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As wind turbine capacities increase, the demand for improved stability and reliability has intensified. Traditional rolling bearings used as wind turbine main bearings often prove insufficient under conditions of the low speeds, heavy loads, frequent start-stop cycles, and complex load environments, along with significantly high maintenance costs. Sliding bearings offer a promising alternative, yet research on high-performance materials tailored for Wind Turbine Main Shaft Sliding Bearings (WTMSSB) is limited. This study investigates the tribological behavior and failure mechanisms of several sliding bearing materials under complex operational conditions. Multi-condition friction and wear tests were conducted to evaluate the friction coefficient, friction temperature rise, and volume wear rate of Babbitt alloy (ZChSnSb11–6), bimetal CuSn10Pb10, pure PEEK, and the 10 % PTFE-filled modified PEEK composites. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to analyze the microstructural features and elemental distributions on wear surfaces and wear debris. The 10 % PTFE-filled modified PEEK composite demonstrated superior self-lubricating properties and wear resistance under both lubricated and dry friction conditions, showing strong potential for complex load environments. While Babbitt alloy exhibited low friction under oil lubrication, its high wear rate and susceptibility to adhesive failure under dry conditions limit its applicability. Bimetal CuSn10Pb10 displayed consistently high friction and poor wear resistance across all conditions, with a tendency for seizure. This study provides robust experimental evidence for optimizing sliding bearing materials for WTMSSB and offers guidance for future material development and practical applications. • Comprehensive tests reveal tribological behavior and failure mechanisms of sliding bearings under typical wind turbine conditions. • PEEK composites show excellent self-lubrication and wear resistance, offering great potential for wind turbine bearing applications. • Babbitt alloy excels under lubrication but suffers high-temperature softening and adhesive wear, leading to failure in dry friction. • Bimetal CuSn10Pb10 faces high seizure risk and excessive frictional wear under dry friction conditions. [ABSTRACT FROM AUTHOR]

The hydraulic actuator system (HAS) for wet clutches in heavy-duty vehicle transmissions is required to have a fast response and high precision in the pressure regulation procedure. Conventional pressure control valves for HAS are almost slide spool structures, which perform a large flow force at a high flow rate. An open-center spool structure is designed and developed in this paper, which is a combination of a traditional slide spool and a valve sleeve. It has an orifice-groove combination throttling orifice, which can take into account the large through-flow capacity and small flow force. Firstly, to deeply understand the mechanism of pressure variation in the clutch chamber, a high-fidelity dynamic characteristic mathematical model of HAS considering the oil temperature is proposed. Secondly, the functional relationship between the oil temperature on the medium physical property parameters and the orifice thermal flow parameters in the model is deduced in detail. An experimental bench to measure the pressure valve dynamic performance and actuator pressure regulation characteristics in a wide temperature domain is then designed and implemented to validate the accuracy of the simulation model. Finally, the mechanisms of oil temperature and system pressure on pressure impact and pressure response are quantitatively analyzed in association with a supervised learning algorithm. The feasible domains of the two adjustable variables are also explored. This study provides a new perspective on dynamic control and energy saving of HAS pressure valves and a new method for the prediction of HAS performance under complicated operating conditions. • The orifice migration and straightening effect of OPRV under thermal flow conditions are investigated. • A maximum HAS pressure error of 0.8 bar between simulation and experiment is obtained. • A prediction surrogate model for actuator performance is proposed by utilizing RBF. • The feasible domain of oil temperature and system pressure is proposed for the shift impact. [ABSTRACT FROM AUTHOR]

• We built a left heart circulatory pulsatile flow generation system to simulate left ventricular under physiological conditions. • We used time-resolved particle image velocimetry to study blood flow downstream of two bileaflet mechanical valve shapes. • We tracked the LCS using the FTLE method. • The results of this paper can provide reference and experimental data to support the optimized design leaflets shape of BMHV. When a bileaflet mechanical heart valve is surgically implanted into the body, the downstream left ventricular blood flow pattern becomes complex, which is directly related to many postoperative complications. To investigate the hemodynamic properties associated with mechanical heart valve design, we built a left heart circulatory pulsatile flow generation system to simulate left ventricular flow and pressure under physiological conditions. We used time-resolved particle image velocimetry to study left ventricular blood flow downstream of two types of bileaflet mechanical heart valve: one with planar leaflets and one with cambered leaflets. Blood flow downstream of two different bileaflet mechanical valve shapes was assessed. The experimental results show that the bileaflet valve with a triple-jet pattern creates a three-dimensional vortex ring with a complex topology. In addition, the robust jet mode can introduce high shear stresses into the ventricular blood flow. Compared with the planar valve, the jet produced by the cambered valve has a more uniform velocity distribution, its vortex structure moves farther, and its shear stress distribution is more straightforward and continuous. Furthermore, the channel formed between the cambered valve vortex structure and the left ventricle wall surface is highly favorable for scouring the apical position and facilitating the transport of blood to the aortic orifice. Therefore, the shape of the leaflets of a bileaflet mechanical valve can significantly impact the left ventricular blood flow pattern and the blood transport process. Rational optimization of the design of the leaflet shape and improvement of the mechanical valve's hemodynamic characteristics can reduce complications after valve replacement. [ABSTRACT FROM AUTHOR]

• A Constructure-Kinematics-Materials-Craftsmanship (CKMC) method was proposed. • Failure of the crankshaft originates from the high-cycle fatigue of the fillet. • Material defects and lack of nitride layer at fillets accelerate failure process. • Recommendations for preventing future failures were presented. Crankshaft fracture is a typical failure form of reciprocating high-pressure plunger pump. Different from traditional power machinery, the number of plungers in plunger pumps is usually odd, which leads to unbalanced radial force of the crankshaft and greatly increases the risk of failure. The crankshaft of a 250 kW high-pressure plunger pump was fractured, and the fracture morphology was river-shaped, which was a typical fatigue failure. To trace the failure of the crankshaft, a Constructure-Kinematics-Materials-Craftsmanship (CKMC) method was brought out. The microstructure of the damage zone was observed, and a three-dimensional transient finite element model was established to find the most dangerous zone and damage mechanism. The results show that high-cycle fatigue of fillet zone is the main reason for crankshaft fatigue failure. Material defects and lack of nitrided layer at fillet are the key factors to accelerate crankshaft failure. Finally, recommendations for preventing future failures were presented. [ABSTRACT FROM AUTHOR]