Stages of Wear
Under normal mechanical and practical procedures, the wear-rate normally changes through three different stages(ref.4):
- Primary stage or early run-in period, where surfaces adapt to each other and the wear-rate might vary between high and low.
- Secondary stage or mid-age process, where a steady rate of ageing is in motion. Most of the components operational life is comprised in this stage.
- Tertiary stage or old-age period, where the components are subjected to rapid failure due to a high rate of ageing.
The secondary stage is shortened with increasing severity of environmental conditions such as higher temperatures, strain rates, stress and sliding velocities etc.
In explicit wear tests simulating industrial conditions between metallic surfaces, there are no clear chronological distinction between different wear-stages due to big overlaps and symbiotic relations between various friction mechanisms. Surface engineering and treatments are used to minimize wear and extend the components working life.
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