ISSN:
1013-9826
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
This paper explores the so-called “margin failures” observed in loaded curved bi-layerstructures. Hemispherical bi-layer model test specimens consisting of glass shells with varyingmargin geometry filled with epoxy resin, simulating brittle crowns on tooth dentine, are loaded withcompliant indenters along the (convex) axis of symmetry. Using this unique setup, the influence ofmargin geometry on margin failure is examined. Nearly all previous studies have utilised hardspherical indenters of various radii, and examined crack initiation and evolution at the contact point.However, the modes of fracture observed in this traditional contact problem, surface cone crackingor flexure-induced radial cracking initiate close to or inside the (small) contact area, and thus notexplain the margin failures commonly observed by dentists. Crack growth at the margins distantfrom the contact zone cannot be generated under indentation using hard spherical indenters. The useof a compliant (soft) indenter distributes the indentation force over a large contact area, generating acompressive zone underneath the contact, and effectively inhibiting the modes of fracture typicallyobserved using hard indenters (radial and cone cracking). Consequently, significant tensile stressesat the support margin become dominant, and the focus shifts to fracture initiating at the supportmargins. In this study, cylindrical indenters composed of PTFE Teflon, with a modulus severalorders of magnitude lower than the indented materials, are used to examine margin fracture inbrittle crown like structures. The specific focus is the effect of margin geometry – Chamfered;Round; Shoulder margins are examined, and their influences on crack initiation and damageevolution are reported
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/53/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.334-335.573.pdf
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