The effect of particle concentration on the sand erosion damage of polystyrene was investigated by using the sand-blasting type test method. Glass-beads with diameter of 120 and 150μm were used as impacting particles. The impact velocity was varied from 15m/s to 100m/s, the particle concentration defined as the weight of particles contained in a blasting air was from 0.2g/l to 30g/l, and the impact angle was from 30 deg to 90 deg.
The erosion rate decreased gradually until a certain value of particle concentration was reached, and then decreased abruptly with an increase of particle concentration. Corresponding to this behavior, two different erosion damage mechanisms were observed.
At relatively low impact velocity and/or particle concentration, so called the ring-pattern damage was observed and the damaged pattern changed to imperfect shape with an increase of particle concentration. This was due to the interference of impacting and rebounding particles. Consequently, the erosion rate decreased as the result of lowering of average impact velocity.
In the other damage mechanism, so-called heat-deformation damage, which was observed at relatively high impact velocity and/or particle concentration, large deformation of material occurred remarkably. This was due to softening of material by heat generated by particle impact, and the weight loss, therefore, decreased.
The damage transition from the ring-pattern to the heat-deformation depended on impact velocity and particle concentration, e.g. it occurred at lower particle concentration when impact velocity was relatively high and vice versa. These behaviors were also discussed from the viewpoint of kinetic energy of impacting particles.