Tensile Stress-Strain Response of Sintered Silicon Nitride Ceramic at Elevated Temperatures.

Abstract

The tensile tests were performed for the sintered silicon nitride ceramic at displacement rates, δ=0.6, 0.06 and 0.006 mm/min in the temperature range from room temperature to 1400°C. According to the measurements of tensile displacement, the load P vs. displacementδrelationship was markedly influenced by test temperature and displacement rate. Young's modulus decreased with an increase in test temperature. The tensile strength was also reduced with increase in test temperature and decrease in displacement rate. The nominal stress-strain relationship was calculated from the measured P-δrelationship, under each test condition. Moreover, these stress-strain relationships were corrected so that the P-δcurve calculated using the elastic-plastic finite-element method agreed with the measured P-δcurve. The corrected stress-strain response seems to give the intrinsic response of the sintered silicon nitride ceramic at elevated temperatures. Furthermore, the development of the inelastic deformation zone was calculated through the elastic-plastic finite-element method on the basis of the corrected stress-strain curve at elevated temperatures.