Impact depth on glass surface caused by sand particles
Résumé
Brittle materials in general and particularly glass are very sensitive to dynamic particles impacts of different nature. The ancient objects in glass (building, monuments) and some precious objects are subjected to atmospheric aggressions such as humidity, sand particles, hail,etc.). Their surfaces are however, often exposed to severe climatic conditions in an environment where the sand wind is a daily phenomenon or beach wind. Many degradation processes due to erosion affect significantly surfaces of buildings that are part of the Cultural Heritage. This work presents a physical analysis of the degradation of glass surface by sandblasting as environment subject. The optical and mechanical variation properties caused by degradation are originally due to the existence of defects (superficial cracking, scaling, craters, corrosion etc.). We are therefore interested in determining the influence of the most essential sandblasting parameters (air flow velocity and sand grains size) on the crater depths. The erosion test was carried out in order to study the singular impacts and the surface development and consequently to elucidate the material removal phenomenon. However, impact depth is strongly varied with the sand grains speed as well as the size. It was found that the transition in the erosion mechanism arises in dependence of the eroding particles characteristics. This mechanism examined in this work by optical microscopy seems to be done by singular indentation and interaction of the cracks to the adjacent impacts. The impact of solid particles on the surface may be used as the basis for measuring the mechanical strength of surfaces. The experiments showed that the approach was effective in discriminating the different parameters (e.g. size of impacting particles and velocity of air flow of projected particles) used in the test that may affect the roughness of glass surfaces which in turns provoke optical transmission and mechanical strength. © (2012) Trans Tech Publications, Switzerland.