A rotor system supported by roller bearings displays very complicated nonlinear behaviors due to nonlinear Hertzian contact forces, radial clearances and bearing waviness. This paper presents nonlinear bearing forces of a roller bearing under four-dimensional loads and establishes 4-DOF dynamics equations of a rotor roller bearing system. The methods of Newmark-β and of Newton-Laphson are used to solve the nonlinear equations. The dynamics behaviors of a rigid rotor system are studied through the bifurcation, the Poincarè maps, the spectrum diagrams and the axis orbit of responses of the system. The results show that the system is liable to undergo instability caused by the quasi-periodic bifurcation, the periodic-doubling bifurcation and chaos routes as the rotational speed increases. Clearances, outer race waviness, inner race waviness, roller waviness, damping, radial forces and unbalanced forces—all these bring a significant influence to bear on the system stability. As the clearance increases, the dynamics behaviors become complicated with the number and the scale of instable regions becoming larger. The vibration frequencies induced by the roller bearing waviness and the orders of the waviness might cause severe vibrations. The system is able to eliminate non-periodic vibration by reasonable choice and optimization of the parameters

Purpose: – The purpose of this paper is to find a new logarithmic profile model of cylindrical roller bearing, which is expected to avoid edge effect and allow a straight portion on the roller considering uniform pressure distribution and easier manufacturing. Design/methodology/approach: – A new logarithmic cylindrical roller profile model using three parameters is proposed. Contact model between roller and rings and quasi-static model of roller bearing are given to obtain contact pressure distribution and solved by multi-grid and Newton–Raphson method. Optimization of modified reference rating life model of the roller bearing is proposed by using genetic algorithms. Findings: – Under heavy load or tilting moment conditions, modified reference rating life of cylindrical roller bearing may increase greatly by optimization of three design parameters using the new logarithmic profile model. Originality/value: – The results of the present paper could aid in the design of logarithmic profile of cylindrical roller bearing and increase fatigue life of cylindrical roller bearing.

Surface coatings have proven highly effective in addressing the critical challenges of friction, wear, and corrosion on steel substrates, which are responsible for over 80% of mechanical failures in industrial applications. Recent research highlights that advanced coatings—such as ceramic carbides/nitrides, high-entropy alloys, and metal-matrix composites—significantly enhance hardness, wear resistance, and environmental durability through mechanisms including protective oxide film formation, solid lubrication, and microstructural refinement. Moreover, these coatings exhibit robust performance under combined tribological-corrosive (tribocorrosion) conditions, where synergistic interactions often accelerate material degradation. Key developments include multilayer and composite architectures that balance hardness with toughness, self-lubricating coatings capable of in situ lubricant release, and active or self-healing systems for sustained corrosion inhibition. Despite these advances, challenges remain in predicting coating lifetime under multifield service conditions and optimizing interfacial adhesion to prevent delamination. Future efforts should prioritize multifunctional coating designs, improved tribocorrosion models, and the integration of sustainable materials and AI-driven process optimization. This review consolidates these insights to support the development of next-generation coatings for extending the service life of steel components across demanding sectors such as marine, aerospace, and energy systems.

Magnetic and magnetocaloric properties of the amorphous Fe_92−xZr₈B_x ribbons were studied in this work. Fully amorphous Fe₈₉Zr₈B₃, Fe₈₈Zr₈B₄, and Fe₈₇Zr₈B₅ ribbons were fabricated. The Curie temperature (T_c), saturation magnetization (M_s), and the maximum entropy change with the variation of a magnetic field (−ΔS_m^peak) of the glassy ribbons were significantly improved by the boron addition. The mechanism for the enhanced T_c and −ΔS_m^peak by boron addition was studied.

Flexible rotor systems supported by angular contact ball bearings display very complicated nonlinear behavior due to clearance and nonlinear Hertzian contact force. In this paper, a nonlinear vibration theoretical model for a flexible rotor-bearing system is derived in which the dynamic model of the shaft element, disk, coupling, nonlinear contact deformations and forces of the ball bearing are established. Nonlinear responses and orbits analysis of a flexible rotor angular contact ball bearing system are studied using the numerical integration method and maximal Lyapunov exponent. Bifurcation and stability of periodic motion of the flexible rotor-bearing system are studied using the continuation-shooting method and Floquet multipliers. Influences of initial contact angles, unbalance, damping factor, axial preloads, bending moments, stiffness ratio and rotating speed on stability and the bifurcation of periodic motion of the rotor-bearing system are analyzed. Finally, the theoretical model for a flexible rotor-bearing system is experimentally verified.

The tribological performance of PTFE and PTFE-based composites filled with aramid fiber and ZnO nanoparticles in dry sliding and liquid nitrogen (LN ₂ ) conditions was studied comparitively. The wear scars on the test specimen were observed by scanning electron microscopy (SEM). The transfer films of the composite material formed on the sliding interfaces were studied by X-ray photoelectron spectroscopy (XPS). The tribological test results of the tribo-pairs with two ANSI 440C steel pins sliding on a composite disk showed that, compared with the pure PTFE, the friction coefficient of the PTFE-based composites filled with both aramid fiber and ZnO nanoparticles is reduced in dry sliding in room temperature (RT) air, whereas its friction coefficient is increased in LN ₂ . The friction coefficient of the composite filled with 5 wt% ZnO nanoparticles alone increases compared to unfilled PTFE in both RT air or in LN ₂ conditions. While in LN ₂ , the friction coefficient of the same 5% ZnO material is lower, and the wear resistance is higher than those under dry sliding, the C–F bond cleavage in PTFE was found in transfer films formed in dry sliding or LN ₂ conditions, and the F atoms were combined with Fe atoms from the sliding steel pins.