Chapter 6 Ceramic Materials Testing and Fracture Mechanics

2016 ◽  
pp. 353-445
Author(s):  
Garth Hastings ◽  
Ishbel Gair ◽  
D. Daily
Keyword(s):  
Fracture Mechanics ◽  
Ceramic Materials ◽  
Materials Testing

Fracture Mechanics and Toughening Mechanisms Analysis of Ce-TZP/Al2O3 Nanocomposite for Biomedical Applications

2007 ◽  
Vol 330-332 ◽  
pp. 337-340 ◽  
Author(s):  
Giuseppe Pezzotti ◽  
Kiyotaka Yamada ◽  
S. Shiroyama ◽  
Masahiro Nawa
Keyword(s):  
Fracture Mechanics ◽  
Biomedical Applications ◽  
Ceramic Materials ◽  
Zirconia Ceramics ◽  
Toughening Mechanisms ◽  
Microstructural Design ◽  
And Performance ◽  
Polymorph Transformation

Zirconia ceramics were introduced in the seventhies for use as structural biomaterials after laboratory tests and simulator studies. However, nowadays concerns remain about their reliability in vivo, despite published clinical studies have already established the safety and the good tribological performance of these materials. It is still unclear what level of reliability can be achieved in ceramic biomaterials and how much their toughness level can be enhanced by microstructural design. The polycrystalline nature of ceramic materials may make both the observed properties and performance very scattered. In particular, the grain size and other microstructural features likely play a fundamental role in the mechanical behavior of the material. In this paper, we propose a set of fracture mechanics assessments, aimed to establish the quantitative amount of toughness achievable in a zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite), and in situ confocal Raman spectroscopy to visualize toughening mechanisms, including polymorph transformation and residual stress fields stored around the crack path.

Grinding Mechanisms and Strength Degradation for Ceramics

1989 ◽  
Vol 111 (2) ◽  
pp. 167-174 ◽  
Author(s):  
S. Malkin ◽  
J. E. Ritter
Keyword(s):  
Fracture Mechanics ◽  
Specific Energy ◽  
Ceramic Body ◽  
Ceramic Materials ◽  
Strength Degradation ◽  
Indentation Fracture ◽  
Main Research ◽  
Grinding Conditions ◽  
Workpiece Interaction ◽  
Insight Into

This paper presents a critical review and evaluation of our fundamental knowledge of the grinding mechanisms for ceramic materials and their influence on the finished surface and mechanical properties. Two main research approaches are identified: a “machining” approach and an “indentation fracture mechanics” approach. The machining approach has typically involved measurement of the grinding forces and specific energy coupled with microscopic observations of the surface morphology and grinding detritus. Any proposed mechanisms of abrasive-workpiece interaction must be consistent with the magnitude of the specific energy and its dependence on the grinding conditions. The “indentation fracture mechanics” approach assumes that the damage produced by grinding can be modeled by the idealized flaw system produced by a sharp indentor. Indentation of a ceramic body is considered to involve elastic/plastic deformation with two principal crack systems propagating from the indentation site: lateral cracks which lead to material removal and radial/median cracks which cause strength degradation. Each of these approaches provides important insight into grinding behavior and strength degradation, but each has its shortcomings. Further efforts to develop a fundamental model for grinding of ceramics would benefit from the integration of both of these approaches.

Flexible Pipes Subjected to SCC CO2: Review and Means to Increase Reliability on Service Life Applied to Brazilian Pre-Salt Fields

2021 ◽  
Author(s):  
Mauricio Brandao ◽  
Fabio Pires ◽  
Ingrid Poloponsky ◽  
Fabio Santos ◽  
Diogo Lopes
Keyword(s):  
Fracture Mechanics ◽  
Service Life ◽  
Failure Mode ◽  
High Pressures ◽  
Small Scale ◽  
Materials Testing ◽  
Metallic Material ◽  
Remaining Service Life ◽  
Flexible Pipes ◽  
High Concentrations

Abstract Flexible Pipes were widely used in Brazil offshore developments and the challenge on overcoming increasing water depths, high pressures and fluids with high contaminants was always present. In 2017 a new failure mode, called SCC CO2 was disclosed bringing such disruption in the use of this equipment since, at that time, the conditions observed in Brazilian Pre salt were like the "perfect storm" for the failure mode to happen. It had high concentrations of CO2, therefore high permeation in the anulus, high stresses and the possibility to have anulus flooded as result of an outer sheath breach or even due to permeated water. These were the triple conditions needed to have the failure, considering that all metallic material used in the pipe were subjected to this phenomenon. Since the discovery was made, several test campaigns to better understand and replicate the phenomena started. They covered pipe retrieved from field dissection, several small-scale materials testing, and fracture mechanics to create reliable crack propagation calculations. There were 3 mains focus areas; to understand how to deal with the installed fleet, to define the conditions in which a crack would appear and define, using fracture mechanics, how long a crack would take to break the wire. In other words, it was intended to define what is the remaining service life. As a result of this investigation some initial beliefs like that all materials were subjected to the phenomena and that a solution was far away were somehow reduced and reshaped. There was also the initiative to embark on technology for detection of the anulus condition, mainly to define if it is flooded or not. Some ROV inspection means were added to the endfitting and some sensors were added to the interconnected pipe sections that allow conditioning monitoring or inspection from the floating unit, not using a ROV. This paper will cover the improvements done since the disclosure of the phenomena in 2017, reviewing what is known about it so far, what is still to be discovered and how the results achieved to date can contribute for a more reliable and longer service life for the flexible pipes to be applied in a rich CO2 environment.

Thermo-Mechanical Wear Mechanisms of Ceramic Materials

2007 ◽  
Author(s):  
Sang-Woo Kim ◽  
Seung-Hun Lee ◽  
Jun-Seok Park ◽  
Seock-Sam Kim
Keyword(s):  
Fracture Mechanics ◽  
Wear Mechanisms ◽  
Peclet Number ◽  
Thermal Load ◽  
Ceramic Materials ◽  
Wear Model ◽  
Dimensional Parameter ◽  
Mechanical Wear ◽  
Péclet Number ◽  
Lubricated Sliding

This paper was investigated the thermo-mechanical wear mechanisms of ceramic materials under lubricated sliding condition based on the fracture mechanics. Thermo-mechanical wear model for ceramic materials was proposed, and non-dimensional parameter T for evaluation of ceramic materials was also proposed. Non-dimensional parameter T is consist of thermal load (Th) and Peclet number (Pe).

scholarly journals Survival Predictions of Ceramic Crowns Using Statistical Fracture Mechanics

2017 ◽  
Vol 96 (5) ◽  
pp. 509-515 ◽  
Author(s):  
S. Nasrin ◽  
N. Katsube ◽  
R.R. Seghi ◽  
S.I. Rokhlin
Keyword(s):  
Fracture Mechanics ◽  
Survival Probability ◽  
Survival Rates ◽  
Fracture Initiation ◽  
Ceramic Materials ◽  
Material Surface ◽  
Analysis Model ◽  
Element Analysis ◽  
Ceramic Crowns ◽  
Fatigue Failures

This work establishes a survival probability methodology for interface-initiated fatigue failures of monolithic ceramic crowns under simulated masticatory loading. A complete 3-dimensional (3D) finite element analysis model of a minimally reduced molar crown was developed using commercially available hardware and software. Estimates of material surface flaw distributions and fatigue parameters for 3 reinforced glass-ceramics (fluormica [FM], leucite [LR], and lithium disilicate [LD]) and a dense sintered yttrium-stabilized zirconia (YZ) were obtained from the literature and incorporated into the model. Utilizing the proposed fracture mechanics–based model, crown survival probability as a function of loading cycles was obtained from simulations performed on the 4 ceramic materials utilizing identical crown geometries and loading conditions. The weaker ceramic materials (FM and LR) resulted in lower survival rates than the more recently developed higher-strength ceramic materials (LD and YZ). The simulated 10-y survival rate of crowns fabricated from YZ was only slightly better than those fabricated from LD. In addition, 2 of the model crown systems (FM and LD) were expanded to determine regional-dependent failure probabilities. This analysis predicted that the LD-based crowns were more likely to fail from fractures initiating from margin areas, whereas the FM-based crowns showed a slightly higher probability of failure from fractures initiating from the occlusal table below the contact areas. These 2 predicted fracture initiation locations have some agreement with reported fractographic analyses of failed crowns. In this model, we considered the maximum tensile stress tangential to the interfacial surface, as opposed to the more universally reported maximum principal stress, because it more directly impacts crack propagation. While the accuracy of these predictions needs to be experimentally verified, the model can provide a fundamental understanding of the importance that pre-existing flaws at the intaglio surface have on fatigue failures.

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