetic field (TMF), magnetic Barkhausen noise (MBN), and incremental permeability (IP) were employed for in the simultaneous, quantitative prediction of target properties (bidirectional residual stress, surface hardness, and case depth) in the 45 steel plate. The bidirectional magnetic signals and target properties were measured experimentally. The results of Pearson correlation analyses revealed that most parameters of the MBN and IP signals are strongly correlated with both residual stress and surface hardness under the influence of multiple target properties. The multiple linear regression (MLR) model demonstrated highly accurate quantitative prediction of residual stress and hardness in the y-direction. However, the simultaneous prediction of residual stress and case depth in the x-direction proved less effective than expected. To address this limitation, an inversion method was developed based on the regression model with the single parameter as the dependent variable and the target properties as the independent variable. By incorporating known magnetic parameters and target properties, the model effectively determined the unknown target properties. After applying the method, the coefficient of determination (R²) for x-direction residual stress increased from 0.89 to 0.96 and the absolute error (AE) of case depth decreased from 0.10 mm to 0.04 mm for case depths below 0.15. Full article

While L-PBF research continuously expands technologically towards more complex-shaped components and effective scanning strategies, the customization of the mechanical performance of these components to specific applications is still challenging. The presence of high process-induced residual stress levels frequently makes the current (standard) mechanical testing procedures ineffective or even inappropriate. The current engineering design principles cannot be applied to L-PBF components as the available mechanical properties are apparent (i.e., space and residual stress dependent properties). It is the aim of this work to overcome the aforementioned limitations by presenting a comprehensive methodology that can be used to determine the mechanical performance of an L-PBF 316L deposit along (five) pre-specified directions, denoted as performance lines (PLs), and in six special key regions, denoted as performance zones (PZs), through the nanoindentation test (PL-nIIT). The PLs determine the gradients of the indentation properties across the deposit, while the PZs exhibit the orientation-dependent mechanical performance in a specified number of regions of the deposit. The latter can be used for benchmarking, mechanical design, or performance customization. The frequently resorted to indentation modulus and hardness have thus been complemented with a new indentation size effect-free property (i.e., the loading stiffness rate, LSR) to help discriminate the presence of residual stress at different depths in the given deposit. A decreasing mild compressive residual stress was determined along the build direction of the deposit as revealed by the decreasing values of the relative LSR, H_IT, and E_IT (from the root to the top dome, i.e., 47.8 to 43.4, 2.57 to 2.49, and 216 to 202 GPa, respectively). Full article

JIS SCM440 steel is commonly used in precision parts after induction-hardening heat treatment. The fatigue behavior of induction-hardening parts largely depends on the combination of hardening depth and the magnitude and distribution of hardness and compressive residual stress. Therefore, it is necessary to determine the effects of different prior microstructures on the properties of JIS SCM440 steel after induction hardening. In the present study, the effects of prior microstructure (including spheroidized, annealed, normalized, and quenched and tempered) on the microhardness, hardening width, and residual stress of the induction-hardened specimens are investigated. The experimental results showed that the distribution behavior of residual stress in the hardened zone and heat-affected zone is due to the temperature gradient of the induction-hardening treatment. The hardened center appeared as compressive residual stress due to the martensitic transformation, which was accompanied by volume expansion. On the contrary, tensile residual stress will be generated in the heat-affected zone of incomplete phase transformation. The prior microstructure can affect the residual stress magnitude and distribution of microhardness and residual stresses due to the content of the cementite dissolved into the austenite at high temperatures. The difference in the carbon content of martensite after quenching will result in obvious differences in properties. The induction-hardened specimens with a normalized prior microstructure have the highest residual tensile stress in the heat-affected zone. The maximum residual tensile stress was 371 MPa in the heat-affected zone. The induction-hardened specimens with a quenched and tempered prior microstructure have the deepest hardening depth and widest residual compressive stress distribution range. The highest microhardness was 764 HV_0.3, while the maximum residual compressive stress was −752 MPa. Full article

The direct energy deposition arc process is widely used for fabricating medium and large components with moderate geometric complexity but often results in coarse microstructures and inconsistent hardness. This study introduces a hybrid manufacturing approach combining the friction stir burnishing process with the direct energy deposition arc by a gas–metal arc welding technique to refine the microstructure and enhance the microhardness of components fabricated from austenitic stainless steel 316L. Our former study used an aluminum alloy (A5052) friction stir burnishing tool, demonstrating significant microhardness improvement and grain refinement. However, it also faced notable challenges under high-heat and -friction conditions, including the effect of material adherence to the workpiece during processing. Therefore, this study introduces a newly developed friction stir burnishing tool made from copper (C1100) and compares its performance with the aluminum alloy tool regarding microhardness enhancement and microstructure refinement. The results indicate that the specimen processed by direct energy deposition arc combined with the copper friction stir burnishing tool demonstrated the best overall performance in grain refinement and hardness enhancement. Specifically, it achieved the highest average microhardness of 250 HV at 50 µm depths, compared to 240 HV for the aluminum alloy tool. The statistical analysis showed that both tools led to significant improvements over specimens processed without them. The statistical analysis confirmed a notable reduction in secondary dendrite arm spacing across all depths, with the copper tool demonstrating the most refinement. Additionally, a preliminary investigation of corrosion behavior revealed tool-dependent differences. Overall, this study offers a promising approach to improving additive manufacturing, particularly for industries with less stringent surface finish requirements. It could potentially reduce post-processing time and cost. Future research should explore different process parameters and assess long-term corrosion performance to develop this hybrid technique further. Full article

This study evaluates selected flame retardants on the basis of their influence on the change of fire-technical parameters of soft and hard woods (spruce and oak) during exposure to a flame heat source. The parameters evaluated were mass loss, mass loss rate and depth of the charred layer. The experiments were carried out on simple test equipment on which the samples were exposed to direct flame while their mass was monitored. The measured data and their statistical evaluation showed a significant dependence of the mass loss on the type of retardant used (inorganic salt-based flame retardant—IS and intumescent flame retardant—IFR) and on the type of wood species. In spite of the same reaction to fire class specified by the manufacturers for both types of retardants studied, significant differences were observed in the parameters monitored. The mass loss, mass loss rate and charred layer reached much lower values when using IFR retardant, whose efficiency was higher in the order of tens of percent compared to the use of IS retardant. The use of IFR flame retardant reduced the depth of the charred layer on oak samples by up to 84% compared to untreated samples, indicating its high effectiveness and potential to increase the fire resistance of wooden structures. These results show that IFRs are more effective in the parameters studied compared to ISs despite their equal class of reaction to fire, which may have wider implications for the construction industry and highlight the need for a thorough evaluation of flame retardants based on their performance under real-world conditions. Full article

This article presents an example of the treatment of rock mass disturbed by shallow mining of hard coal in the Małopolska voivodeship, Poland. Considering various methods of rock mass recognition and ways of eliminating shallow voids, recipes for sealing slurries containing mainly liquefiers were developed and used in drilling and injection works in a 10 m-long hole. The course and intensity of rock layer deformation phenomena depend on both natural conditions and the mining method used. At a small depth of hard coal mining (up to 100 m below ground level), the fracture zone may reach the ground surface. In such conditions, sinkholes of various sizes may form on the ground surface. The proposed recipes for sealing slurries, as well as the presented technology for carrying out backfilling works, can be very useful at the stage of selecting the method for liquidation of shallow-lying voids in the carboniferous rock mass. Full article

This study aimed to evaluate the depth of cure (DoC) of bulk-fill composite resins, measured by the bottom-to-top Vickers microhardness ratio, using different light-curing units (LCUs): single-wave LED, polywave LED, and halogen. Six bulk-fill composites—Tetric EvoCeram Bulk Fill, X-tra base, SonicFill, Venus Bulk Fill, SDR, and Filtek Bulk Fill—were tested. Four LCUs, including one halogen (Elipar Trilight) and three LEDs (Demi Ultra, Valo, and Bluephase style), were employed for polymerization. Vickers hardness measurements were taken at depths of 1 mm to 5 mm. One- and two-way ANOVA (α = 0.05) were used for data analysis. The results revealed significant differences in microhardness and microhardness ratios among the composites at depths of 4 mm and beyond, depending on the LCU used. It was observed that most bulk-fill composites showed an adequate DoC up to 4 mm, but the effectiveness varied with different LCUs. Importantly, polywave LED LCUs did not exhibit a superior advantage in achieving depth of cure compared to monowave LED LCUs for composites containing multiple photoinitiators. These findings suggest that while several factors affect the DoC, the type of LCU plays a crucial role, and polywave LEDs may not offer additional benefits over monowave LEDs. Full article