| A novel particle-impact experiment was developed and used to study the dynamic fragmentation of brittle materials. In the experiment a small, spherical particle of a brittle material impacts against a thick, hard anvil. Unlike conventional particle-impact experiments, observations and measurements are focused on dynamic failure processes in the particle, minimizing, if not completely eliminating, damage to the target during the impact process. The impact process is observed using high-speed photography. Results are presented for aluminum oxide, silicon nitride and soda-lime glass particles striking a titanium diboride anvil. The radius of the particles ranged from 0.40 mm to 3.18 mm. It is observed that above a certain threshold velocity the particle undergoes fragmentation upon impact, and the particle fragments in a characteristic fragmentation pattern. This threshold velocity depends on the particle material properties, and decreases with increasing particle radius. The fragmentation patterns were dramatically different for the glass and ceramic particles: the ceramic particles disintegrated into numerous fragments. For the ceramic particles, the size dependence of the threshold velocity was explained by using a cohesive zone model to represent the dynamic failure of glass under these conditions is governed by deformation in shear. This new experiment provides a means of studying the threshold conditions for dynamic fragmentation of brittle materials, and illustrates some of the issues involved in the development of constitutive models for problems involving impact and dynamic fragmentation in brittle materials. |
