ISSN:
1551-2916
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
,
Physik
Notizen:
Mullite/Al2O3 functionally graded ceramics (FGCs) have been obtained by sequential slip casting and subsequently firing at 1650°C in air. Functionally graded layered dense (similar/congruent99% of the theoretical density) compacts, with five different layers with thickness ranging from 670 to 850 µm, were obtained. The layer composition was gradually changed from 100% mullite to 80% mullite/20% alumina. The elastic modulus, the flexure strength, and the fatigue life of the monolithic (80% mullite/20% alumina) and mullite/alumina FGCs were measured by means of four-point bending tests. The mullite/alumina FGCs exhibited lower strength than the monolithic material but the fatigue resistance and reliability were improved in the high cycle fatigue regime. These results were rationalized in terms of the residual stress distribution in the FGCs, which was computed using a description of stresses and strains in the multilayer composite based on the simple beam analysis. The tensile residual stresses which developed in the surfaces were responsible for the lower strength, while the compressive residual stresses within the bulk arrested the fatigue crack and improved the fatigue life of the FGC material.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1151-2916.1998.tb02509.x
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