Visualization of transformation toughening of zirconia ceramics during dynamic fracture

2021 ◽  
Vol 118 (23) ◽  
pp. 231901
Author(s):  
Sota Takagi ◽  
Koji Inukai ◽  
Nobuaki Kawai ◽  
Shunsuke Nozawa ◽  
Atsushi Kyono ◽  
...  
Keyword(s):  
Dynamic Fracture ◽  
Transformation Toughening ◽  
Zirconia Ceramics

Strain analysis in composite ceramics

1986 ◽  
Vol 44 ◽  
pp. 494-497
Author(s):  
W. M. Kriven
Keyword(s):  
Strain Field ◽  
Strain Analysis ◽  
Processing Temperature ◽  
Transformation Toughening ◽  
Zirconia Ceramics ◽  
Volume Increase ◽  
Analysis Technique ◽  
Fundamental Understanding ◽  
Contrast Analysis ◽  
Elastic Strain Field

Significant progress towards a fundamental understanding of transformation toughening in composite zirconia ceramics was made possible by the application of a TEM contrast analysis technique for imaging elastic strains. Spherical zirconia particles dispersed in a large-grained alumina matrix were examined by 1 MeV HVEM to simulate bulk conditions. A thermal contraction mismatch arose on cooling from the processing temperature of 1500°C to RT. Tetragonal ZrO2 contracted amisotropically with α(ct) = 16 X 10-6/°C and α(at) = 11 X 10-6/°C and faster than Al2O3 which contracted relatively isotropically at α = 8 X 10-6/°C. A volume increase of +4.9% accompanied the transformation to monoclinic symmetry at room temperature. The elastic strain field surrounding a particle before transformation was 3-dimensionally correlated with the internal crystallographic orientation of the particle and with the strain field after transformation. The aim of this paper is to theoretically and experimentally describe this technique using the ZrO2 as an example and thereby to illustrate the experimental requirements Tor such an analysis in other systems.

scholarly journals Effects of Finish Line Design and Fatigue Cyclic Loading on Phase Transformation of Zirconia Dental Ceramics: A Qualitative Micro-Raman Spectroscopic Analysis

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 863 ◽  
Author(s):  
Roberto Sorrentino ◽  
Chiara Ottavia Navarra ◽  
Roberto Di Lenarda ◽  
Lorenzo Breschi ◽  
Fernando Zarone ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Dental Ceramics ◽  
Transformation Toughening ◽  
Zirconia Ceramics ◽  
Finish Line ◽  
Chewing Simulation ◽  
Before And After ◽  
One Year ◽  
Line Design ◽  
Chewing Activity

Objectives: Stresses produced during the fabrication of copings and by chewing activity can induce a tetragonal-to-monoclinic (t–m) transformation of zirconia. As a consequence, in the m-phase, the material is not able to hinder possible cracks by the favorable mechanism known as “transformation toughening”. This study aimed at evaluating if different marginal preparations of zirconia copings can cause a premature phase transformation immediately after manufacturing milling and after chewing simulation. Methods: Ninety copings using three commercial zirconia ceramics (Nobel Procera Zirconia, Nobel Biocare Management AG; Lava Classic, 3M ESPE; Lava Plus, 3M ESPE) were prepared with deep-chamfer, slight-chamfer, or feather-edge finish lines (n = 10). Specimens were tested in a chewing simulator (CS-4.4, SD Mechatronik) under cyclic occlusal loads simulating one year of clinical service. Raman spectra were acquired and analyzed for each specimen along the finish lines and at the top of each coping before and after chewing simulation, respectively. Results: Raman analysis did not show any t–m transformation both before and after chewing simulation, as the typical monoclinic bands at 181 cm−1 and 192 cm−1 were not detected in any of the tested specimens. Conclusions: After a one-year simulation of chewing activity, irrespective of preparation geometry, zirconia copings did not show any sign of t–m transformation, either in the load application areas or at the margins. Consequently, manufacturing milling even in thin thickness did not cause any structural modification of zirconia ceramics “as received by manufacturers” both before and after chewing simulation.

Study of Transformation Toughening Behavior of an Edge Through Crack in Zirconia Ceramics with the Cohesive Zone Model

2018 ◽  
Vol 10 (06) ◽  
pp. 1850066 ◽  
Author(s):  
Bo Liu ◽  
Nian Liu ◽  
Jun Luo ◽  
Zhongmin Xiao
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Constitutive Law ◽  
Scale Transformation ◽  
Small Scale ◽  
Zone Model ◽  
Structural Level ◽  
Transformation Toughening ◽  
Zirconia Ceramics ◽  
Propagation Behavior

The transformation toughening behavior of a finite edge through crack in zirconia ceramics is studied with a three-dimensional finite element model. The continuum-based constitutive law of zirconia ceramics is implemented into a user-defined subroutine in ABAQUS to simulate the loading and unloading mechanical response of zirconia ceramics. We have given up the small-scale transformation assumption. The propagation behavior of a finite edge through crack in a zirconia plate is simulated at the structural level with the cohesive zone model and compared with the case in which the material is purely elastic. The influences of the stress state, the cohesive strength, the shear transformation strain and the activation energy threshold on the size of the transformation zone and the crack propagation behavior are systematically discussed. The numerical method and results presented in this work may be helpful for the design of engineering components made of zirconia ceramics.

scholarly journals Investigation on the Effect of Dynamic Fracture Toughness to Zirconia Ceramic Grinding Performance with Different Grain Sizes

2021 ◽  
Author(s):  
Can Yan ◽  
Zhaohui Deng ◽  
Tao Xia ◽  
Wei Liu ◽  
Hua Zhang
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
Material Removal ◽  
Dynamic Fracture Toughness ◽  
Grinding Force ◽  
Subsurface Damage ◽  
Material Removal Mechanism ◽  
Zirconia Ceramics ◽  
Grain Sizes ◽  
Damage Depth

Abstract To reveal the material removal mechanism of zirconia ceramics, an improved prediction models of the critical grinding force and maximum subsurface damage depth models are developed based on the dynamic fracture toughness. The effects of three different grain sizes on the material removal mechanism during brittle- ductile transition process of zirconia ceramics is analyzed through grinding experiments. And the influence of grain size on grinding force, workpiece surface roughness, surface fragmentation rate and subsurface damage depth in grinding are discussed. The results of the experiment results indicated that the value of dynamic fracture toughness tends to decrease with an increase in equivalent grinding thickness, and the ductile removal range of zirconia ceramics expands for the reason that the critical grinding force considering dynamic fracture toughness is higher than the static grinding force considering static fracture toughness, and the maximum subsurface damage depth is closer to actual maximum subsurface damage depth. Besides the smaller the grain size of zirconia ceramics, the higher the surface quality of grinding.

AEM investigation of ZrO2 solid solution formation in ZrO2/mullite composites

1984 ◽  
Vol 42 ◽  
pp. 408-409
Author(s):  
T. R. Dinger
Keyword(s):  
Solid Solution ◽  
Ion Beam ◽  
Analytical Electron Microscopy ◽  
Transformation Toughening ◽  
Solid Solution Formation ◽  
Solution Formation ◽  
Propagating Crack ◽  
Analytical Electron ◽  
Microcrack Toughening ◽  
Made In

Zirconia (ZrO2) is often added to ceramic compacts to increase their toughness. The mechanisms by which this toughness increase occurs are generally accepted to be those of transformation toughening and microcracking. The mechanism of transformation toughening is based on the presence of metastable tetragonal ZrO2 which transforms to the monoclinic allotrope when stressed by a propagating crack. The decrease in volume which accompanies this transformation effectively relieves the applied stress at the crack tip and toughens the material; microcrack toughening arises from the deflection of a propagating crack around sharply angular inclusions.These mechanisms, however, do not explain the toughness increases associated with the class of composites investigated here. Analytical electron microscopy (AEM) has been used to determine whether solid solution effects could be the cause of this increased toughness. Specimens of a mullite (3Al2O3·2SiO2) + 15 vol. % ZrO2 were prepared by the usual technique of mechanical thinning followed by ion beam milling. All observations were made in a Philips EM400 TEM/STEM microscope fitted with EDXS and EELS spectrometers.

Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02

1985 ◽  
Vol 43 ◽  
pp. 222-223
Author(s):  
J. Y. Koo ◽  
M. P. Anderson
Keyword(s):  
Electron Diffraction ◽  
Ionic Conduction ◽  
Electron Diffraction Study ◽  
Ceramic Materials ◽  
Bright Field Image ◽  
Transformation Toughening ◽  
Ion Milling ◽  
Thin Foils ◽  
Carbon Coated ◽  
Convergent Beam

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.

Crystallization of MgO • Al2 • SiO2 • ZrO2 glasses

1986 ◽  
Vol 44 ◽  
pp. 440-441
Author(s):  
M. A. McCoy
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Powder Processing ◽  
Glass Composition ◽  
Ceramic Powder ◽  
Transformation Toughening ◽  
Ceramic Powder Processing ◽  
Processing Techniques ◽  
Ceramic Matrices

Transformation toughening by ZrO2 inclusions in various ceramic matrices has led to improved mechanical properties in these materials. Although the processing of these materials usually involves standard ceramic powder processing techniques, an alternate method of producing ZrO2 particles involves the devtrification of a ZrO2-containing glass. In this study the effects of glass composition (ZrO2 concentration) and heat treatment on the morphology of the crystallization products in a MgO•Al2•SiO2•ZrO2 glass was investigated.

Dynamic Fracture Mechanics

1990 ◽  
Author(s):  
L. B. Freund
Keyword(s):  
Fracture Mechanics ◽  
Dynamic Fracture ◽  
Dynamic Fracture Mechanics

Universal features of the microbranching instability in dynamic fracture

1998 ◽  
Vol 78 (2) ◽  
pp. 243-251
Author(s):  
Eran Sharon, Jay Fineberg
Keyword(s):  
Dynamic Fracture
Sign in / Sign up

Export Citation Format

Share Document