Measurement of the High Temperature Elastic Modulus of Alumina Ceramics by Different Testing Methods

摘要

Alumina ceramics are widely used in the demanding high temperature applications in which the high temperature elastic moduli (E_(HT)) is a key property for their reliability and safety. In this paper, the elastic modulus of alumina was determined by dynamic method (impulse excitation technique) and static tests (three-point bending test and four-point bending test). For the static tests, the relative method was applied to determine the accurate deflection measurement in the heating furnace. The measured results revealed that the modulus of alumina slowly decreased from RT to 1000 癈 and rapidly decreased with the increasing temperatures from 1000 癈 to 1300癈. The E_(HT) evaluated by dynamic method were higher than that tested by static tests with the reason of that impulse excitation technique only applied small forces onto a sample such that defects activity is negligible. Also the resonant frequencies couldn't be measured easily at high temperature, because the vibration signal emitted by the sample was weak. The static approaches combined with relative method were beyond the limit to high temperatures, and they can be also used to evaluate the ultra-high temperature modulus.