Generalized master curve procedure for elastomer friction taking into account dependencies on velocity, temperature and normal force

Abstract

In the sliding contact of elastomer on a rigid substrate, the coefficient of friction may depend on a large number of system and loading parameters, including normal force, sliding velocity, shape of contacting bodies, surface roughness and so on. It was argued earlier that the contact configuration is determined more immediately through the indentation depth than the normal force, and thus the indentation depth can be considered as one of "robust governing parameters" of friction. Both models of friction of simple shapes and fractal surfaces demonstrate that the coefficient of friction of elastomers should be generally a function of dimensionless combinations of sliding velocity, surface gradient, relaxation time and size of micro-contacts. The relaxation time does depend only on temperature and the surface slope and the size of micro contacts mostly on the indentation depth. Based on this general structure of the law of friction, we propose a generalized master curve procedure for elastomer friction where the significant governing parameter -indentation depth (or normal force) was taken into account. Unlike the generation of the classical master curve by horizontal shifting of dependence "friction -logarithm of velocity" for different temperatures, in the case of various indentation depth the shifting in both horizontal and vertical direction is required. We experimentally investigated coefficient of friction of elastomer on sliding velocity for different indentation depths and temperatures, and generated a 'master curve' according to this hypothesis.

Harnessing Friction in Intertwined Structures for High‐Capacity Reusable Energy‐Absorbing Architected Materials

“…The plate was rotated to control the sliding speed, meanwhile, F z was maintained to be an almost constant. Considering that μ relies on normal contact stress [ 54 ] and elastomer thickness, we prepared two elastomer discs of thicknesses t = 0.4 and 1.3 mm, representing the thickness of the elastomer in the architected materials, which varies along the rod. The corresponding applied normal forces are F z = 1.1 and 3.0 N respectively, to ensure the nominal normal contact stress acted on the steel sphere approaches the average normal stress applied to the rods, about 0.53 MPa according to the finite element method (FEM) simulations (for details see Figure S3 b and Figure S4 , Supporting Information), where the constitutive behavior of the silicone elastomer is assumed to follow the third order Ogden hyperelastic model [ 55 ] (see Section 4 and Figure S5 , Supporting Information).…”

Editorial: Contact Mechanics Perspective of Tribology

“…The study also attracts attention of researchers to the fact that at small contact area the statistics of the contact profile is not the same as that of the full rough surface. This dependence maybe the reason for the weak dependency of the coefficient of friction of elastomer materials on the normal load [Popov et al (2018)].…”

Transient and Steady Sliding Friction of Elastomers: Impact of Vertical Lift

“…Among various elastomers, rubber is the material that has received the most attention in various practical applications (e.g., tires, seals, and shoes). Since the study done by Grosch (1963) showing the master curve of friction coefficient according to Williams-Landel-Ferry (WLF) theory (Williams et al, 1955), the importance of viscoelasticity has been recognized, and the dependence of the friction coefficient on temperature and velocity has been investigated [e.g., Popov et al (2018)]. More recently, several swollen polymers showing high elasticity and ultra-low friction (e.g., hydrogels and polymer brushes) have been found (Gong et al, 2001;Nomura et al, 2011), some of which are being developed toward practical applications (Belin et al, 2018;Tadokoro et al, 2020), and their tribological properties have also been discussed in relation to their viscoelastic properties (Mizukami et al, 2019).…”