Guizhou Electromechanical Research and Design Institute

Urban rail wheels endure prolonged exposure to frequent starts and stops, heavy cyclic loads, and complex track conditions, which often lead to premature failure modes such as wear, fatigue cracking, and corrosion in conventional wheel materials. These limitations restrict their ability to meet the evolving demands of modern rail systems for enhanced durability and performance. To address this, the present study uses laser cladding to deposit high-entropy alloy coatings with systematically varied aluminium content onto wheel substrates. The study compares phase composition, microstructure, and mechanical properties across the different coatings. Results show that increasing Al content transforms the coating microstructure from a single face-centred cubic (FCC) phase to a dual-phase structure of FCC and body-centred cubic (BCC) phases, accompanied by notable grain refinement. Among the variants, the CrMnFeCoNi(Al)8 coating has the densest microstructure and the most favourable mechanical performance. It achieves a microhardness of 399.62 HV0.5 in the as-clad state and 450 ± 5 HV0.5 after heat treatment, representing an increase of approximately 12.6%. This coating also demonstrates improved corrosion resistance, with an open-circuit potential 0.07 V higher than the CL60 substrate. Multi-body dynamics simulations confirm that the clad wheels maintain excellent operational stability and safety under service conditions.

Introduction O-ring seals are critical to ensuring the reliability of mechanical systems under harsh operating conditions. However, the classical parallel plate leakage model often neglects the effects of surface roughness and radial pressure distribution, leading to insufficient prediction accuracy. This study addresses this limitation by extending the classical parallel plate leakage theory to develop an optimized circular plate gap leakage model for O-rings. Methods A leakage rate correction factor μ 1 is introduced to quantify the effect of surface roughness, establishing an equivalent relationship between the micro-scale rough interface and the ideal smooth surface. The leakage rates of rough surfaces with different roughness levels under various differential pressures are theoretically calculated. Experimental validation is carried out under differential pressures of 0.3 MPa and 0.6 MPa, as well as surface roughness Ra values of 0.8 μm, 1.6 μm, and 3.2 μm. Results At a differential pressure of 0.4 MPa, the leakage rate reaches 0.67 × 10 −12 m 3 /s when Ra = 3.2μm , which is 1.8 times that of the case with Ra = 0.8μm. Experimental results show that: (1) At the same surface roughness, the cumulative leakage volume increases with the increase of differential pressure; when Ra = 1.6μm, the cumulative leakage volume at 0.6 MPa is approximately 1.5 times that at 0.3 MPa. (2) At the same differential pressure, a larger Ra results in a higher cumulative leakage volume; at 0.3 MPa, the cumulative leakage volume at Ra = 3.2μm is about 1.7 times that at Ra = 0.8μm. Overall, the leakage rate increases almost linearly with the increase of both differential pressure and surface roughness. The relative error between theoretical and experimental values is within 15%. Discussion The relative error within 15% confirms the reliability of the proposed model. However, uncertainties in the model primarily stem from unaccounted factors, including high temperature, long-term O-ring aging, extreme high pressure, and idealized model assumptions. Consequently, the model is only valid under conditions of room temperature, low pressure, and short-term service. Nevertheless, this work provides a robust analytical framework for O-ring leakage prediction and sealing performance optimization in engineering applications.

Acute liver injury and cardiovascular disease interact, forming a mutually exacerbating vicious cycle. However, the dynamic influence of hepatic vascular impedance on cardiac function has not been systematically elucidated. To address this gap, a closed-loop hemodynamic model based on lumped parameters was developed, encompassing the heart, liver, and the systemic arterial and venous circulation. This model was used to analyze how alterations in hepatic vascular impedance influence cardiac function and to provide a theoretical foundation for understanding liver-heart comorbidities. Healthy subjects served as the control group, while acute liver injury was simulated by proportionally increasing hepatic microvascular resistance. Changes in cardiovascular hemodynamic parameters were then systematically compared across conditions. As the severity of acute liver injury increases, the peak aortic flow and total cardiac output significantly decrease, with stroke volume reduced by approximately 17%. The left ventricular end-diastolic volume and stroke work are markedly diminished. Effective arterial elastance increases by about 20.7%, and the left ventricular ejection fraction decreases by approximately 4%. Furthermore, the change in hepatic arterial flow is considerably greater than that in portal vein flow. This closed-loop hemodynamic model reveals that acute liver injury leads to a reduction in preload and an increase in afterload, thereby causing abnormalities in both systolic and diastolic cardiac function. Global sensitivity analysis demonstrated that changes in presinusoidal vascular resistance serve as the major contributors to the resulting cardiac dysfunction. These findings provide a theoretical basis for understanding the interplay between liver and heart, and offer a feasible method for pre-assessing cardiovascular risk in patients prior to liver resection or transplantation.

The effects of Ca doping content on the crystal structure, electronic transport, thermal transport, and mechanical properties of In2O3 were systematically studied by means of X-ray diffraction (XRD), thermoelectric performance test, and first-principles calculation. XRD analysis shows that Ca2+ can be completely solid-dissolved into the In2O3 lattice to form a single-phase solid solution without the formation of impurity phases, and the lattice constant increases linearly with the increase in doping content, confirming that Ca2+ successfully replaces In3+ and triggers lattice expansion. The results of thermoelectric performance tests show that Ca doping can significantly improve the electrical conductivity of the material. The essence is that Ca doping introduces a large number of free electrons through the charge compensation effect, and coordinately regulates the carrier concentration and mobility to optimize the electronic transport performance. In terms of thermal transport performance, Ca doping leads to a decreasing trend of the total thermal conductivity of the material. The core mechanism is that the difference in ionic radius between Ca2+ and In3+ causes lattice distortion, enhanced mass fluctuation scattering, and defect scattering. At the same time, the decrease in Young’s modulus intensifies phonon scattering, resulting in a significant decrease in lattice thermal conductivity (dominating the change in total thermal conductivity), while the electronic thermal conductivity increases slightly but accounts for a very low proportion. Under the synergistic optimization of electrical and thermal transport, the thermoelectric figure of merit (ZT) of the material increases from ~0.05 to ~0.239, with particularly prominent effects in the medium and high-temperature range.

The microstructure and properties of gray cast iron are closely related. For gray cast iron with pearlite matrix, adjusting graphite characteristics to improve casting performance is the most effective method. It is of great significance to analyze the relationship between graphite characteristics and properties of gray cast iron for the development of gray cast iron with high tensile strength and high thermal conductivity. Regression models of graphite characteristics and properties of gray cast iron was established, including tensile strength and thermal conductivity. By calculating the coefficients of the two models, the different effects of graphite characteristics on the properties of gray cast iron were obtained. By testing the regression models, the feasibility of the regression analysis method in the performance analysis of gray iron castings was determined. According to the analysis results, some improvement schemes are put forward to improve the performance of castings.

ABSTRACT Flame‐retardant fabrics require both washing durability and skin affinity. However, their development faces significant challenges due to the weak interaction between flame retardants and fabrics, and the generally high mass loading needed to achieve effective flame retardancy. Herein, we developed halogen‐ and formaldehyde‐free flame‐retardant wool/nylon (W/N) fabric through covalent grafting of bio‐resourced pyridoxal phosphate (PP). The grafting achieved a very low weight gain of 3.3%, yet the resulting W/N‐PP fabric exhibited a high limiting oxygen index (LOI) of 31.3%, corresponding to an 18.1% increase over pristine W/N fabric. Meanwhile, the peak heat release rate (PHRR) and total heat release (THR) of the obtained W/N‐PP were reduced by 46.4% and 17.2%, respectively. Benefiting from the covalent linkage established via the Schiff base reaction between PP and the W/N fabric, the W/N‐PP demonstrates superior washing durability. After 24 h of washing, the flame‐retardant performance of W/N‐PP was retained. Moreover, W/N‐PP also retains the outstanding mechanical properties of pure W/N fabric. This facile and environmental process provided a powerful basis for technology and potential industrial applications.