Mechanical responses of silicon nitrides under dynamic indentation

Mechanical responses of five silicon nitrides have been experimentally studied by using dynamic and standard hardness tests. The indentation loads ranged from several newtons to several hundred newtons. In the dynamic test, a load pulse with ∼100 μs rise time was achieved. Indentation size effect (ISE) and loading rate effects on the Vickers hardness were observed for the silicon nitrides. The ISE was further characterized by using the Meyer law and the energy-balance or proportional specimen resistance (PSR) model. The conventional brittleness approach is not satisfactory in characterizing transition between plasticity and fracture, and a new brittleness concept is proposed based on the PSR model that appears to capture the dynamic indentation responses of the materials.