Surface Damage of Silicon Nitride by Glass Bead Collision

Abstract

In this work, repeated impact test by glass beads of which diameter is 4mm were carried out for a silicon nitride plate. The impact angles of a glass bead against the silicon nitride plate surface were changed from 90 to 45 degrees. The plate specimen was fractured due to a corn type of crack propagation. The impact angle effect on the number of cycles to fracture was reasonably explained if the normal component of the impact velocity onto the specimen plate surface was considered. In addition, the two-point impact test was carried out to understand multi-site impact damage. The second impact points were sifted by 0.5mm, 1.0mm and 2.0mm from the first impact point. The first impact was continued until 150times and 200times. Then, the second impact was continued until the fracture took place in the specimen. When the second impact point was 0.5mm far from the first impact point. the number of the second impact repetition was apparently decreased as compared with the result of the virgin specimen. Those experimental results could reasonably be understood from the dynamic stress analysis results.