Search Results (4,107)

2.5D C/SiC composites are characterized by high hardness and brittleness. These properties render the composites prone to fiber fracture, burr formation and matrix damage during grinding for hole-making. This study systematically investigates the material removal mechanism, tool wear behavior and machining quality evolution process during diamond core drill grinding for hole-making. Through experiments, the effects of grinding angle and grinding force and the thermal effects on material removal characteristics and hole wall machining quality were analyzed, and the stagewise characteristics of tool wear and the correlation between processing parameters and machining quality were clarified. The results indicate that the wear of diamond core drills undergoes a three-stage evolution: slight abrasive grain shedding at the initial stage, local damage and wear loss at the middle stage, and large-scale abrasive grain peeling followed by tool failure at the late stage. As wear aggravates, the machining axial force increases remarkably and the grinding temperature rises drastically. Hole wall defects gradually develop from minor initial fiber fracture into complex failure modes including burrs, fiber pull-out and matrix damage. In particular, the morphological degradation at the hole exit is the most severe. This study verifies that the optimization of process parameters and tool design can improve machining quality, and provides theoretical guidance and an experimental basis for the efficient and precise machining of high-performance composites. Full article

Single-crystal diamond (SCD) has the characteristics of a hard surface and stable chemical properties, making it difficult to achieve ultra-smooth and ultra-low-damage surface polishing using conventional polishing slurries. In this study, a novel green chemical mechanical polishing (CMP) slurry containing only hydrogen peroxide, nicotinic acid, silica (SiO₂) abrasive particles and deionized water was developed to achieve ultra-smooth, ultra-low-damage (0.5 nm) and atomic-scale surface roughness (Ra 0.473 ± 0.035 nm) polishing of SCD. Additionally, the influence of diamond, silicon carbide and SiO₂ abrasive particles on the surface quality of SCD after CMP was investigated by single-factor experiments. Based on XPS characterization, the mechanism of SCD CMP was revealed: the SCD surface was first oxidized to form C-O and C=O groups, and then these groups were removed under the mechanical action of SiO₂ abrasives, ultimately achieving atomic-scale removal of the material. Full article

Wire Laser Additive Manufacturing (WLAM) has emerged as a promising alternative for the fabrication and repair of components subjected to severe wear conditions due to its high deposition rate, efficient material utilization, and localized thermal control. In this study, the WLAM process using DUR600 wire as the feedstock material for the deposition of abrasion-resistant coatings was investigated. The deposited specimens were characterized by optical emission spectroscopy (OES), X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), Vickers microhardness testing, and dry sand/rubber wheel abrasion testing in accordance with ASTM G65. The deposits exhibited a predominantly martensitic microstructure with retained austenite, as confirmed by XRD. Hardness values ranged from 749 to 817 HV, with an average of 783 ± 18 HV, while the average volumetric loss in the abrasive wear test was 150.26 mm³. This behavior was attributed to the presence of the martensitic matrix and retained austenite, whose combined effect directly influences the tribological performance of WLAM coatings produced using DUR600 wire. Full article

The long-term success of zirconia restorations depends on the durability of the resin–zirconia bond. This study evaluated the microshear bond strength (μSBS) of an MDP-containing universal adhesive, Scotchbond Universal Plus Adhesive, compared with its predecessor, Scotchbond Universal Adhesive, when bonded to three generations of CAD/CAM-fabricated zirconia ceramics. Sixty zirconia specimens were fabricated from 3Y-TZP (IPS e.max ZirCAD), 4Y-PSZ (IPS e.max ZirCAD MT), and gradient zirconia (IPS e.max ZirCAD Prime; 3Y-TZP/5Y-PSZ). Following polishing, sintering, and airborne-particle abrasion with 50 μm Al₂O₃ particles, specimens received either Scotchbond Universal Plus Adhesive or Scotchbond Universal Adhesive. Resin cement cylinders were bonded with a dual-cure resin cement and subjected to thermal cycling (20,000 cycles; 5–55 °C) prior to μSBS testing. Data were analyzed using one-way ANOVA, independent-samples t-tests, and Fisher’s exact test (α = 0.05). Significant differences in μSBS were observed among zirconia generations for both adhesive systems (p < 0.05). The highest bond strengths were recorded for 4Y-PSZ bonded with Scotchbond Universal Adhesive (15.36 ± 3.00 MPa) and Scotchbond Universal Plus Adhesive (14.67 ± 4.52 MPa), whereas the lowest values were obtained for 3Y-TZP (8.91 ± 3.53 MPa and 9.20 ± 3.52 MPa, respectively). No significant differences were detected between the two adhesive systems within any zirconia generation (p > 0.05). Failure mode analysis revealed predominantly adhesive and mixed failures, with no significant differences in the distribution of failure modes among groups (p > 0.05). In conclusion, zirconia generation significantly influenced bond strength, whereas Scotchbond Universal Plus Adhesive demonstrated bonding performance comparable to that of Scotchbond Universal Adhesive after thermocycling. Among the tested substrates, 4Y-PSZ exhibited the most favorable bonding performance. Full article

The Böhme abrasion test (EN 14157) is widely used to evaluate the wear resistance of natural stones; however, the abrasive powder specified by TS 699 requiring 70–80 wt.% crystalline Al₂O₃ is not commercially available in the Turkish market. Commercially supplied abrasives deviate substantially from both the prescribed chemical composition and the grain-size distribution of TS 699, introducing a recognized but unresolved source of variability in Böhme abrasion measurements. This study evaluates the influence of abrasive type and particle-size distribution on Böhme abrasion performance with the aim of identifying which available abrasive material yields the most reliable and reproducible test results. The emphasis is therefore metrological—on test repeatability and standardization—rather than on ranking the abrasion resistance of the stones. Six natural stones representing contrasting lithologies—four crystalline marbles, one limestone, and one granite—were tested using five abrasive powders: two locally produced natural emery abrasives (Emery-1 and Emery-2), silicon carbide (SiC), white corundum, and brown corundum. Each abrasive was evaluated under both standardized graded conditions prepared in accordance with TS 699 and heterogeneous ungraded conditions reflecting common industrial practice. Chemical analyses confirmed that both emery abrasives deviate markedly from TS 699 specifications, with Al₂O₃ contents (~57.7 wt.%) well below the required range and Fe₂O₃ (~24 wt.%) considerably exceeding the standard limit. Sieve analyses further revealed substantial particle-size deviations in several commercial abrasives. One-way ANOVA demonstrated that abrasive type exerts a statistically significant influence on abrasion performance (F = 8.99, p < 0.05, η² = 0.297). SiC consistently produced the highest abrasion values, followed by corundum-based abrasives, while emery abrasives showed comparatively lower but stable performance. Independent-samples t-tests showed that particle-size grading significantly affected abrasion performance only for brown corundum (p < 0.05), attributable to its markedly elevated coarse particle fraction. Petrographic analysis, XRD, and SEM–EDS characterization of the investigated rocks confirmed that abrasion response is additionally modulated by rock mineralogy and microstructure. Under standardized grading conditions, SiC provided the most consistent and reproducible results across all lithologies, supporting its suitability as the reference abrasive for inter-laboratory Böhme testing. Locally produced emery abrasives, despite their chemical non-compliance with TS 699, yielded stable and reproducible outcomes under controlled grading, supporting their potential as cost-effective alternatives for routine testing. Full article

To address the pervasive engineering challenges of rigid interference and subpar machining efficiency encountered during the complex freeform surface polishing of P20 mold steel, this study proposes and fabricates a structurally designed, five-petal composite compliant polishing tool via fused granulation fabrication (FGF). The tool structurally integrates a passive thermoplastic polyurethane (TPU) compliant buffer layer with an active PA66/diamond micro-cutting functional layer, achieving monolithic precision assembly through dual-temperature-zone 3D printing. Tensile mechanical characterization (n = 6) reveals that the composite interface attains an average ultimate tensile strength (UTS) of 59.39 ± 15.41 MPa (with a peak of 78.90 MPa) and an average elongation at break of 27.42 ± 7.41%, demonstrating exceptional structural robustness and fracture toughness under heavy-load abrasive machining conditions. During adaptive polishing validations on complex convex topographies and deep concave mold cavities, the compliant tool effectively compensated for normal vector spatial errors intrinsic to three-axis CNC machining via passive geometric adaptation. Topographical evaluations suggest a ductile-regime, differential asperity planarization material removal paradigm, which is attributed to the macroscopic 3D elastic deformation of the tool synergized with the proposed compliance of the polymer matrix. Following high-intensity sequential polishing regimens, the original macroscopic milling striations were substantially reduced. Quantitative profilometric analysis reveals that the average surface roughness of the convex profiles decreased from an initial 13.33 µm to 7.42 µm, while that of the restrictive deep concave features was reduced from 10.84 µm to 4.11 µm. Ultimately, this technological framework circumvents the traditional reliance on capital-intensive, six-degree-of-freedom robotic platforms, providing a scalable automated polishing protocol compatible with standard CNC systems for the cost-effective surface planarization of precision molds. Full article

Asphalt pavement wearing courses are directly exposed to hydrodynamic scouring, fuel erosion, freeze–thaw action, and traffic abrasion, leading to accelerated surface deterioration, skid-resistance loss, frequent maintenance, and increased life-cycle carbon emissions. To address these challenges, this study developed an organosilicon-based erosion- and skid-resistant asphalt wearing course (OES-AWC) through a stepwise material design strategy. An organosilicon-treated asphalt concrete matrix was first prepared to improve resistance to moisture damage, fuel erosion, and ice adhesion, and its curing behavior and optimal dosage were determined. A skid-resistant surface layer was then designed by optimizing the anti-skid aggregate type, organosilicon-to-aggregate ratio, and surface texture. Finally, waterborne epoxy resin was introduced to enhance aggregate anchorage, and the integrated OES-AWC was evaluated in terms of abrasion durability, rutting resistance, long-term skid resistance, and life-cycle impacts. The results show that organosilicon treatment forms a hydrophobic siloxane network, which improves the moisture damage, fuel erosion, and anti-icing resistance of asphalt concrete by 22.0–41.1%. Emery aggregates and the optimized surface structure enhance friction stability, while waterborne epoxy resin significantly suppresses aggregate stripping under repeated wheel loading. Compared with conventional asphalt wearing courses, the optimized OES-AWC increased wear durability by 148.1% while maintaining stable skid resistance under prolonged abrasion. Life-cycle assessment further demonstrates that OES-AWC can reduce carbon emissions by 47.2% and overall costs by 25.0%, with a probability exceeding 90% according to the uncertainty analysis. These findings indicate that OES-AWC provides a durable, low-carbon, and cost-effective maintenance strategy for asphalt pavements exposed to complex service environments. Full article

Background/Objectives: In vitro simulation of dental wear is essential for preclinical evaluation of dental materials, but available devices differ widely in operating principles and simulated oral conditions. This scoping review mapped devices used to reproduce dental wear and oral aging and classified them according to the dominant wear mechanism. Methods: Searches were conducted in PubMed/MEDLINE, Scopus, Web of Science Core Collection, Embase, and Google Scholar for records published between 1985 and 2026. Eligible sources reported an identifiable in vitro device or setup, a dental material or hard-tissue substrate, and extractable device-level data on operating principles, parameters, environment, antagonist, or outcomes. Results: Sixty-eight reports were retained and consolidated into 19 devices or device families. The systems included two-body chewing simulators, three-body wear machines, robotic or multiaxial masticatory platforms, tribometers, toothbrushing abrasion devices, erosion and pH-cycling systems, tribocorrosion setups, and multifunctional oral aging simulators. Device development showed a transition from mainly mechanical wear testing toward integrated platforms combining load, sliding, thermocycling, saliva or electrolyte exposure, pH control, chemical challenge, biofilm-related conditions, and electrochemical monitoring. Reporting remained heterogeneous, particularly for load, cycle number, frequency, sliding distance, antagonist material, medium, temperature, pH, and outcome measurement. Conclusions: Device selection should be based on the dominant wear mechanism, material type, and research objective. More complete source-level reporting is needed to improve reproducibility and comparability. Full article

This study presents a computational analysis of degradation caused by cavitation and hydro-abrasive erosion in a low-head axial microturbine ($H=4\mathrm{m}$), incorporating strategic air injection as a passive mitigation technique. Using Computational Fluid Dynamics (CFD) within ANSYS CFX 2025 R2, the study investigates hydrodynamic performance and the spatial distribution of surface wear across the runner blades. The turbine geometry was developed from aerofoil profiles mapped onto cylindrical coordinates, using a structured three-dimensional mesh with localized refinement to ensure grid independence. Physical modeling employed the Shear Stress Transport (SST) turbulence model, with cavitation dynamics governed by the Rayleigh–Plesset equation and sediment transport modeled using a Lagrangian framework incorporating the Finnie erosion model. The numerical framework showed good agreement with reference characteristic curves, confirming its predictive accuracy. The results indicate that vapor cavities form predominantly on the suction side, whereas solid particle erosion highly concentrated on the pressure side of the blades, where the outer $20\%$ of the span accounts for over $91\%$ of the total erosion intensity. Parametric assessments of controlled air injection revealed a highly non-linear mitigation response, identifying IAVF 2 as the optimal air-injection case. This configuration reduced integrated erosion by $0.95\%$ and maximum localized erosion by $6.17\%$. In contrast, excessive air volumes accelerated material removal due to localized flow distortion. The findings indicate that carefully controlled air injection is a viable strategy for extending the operational lifespan of small-scale hydropower assets. Full article

The workability of abrasive tools for precision grinding is significantly affected by the quality of active surface of grinding wheel in terms of the number, form, and sharpness of active abrasive grains. The aim of this study is to introduce a method for optimizing the abrasive tools based on active surface topography analysis, tool wear diagnostics, and numerical simulation of micro-cutting by one active grain and abrasive aggregate. Particular attention is given to the Shos parameter, which characterizes the machining potential of a grinding wheel by combining information on the height and sharpness of active abrasive grain vertices. Changes in this parameter allow observation of the blunting and wear of the active surface. Numerical simulation shows that material removal by one active grain and by an abrasive aggregate differs significantly. According to the obtained data, under the assumed micro-cutting conditions, the aggregate geometry reduced lateral material displacement and promoted chip formation. The coefficient of material removal efficiency for aggregate was equal to kr = 0.93 compared to kr = 0.37 for one grain. Therefore, abrasive aggregates have an effect on the material removal process and may support the improvement of the stability of precision grinding. Thus, it can be concluded that further improvements in abrasive tools require considering controlled active surface structures and abrasive aggregates, as well as diagnostic parameters that relate tool topography to wear and machining efficiency. Full article

Cementation of indirect restorations has undergone a profound change over the past century, evolving from a philosophy of purely mechanical cementation to sophisticated biomaterials science based on adhesion. The aim of this narrative review is to provide essential context for understanding contemporary clinical decision-making. A key aspect is the structural and compositional characteristics of enamel and dentin as bonding substrates, underlining why enamel remains the gold standard, while dentin continues to present significant challenges. The synthesis is based on evidence of adhesive strategies for the four main classes of contemporary restorative materials, such as glass-ceramics (lithium disilicate and leucite), polycrystalline zirconia, resin-matrix ceramics (hybrid ceramics), and indirect composites. Each material was detailed in terms of surface penetration (e.g., hydrofluoric acid etching and air abrasion), chemical coupling (e.g., silanization and MDP-based primers), and appropriate resin cement selection (light-cured, dual-cured, or self-adhesive). A step-by-step clinical protocol is synthesized based on current evidence, integrating critical techniques such as immediate dentin sealing and optimized polymerization. This review concludes that while adhesive resin cements provide predictable long-term results, significant challenges remain, guiding future clinical research and innovation. Full article

The SP Gas Storage is situated in the SP-Xingcheng structural belt, where volcanic gas reservoirs are widely distributed and characterized by abundant primary microfractures and pore structures. The developed pores and fractures degrade the petrophysical properties of reservoirs and render volcanic basement rocks highly abrasive. In addition, pore-fracture systems alter the internal stress field of formations, which substantially increases the risk of wellbore instability and the collapse of injection and production wells. This poses great challenges to drilling operations and the safe running of the gas storage in this block. To systematically clarify the wellbore instability mechanism of large-diameter wellbores and address the drilling engineering problems in the study area, a dedicated experimental scheme for large-diameter wellbore stability was designed in this work. Laboratory true triaxial tests were conducted on wellbore stability with different borehole sizes, and basic mechanical parameter tests of reservoir rocks were also completed. This study systematically investigates the evolution of rock mechanical parameters and the surrounding stress-reconstruction mechanism induced by pore-forming unloading and identifies the dominant internal mechanism of wellbore instability under large-diameter conditions. A clear distinction is made between the formation stress redistribution caused by stratum exposure and unloading during drilling and formation stress evolution during the subsequent injection and production of the gas storage. On this basis, the fracture initiation threshold, propagation paths, and morphological evolution in thin interbedded sandstone–mudstone reservoirs are further analyzed. Combined with rock mechanical parameters and in situ stress balance conditions, criteria and quantitative evaluation methods for wellbore instability discrimination are finally established. Full article

ZERODUR glass-ceramic is widely used in ultra-precision optical components because of its extremely low thermal expansion and excellent dimensional stability. However, its two-phase microstructure, composed of crystalline and amorphous phases with different mechanical properties, may cause non-uniform material removal during magnetorheological polishing, thereby limiting further improvement of nanoscale surface quality. To address this issue, this study investigates the effect of oxide abrasives on the surface homogenization of ZERODUR. A single-particle abrasive–workpiece contact model based on modified Hertz contact theory and elastoplastic contact analysis was established to compare the indentation responses of CeO₂, SiO₂, and ZrO₂ abrasives in the two constituent phases. Magnetorheological polishing experiments were conducted under identical process parameters, and the polished surfaces were characterized by AFM over scan areas of 2 μm × 2 μm, 5 μm × 5 μm, and 10 μm × 10 μm. The results show that all three abrasives improved the surface quality of the ring-polished substrate, with ZrO₂ achieving the best surface homogenization performance. The lowest roughness, Ra = 0.104 nm, was obtained at a 2 μm field of view, and the ZrO₂-polished surface showed more stable roughness evolution across different scan sizes than the CeO₂- and SiO₂-polished surfaces. These results indicate that the elastic modulus, hardness, and mechanical compatibility of abrasives with ZERODUR play key roles in governing contact stress, indentation behavior, and final surface quality. This work addresses the lack of mechanistic understanding of abrasive-dependent surface homogenization in the magnetorheological polishing of two-phase ZERODUR glass-ceramic. The main innovation is the integration of contact-mechanics-based abrasive–workpiece modeling with multi-scale AFM characterization to clarify how abrasive mechanical compatibility affects nanoscale surface uniformity and to guide abrasive selection for ultra-smooth optical manufacturing. Full article

The food packaging sector widely relies on polymeric materials, and as sustainability concerns grow, commodity polymers need to be replaced with innovative and more sustainable materials. Thermoplastic polyurethane (TPU) is a versatile elastomeric polymer characterized by flexibility, strength, chemical and abrasion resistance, and biocompatibility. However, it presents some limitations, notably in terms of functional properties (i.e., barrier properties). The use of nano-sized renewable fillers, such as cellulose nanocrystals (CNCs), may improve these properties, extending the applicability range of TPU. In this work, bio-based TPU nanocomposites were obtained by adding commercial silane-modified cellulose nanocrystals (Si−O−CNC) at different contents (1–5 wt.%). The nanocomposites were produced via melt mixing followed by compression molding and were characterized in terms of chemical (FTIR), morphological, thermal, mechanical, rheological, wettability, and barrier properties (i.e., water vapor permeability, WVP and oxygen transmission rate, OTR). The presence of Si−O−CNC promoted hydrogen bonding interactions with the TPU matrix, affecting the microphase separation and organization of the hard segments. These microstructural changes improved thermal stability, reduced WVP and OTR, and increased tensile properties at lower nanofiller contents (1–3 wt.%). At higher contents, partial nanofiller aggregation was observed, leading to a reduction in mechanical performance. Overall, these results suggest that TPU/Si−O−CNC nanocomposites have promising potential as sustainable food packaging materials. Full article

Fe-Cr-C-based coatings were fabricated on Q690 steel via ultrasonic vibration-assisted plasma cladding at varying ultrasonic powers (0–65 W) with a fixed frequency of 18.5 kHz. The coatings primarily consisted of martensite, retained austenite, and (Cr,Fe)₇C₃ carbides, along with (Cr,Fe,Mo)-B borides along grain boundaries. Increasing ultrasonic power promoted cavitation and acoustic streaming, which refined columnar dendrites, reduced elemental segregation (notably for B and Mo), and increased the fraction of fine equiaxed grains without altering phase composition. As a result, the average microhardness increased from 797.1 to 828.5 HV0.1. The friction coefficient decreased from 0.675 to 0.626, while the wear-track width, wear depth, and wear mass loss decreased from 4.0 mm to 2.5 mm, from 112.5 μm to 32.4 μm, and from 20.40 mg to 4.75 mg, respectively. The wear mechanism shifted from severe adhesive wear to mild abrasive wear. These results demonstrate that increasing ultrasonic vibration power effectively refines the solidification microstructure and significantly improves the hardness and wear resistance of plasma-clad Fe-Cr-C-based coatings. Full article