Tribological studies on the surface of glasses by lateral indentation technique

Glass is a material particularly sensitive to surface damage when exposed to abrasive loads and scratching. Such local mechanical contacts not only compromise the surface quality and mechanical performance, but also degrade the visual appearance of material. Understanding abrasive damage and the underlying material properties has therefore been a subject of significant interest. Hence instrumented lateral nanoindentation has been employed in this thesis to obtain quantitative and quantitative information on the onset of scratch-induced surface of three silicate glasses and one metallic glass in low load and high load regimes. First, the role of compaction and shear flow in the deformation caused by lateral indentations on silicate glasses is quantified through classical relaxation experiments. In the anomalous glasses, the main mechanism of plastic deformation in lateral indentations was revealed to be densification, while in the normal glasses, shear flow played a considerable role. Furthermore, lateral indentation was used to study the appearance of wavy patterns formed by sliding on a compliant surface which was investigated later by post mortem AFM technique. The average repetition distance of the ripples which is in the sub-$\mu$m range was displayed to be dependent on the scratching velocity. Additionally, a correlation was noticed between scratching velocity (loading rate) and the formation of microabrasion regime in vitreous silica when analysing the data through Weibull distribution. The quantitative information obtained through Weibull distribution analysis showed the considerable role of tested volume in the appearance of different types of flaws. Not only scratching velocity, but also loading can influence the deformation behaviour of glasses. This was further exhibited by analysis of pop-in loads when performing lateral indentations on the surface of a metallic glass.


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