To investigate the impact of the length to diameter ratio (LDR) on the lubrication performance of misaligned journal stern bearings, a lubrication model was developed and solved using numerical methods, with experimental validation. Results show that, unlike aligned bearings, the lubrication performance of misaligned bearings initially improves as the LDR increases, reaches an optimal state, and then declines. The LDR corresponding to this optimal state is defined as the optimal length-to-diameter ratio (LDRopt). Further analysis indicates that LDRopt decreases with increasing dimensionless load, misalignment angle, and bearing diameter. A mathematical relationship between LDRopt and these parameters was established using nonlinear fitting. Validation through case studies confirmed its accuracy, demonstrating its high practical value.

Water-lubricated bearings are critical components in marine propulsion systems. They must reliably sustain load transmission and accommodate vibration propagation under demanding operating conditions. Bearing performance directly affects propulsion efficiency, operational reliability, and onboard noise emissions. This study proposes a novel laminated water-lubricated bearing design to mitigate propulsion-shaft noise and improve crew survivability. A coupled fluid-structure-acoustic (FSA) model is developed to characterize the bearing response under representative operating conditions. The effects of key operating and structural parameters on lubrication performance and noise radiation are systematically quantified. In addition, the influence of soft-hard material combinations on fluid-structure interactions is examined, elucidating the relationship between bearing deformation and the resulting stress-strain response across different scenarios. The results advance the understanding of multiphysics coupling in water-lubricated bearings and provide a theoretical basis for optimizing and deploying modern laminated bearings, thereby underscoring their engineering significance.

To investigate the dynamic characteristics of the stern bearing lubrication film during rudder maneuvers, this study employs the displacement superposition method to describe the bidirectional deformation and geometric posture of the stern bearing. A lubrication model is developed, and a computational method for determining dynamic parameters is proposed. The model is solved numerically to analyze the effects of varying operating conditions and structural parameters. Results indicate that increases in both vertical and horizontal loads enhance the lubrication film's dynamic parameters, with vertical loads exerting a stronger influence, and that the stern bearing is more sensitive to vertical displacement disturbances. Compared to right rudder maneuvers, left rudder maneuvers produce greater dynamic parameters in the lubrication film. Further analysis reveals that increasing the length-to-diameter ratio reduces dynamic parameters, whereas increasing the clearance ratio enhances them, and that both ratios have a pronounced effect on parameters associated with vertical displacement.

This study establishes a generalized Reynolds equation model that incorporates the bending deformation of the stern shaft journal under combined vertical and horizontal loads. The journal deflection was obtained via finite element analysis, and cubic polynomials were used to construct spatial attitude functions. These fitted expressions were then integrated into the lubrication model to assess the effects of shaft deformation on stern bearing performance. Results show that increasing vertical and horizontal loads lead to a reduction in minimum film thickness, a rise in maximum film pressure with greater unevenness, and a higher friction coefficient. The lubrication regime shifts from hydrodynamic to mixed lubrication, with increased local contact pressure and wear risk. Under equal-magnitude lateral loads, negative horizontal loading (right turning) offers better lubrication than positive loading (left turning), and slight right turning even outperforms straight sailing. The study provides a theoretical basis for analyzing and optimizing stern bearing lubrication performance under shaft deformation.

The electro-hydraulic (EH) system is a critical subsystem of thermal power plant generating units, which regulates the opening of turbine steam valves via solenoid valves. Solenoid valve sticking failure poses a severe threat to the operational safety of generating units. In this study, macroscopic inspection, surface micromorphology analysis, metallographic testing, and hardness measurement were conducted on faulty solenoid valves. The results confirm that valve sticking is induced by three-body abrasive wear. Furthermore, particle composition analysis was performed on oil samples collected from both the EH system oil tank and faulty solenoid valves, verifying that the sticking-causing contaminants are stainless steel particles. Subsequently, the filtration performance of brand-new EH system filter elements was comprehensively evaluated. Micromorphology and microarea composition characterization of the filter element inner wall, as well as composition testing of detached particles, further demonstrates that the stainless steel particles responsible for valve sticking originate from inner-wall shedding of the filter element. Finally, the intrinsic sticking mechanism of the solenoid valve was systematically analyzed. Numerical results show that the maximum frictional resistance generated by a single hard particle is 0.034 N, and particle accumulation exceeding 142 particles within the valve clearance will trigger solenoid valve sticking. This study provides a feasible diagnostic method and technical reference for similar solenoid valve faults, facilitating the prevention of sticking failures in EH system solenoid valves in practical engineering.

As key components in efforts to achieve green and sustainable development in machinery, water-lubricated stern bearings are increasingly replacing traditional oil-lubricated bearings. However, water’s inherent properties—such as low viscosity and poor film-forming ability—can induce severe friction-induced vibration and noise under specific operational conditions. These issues not only accelerate wear but also compromise the vessel’s reliability and acoustic stealth, thereby limiting their wider application. This paper provides a comprehensive review of the research progress relating to friction-induced vibration in water-lubricated bearings. It delves into the underlying mechanisms, critiques the primary methodologies used in numerical simulations, summarizes key experimental approaches, and synthesizes the prevailing vibration suppression strategies. Finally, the study clearly outlines existing challenges and proposes directions for future research.

This study addresses the challenges associated with friction-induced liquid film temperature rise and film thinning in shipborne water-lubricated bearings. A laminated bearing design is proposed in which an ultra-high-molecular-weight polyethylene composite layer (UHMWPE) is inserted between the rubber liner and the metal backing. A coupled thermo-hydro-mechanical multiphysics framework is developed to quantify interactions among thermal, hydrodynamic, and structural responses. Systematic analyses are performed to evaluate the effects of key parameters, including eccentricity ratio, rotational speed, and rubber and UHMWPE layer thickness. The analysis focuses on water film pressure, load-carrying capacity, frictional power loss, and the deformation and stress fields within the liner structure. The results clarify the coupling mechanisms linking structural parameters, thermal effects, and thermally induced deformation. Under thermal loading, increasing eccentricity nonlinearly increases interfacial stress and modifies lubrication performance. Rotational speed primarily governs load-carrying capacity and frictional power dissipation and also increases the risk of cavitation and operational instability. These effects become more pronounced when rotational speed exceeds 1000 r/min and eccentricity ratio exceeds 0.8. Furthermore, thermophysical mismatch between rubber and UHMWPE delays interlayer heat transfer and promotes progressive accumulation of through thickness temperature gradients, which redistributes the stress field and reconfigures the water film pressure. This process establishes a detrimental negative feedback loop that further degrades lubrication conditions and accelerates performance degradation. Overall, these findings provide a robust theoretical basis for the design and optimization of multilayer water-lubricated bearings.

High-load structural materials inherently transmit vibrations with high efficiency, leading to a fundamental trade-off between load-bearing capacity and vibration isolation, particularly in practical engineering environments such as large-scale machinery applications. This trade-off is especially evident in porous structures represented by triply periodic minimal surface (TPMS) lattices. These structures offer high specific strength and lightweight load-bearing capacity yet lack adequate low-frequency vibration isolation, with their mechanical and damping performances strongly volume fraction-dependent. Bioinspired by cat paw pads, we proposed a novel strategy integrating topological discretization with a viscoelastic interpenetrating phase to address this challenge. Results show that the TPMS-Gyroid lattices with 1–8 interlacing cells were fabricated via laser powder bed fusion at a constant volume fraction and infiltrated with silicone rubber. Multi-path load transfer enables uniform stress distribution, silicone rubber constrains strut deformation, enhances energy absorption, and extends fatigue life through interfacial friction and viscoelastic dissipation. Shaker tests confirm improved low-frequency vibration level difference (VLD) via lowered natural frequency and enhanced damping ratio. Experimental validation in a ship propulsion shaft system demonstrates the hybrid metamaterial achieves 39 dB VLD at 55 Hz and up to 1201% higher vibration attenuation than solid bearings under realistic axial displacements, while maintaining excellent load-bearing performance. These results provide a scalable design approach for high-load, low-frequency vibration isolation in large-scale machinery, automated industry, and electronic devices.

Water-lubricated bearing materials for ships suffer severe wear under low-speed operation and heavy load conditions. Integrating graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) into ultra-high molecular weight polyethylene (UHMWPE) can improve its tribological properties. However, the cooperative modification mechanism governing these enhancements has not yet been elucidated. This report describes the preparation of a series of composites, i.e., UHMWPE/GO, UHMWPE/MWCNTs, and UHMWPE/GO-MWCNTs (GCNTs), which were fabricated by incorporating GO, MWCNTs, and GCNTs, respectively, into the UHMWPE matrix. The frictional and wear properties of these materials are investigated experimentally and through molecular dynamics (MD) simulation. The results show that the wear rates of UHMWPE/GO, UHMWPE/MWCNTs, and UHMWPE/GCNTs are all reduced relative to that of pure UHMWPE. In particular, the friction coefficient and wear rate of UHMWPE/GCNTs are the lowest under a heavy load (40 N), with reductions of 63.5 % and 56.7 %, respectively, compared with pure UHMWPE. Additionally, UHMWPE/GCNTs have lower molecular mobility. The "GO-MWCNTs-GO" sandwich structure formed by GO and MWCNTs on the surface of the UHMWPE provides more effective lubrication, which reduces the friction coefficient and wear of UHMWPE/GCNTs, thus improving the overall frictional properties of the material.

Significant vibration coupling exists between the propulsion shaft system and the shell, as well as between the inner and outer shells of underwater vehicles. An in-depth study of these coupling mechanisms helps reveal the vibro-acoustic response characteristics of the stern section of underwater vehicles. This article establishes the dynamic equations for the inner and outer shells based on Flugge shell theory. Then, the dynamic model of the double-layer shell is developed by the displacement continuity conditions and internal force balance conditions between the intercostal structure and shells. Subsequently, the annular flow field between the inner and outer shells is solved using the Helmholtz wave equation and the displacement continuity conditions at the shell surface. The dynamics model of the propulsion shaft system is established using the Euler-Bernoulli beam theory. The bearings are simplified as a stiffness-damping system, serving as the connecting structure between the shaft and the double-layer shell. By balancing the bearing forces between the shaft and the shell, the dynamic model of the propulsion shaft system - double-layer shell coupling system is finally established. The impact of variations in bearing parameters and the connection form between the double-layer shells on the vibro-acoustic characteristic of the propulsion shaft - double-layer shell coupling system is discussed in detail. This study provides theoretical support for vibration and noise reduction in the stern of underwater vehicles.

The transom of the ship exhibits clear flexural distortion as a result of propeller gravity. At the same time, non-linear deformation is readily produced under external load because of the material's viscoelastic properties. This causes a significant eccentric load on the stern bearing and exacerbates the wear and local friction phenomena. The lubrication and bearing mechanism of maritime water-lubricated stern bearings have not been fully investigated under eccentric load and creep working circumstances. This research uses a ring-block friction and wear test prototype to replicate the eccentric load of the stern bearing passing through the counterweight discs in order to examine the effects of creep and eccentric load on the tribological properties of various water-lubricated bearing materials. In this test, PTFE and NBR are utilized. The journal utilized was ZCuSn10Zn2. At various speeds and counterweights, creep and non-creep were measured for the friction coefficient and wear volume loss, and laser confocal was used to see and analyze the wear surface. The experimental shows that eccentric load is the cause of the journal's deflection deformation. This increases the amount of direct contact between the journal and the bearing, raising the friction coefficient and wear. The wear volume of PTFE and NBR rises by 47.6% and 85.5%, respectively, under eccentric load in comparison to the average load. Concurrently, the eccentric load causes the sample's wear width and depth to grow close to the load end, resulting in a wedge-shaped wear morphology. In addition to increasing wear and friction coefficients, creep also reduces the mechanical performance between the journal and the bearing, resulting in deeper plough and more metal debris on the bearing surface after creep. The wear mechanisms after creep and eccentric load remain adhesive wear and abrasive wear.

Water-lubricated bearings are prone to severe abrasive wear under low-speed and heavy-load conditions. Therefore, developing ultra-high molecular weight polyethylene (UHMWPE) composites with superior wear resistance is crucial for water-lubricated bearings. Herein, the tribological behavior of a novel UHMWPE/Silicon dioxide/Molybdenum disulfide (SiO2/MoS2) composite was investigated through a combined experimental and molecular dynamics (MD) simulation. The results demonstrated that the synergistic effect of SiO2 and MoS2 significantly improves the tribological properties of UHMWPE. Compared to pure UHMWPE, the composite exhibits a 62.96% reduction in wear rate and achieves an average friction coefficient as low as 0.044. Furthermore, MD simulations visually reveal the synergistic lubrication mechanism formed at the friction interface due to the structural differences between the two fillers, effectively enhancing interfacial slip between the composite and the counterpart ball.

Nitrile Butadiene Rubber (NBR) is commonly used in ships’ water-lubricated tail bearings. However, sediment in the water significantly affects these bearings’ friction and wear performance. This study investigates NBR test blocks’ friction and wear behavior in conjunction with ZCuSn10Zn2 copper ring friction pairs within a sediment-laden water lubrication environment. Two primary factors were considered: sediment particle concentration and sediment particle size. Friction and wear tests were conducted under pure water and sediment-laden conditions using the ZY-1 ring block friction and wear tester. The friction coefficients, wear quantities, and variations in mass concentrations and sediment particle sizes were measured and compared. The surface morphology of the test blocks was analyzed using a laser confocal microscope. The findings indicate that as sediment concentration increases, the particle size’s impact on NBR’s abrasive wear diminishes. The variation in particle size directly influences the number of particles that penetrate the interface between the friction partners and the nature of three-body wear. Conversely, changes in particle concentration primarily affect the extent of wear; specifically, both the wear volume and the average coefficient of friction of the NBR specimens increase with rising sediment concentration. The wear mechanisms observed on the surface of the NBR test blocks are predominantly characterized by micro-cutting, rolling wear, and the coexistence of both wear modes. This study offers valuable insights for the design and optimization of water-lubricated bearings.

This study focuses on low-speed, heavy-load water-lubricated bearings by developing a mixed lubrication model that accounts for elastic deformation effects. The model is solved using the finite difference method, and experimental tests verify its accuracy. The elastic properties of the bearing materials are characterized by the composite elastic modulus (CEM), which enables analysis of how CEM affects the lubrication performance of water-lubricated stem bearings under mixed lubrication. Results indicate that, under identical load conditions, a higher CEM slows the rate at which water film thickness increases as speed increases, thus requiring a higher rotational speed for the bearing to enter the hydrodynamic lubrication regime. Conversely, lowering the CEM increases the water film's load-bearing capacity, boosts minimum film thickness, and improves the bearing's lubrication state. A reduced CEM also lowers the liftoff speed, decreases the magnitude and area of solid contact, alleviates stress concentration, and consequently extends bearing life. Additionally, a lower CEM reduces the friction coefficient, which in turn lowers the risk of friction-induced failure.

In sediment environments, water-lubricated rubber bearings are inevitably subjected to particle abrasion, especially during frictional vibration. However, the invasion-migration-wear mechanism of hard particles under frictional vibration excitation remains unclear. This study analyzes the contact strain at the friction interface and the dynamic response of the friction system by constructing a visualized friction pair at the interface and employing digital image processing technology. The results reveal that the friction-induced vibration in the water-lubricated rubber bearing-rotor system primarily manifests as chatter and squeal. Chatter represents a more intense stick–slip behavior, during which larger sediment particles are allowed to invade. These invading particles tend to sink deeper into the friction pair during the stick phase and migrate with the water flow during the slip phase, leading to combined wear in the form of scratches and pits. During squeal, the amplitude of stick–slip behavior is relatively small, allowing only small sediment particles to invade, which result in scratches on the bearing surface. When the system does not experience friction vibration, sediment particles are unlikely to enter the friction interface, even in a sediment-rich environment, and therefore, no significant wear occurs.

Herein, a novel composite of ultra-high molecular weight polyethylene (UHMWPE) reinforced with graphene oxide/silica/molybdenum disulfide (GO/SiO2/MoS2) was developed. Its tribological properties under water lubrication were systematically studied through both experimental and molecular dynamics (MD) simulation. The results indicate that the synergistic effect of GO, SiO2, and MoS2 significantly enhances the tribological performance of the composite. Compared to pure UHMWPE, the composite exhibits an 84.4 % reduction in wear rate and achieves an average friction coefficient as low as 0.031. Furthermore, the MD simulation visually illustrates the cooperative lubrication behavior at the friction interface, attributed to the structural differences of the three fillers. This study demonstrates promising potential for the development of high-performance waterlubricated bearing materials.

Three Gorges ship lift chamber is the main component of Three Gorges ship lift, so it is very important to monitor the structural performance of the ship lift chamber. The structure monitoring system of Three Gorges ship lift is established, which can monitor the strain and temperature of the main structure of ship lift. According to the monitoring data, the strain and temperature monitoring system of the ship lift is built, and the digital twin system of the ship lift is further constructed. This system can carry out safety assessment of the ship lift structure and real-time monitoring of the performance of the ship lift in the whole life cycle, which is of great significance to the scientific maintenance of the ship lift.

In order to improve the accuracy of the deformation reconstruction method based on the Ko displacement theory, a beam deformation reconstruction method based on CEEMDAN-HT-GMM-KO is proposed in this study. The method uses the CEEMDAN method to decompose the original signal and the GMM method to identify the noise so as to complete the noise reduction of the original data. A three-dimensional (3D) laser scanner was used to verify the results of strain information reconstruction before and after noise reduction. The results show that the average relative error of strain information reconstruction results after noise reduction is 4.54%. This method can eliminate the noise in the strain information and verify the accuracy of the deformation reconstruction method based on the Ko displacement theory in the overhanging beam under the condition of pre-deformation, providing a new method for the health monitoring of large steel structures.

Herein, the amorphous state model of ultra-high molecular weight polyethylene (UHMWPE) filled with nano-ZnO, nano-SiO2 and binary mixture (SiO2-ZnO) was established by molecular dynamics simulation (MD). The model was optimized geometrically and dynamically. The friction model of composite material and copper friction pair was established. By extracting mean square displacement (MSD), kinetic energy, RDF, binding energy and interface temperature of modified UHMWPE during friction, the tribological mechanism of modified UHMWPE by SiO2-ZnO was revealed. The experimental results showed that the wear of UHMWPE composites filled with nanoparticles was lower than that of pure UHMWPE composites. Among them, the addition of SiO2-ZnO nanoparticles made the UHMWPE composite have the lowest molecular mobility and the most stable structure, so it had the lowest wear rate. Compared with pure UHMWPE, the deformation length of the matrix was reduced by 31.9%. This paper provides theoretical support for the development of green ships and ship reliability.