Journal of Tribology
ISSN / EISSN : 0742-4787 / 1528-8897
Published by: ASME International (10.1115)
Total articles ≅ 4,986
Latest articles in this journal
Journal of Tribology pp 1-16; https://doi.org/10.1115/1.4052422
This paper proposes a novel dual-drive hydrostatic lead-screw system (DDHLS). The design enables a lower feed speed and a better transmission performance than the conventional hydrostatic lead screw (HLS). Considering the nut-misalignment, the lubricating mathematical model of the DDHLS is established based on the perturbation method and solved by the finite difference method. The influences of the nut-radial-displacement, the nut-tilt, and the dual-drivable design on the transmission performance of the DDHLS are researched. The results show the nut-misalignment can regularly reduce or increase the axial load capacity, the axial stiffness coefficient, and the axial damping coefficient. Significantly, the dual-drivable design can improve the axial load capacity and the axial stiffness coefficient while hardly affects the axial damping coefficient.
Journal of Tribology, Volume 144, pp 1-38; https://doi.org/10.1115/1.4052255
This paper provides the main causes of asymmetric or directional deformation of surface roughness based on a transient non-Newtonian thermal elastohydrodynamic lubrication (EHL) model, where the contact materials have different thermal conductivities and elastic moduli. In order to obtain the actual shape of the surface asperity, the surface shapes of contact bodies are evaluated separately. It is clarified that the asymmetric deformation of the asperities appears due to two causes. One depends on the slide-roll ratio (SRR) and the difference in thermal conductivity between contact materials, and the other is caused by the contact pressure between the asperities through the oil film.
Journal of Tribology, Volume 144, pp 1-14; https://doi.org/10.1115/1.4052217
Running-in of the main bearings of a diesel engine is a crucial process before service. The running-in period can be divided into several stages, in which different running-in conditions are used. This is termed as multi-stage running-in, which is a good way to enhance running-in quality. In order to reveal the evolution of phase trajectory and compare the running-in quality, the running-in tests were performed with the material of a bearing bush (Sn-11Sb-6Cu) and shaft (AISI 1045). The running-in quality was comprehensively evaluated via friction coefficient, phase trajectory, and surface topography. Results indicate that the phase trajectories show a trend of stage-by-stage convergence. A multi-stage running-in can achieve a more stable attractor, lower friction coefficient and smoother surface, that is, a better running-in quality than the constant running-in scheme. This study provides a reference for formulating running-in specifications for sliding bearings.
Journal of Tribology pp 1-22; https://doi.org/10.1115/1.4052363
Promoting the martensitic transformation through optimum microalloying with Fe and/or Mn was observed to be an effective method to enhance the wear resistance of the Cu50Zr50 at. % shape memory alloy (SMA). Among all the potential microelements and concentrations, partial replacement of Cu by up to 1 at. % Fe and Mn is of interest since from density functional based calculations large minimization of the stacking fault energy (SFE) of the B2 CuZr phase is predicted. For this reason, an effective martensitic transformation is expected. The largest decrease of the SFE from 0.36 J/m2 to 0.26 J/m2 is achieved with partial replacement of Cu by 0.5 at. % Fe. This results in the highest martensitic transformation upon wear testing, especially at highest load (15 N) for which the mass loss is 0.0123 g compared to 0.0177 g for Cu50Zr50 and a specific wear rate of 5.9 mm3/Nm, compared to 8.5 for mm3/Nm for Cu50Zr50. This agrees with the low coefficient of friction of 0.48±0.05 and low roughness of 0.200±0.013 μm of the Fe-containing alloy compared to that for Cu50Zr50, 0.55 and 0.415±0.026 μm, respectively. All the worn surfaces show the formation of abrasive grooves, being shallowest for the more wear resistant 0.5 at. % Fe alloy. The second more wear resistant alloy contains 0.5 at. % Mn. Wear mechanisms of abrasion, adhesion and delamination have been identified.
Journal of Tribology, Volume 144; https://doi.org/10.1115/1.4052172
The Morton effect (ME) occurs when a bearing journal experiences asymmetric heating due to synchronous vibration, resulting in thermal bowing of the shaft and increasing vibration. An accurate prediction of the journal's asymmetric temperature distribution is critical for reliable ME simulation. This distribution is strongly influenced by the film thermal boundary condition at the pad inlets. Part I utilizes machine learning (ML) to obtain a two-dimensional radial and axial distribution of temperatures over the leading-edge film cross section. The hybrid finite volume method (FVM)—bulk flow method of Part I eliminated film temperature discontinuities and is utilized in Part II for improving accuracy and efficiency of ME simulation.
Journal of Tribology, Volume 144, pp 1-45; https://doi.org/10.1115/1.4052171
Uncertainty in mixing coefficients (MCs) for estimating pad leading-edge film temperature in tilt pad journal bearings reduces the reliability of predicted characteristics. A three-dimensional hybrid between pad (HBP) model, utilizing computational fluid dynamics (CFD) and machine learning (ML), is developed to provide the radial and axial temperature distributions at the leading edge. This provides an ML derived, two-dimensional film temperature distribution in place of a single uniform temperature. This has a significant influence on predicted journal temperature, dynamic coefficients, and Morton effect response. An innovative finite volume method (FVM) solver significantly increases computational speed, while maintaining comparable accuracy with CFD. Part I provides methodology and simulation results for static and dynamic characteristics, while Part II applies this to Morton effect response.
Journal of Tribology pp 1-23; https://doi.org/10.1115/1.4052330
A semi-analytical model (SAM) to tackle the steady-state elastic frictional rolling contact problem involving composites is presented. Specifically, the frictional rolling contact is categorized into two subtypes, namely normal and tangential problems, and the conjugate gradient method (CGM) is used to figure out the normal pressure and tangential traction. In SAM, the equivalent inclusion method (EIM) is applied to analyze the influence of composites on the matrix, and the displacement disturbance resulting from such composites is added to the total surface displacement, which implements the coupling between surface contact and composites. The accuracy of the proposed model is verified by the finite element model. The effects of composites on the frictional rolling contact behavior are investigated. The results indicate that Young's modulus, as well as the size and location of the composites, are correlated with the distributions of tangential traction, subsurface stresses and the sizes of stick and sliding zones.
Journal of Tribology pp 1-28; https://doi.org/10.1115/1.4052331
This paper presents the effects of carriage flexibility on the friction force in linear ball guides, which includes hydrodynamic rolling friction, elastic hysteresis friction, slip friction, and drag friction. To this end, we developed a computational model for the friction force in linear ball guides that accounts for the carriage flexibility. The model was validated through experiments, and the results prove that it provides more accurate friction-force estimates than the conventional model under the assumption of a rigid carriage. Subsequently, we examined the effects of external load, preload, and speed on the friction force. Among several friction components, hydrodynamic rolling friction makes a major contribution to the total friction force. Ball contact loads, which significantly vary with carriage flexibility, were found to influence the hydrodynamic rolling, elastic hysteresis, and slip friction forces. The proposed model considering carriage flexibility in linear ball guides is expected to find use in the design and operation of linear-ball-guide systems.
Journal of Tribology pp 1-31; https://doi.org/10.1115/1.4052329
Galling is a recurring phenomenon in deep drawing processes which requires frequent maintenance of tools to improve the product surface quality. Adhesive transfer of softer material on the hard tool surface results in sharp features which causes surface roughening of the dies and deterioration of deep drawn products. In this article, an adhesive wear model based on deterministic approach is developed to predict the galling behavior in a deep drawing process. The model uses the surface topography, material properties and contact conditions to predict the surface roughening of tool surfaces under perfectly plastic conditions. The adhesive transfer of material is considered by the growth of the asperities based on its geometry for the increase in height and radial direction by preserving the original shape and volume consistency. The results of the multi-asperity models shows the growth of transfer layer and its effects due to load, sliding cycle, sliding distance and affinity of the materials. The results shows the influence of the above-said parameters and its applicability for deep drawing process conditions. The simulated results shows an 85% level of confidence in comparison with the experiments from literature for the prediction of the surface evolution due to galling mechanism.
Journal of Tribology pp 1-32; https://doi.org/10.1115/1.4052279
This paper presents a finite element (FE) model to investigate the effect of prior austenite grain refinement on rolling contact fatigue (RCF). RCF life was determined using continuum damage mechanics (CDM), which simulated material deterioration as a function of cycle. CDM calculations in this investigation considered the subsurface shear reversal to be responsible for RCF failure. To establish the CDM critical parameters torsion stress-life data from open literature of three different grain sizes for the same material was used. It was observed from the torsion S-N data that the resistance stress exhibits a linear relationship with grain diameter. As grain diameter was refined, the resistance stress increased. The damage rate exponent displayed no relation to grain diameter; hence, the average value from the three torsion S-N curves was used in this investigation. In order to assess the effect of grain refinement on RCF life, a series of unique material microstructures were constructed using the Voronoi tessellation process at eight mean grain diameters. FE simulations were devised at three contact pressures per grain size. The RCF results at the eight grain diameters indicate that fatigue performance is improved exponentially with finer grain diameter. The observed life improvements from the RCF simulations resulting from grain refinement exhibit good corroboration with existing experimental results found in open literature. A single predictive fatigue life equation was constructed from this investigation's RCF simulations to evaluate the stochastic RCF performance, given grain diameter and contact pressure, of non-conformal contacts.