Effect of impact angle on glass surfaces eroded by sand blasting

In a previous work, we studied the effects of sand blasting on the roughnes s, the optical transmission and the mechanical strength of a soda lime glas s for sand blasting durations up to 150 min and under a constant impact ang le of 90 degrees. In the present work, we examine the effect of impact angl es (30 to 90 degrees) for relatively small durations up to 60 min on the su rface roughness and the optical transmission. The roughness increases and t ends towards a plateau, while the optical transmission decreases and lends towards a threshold estimated at about 50% of the initial transmission. We noticed that the samples erosion damage becomes weaker for impact angles le ss than 90 degrees (90 degrees angle corresponds to the flux normal to the samples). Microscopic observations reveal that the damage is similar to tha t of sharp indentation damage type Vickers indentation. There is formation of a plastic imprint with radial cracks and some scaling caused by the deve lopment of lateral cracks that extend and curve up to the surface. From the expression of the damage rate as defined in the literature, we introduced a function relating the impact angles and the sand blasting durations to th e optical transmission. The experimental data obtained seem to fit quite we ll to the proposed function. (C) 2000 Elsevier Science Ltd. All rights rese rved.