A STUDY OF IMPACT BEHAVIORS OF Si_3N_4 CERAMICS AT ELEVATED TEMPERATURE

摘要

The internal friction of Si_3N_4 ceramics at elevated temperature and under impact loading is investigated analytically and experimentally. A composite sphere model in the microstructure is established to describe the viscoelastic behaviors of Si_3N_4 ceramics. From this model, a two-parallel-Maxwell-body mechanical model is deduced and used to explain the test results of internal friction. The viscoelatic behaviors is studied by the method of split Hopkinson pressure bar at elevated temperatures. A method to determining the internal friction is suggested, and the internal friction of Si_3N_4 at the frequency of 7.7kHz is evaluated.