ABSTRACT
The objective of the present work is to perform a scratch test to measure the abrasion wear resistance of metallic sheets. Besides, the deformation modes and the friction processes involved during the scratching will be investigated in order to get a better insight into the wear mechanisms observed at the macroscopic scale. The study of scratch formation will be combined with an analysis of the frictional response of the tested materials. The effect of the tip radius of 0.04, 0.3 and 0.45 mm of the indenters on the friction coefficient displayed by scratching metallic sheets of aluminium, steel and brass is discussed.
It was found that, metallic sheets scratched by all indenters showed lower friction coefficient for lubricated surface than dry ones, where friction coefficient slightly increased with increasing normal load. For dry aluminium surface friction coefficient significantly increased up to maximum value, (1.4), then decreased with increasing load for 0.03 mm tip radius. The relative decrease in friction displayed by lubricated steel was relatively lower compared to that observed for aluminium. At 12 N friction coefficient showed consistent trend with further load increase due to the strain hardening of steel. The scratch of brass sheet displayed higher values of friction coefficient than steel and lower than aluminium. Friction coefficient significantly increased up to maximum then decreased with increasing load for dry and lubricated surfaces.
Increasing the tip radius of the indenter up to 0.3 mm showed an increase in friction coefficient of aluminium sheet. Scratch of the steel sheet showed relative friction decrease compared to that observed for aluminium. The difference in friction values between dry and lubricated surfaces was small. As the tip radius of the indenter increased to 0.45 mm friction coefficient decreased for aluminium sheet. As the load increased the difference in friction coefficient between dry and lubricated conditions increased. The lubricated steel surface showed an increasing trend with load increase with lower friction values. The friction difference represented higher values at higher loads. The lowest friction values were represented by brass sheet. The influence of lubrication on the friction coefficient is clearly noticed at higher values of load.