Differences in Tribological Behaviors upon Switching Fixed and Moving Materials of Tribo-pairs including Metal and Polymer

Abstract

The coefficient of friction (COF) between two materials is usually believed to be an intrinsic property of the materials themselves. In this study, metals of stainless steel (304) and brass (H62), and polymers of polypropylene (PP) and polytetrafluoroethylene (PTFE) were tested on a standard ball-on-three-plates test machine. Significantly different tribological behaviors were observed when fixed and moving materials of tribo-pairs (metal/polymer) were switched. As an example, under the same applied load and rotating speed, the COF (0.49) between a rotating PP ball and three fixed H62 plates was approximately 2.3 times higher than that between switched materials of tribo-pairs. Meanwhile, the COF between H62 and PTFE was relatively stable. The unexpected tribological behaviors were ascribed to the thermal and mechanical properties of tribo-pairs. Theoretical analysis revealed that the differences in the maximum local temperature between switching the fixed and moving materials of tribo-pairs were consistent with the differences in the tested COF. This result indicated the precise prediction of the COF of two materials is complexcity, and that thermal and mechanical properties should be properly considered in designing tribo-pairs, because these properties may significantly affect tribological performance.

Colloid thermophoresis in the dilute electrolyte concentration regime: from theory to experiment

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“…52 Thus, we incorporated the thermal conductivity prefactor into the derived equations to account for this effect, and the hydration entropy contribution to the Soret coefficient is now defined as:where k cp and k s are the thermal conductivities of the colloidal particle and the solvent, respectively, with reported values for our case provided in the ESI† (see Table S2). 53–56 Here, the thermal conductivity solvent is assumed to be equal to the thermal conductivity of DI water due to the dilute concentration of colloidal particles.…”

Performance of new synthesized emulsifiers in ecofriendly metal cutting fluid formulations

“…A tribology measuring cell connected to Physica MCR-502 controlled-stress rheometers was used to conduct tribological tests [33][34][35] . A ball-on-pyramid principle governs the setting of the tribology accessory 36 .…”

Single‐phase fluid mass transfer in petroleum processing and petrochemical technology: Theory and application

“…Generally, both the Forchheimer-Darcy flow model and the Brinkman-Forchheimer-extended Darcy flow model can be used to describe the problems in the fixed bed, 20 and differential pressure (Δp) linearly increases with the increasing of Darcy's velocity (u D ), finally turning to a new equilibrium value of floating particle in the fluidized bed (Figure 5), which is due to adjustment of particles flow to overcome friction force between particles. 21,22 However, there are some questions on Brinkman-Forchheimer-extended Darcy flow model's applicability such as the limitations on the transition of phase interface. 23 Therefore, it is a long way to reach a perfect theory describing porous media with molecular diffusion (Section 2.1) and convective diffusion (Section 2.2) in fixed bed and fluidized bed.…”