Miquel Turon-Vinas1, Marc Anglada2. 1. CIEFMA, Department of Materials Science and Metallurgical Engineering, EEBE, Universitat Politècnica de Catalunya, C/d'Eduard Maristany, 10-14, 08930 Barcelona, Spain. 2. CIEFMA, Department of Materials Science and Metallurgical Engineering, EEBE, Universitat Politècnica de Catalunya, C/d'Eduard Maristany, 10-14, 08930 Barcelona, Spain. Electronic address: marc.j.anglada@upc.edu.
Abstract
OBJECTIVE: The aim of the paper is to determine and discuss the correlation between the fracture toughness and the fracture stress in zirconia transforming ceramics with a small artificial crack. As an R-curve behaviour is usually present in transforming ceramics for both small and long cracks, predictions of the fracture stress can only be done with an accurate knowledge of the R-curve and crack dimensions. METHODS: First, basic concepts of fracture mechanics, strength and testing of ceramic materials are introduced. This is followed by a very brief introduction to zirconia dental ceramics and to strength degradation by hydrothermal ageing of 3Y-TZP. Fracture toughness of 3Y-TZP and 12Ce-TZP are then determined for a short (∼50μm) sharp edge crack produced by ultra short pulsed laser ablation on prismatic bending bars in four point bending. The crack size is small but large enough for controlling fracture and for applying elastic fracture mechanics. RESULTS: In both materials the determined fracture toughness is similar, in spite of their difference R-curves. The results of fracture toughness and fracture stress are analysed by using a simple function to represent the R-curve, but which contains the main ingredients of experimental R-curves extracted from the literature either for short or long cracks in 12Ce-TZP. SIGNIFICANCE: It is concluded that the high R-curves reported in the literature for long and short cracks in 12Ce-TZP and 3Y-TZP might have only a marginal influence on the fracture resistance with cracks of the size studied. This effect is of more significance in 12Ce-TZP. The use of an ideal and simple model of R-curve is presented as a useful guide to predict whether the fracture stress will be enhanced by an existent R-curve.
OBJECTIVE: The aim of the paper is to determine and discuss the correlation between the fracture toughness and the fracture stress in zirconia transforming ceramics with a small artificial crack. As an R-curve behaviour is usually present in transforming ceramics for both small and long cracks, predictions of the fracture stress can only be done with an accurate knowledge of the R-curve and crack dimensions. METHODS: First, basic concepts of fracture mechanics, strength and testing of ceramic materials are introduced. This is followed by a very brief introduction to zirconia dental ceramics and to strength degradation by hydrothermal ageing of 3Y-TZP. Fracture toughness of 3Y-TZP and 12Ce-TZP are then determined for a short (∼50μm) sharp edge crack produced by ultra short pulsed laser ablation on prismatic bending bars in four point bending. The crack size is small but large enough for controlling fracture and for applying elastic fracture mechanics. RESULTS: In both materials the determined fracture toughness is similar, in spite of their difference R-curves. The results of fracture toughness and fracture stress are analysed by using a simple function to represent the R-curve, but which contains the main ingredients of experimental R-curves extracted from the literature either for short or long cracks in 12Ce-TZP. SIGNIFICANCE: It is concluded that the high R-curves reported in the literature for long and short cracks in 12Ce-TZP and 3Y-TZP might have only a marginal influence on the fracture resistance with cracks of the size studied. This effect is of more significance in 12Ce-TZP. The use of an ideal and simple model of R-curve is presented as a useful guide to predict whether the fracture stress will be enhanced by an existent R-curve.
Authors: Stephanie Assimakopoulos Garófalo; Martin Wehner; Andreas Dohrn; Marin Dean Bilandžić; Christian Roos; Richard Johannes Wierichs; Hendrik Meyer-Lueckel; Ana Cecilia Corrêa Aranha; Marcella Esteves-Oliveira Journal: Clin Oral Investig Date: 2021-08-17 Impact factor: 3.606
Authors: Yifeng Liao; Max Gruber; Henry Lukic; Si Chen; Spiro Megremis Journal: J Biomed Mater Res B Appl Biomater Date: 2020-06-20 Impact factor: 3.368