This Article Abstract Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Kim, J.-W. Articles by Zhang, Y. Search for Related Content PubMed PubMed Citation Articles by Kim, J.-W. Articles by Zhang, Y. Pubmed/NCBI databases Substance via MeSH Social Bookmarking                         What's this?

Sliding Contact Fatigue Damage in Layered Ceramic Structures

Department of Biomaterials and Biomimetics, New York University College of Dentistry, 345 E. 24th St., Room 813C, New York, NY 10010, USA

View larger version (15K): [in this window] [in a new window]   Figure 1. Schematic of contact with load-slide action. (a) Tooth eccentric occlusal position of right side first molar. Arrow indicates direction of sliding as teeth move to centric occlusion. Relative tooth radii at buccal cusp contacts are shown. (b) Experimental arrangement for indentation of brittle layer on compliant substrate with superposed tangential force component.

View larger version (85K): [in this window] [in a new window]   Figure 2. Side view video sequence of cone cracks evolving in glass plate on polycarbonate bilayer with (a) uni-axial and (b) bi-axial loading, following various numbers of cycles n. Indentation with tungsten carbide (WC) sphere of radius r = 1.5 mm, in water. Only the glass plate of thickness d = 1 mm is shown here. Note in (a) that outer cone (O) forms first, but inner cones (I) propagate to the glass/polycarbonate interface, while in (b) partial cones (P) penetrate the glass layer. Also shown here are the top view optical micrographs of a (c) glass/polycarbonate bilayer and (d) LAVA porcelain-veneered zirconia subjected to single-cycle bi-axial loading at Pm = 120 N, with a WC sphere of r = 1.5 mm, in water. Note: The damage patterns are similar in glass and porcelain. Arrows in (b), (c), and (d) indicate the sliding direction for the bi-axial test.

View larger version (18K): [in this window] [in a new window]   Figure 3. Plot of crack depth h as a function of number of cycles n in glass/polycarbonate bilayer, for (a) R-ratio fatigue, (b) uni-axial fatigue, and (c) bi-axial fatigue. Indentation with WC sphere of radius r = 1.5 mm, maximum load Pm = 120 N, in water. Failure occurred when crack depth h reached the glass/polycarbonate interface (top of the vertical axis, glass thickness d = 1000 µm) at a critical number of cycles nF (vertical dashed lines). Note: Crack growth was substantially enhanced in bi-axial loading. Each graph consists of three runs, indicated by , , or .

View larger version (15K): [in this window] [in a new window]   Figure 4. Schematic demonstrating water entrapment model for fatigue loading with (a,b) uni-axial and (c,d) bi-axial configurations. Shaded area beneath contact designates approximate compression zone. The inclination angles for partial and outer cones in uni-axial and bi-axial loading are ' and , respectively. (a) Water enters the inner cone crack (I) prior to contact engulfment. (b) As the indenter contact expands, the water is trapped and is squeezed toward the crack tip, causing downward penetration. Note: In (a) and (b) outer cone cracks, (O) always lies in the Hertzian tensile field outside the contact, and water is never trapped in this crack. (c) Water enters the partial cone crack (P) at the trailing edge of the contact at the n cycle. (d) As the indenter slides across the surface in the n + 1 cycle, compressive crack-mouth pinching squeezes the water toward the crack tip. Cyclic contact repeats the process, forcing more water into the crack in successive cycles. Arrows in (c) and (d) represent the sliding direction for the biaxial test. +Tension; -compression.

View larger version (9K): [in this window] [in a new window]   Appendix Figure. Schematic showing cone crack geometry in brittle layers with (a) uni-axial and (b) bi-axial loading. To first approximation, cone geometry in (b) remains ’symmetrical’ around the realigned load axis, with a portion of the cone intersecting the top surface (arrow), resulting in partial cones.

Journal of Dental Research, Vol. 86, No. 11, 1046-1050 (2007)
DOI: 10.1177/154405910708601105


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?