The effects of particle size and friction coefficients of Fe-Ni-Mo steel powder on their filling behavior by a discrete element method (DEM) simulation were investigated. Our original DEM code based on FDPS (Framework for Developing Particle Simulator) was used for these simulations. First, the difference between the experimental and simulated values of the apparent density (simulation error) depends on the particle size, and in this case, the minimum level (＜10%) was reached when the particle size was 300-500 μm. In addition, the simulation with a 500 μm particle size model were found to yield an equivalent simulation accuracy in 1/5 the computation time of the 300 μm model. Next, the additives-induced decreases in the friction coefficients were applied to the simulation. In the experiment, the additives increased the apparent density by 6.7%, whereas in the simulation, it increased by 7.1%, showing that the differences in the friction coefficients can be qualitatively and quantitatively reproduced in the simulation. These results indicated that this simulation method can contribute to increasing the efficiency and speed of materials and manufacturing process development of sintered metal products.

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A balanced ceramic hybrid bearing incorporates an optimal mix of ceramic and steel rolling elements, balancing performance with manufacturing costs, which is crucial for many industrial products. The performance, tribological aspects and working mechanisms of balanced ceramic hybrid bearings are studied in detail based on an analysis of published data and further assessments. Balanced ceramic bearing’s static and dynamic load capacities are discussed and related to current bearing standards. A method for rating the lifespan of balanced ceramic hybrid bearings is proposed and validated using endurance test data. The fatigue life calculation allows for an assessment of the performance of this design against current solutions. The new calculation method is exemplified through a bearing application case. Bearing applications that can benefit from balanced ceramic bearings are identified, and their market potential is explored.

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Lighter weight and higher power density are major trends in electric vehicles (EV). To realize these market needs, speed and torque in electric motors increases continuously and light Al alloy housings are commonly used as the bearing seat in the power transmission system. To ease mounting, there is a loose fit between the bearing outer rings (OR) and the housing. Ring creep, i.e. a slow unidirectional movement of the bearing OR may occur. This ring creeping in combination with a high load may cause significant wear on the softer housing. The wear may result in mis-alignment and damage of the bearings and gears. In this study, it is shown that abrasive wear is the dominant wear mechanism during ring creep in EV power transmission system tests. To simulate the ring creep wear, a creep wear model based on the creep by strain mechanism was developed with the SKF BEAST software. Input data for the coefficient of friction and the wear coefficient were obtained from an in-house developed Ring-on-Ring test setup. The model was verified with a power transmission system test, showing good agreement between simulated and measured wear depth. Finally, remedies are proposed to minimize the ring creep wear.

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In radial rolling bearings, a phenomenon called creep occurs in the outer ring (the stationary/fixed raceway) when the bearing is subjected to excessive load. This study aims to investigate creep in the fixed thrust washers of thrust rolling bearings, a different bearing type designed to support axial loads. We examined the behavior of creep in thrust needle roller bearings with washers of various thicknesses and then compared results to those found through FEM analysis. The results showed that creep in the fixed raceway of thrust rolling bearings is similar to that in radial rolling bearings [1], with rolling friction having little effect and applied thrust load and raceway thickness having substantial impacts.

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The present study investigated the tribocorrosion behavior and mechanisms of nickel-aluminum bronze alloys in artificial seawater, offering theoretical support for the advancement and application of marine’s equipment. The study examined the alloy’s tribological performance, electrochemical properties, and the synergistic effect of corrosion and wear using a reciprocating wear tester. Wear scars were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrated a positive synergistic effect between corrosion and wear, with this effect being more significant at lower loads. Of the factors influencing the total tribocorrosion rate, the most critical was the change in wear rate caused by corrosion. Damage analysis revealed that wear samples under cathodic protection suffered severe abrasive wear, while unprotected wear samples developed tribocorrosion products, mainly consisting of Cu₂O, CuO and Al₂O₃, which accelerated the damage of NAB alloy. Corrosive wear was identified as the primary wear mechanism in these conditions. The amount of remained surface tribocorrosion products was largest under medium load wear test (7.6 N).

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Hydraulic control systems, known for their efficiency and high responsiveness, are widely used in industries such as aerospace, automotive, and construction. Recent advancements have integrated mechatronics and intelligent systems into traditional hydraulics, improving precision and functionality. However, challenges such as cavitation erosion in hydraulic valves remain critical, especially in automotive linear solenoid valves. Cavitation occurs when liquid pressure drops below its vapor pressure, forming bubbles that collapse violently, causing erosion and potentially degrading valve performance. This study examines the impact of glycol-based hydraulic fluids on cavitation erosion. Observation of the wear surface and elemental analysis revealed that the synergistic effects of the corrosive action of the hydraulic fluid and the impact pressure of cavitation caused severe valve wear in the experiment using Fluid A. Experiments with different base oils and additives for the hydraulic fluid suggested the types of additives that promote corrosion and the methods and mechanisms used to inhibit corrosion.

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