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.

Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited

1995 ◽  
Vol 53 ◽  
pp. 168-169
Author(s):  
Koenraad G F Janssens ◽  
Omer Van der Biest ◽  
Jan Vanhellemont ◽  
Herman E Maes ◽  
Robert Hull
Keyword(s):  
Electron Diffraction ◽  
Strain Field ◽  
Elastic Strain ◽  
Strain Analysis ◽  
Local Strain ◽  
Contrast Imaging ◽  
Strain Characterization ◽  
Physical Mechanisms ◽  
Diffraction Contrast ◽  
Transmission Electron

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.

Elastic Strain Energy of Dislocations in Ice

1971 ◽  
Vol 49 (16) ◽  
pp. 2181-2186 ◽  
Author(s):  
W. R. Tyson
Keyword(s):  
Elastic Constants ◽  
Strain Field ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
High Mobility ◽  
Anisotropic Elasticity ◽  
Hexagonal Ice ◽  
Complete Set ◽  
Elastic Strain Field

The energy stored in the elastic strain field of dislocations in hexagonal ice is calculated using anisotropic elasticity and the most complete set of elastic constants available. Ice is elastically fairly isotropic, and it is proposed that the high mobility of dislocations on the basal plane is due to dissociation of perfect dislocations on this plane.

scholarly journals Strain Analysis of the Nuozhadu High Rockfill Dam during Initial Impoundment

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Xiaolong Lv ◽  
Shichun Chi
Keyword(s):  
Shear Strain ◽  
Strain Field ◽  
Tensile Strain ◽  
Strain Analysis ◽  
Smoothing Method ◽  
Regulatory Agencies ◽  
Strain Concentration ◽  
Rockfill Dam ◽  
High Rockfill Dam

The safety of rockfill dams during initial impoundment has always been an issue of interest for regulatory agencies. Specifically, it is necessary to identify potential tensile strain zones and shear strain concentration zones in which cracks may form. In this paper, a meshless smoothing method is proposed to construct the strain field of a prototype dam based on monitoring displacement data. For verification, this method is applied to calculate the strain field of the Nuozhadu core wall rockfill dam. The results show that the proposed method can provide regulatory agencies with an effective tool for dam inspection during initial impoundment.

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.

Artificial epitaxy in an elastic strain field

1985 ◽  
Vol 73 (3) ◽  
pp. 551-557 ◽  
Author(s):  
Yu.A. Bityurin ◽  
S.V. Gaponov ◽  
A.A. Gudkov ◽  
V.L. Mironov
Keyword(s):  
Strain Field ◽  
Elastic Strain ◽  
Elastic Strain Field
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