Desenvolvimento de um equipamento para avaliar propriedades elásticas de cerâmicas refratárias a altas temperaturas pelo método de ressonância de barras.
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Data
2002-09-12Autor
Paiva, Antônio Ernandes Macêdo
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The knowledge of the elastic properties has been of fundamental
importance for the understanding of the limitation of the useful life of structural
refractory ceramics. Those properties characterize the elastic rigidity of the
materials and represent a requirement for the specific classification of the
materials and their mechanical characteristics. The determination of properties,
such as, Young s modulus (E), shear modulus (G) and Poisson s ratio (µ) are
important for the determination of several important mechanical properties. In
this work the dynamic method of bar resonance was used to obtain those three
elastics properties. It consists in the stimulation of a sample with variable
frequency, in order to obtain the fundamental frequency and their harmonics of
natural vibration of the body. Considering the density and the geometry of the
sample the elastic properties of the material are obtained. Therefore, the
objective of this work was to develop an automatic equipment to measure E, G
and µ as a function of the temperature using the technique of bar resonance
and a software that controls the system. As exemplification of the use of that
software and of that equipment, a study of the influence of the aggregate s size
(DL = 2800, 4750 and 8000 µm) and of the Andreasen s coefficient of particle
size distribution (q = 0,21; 0,26 and 0,31) on the thermal shock damage in
alumina refractory castables was accomplished. Besides, other study about the
influence of the porosity on the elastic properties of cellular ceramics processed
by gelcasting was also carried out. The dependence of E and G on the porosity
according to models found in the literature was confirmed. The dependence of
the elastic moduli on the temperature of for those foams was also evaluated.