Search Results (2,057)

Statistical monitoring of lifetime processes is commonly based on a single process characteristic, which may fail to detect distributional changes that affect different aspects of process behavior. This study proposes a component-wise adaptive joint exponentially weighted moving average (EWMA) control chart for simultaneously monitoring a Weibull lower quantile and Shannon entropy. Unlike conventional joint monitoring schemes that apply a common smoothing mechanism, the proposed framework preserves the quantile and entropy as separate standardized components, adaptively updates each according to its own departure, and subsequently combines them through a correlation-adjusted quadratic statistic that retains their dependence. Control limits are calibrated by Monte Carlo simulation to achieve a target in-control average run length of approximately 370. Extensive simulations consider scale, shape, and combined Weibull parameter shifts, together with quantile-preserving and entropy-preserving alternatives specifically designed to isolate changes in the individual characteristics. Comparisons with single-component Q-EWMA and H-EWMA charts and a fixed joint EWMA chart demonstrate that the proposed procedure maintains the desired in-control performance while providing robust and balanced detection across heterogeneous process changes. Its advantage is particularly evident when one monitored characteristic remains relatively stable while the other changes substantially, a setting in which single-characteristic charts may become insensitive. Practical applicability is demonstrated through two complementary real-data applications involving medical rehabilitation length-of-stay data and rolling-contact fatigue-life data under different lubrication conditions. In both settings, the proposed chart successfully identifies meaningful distributional departures, while the component-wise adaptive mechanism responds selectively to the relative magnitudes of quantile and entropy changes. Overall, the proposed framework provides a robust and flexible monitoring strategy for heterogeneous lifetime-process changes without requiring prior knowledge of whether deterioration will primarily affect lower-tail performance, distributional uncertainty, or both. Full article

During practical service, the interfaces of hydraulic reciprocating seals experience complex coupling interactions of lubrication, contact stress and thermal effects. Reliance solely on standard indicators including leakage rate and cycle count cannot capture latent interfacial risks originating from lubrication failure, contact overload and thermal accumulation under designated operating conditions, which greatly limits the evaluation and optimal selection of hydraulic reciprocating seal configurations for targeted service scenarios. This work presents a multi-state monitoring approach based on ultrasonic oil-film measurement and fiber Bragg grating contact-stress sensing, and constructs a multi-dimensional evaluation indicator system for seal-interface latent risks. Combined with an interface–risk-coupled weighting strategy, indicators such as oil-film thickness, contact stress and interface temperature are utilized to quantify seal-interface risks and enable comprehensive performance assessment and comparison among different seal configurations. Long-cycle comparative experiments were conducted on three VL combined-seal configurations at 2 MPa, 21 MPa and 35 MPa via a high-speed hydraulic reciprocating seal performance-test rig. The results show clear pressure-dependent adaptability: the 2.2 mm configuration achieved the highest closeness coefficient at 2 MPa ($C_i=0.8176$), whereas the 2.1 mm configuration ranked first at 21 and 35 MPa, with $C_i=0.6992$ and $0.9252$, respectively. These results provide a quantitative basis for structural optimization and operating-condition-matched configuration selection. Full article

In general, the properties of alloy steels and special steels provide significant advantages to the end product. However, these properties often complicate the machining process, particularly in terms of machinability. The formation of a built-up edge (BUE) is a widely recognized phenomenon in the machining of austenitic stainless steels. It is closely associated with changes in cutting performance, tool wear, and surface integrity. Complex adhesive and plastic deformation processes drive BUE development under severe contact conditions at the tool–chip interface. Consequently, the geometrical characteristics and surface roughness of cutting inserts are expected to significantly influence the initiation and growth of adhered material layers on the cutting edge. The insert shape dictates the cutting forces and chip flow. In contrast, insert roughness (and micro-geometry) strongly influences friction and material sticking at the tool–chip interface. This article analyzes the processes in the material-tool contact system and their relationship to geometry, rake-face surface parameters, and BUE development when turning AISI 316L steel under dry and minimal lubrication conditions. The results indicate that BUE development is associated with the combined effects of chip-breaker geometry, rake-face roughness parameters (R_q, R_sk, and R_ku), and cutting conditions. Cooling, including the use of an ionic liquid–water suspension, reduces the insert’s susceptibility to adhesion. Full article

The incorporation of various types of fillers is critical to enhancing the starved oil lubrication performance of PEEK matrix composites. In this work, PEEK composites reinforced with h-BN and SCFs were fabricated via a hot-pressing method, and the friction and wear behaviors under dry sliding and starved oil lubrication were systematically investigated. Surface oil wettability and Vickers hardness were characterized, and tribological tests were conducted on a ball-on-disk reciprocating tribometer. Worn surface topography and wear mechanisms were elucidated through laser scanning confocal microscopy and scanning electron microscopy. The results show that h-BN effectively reduces the friction coefficient through its solid lubrication effect, while SCFs significantly improve the hardness and load-bearing capacity of the PEEK matrix. Under dry sliding conditions, the PEEK composite containing h-BN and SCFs achieves the lowest wear rate of 10.3 × 10⁻⁵ mm³/(N·m), which is 74.6% lower than that of pure PEEK, indicating a synergistic anti-wear effect. Under starved oil lubrication, PEEK/h-BN maintains the smoothest and lowest friction, and the presence of SCFs further improves wear resistance of PEEK composites despite a slight increase in friction. In addition, the fillers’ incorporation reduces the surface oil wettability of the PEEK composites; the dominant wear mechanism hence transforms from severe adhesive wear and plastic deformation in pure PEEK to mild abrasive wear. Full article

A three-dimensional thermo-elasto-hydrodynamic (TEHD) lubrication model is presented for the high-pressure deep-grooved mechanical seal employed. The thermo-elasto deformation behaviors of the seal rings are investigated using the finite element method (FEM). The parametric studies are conducted to explore the deformation characteristics of the seal face and sealing performance under different operating conditions. The results reveal that the deep-grooved face seal induces circumferential waviness deformation of the seal face, generating the hydrodynamic wedge effect dominated by the axial mechanical deformation along the circumferential direction. However, a significant hydrostatic effect produced by the deformation of the seal face along the radial direction is dominant in the load-carrying capacity of the fluid film. The thermo-mechanical coupling deformation of the seal face decreases with increasing fluid pressure and increases as the spring force and rotational speed increase. The leakage rate increases with higher fluid pressure, while it decreases with increased spring force and rotational speed. The axial stiffness of the fluid film increases with greater spring force and rotational speed but decreases with increasing fluid pressure. These findings can serve as theoretical guidance for developing high-pressure deep-grooved mechanical seals with enhanced reliability and stability. Full article

Molybdenum disulfide (MoS₂) dry film lubricants (DFLs) are widely used in aerospace mechanisms when conventional liquid lubricants are impractical. While the effects of environment on MoS₂ are well established, the influence of substrate characteristics and operating conditions remains less understood. In this work, three commercial MoS₂-based DFLs (Lube-Lok 4396, Everlube 620C, and Everlube 9002) were applied to five aerospace-relevant substrate materials and characterized in terms of surface roughness, flatness, coating thickness, friction, wear life, and load-carrying capacity. Vendor surface preparation and DFL deposition increased roughness, reduced flatness, and shifted the surface toward a more peak-dominated morphology, with the magnitude of these changes depending on both the substrate and coating. Tribological performance was evaluated for a subset of the samples which showed that friction was substantially lower in dry nitrogen than in ambient air, increasing contact pressure reduced friction, and sliding speed had little effect. Lube-Lok 4396 exhibited the longest wear life and highest load-carrying capacity, while Everlube 620C exhibited the lowest friction. Measured friction, wear life, and load-carrying capacity also differed from vendor specifications. These results highlight the effects of substrate material, surface preparation, and operating conditions on the surface characteristics and tribological performance of commercial MoS₂ DFLs for aerospace applications. Full article

The use of engine oil additives is a widespread approach to improve the performance of internal combustion engines. Among them, anamegators are applied in order to optimize tribological processes in the lubrication system and increase the energy efficiency of the engine. This study examines the impact of the Gold Ozirol MP-8 anamegator on the main operational and environmental performance of the diesel engine of the Kubota GL-23 tractor under real operating conditions. Changes in specific fuel consumption, effective power, noise levels and smoke of exhaust gases within a busy operating cycle are monitored. The analysis of the results obtained shows a trend towards improving energy efficiency and reducing harmful emissions due to the application of the anamegator. The data obtained make it possible to evaluate the applicability of the product as a means of optimizing the performance and environmental characteristics of tractor engines in the conditions of intensive agricultural operation. Full article

Accurate modeling of the tooth friction coefficient is central to analyses of efficiency, vibration, and durability in enclosed gear drives. Physics-based models describe these contacts using a large set of coupled thermal, contact, and lubrication laws whose individual parameters have uncertainties that are difficult to propagate. This study proposes a compact alternative: the HAF model, a three-parameter phenomenological description of the friction coefficient as a function of the slide-to-roll ratio (SRR). The three parameters have distinct tribological interpretations: h (hysteresis) governs the steepness of the sigmoidal transition, a (attrition) governs the slope of the plateau, and ν (friction level) governs the overall magnitude. The model is calibrated using nonlinear regression with fourteen two-disc traction curves acquired with a one-factor-at-a-time (star) design around a reference operating point (1.6 GPa, 80 °C, and 20 m/s): the contact pressure (1.2, 1.6, and 1.9 GPa), the injection temperature (40, 80, and 100 °C), and the mean speed (10, 20, and 30 m/s) are each varied in turn, for both smooth and rough discs. Parameter uncertainty is quantified using the residual-resampling bootstrap (BIG) established in a companion paper and applied over 10⁵ iterations; it yields near-Gaussian, weakly correlated parameter distributions. The three HAF parameters are then expressed as linear functions of load, temperature, speed, and roughness; least-squares inference across the fourteen conditions shows that eleven of the fifteen regression coefficients differ significantly from zero at the 5% level, with roughness having the strongest effect on the friction level (t = 7.98). Substituting these laws into the HAF equation and reoptimizing the resulting expression globally yields a single closed-form model that reproduces the measured friction coefficient with a residual spread of σ ≈ 0.001 in friction-coefficient units (R² ≈ 0.996) and approximately Gaussian, zero-mean, and homoscedastic residuals with no evident systematic structure. Being differentiable and equipped with bootstrap confidence intervals, the model predicts friction throughout the tested operating envelope—across which the maximum friction coefficient varies by a factor of eight, from 0.0049 to 0.0388—and supports gradient-based optimization of low-friction operating conditions. The contribution of this study is a compact, interpretable, and statistically characterized predictive law for tooth friction, expressed in closed form as a function of the operating conditions and of the surface state. Full article

The premature degradation of aluminium extrusion dies remains one of the major challenges affecting process efficiency, product quality, and tooling costs. Although numerous studies have investigated wear mechanisms and proposed solutions such as surface treatments, coatings and lubrication, the absence of a generic and reproducible laboratory methodology for evaluating tribological performance under representative extrusion die contact conditions limits the objective and systematic comparison of alternative tribological solutions. This study proposes and experimentally validates a generic tribological methodology for laboratory simulation of aluminium extrusion die contacts. Rather than reproducing the complete extrusion process, the methodology isolates the dominant physical mechanisms governing die degradation and reproduces their essential characteristics under controlled laboratory conditions, providing a representative platform for systematic tribological investigations. The methodology was developed through the selection and scaling of representative contact parameters, including contact geometry, normal load, sliding velocity and operating temperature. The experimental programme incorporated physical similarity principles, a controlled run-in procedure and repeated use of the same hardened steel counterface to reproduce cumulative die exposure under successive aluminium contacts. Two aluminium alloys (AA6063 and AA6082) were evaluated using a small ring-on-disc configuration against a hardened GCr15 steel counterface. Experimental validation was carried out using two extrusion lubricant systems, complemented by three additional commercial lubricants to assess the robustness and general applicability of the proposed methodology. The experimental results demonstrate that the proposed methodology provides repeatable and sufficiently sensitive measurements of friction and wear, allowing clear differentiation between lubricant systems and aluminium alloy–lubricant combinations while maintaining representative contact conditions. The study also demonstrates that steady-state friction should be identified from the actual friction evolution rather than by applying a fixed averaging interval. Although lubricant evaluation is employed here as the experimental validation case, the proposed methodology is intended as a generic experimental framework applicable to the assessment of surface treatments, coatings, tool materials, lubrication systems, and other tribological strategies aimed at extending extrusion die service life. Full article

Tribology, the science of friction, wear, and lubrication, governs the reliability of nearly every mechanical system. Tribological contacts account for approximately 23% of global energy consumption, including 20% used to overcome friction and 3% associated with remanufacturing worn components. Nevertheless, the field has remained constrained by low experimental throughput, operator variability, and a scarcity of standardized, reusable datasets. This review surveys two converging trends positioned to address these limitations: the development of robotic and automated platforms for tribological experimentation, and the growing application of artificial intelligence to tribological analysis. High-throughput tribometer architectures, robotic specimen preparation, and multi-modal in situ sensing are examined as components of an emerging automated tribometry infrastructure. Supervised learning, physics-informed neural networks, and Bayesian optimization are reviewed as AI methods organized by the data regime in which they operate. The convergence of these trends in closed-loop autonomous tribological experimentation is assessed, including system architecture, optimization target specification, current partial implementations, and tribology-specific integration barriers that distinguish this domain from adjacent self-driving laboratory applications. Application domains spanning industrial machinery, biomedical implants, and aerospace and automotive drivetrains are discussed. Key challenges including dataset standardization, model transferability, and hardware-software integration complexity are identified. Prospects for fully autonomous tribological discovery pipelines are outlined, with emphasis on open-access data infrastructure and physics-constrained learning as the enabling conditions for the field. Full article

Warm-mix asphalt (WMA) reduces mixing and compaction temperatures through wax additives, chemical additives, and foaming techniques, but their dominant mechanisms, performance trade-offs, and evaluation priorities differ. This structured narrative review synthesizes evidence for Sasobit, Evotherm, and Advera as representative technologies across mixture, binder and mastic, interfacial and microstructural, and molecular scale. Sasobit-type wax additives improve construction-stage fluidity and high-temperature stability through viscosity–temperature regulation and wax crystallization, while low-temperature and fatigue risks require attention. Evotherm-type chemical additives enhance wetting and moisture resistance through surface-active adsorption, thin-film lubrication, and improved interfacial adhesion, with high-temperature shear resistance requiring verification. Advera-type zeolite foaming extends the compaction window through water release and microbubble formation, but residual moisture and wet-condition durability remain critical concerns. On this basis, technology-specific cross-scale evidence chains are established, and a mechanism-oriented evaluation framework is proposed, linking engineering scenarios, dominant mechanisms, reduced-temperature mix design feasibility, durability constraints, and applicability assessment. Mixture performance serves as the final criterion, while binder and interfacial evidence supports risk screening and molecular evidence provides mechanistic interpretation. The framework supports targeted material selection, experimental design, risk diagnosis, and process optimization. Full article

Polyisobutylene succinic anhydride (PIBSA) is an important intermediate for ashless dispersant additives used in lubricant formulations, where conversion and exo-selectivity strongly influence product performance. In this work, the thermal synthesis of PIBSA derived from highly reactive polyisobutylene (HR-PIB) 1300 and 2300 was systematically investigated using a full factorial experimental design to evaluate the effects of feed molar ratio, reaction temperature, and stirring rate on conversion and exo-PIBSA yield. Structural confirmation was performed using ¹H NMR spectroscopy, gel permeation chromatography (GPC), and saponification value analysis. HR-PIB 1300 achieved conversions of 60–94%, while HR-PIB 2300 achieved conversions of 75–88% under the investigated conditions. A clear molecular-weight-dependent trade-off between conversion and exo-selectivity was observed. For PIBSA 1300, higher temperatures increased conversion but reduced selectivity, resulting in exo-PIBSA yields of 24–56%. In contrast, PIBSA 2300 achieved yields of up to 71%, highlighting the importance of mixing and mass-transfer effects in higher-viscosity systems. These findings demonstrate that optimal thermal maleation conditions are strongly dependent on polymer molecular weight and provide mechanistic insight for future optimization of industrial PIBSA production. Full article

To mitigate the deterioration of the tribological performance of end-face friction pairs under low-speed conditions, this study investigated a water-lubricated CF/PEEK–316L stainless steel end-face friction pair. Surface micro-textures with different depth-to-diameter ratios and texture area ratios were fabricated on the 316L stainless steel surface to evaluate the effects of texture parameters and sliding speed on tribological performance. The results showed that appropriately designed micro-textures effectively reduced the coefficient of friction and improved the wear characteristics of the friction pair. Among the tested conditions, the CF/PEEK–316L stainless-steel tribo-pair with a 316L counterface textured at ε = 0.05 and s = 10% exhibited the lowest average friction coefficient. At 200 rpm, this textured tribo-pair exhibited an average friction coefficient approximately 34.8% lower than that of the untextured tribo-pair. Furthermore, laser micro-textures suppressed interfacial material transfer and mitigated adhesive wear and three-body abrasive wear by capturing wear debris. Gear-pump prototype tests further showed that the textured surface improved flow-delivery and volumetric-efficiency performance, while promoting more uniform end-face wear morphology, indicating its potential application in practical gear-pump components. The findings provide guidance for surface-texture design and tribological-performance optimization of polymer/metal end-face friction pairs. Full article

To quantitatively evaluate the skeleton design of the MaFF method, this study addresses five dimensions: gradation control, test method, quantitative model, correction conversion, and design method. First, the deviation coefficient method is proposed based on the Talbot method. Unlike conventional design restricted to n = 0.3–0.7, this method takes the maximum density curve at n = 0.45 as the reference and enables flexible adjustment of $V_{ag}$ by controlling the 4.75 mm sieve passing rate. This provides a theoretical basis for discontinuous gradation design. Second, the wet mixing test is developed to overcome aggregate segregation and inadequate lubrication inherent in the dry tamping method, offering a new detection approach that better reflects the actual skeleton structure in the mixture. The optimum parameters were determined as 2% asphalt content, layered loading, one-sided tamping and 75 blows. Using 11 gradations, the wet mixing tests show that $V_{ag}$ increases from 24.13% to 38.29% as λ increases from 0 to 1.0, with a strong linear correlation (R² = 0.996). CT scanning validation indicates that the wet method results are 83–86% of those from 3D reconstruction, yielding a recommended reduction coefficient of 0.84. These findings systematically refine the MaFF method into a complete skeleton design framework. For the specific material system investigated (diabase aggregate, ultra-high-viscosity asphalt, maximum nominal particle size of 13.2 mm), this study provides a preliminary technical reference for FMA mix design. However, broader validation across diverse materials and field conditions is required before generalization. Full article

Acoustic emission (AE) monitoring has been widely employed for condition assessment of mechanical seals. However, the physical origin of high-frequency AE activity under elastohydrodynamic lubrication (EHL) conditions remains insufficiently understood. To address this, a physics-based forward-modelling framework is developed by integrating transient EHL analysis, dynamic interfacial load mapping, and piezoelectric signal transduction. The simulated AE responses are compared with experimental measurements acquired from a GM150 sensor under both normal and defect operating conditions. The results indicate that dynamic oil-film pressure fluctuations provide a physically plausible excitation mechanism for high-frequency AE activity under EHL conditions. The present study provides a mechanistic relationship between lubrication behavior and AE responses, providing a physics-based foundation for the interpretation of AE signals and condition monitoring of lubricated mechanical seal systems. Full article