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Abstract

Elastomers are commonly used in applications which experience repeated impacts by hard abrasive particles at high or moderate strain rates. The goal of the current work is to develop a simple and cost effective methodology involving scratch testing and modeling for capturing the failure and wear behavior of elastomeric materials. The high failure strains as well as the extremely good wear resistance of elastomers make this task a formidable challenge. Modeling of a scratch test, however, seems to be promising in this regard.

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The stress and fracture conditions of a coated surface, that are the origin to wear, were analysed by three-dimensional finite element method (FEM) modelling on microlevel, by stress and strain computer simulations and by experimental studies with a scratch tester. The studied tribological contact was a 0.2 mm radius diamond ball sliding with increasing load on a thin, 2 μm thick titanium nitride (TiN) coating on a flat high speed steel substrate. The ball was modelled as rigid, the coating linearly elastic and the steel substrate elastic–plastic taking into account strain hardening effects. The stresses and strains generated in the surface during sliding are the result of four different mechanisms: the pulling and pushing by the friction force; the geometrical indent, groove, and torus shaped deformations of the flat surface; the bulk plasticity concentration and curvature minimum effects; and the residual stresses in the coating. In a sliding contact the first crack is initiated at the top of the coating from bending and pulling actions and it grows down through the coating. In the modelled scratch tester system a complex stress field is formed at the surface including remaining residual stresses in the coating behind the sliding contact. The stress fields are very different in a scratched uncoated steel sample. Some residual tensile stresses are formed in the groove behind the tip but they are very much lower than for the TiN coated case. A displacement controlled FEM model was found to better represent the real situation and correspond to experimental results than a force controlled model.
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Conference Paper
Elastomers are frequently used in applications involving repeated impacts of hard abrasive particles on surfaces at high or moderate strain rates. Operational conditions of components experiencing erosive and impact type wear are sometimes difficult to mimic in laboratory conditions, and as such, it is common to approach behaviour and lifetime predictions by meticulously studying different types of single impacts. This is particularly true for characterising and modelling of high strain rate impact events between hard particles and a wearing elastomer surface. This work presents and applies such a methodology for two specific elastomer materials: a natural rubber (NR) and styrene-butadiene rubber (SBR) compounds. The elastomer materials are subjected to quasistatic and dynamic testing conditions for determination of hyper- and viscoelastic material properties. The results are used in an iterative calibration procedure for establishing related constitutive models by applying the Ogden and Prony series models.
Modelling Friction and abrasive wear of elastomers
  • N Békési
N. Békési, Modelling Friction and abrasive wear of elastomers, in: A. Boczkowska (Ed.), Advanced Elastomers -Technology, Properties and Applications, InTech, DOI: 10.5772/50498, 2012, pp. 341-362.