An Effect of a Carbon-Containing Additive in the Structure of a Friction Material on Temperature of the Wet Clutch Disc

This paper consists of two parts. The first one contains a description and methodology of the composite material used as friction material in clutches. Four variants of such material, differing in the type of carbon additive (the elemental graphite, pencil graphite and foundry coke powder of various fractions) were considered. Thermal conductivity, thermal diffusivity as well as the specific heat all materials were determined experimentally. On the inertial IM-58 stand, a simulation of the braking process of the friction pair consisting of a steel disc with friction material and a counterpart in the form of a homogeneous steel disc was carried out. On this basis, averaged coefficients of friction, unchanging in the entire sliding process, were found for the four friction pairs. The experimental data obtained in the first stage were used in the second stage to develop two (2D and 3D) numerical models of the friction heating process of the friction pairs under consideration. For four variants of the friction material, a comparative spatial-temporal temperature analysis was performed using both models. It was found that a simplified axisymmetric (2D) model can be used to estimate the maximum temperature with high accuracy. The lowest maximum temperature (115.6 °C) obtained for the same total friction work was achieved on the friction surface of the material with the addition of GP-1.

The correlation of the vibroacoustic signal with the wear of a ceramic part during frictional interaction with a steel disc

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Influence of Contact Area on Tribo Response of Al 6061 in Ambient and Vacuum Environment

Aluminium alloys are used in spacecraft and aerospace industries because of their unique properties which are lightweight and high strength. The components of aluminium alloys used in aerospace and space environment are subjected to relative motion which results in the tribo-phenomenon. The designer needs tribo response data for designing components geometrical dimensions. The literature reports inadequate tribo response data, more particularly in a vacuum environment (adverse environment). In the present investigation, experiments were conducted using Al 6061 aluminium alloy pins with different diameters. The cylindrical pin diameters were 2mm, 4mm and 6 mm. The cylindrical pins were slid against a hardened En-8 steel disc. The normal pressure was maintained at 0.625 MPa and the sliding speed was 0.5 ms-1. The estimated friction coefficient from monitored frictional force and normal force and the dependency of estimated friction coefficient on sliding distance for cylindrical pins of different diameters were analysed.

Numerical investigation into thermal buckling of friction pairs in hydro-viscous drive under nonlinear radial temperature distribution

Thermal buckling deformation can significantly impact the operating performance of hydro-viscous drive. A thermal buckling finite element shell model was established with the nonlinear radial temperature as the thermal loading condition. The thermal buckling behavior of friction pairs was investigated under three different boundary constraints. Moreover, the influence of thickness and material parameters on the critical buckling temperature was discussed. The simulation results coincide with the failure modes of friction pairs in practice, and the most common ones are the coning mode and the potato chip mode. The ability to resist thermal buckling deformation can be improved as the thickness increases. In addition, the steel disc with outer edge simply supported is more prone to thermal buckling, because the critical temperature is minimum. The thermal expansion coefficient is the primary factor in thermal buckling study, which is inversely proportional to the critical temperature. These provide a theoretical basis for avoiding thermal failure of friction pairs in a hydro-viscous drive.

Comprehensive review of tribometer dynamics-Cycle-based data analysis and visualization

Tribologists often rely on triboexperiments to investigate factors that affect a tribosystem. The inherent dynamic behavior of the respective tribometer setups and its effect on data interpretation remain often unknown. In this study, a comprehensive analysis of sensor data obtained from lubricated and dry triboexperiments is performed. Data are generated on a pin-on-disc test rig with a silicon nitride ball on a steel disc contact with a rotation frequency of ~3 Hz. High-speed acquisition of sensor data up to 5 kHz is performed to resolve changes in the data within individual cycles. The characteristic frequencies of the system and their temporal evolution are determined via time-frequency analysis, which reveals periodic patterns in the sensor data. Cycle-based data evaluation allows the detection of localized events and changes during an operation and considerably reduces the apparent measurement uncertainty, as compared with an unreduced dataset. The data analysis and visualization routines presented herein may serve as a prototype for further application to tribometer setups.

Tribological Performance of Biomass-Derived Bio-Alcohol and Bio-Ketone Fuels

This study relates to developing future alternative fuels and focuses on the effects of a fuel’s molecular structure on its properties and performance in advanced propulsion systems. The tribological performance of various biomass-derived oxygenated alternative fuels, including butanol, pentanol, cyclopentanol, cyclopentanone, and gasoline and their blends with diesel, was investigated. Lubricity tests were conducted using a high-frequency reciprocating rig (HFRR). Cyclopentanone-diesel and cyclopentanol-diesel blends result in smaller wear scar sizes compared to using their neat forms. A lower steel disc contaminated with the alternative fuels during the HFRR tests resulted in worn surface roughness values lower than those of the neat diesel by up to 20%. It is believed that these reductions are mainly due to the presence of the hydroxyl group and the carbonyl group in alcohols and ketones, respectively, which make them more polar and consequently helps the formation of the protective lubrication film on the worn moving surfaces during the sliding process. Overall, the results from this study indicate that environmentally friendly cyclopentanol and cyclopentanone are practical and efficient fuel candidates for future advanced propulsion systems.

Experimental and Numerical Studies on the Inflatable Recyclable Anchor in the Tube Piece Type Based on the Soil-Anchor Interaction Mechanism

This paper deeply studies the characteristics and “uplift bearing capacity” of a novel type of inflatable recyclable anchor in the tube piece. The proposed novel inflatable recyclable anchor in the tube piece type comprises a metallic rod, an inflatable anchorage device, and a recovery device. Fifteen field uplift tests are conducted to investigate the effects of inflation pressure, thickness of the steel disc, embedment length, and time lapse between anchor inflation and pullout on “the uplift bearing capacity.” The results show that “the uplift bearing capacity” of the novel inflatable anchor in the tube piece type increases with the increase of inflation pressure, thickness of the steel disc, and embedment length. With the increase of inflation time, “the uplift bearing capacity” of the novel inflatable anchor experiences an increase after first experiencing a decrease. The finite element analysis method is used to establish a numerical analysis model of the inflatable anchor, and the distribution law of the tensile stress of the surrounding soil during the pullout of the anchor is analysed. Compared with the traditional grouted anchor, the proposed anchor has an obvious superiority in recyclability, reusability, and swifter formation of anchorage force and thus is a resource-saving and environmentally friendly anchor technology.

Tribological Behavior of Steel Reinforced Glass/Epoxy Hybrid Composites

In this paper, the specific wear rate (SWR) and the coefficient of friction (CoF) of steel embedded glass/epoxy hybrid composites were examined and compared. Experiments were carried on the pin-on-disc machine on different types of composite materials like plain composite (steel volume 0%) and hybrid composites (steel volume 5% and 10%) pressed against a rotating steel disc (EN 31). Composites were fabricated using the hand-lay-up method. The volume percentage of steel pin/pipe varied from 0 to 10% and glass fiber from 50 to 60%, while the percentage of epoxy was kept 40% stable. The experiments were carried out on a group of samples for duration 20 minutes for different loads of 70N, 80N, 90N, 100N, and 110N with a varying sliding distance of 1000 m, 1250 m, 1500 m, 1750 m, and 2000 m. The results show that the SWR and CoF vary with different load and sliding distance. In general, CoF rises for some time of rubbing, and then it remains constant for the rest of the testing time. The results obtained show that the SWR and CoF increase with increasing sliding distance and load for all the composites. However, SWR and CoF decrease as an increase in the volume percentage of steel. An SWR of hybrid composite is observed to be reduced by 28.02% and 45.98% with an increasing percentage of steel by 5% and 10% respectively. CoF of hybrid composite is observed to be reduced by 14.11% and 24.02% with an increasing percentage of steel by 5% and 10% respectively. At last, the worn surfaces of the hybrid composites were studied through a Scanning Electron Microscope (SEM). Shallow and fine grooves appeared on the worn surfaces of hybrid composites at low loads and cracks were found in large quantities at high load which increased weight loss.