Influence of residual stresses on strength and toughness of an alumina/alumina-zirconia laminate

Javier Pascual-Herrero

Research output: ThesisDoctoral Thesis

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Abstract

It has been demonstrated that layered structures may present an improved mechanical performance with respect to bulk materials. The existence of compressive residual stresses at the surface is one of the reasons for this enhancement. This work concerns one of the most popular systems in the literature, an alumina/alumina-zirconia laminate. Special attention is given onto structural aspects concerning them. Quantifying how much improvement is possible in terms of strength, reliability, and crack resistance are questions that are addressed through this work, both theoretically and experimentally. The toughness of multilayers is studied since the presence of an R-curve is expected. As it will be explained it is in reality an apparent R-curve which can induce some stable crack propagation but only for some range of crack lengths. The main difference to monolithic materials is that in laminates, the toughening is a function of the crack length and not of the crack extension. Two methods were used to perform calculations on apparent R-curves: the weight function method and the material forces approach. Lastly, the applicability of Weibulls theory to layered brittle materials is investigated. Strength distributions are analytically calculated for materials presenting R-curve and apparent R-curves behavior. Its deviation from Weibulls theory is commented.
Translated title of the contributionEinfluß der Eigenspannungen auf Festigkeit und Bruchzähigkeit von Aluminiumoxid/Aluminiumoxid-Zirkonoxid Laminate.
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Danzer, Robert, Assessor A (internal)
  • Anglada, Marc, Assessor B (external), External person
Publication statusPublished - 2007

Bibliographical note

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Keywords

  • Laminate
  • Mechanical properties
  • Aluminium Oxide

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