Summary of Results of the Effects of Environment on Mechanical Behavior of High-Performance Ceramics

McCullum, Dale E.; Hecht, Norman L.; Chuck, Leon; Goodrich, Steven M.

doi:10.1002/9780470313848.ch20

Cited by 14 publications

(5 citation statements)

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“…Si 3 N 4 power law exponents (z) in air are similar to those in SiC, and they also tend to decrease with increasing temperature (Figure 17). 23,30,169,170 Almost all measurements for various forms of carbon are at room temperature and find z from 50 to 300, [17][18][19]171 but one study done at room temperature and 500°C finds a decrease in z of roughly 50% for two types of Poco graphite, from 113 to 63 and 218 to 128, respectively (Figure 17). 17 For obvious reasons no high temperature studies have been done on silicate glasses, but room temperature z in air and in water are between 10 to 35, 90,94,[172][173][174][175][176][177][178] and pure SiO 2 glass, such as that in optical fiber, tend to have slightly higher values (Figure 17).…”

Section: Parameter Comparisonmentioning

confidence: 99%

“…The only comparison available for Hi-Nicalon TM -S cites z of 12.6 for measurements between 500°C and 800°C in air, 29 and also z of 12.6 for Hi-Nicalon TM between 500°C and 1200°C, which is significantly lower than the z~22 found in this study (Table 3 and Figure 17). However, studies for bulk SiC in air or argon at up to 1600°C typically find much larger values for z (Figure 17), [24][25][26][27]30,31,92,[165][166][167][168] particularly at low temperatures. 25 There is a strong tendency for z to decrease with temperature (Figure 17).…”

Section: Parameter Comparisonmentioning

confidence: 99%

“…28,29 However, besides the one mentioned derivation, the model is strictly empirical; it has no firmly established theoretical basis. The stress intensity exponent z decreases with increasing temperature, 17,30,[92][93][94] so extra parameters may be necessary to describe behavior over a broad range of temperature-stress space.…”

Section: Introductionmentioning

confidence: 99%

“…SCG models have been extensively reviewed. [1][2][3][4][5][6][7][8] They have been developed and applied to glasses, [9][10][11][12][13][14][15] polymers, 16 carbon, [17][18][19] alumina, [20][21][22] Si 3 N 4 , 23 SiC, [24][25][26][27][28][29][30][31] beryllia, 32 quartz, 5,33 and geological materials. 5,34 SCG is an important degradation mechanism for SiC fibers and SiC-SiC ceramic matrix composites (CMCs), 28,[35][36][37][38][39][40] particularly at intermediate temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Subcritical crack growth models for static fatigue of Hi‐Nicalon^TM‐S SiC fiber in air and steam

et al. 2021

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Three subcritical crack growth (SCG) laws were used to model strain-rates and failure times for static fatigue of Hi-Nicalon TM -S SiC fiber tows in air and Si(OH) 4 (g)saturated steam. Models were fit to tow failure times (t f ) and steady-state strain rates (ἑ) for brittle creep measured at 700 to 1100°C under initial applied stresses (σ A ) of 260 to 1260 MPa. A power law, a reaction-rate law, and a bond-energy law were used to describe SCG that caused sequential filament failure, and ultimately tow failure.Two versions of each model were developed. One allowed access of chemisorbed species to flaws throughout the fiber (mode 1) and another only allowed access to flaws at the SiC-SiO 2 interface (mode 2). The stress increase on intact filaments as others fractured and as filaments oxidized, and the increase in stress intensity geometric factors (Y) as crack size increased were incorporated in the models. The fits to data were compared for the different models by using both simple regression analysis and orthogonal distance regression (ODR) analysis. Faster convergence and more consistent results were achieved using ODR analysis. Regression analyses found parameters for all models with similar error in data fits, so validity of a model could not be distinguished by regression analysis alone. For all models, the stress dependence of SCG rates was much stronger in steam than in air, and for most models activation energies were between 300 and 420 kJ/mol, regardless of environment. For the steam environment, the bond-length parameter (δ) for the bond-energy model was very close to the lattice parameter of β-SiC (.436 nm), but in air it was significantly lower at 0.25-0.26 nm, but still larger than the Si-C bond length of 0.189 nm. Other factors suggest that either a bond-energy based law or a modified version of a reaction-rate law are the best choices for a SCG law. Filament strength distributions initially described by Weibull distributions could not be described by such distributions after application of the models. SCG mechanisms are discussed.

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Section: Parameter Comparisonmentioning

confidence: 99%

Section: Parameter Comparisonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Subcritical crack growth models for static fatigue of Hi‐Nicalon^TM‐S SiC fiber in air and steam

et al. 2021

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“…This method allows the characterization of stochastic variables trough numerical simulations and no theoretical inferences. For the tensile strength of both ceramic materials, a Weibull distribution was assumed, and the related parameters were taken from literature [9,10] and Avio database. Fig.…”

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confidence: 99%

Thermo-Structural Analysis of Ceramic Vanes for Gas Turbines

Fersíní

Bianco

Lorenzis

et al. 2006

Advances in Science and Technology

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Advanced structural ceramics such as Hot Pressed Silicon Nitride (HPSN) and Reaction Bonded Silicon Carbide (RBSC), thanks to their low density (3.1 ÷ 3.4 gr/cm3) and to their thermostructural properties, are interesting candidates for aerospace applications. This research investigates the feasibility of employing such monolithic advanced ceramics for the production of turbine vanes for aerospace applications, by means of a finite element analysis. A parametric study is performed to analyse the influence of the coefficient of thermal expansion, the specific heat, the thermal conductivity, and the Weibull modulus on structural stability, heat transfer properties and thermomechanical stresses under take-off and flying conditions. A nodal point that is evidenced is the high intensity of thermal stresses on the vane, both on steady state and in transient conditions. In order to reduce such stresses various simulations have been carried out varying geometrical parameters such as the wall thickness. Several open questions are evidenced and guidelines are drawn for the design and production of ceramic vanes for gas turbines.

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Chemical Corrosion of Liquid-Phase Sintered SiC in Acidic/Alkaline Solutions Part 1. Corrosion in HNO3 Solution

Zhang

Zhang²,

He³

et al. 2016

J. of Materi Eng and Perform

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Summary of Results of the Effects of Environment on Mechanical Behavior of High-Performance Ceramics

Cited by 14 publications

References 0 publications

Subcritical crack growth models for static fatigue of Hi‐Nicalon^TM‐S SiC fiber in air and steam

Subcritical crack growth models for static fatigue of Hi‐Nicalon^TM‐S SiC fiber in air and steam

Thermo-Structural Analysis of Ceramic Vanes for Gas Turbines

Chemical Corrosion of Liquid-Phase Sintered SiC in Acidic/Alkaline Solutions Part 1. Corrosion in HNO3 Solution

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Summary of Results of the Effects of Environment on Mechanical Behavior of High-Performance Ceramics

Cited by 14 publications

References 0 publications

Subcritical crack growth models for static fatigue of Hi‐NicalonTM‐S SiC fiber in air and steam

Subcritical crack growth models for static fatigue of Hi‐NicalonTM‐S SiC fiber in air and steam

Thermo-Structural Analysis of Ceramic Vanes for Gas Turbines

Chemical Corrosion of Liquid-Phase Sintered SiC in Acidic/Alkaline Solutions Part 1. Corrosion in HNO3 Solution

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Subcritical crack growth models for static fatigue of Hi‐Nicalon^TM‐S SiC fiber in air and steam

Subcritical crack growth models for static fatigue of Hi‐Nicalon^TM‐S SiC fiber in air and steam