A descriptive model of wear evolution in rolling bearings

Predicting changes in slip resistance performance with wear evolution is extremely difficult task and at present neither footwear nor flooring industries have a valid and reliable answer. Hence, in order to gain fundamental knowledge on wear mechanism, progressive wear and surface alteration processes of the shoes are investigated during repetitive dry rubbing. It is assumed that geometry changes of the shoe surface caused by wear development would be a major factor that affects the slip resistance performance. With the measurements of slip resistance, wear characteristics of two different shoes are comprehensively investigated based on the surface analyses and microscopic observations. For the systematic investigation of the surface alterations, topographic changes of each shoe were thoroughly examined on a regular time basis. The results show that surface alterations of each shoe were more severe than expected and occurred from the very early stage of sliding. It is also found that initially unstable friction process changed into the steady state friction process in the later stage of the slip resistance tests.

To achieve a higher storage density in a hard disk drive, the fly height of the air bearing slider, as part of the magnetic spacing, has to be minimized. At an ultralow fly height, the intermittent–continuous contact at the head–disk interface (HDI) is unavoidable and directly affects the mechanical and magnetic performance of the hard disk drive, and is of great interest. The HDI wear has a nonlinear and time-varying nature due to the change of contact force and roughness. To predict the HDI wear evolution, an iterative model of Coupled Head And Disk (CHAD) wear, is developed based on the contact mechanics. In this model, a composite transient wear coefficient is adopted and multiple phases of the wear evolution are established. A comprehensive contact stiffness is derived to characterize the contact at the HDI. The abrasive and adhesive wear is calculated based on the extended Archard’s wear law. The plastic and elastic contact areas are calculated with a three-dimensional (3D) sliding contact model. Based on the CHAD wear model, for the first time, the coupling between head and disk wear evolutions is thoroughly investigated. Accelerated wear tests have also been performed to verify the disk wear effect on the slider wear. A wear coefficient drop with time is observed during the tests and it is attributed to a wear mechanism shift from abrasive to adhesive wear. A shift in the type of contact from plastic to elastic accounts for the wear mechanism change.

In this work, we present a mechanical and tribological study at the microscale of sol–gel TiO2–CdO films, which are used in photocatalytic applications. The films were deposited as a good-quality polycrystalline material with majority of CdO or CdTiO3 phases depending on their Ti/Cd concentration ratios. Films with the majority of CdTiO3 phase presented the highest hardness and lowest plastic deformation during the indentation tests. The evolution of wear, friction coefficient, and roughness on the films was quantitatively studied by multiple-passes measurements on a depth-sensing instrumented indentation system. These measurements allowed us to observe the films’ wear mechanisms and correlate them with their microstructure and mechanical properties. To compare the crystal structure, mechanical properties and tribological behavior of these films, we also analyzed sol–gel CdO and TiO2 films deposited under similar conditions.

Microscopic observations of the progressive wear on shoe surfaces that affect the slip resistance characteristics

Wear evolution of electroplated diamond abrasive belt and corresponding surface integrity of Inconel 718 during grinding

Classical tool life models, including Taylor’s law, have been extensively used in machining practice due to their simplicity and empirical robustness. However, these formulations neglect the explicit influence of machining vibrations, which become critical in turning operations involving slender workpieces and dynamic cutting conditions. This limitation often leads to significant discrepancies between predicted and experimentally observed tool life. In this study, a vibration-informed extension of Taylor’s tool life law is proposed by explicitly incorporating the maximum transverse displacement of the workpiece as a governing dynamic parameter. The vibration amplitude is obtained from a nonlinear beam model accounting for large deflections and realistic boundary conditions, representative of turning configurations. The dynamic response is evaluated through a semi-analytical formulation and validated experimentally using measured displacement signals during cutting operations. Tool life experiments conducted under varying cutting speeds and vibration levels demonstrate that the proposed model significantly improves prediction accuracy compared to the classical Taylor formulation. The results reveal a strong correla-tion between increased transverse displacement amplitudes and accelerated tool wear, highlighting the critical role of vibration-induced dynamic effects on wear mechanisms. The proposed approach provides a physically grounded framework for coupling machining dynamics and tool wear, offering enhanced predictive capability for tool life estimation in vibration-sensitive turning processes. The findings of this work contribute to a deeper understanding of the interaction between structural dynamics and wear evolution in machining and offer practical insights for process optimization and chatter-aware tool life management.

Polygonal wear affects driving safety and drastically shortens a wheel’s life. This work establishes a wheel–rail coupled system’s rotor dynamics model and a wheel polygonal wear model, taking into account the wheelset’s flexibility, the effect of the wheelset rotation, and the initial wheel polygon. The energy approach is applied to study the stability of the self-excited vibration of a wheel–rail coupled system. The wheel polygonal wear generation and evolution mechanism is revealed, along with the impact of vehicle and rail characteristics on a wheel’s high-order polygon. The findings demonstrate that wheel polygonal wear must occur in order for the wheel–rail system to experience self-excited vibration, which is brought on by a feedback mechanism dominated by creepage velocity. Additionally, the Hopf bifurcation characteristic is displayed by the wheel–rail system’s self-excited vibration. Wheel polygonal wear is characterized by “fixed frequency and integer division”, and the wheelset flexibility largely determines the fixed frequency of high-order polygonal wear, which is mostly unaffected by the suspension characteristics of the vehicle. By decreasing the tire load, increasing the wheelset’s damping, and choosing a variable running speed, the progression of polygonal wear on wheels can be prevented. Future investigations on the suppression of wheel polygonal wear evolution can be guided by the results.

Assessment techniques for measurement of target erosion/ redeposition in large tokamaks

The heavy ion time‐of‐flight elastic recoil detection analysis (HI‐ERDA) technique was used to investigate the possibility of measuring near‐surface elemental depth profiles of light and mid‐ Z elements in thin films of plasma‐assisted molecular beam epitaxy (PAMBE)‐grown GaN and helium‐implanted titanium. The great advantage of HI‐ERDA is the ability to measure mass‐separated elemental depth profiles simultaneously. However for some materials it is not certain whether HI‐ERDA can be used successfully because significant sputtering or other beam‐induced damage may occur. The damage to the surfaces by a 77 MeV iodine beam was assessed using RBS, AFM and profilometry. The results show that for thin PAMBE‐grown polycrystalline GaN films and for titanium that has been heavily implanted with helium a significant modification of the near‐surface region is caused by the probing heavy ion beam. For the PAMBE‐grown GaN films the most significant loss trend is observed for nitrogen. Surprisingly this was not accompanied by a change in surface topology. In contrast, an almost complete removal of the heavily helium‐implanted surface layer was measured for the titanium specimens. The investigation shows that reference measurements with additional techniques such as RBS, AFM and profilometry have to be performed to ascertain sample integrity before HI‐ERDA data can be used. Copyright © 2004 John Wiley & Sons, Ltd.

Surface modification by substitution: Changing topology of conformational potential energy surfaces

The paper is dedicated to studying of the efficiency of application of the dust control agents not only for their original aims, but also for increasing of oxidation resistance of the solid fossil fuels. The complex investigation included: studying of coals quality alteration after treatment by the selected solution, scanning electron microscopy for investigation of their surface topology changes and, finally, ozonating treatment at low ozone concentrations with kinetic modeling for evaluation of oxidation resistivity. As it was expected, application of the selected solution allows no quality loss for coals. Scanning electron microscopy allowed to visualize the mechanism of working of the dust control agent. It revealed that the studied solution forms a thin smooth film around coal particles. This film tightly binds all the fine particles that were already formed and stored at the coal surface. Also, the solution tends to cover the surface thus decreasing the accessibility of the surface to active oxygen. The latter was proved by treated and untreated coals ozonating processing at low concentrations of ozone. The applied kinetic model allowed evaluation of the total coals activity to ozone decomposition. It was found that the treated coals have twice as low total activity to ozone decomposition as compared with the untreated ones. The latter parameter is closely related to coals oxidation resistivity (the lower the coals activity, the higher the coals oxidation resistivity). Therefore, it was finally concluded that application of the studied dust control agent allows for significant increase of sought-for quality indicator.

Friction and wear are typical irreversible processes. Friction irreversibly degrades and dissipates high quality energy and wear irreversibly removes materials from the load-carrying surface. The two irreversible processes can be presented by entropy production, which is a non-negative quantity based on irreversible thermodynamics and thus serves as a basis for the systematic description of irreversible processes occurring in tribological system. In this paper, a thermodynamic framework has been presented for the mechanisms of friction and wear of continuum materials, where entropy production is used as the sole measure of energy dissipation and material damage evolution in the system. As a result, there is no need for physically meaningless empirical parameters to define the phenomenological frictional and wear parameters to trace tribological evolution in a friction and wear system. To validate the model, predictions are compared with experimental results, which indicate that entropy production can be used as a friction and wear evolution metric. The theory is founded on the basic premise that a solid continuum obeys the first and second laws of thermodynamics.

Condition monitoring and fault detection in roller bearing used in rolling mill by acoustic emission and vibration analysis

Since 1980s, the author's impeller pump has successively achieved the device implantability, blood compatibility and flow pulsatility. In order to realize a performance durability, the author has concentrated in past years on solving the bearing problems of the impeller pump. Recent progress has been obtained in developing durable and permanent impeller blood pumps. At first, a durable impeller pump with rolling bearing and purge system has been developed, in which the wear-less rollers made of super-high-molecular weight polythene make the pump to work for years without mechanical wear; and the purge system enables the bearing to work in saline and heparin, and no thrombus therefore could be formed. Secondly, a durable centrifugal pump with rolling bearing and axially reciprocating impeller has been developed, the axial reciprocation of rotating impeller makes the fresh blood in and out of the bearing and to wash the rollers once a circle; in such way, no thrombus could be formed and no fluid infusion is necessary, which may bring inconvenience and discomfort to the receptors. Finally, a permanent maglev impeller pump has been developed, its rotor is suspended and floating in the blood under the action of permanent magnetic force and nonmagnetic forces, without need for position measurement and feed-back control. In conclusion, an implantable, pulsatile, and blood compatible impeller pump with durability may have more extensive applications than ever before and could replace the donor heart for transplantation in the future.

Analysis of friction-induced vibration and wear characteristics during high-speed train friction braking process