scholarly journals Static Fatigue of SiC/SiC Minicomposites at High Temperatures up to 1200 °C in Air: Multiscale Approach

2021 ◽  
Vol 5 (3) ◽  
pp. 67
Author(s):  
Jacques Lamon ◽  
Adrien Laforêt
Keyword(s):  
Crack Growth ◽  
High Temperatures ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Rupture Time ◽  
Cumulative Distribution ◽  
Initial Stresses ◽  
Static Fatigue ◽  
Time Relation

The present paper investigates the static fatigue behavior of Hi-Nicalon fiber-reinforced SiC–SiC minicomposites at high temperatures in the 900–1200 °C range, and under tensile stresses above the proportional limit. The stress–rupture time relation was analyzed with respect to subcritical crack growth in filaments and fiber tow fracture. Slow crack growth from flaws located at the surface of filaments is driven by the oxidation of free carbon at the grain boundaries. Lifetime of the reinforcing tows depends on the statistical distribution of filament strength and on structural factors, which are enhanced by temperature increase. The rupture time data were plotted in terms of initial stresses on reinforcing filaments. The effect of temperature and load on the stress–rupture time relation for minicomposites was investigated using results of fractography and predictions of minicomposite lifetime using a model of subcritical growth for critical filaments. The critical filament is the one whose failure by slow crack-growth triggers unstable fracture of the minicomposite. This is identified by the strength–probability relation provided by the cumulative distribution function for filament strength at room temperature. The results were compared to the fatigue behavior of dry tows. The influence of various factors related to oxidation, including multiple failures, load sharing, and variability, was analyzed.

scholarly journals Static Fatigue of SiC Multifilament Tows at Temperatures up to 1200 °C in Air

Ceramics ◽  
2019 ◽  
Vol 2 (3) ◽  
pp. 426-440 ◽  
Author(s):  
Jacques Lamon
Keyword(s):  
High Temperatures ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Constant Load ◽  
Rupture Time ◽  
Static Fatigue ◽  
Probability Relation ◽  
Time Relation ◽  
Increasing Temperature

SiC-based fibers are sensitive to delayed failure under constant load at high temperatures in air. Static fatigue at intermediate temperatures < 800 °C was attributed to slow crack growth from flaws located at the surface of fibers, driven by the oxidation of free carbon at grain boundaries. The present paper examines the static fatigue behavior of SiC-based Hi-Nicalon fibers at high temperatures up to 1200 °C and Hi Nicalon S fibers at intermediate temperatures (500–800 °C). The degradation of stress- rupture time relation of multifilament tows with increasing temperature was investigated. Predictions of tow lifetime based on critical filament-based model of tow failure were compared to experimental stress-rupture time diagrams. Critical filaments are characterized by strength–probability relation. The critical filament-based model was found to describe satisfactorily the static fatigue behavior of fiber tows at these temperatures. The influence of various factors on lifetime as well as the origins of variability is analyzed.

Partial Devitrification of Sintered Silicon Nitride During Static Fatigue Testing

1992 ◽  
Vol 287 ◽  
Author(s):  
W. Braue ◽  
G. D. Quinn
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Secondary Phase ◽  
Boundary Phase ◽  
Static Fatigue ◽  
Phase Assemblage ◽  
Transmission Electron ◽  
Stress States

ABSTRACTThe static fatigue behavior of sintered Y2O3/A12O3-fluxed Si3N4 in air is controlled by slow crack growth or creep fracture. Partial devitrification of the amorphous grain boundary phase at 1000°C and 1100°C improves the static fatigue resistance with specimens surviving up to 1500 hrs. during stress rupture experiments. In this study the early stages of partial devitrification during static fatigue testing at 1000°C are investigated by conventional and analytical transmission electron microscopy with emphasis on nucleation and growth of δ-Y2Si2O7 and X1-Y2SiO5 and possible constraints from different stress states. The results show that the stress state does not affect the nature of the secondary phase assemblage. However, the amount of crystallization is higher within the tensile region of the flexural specimens than in areas which experienced compressive stresses.

Evaluation of Tensile Static, Dynamic, and Cyclic Fatigue Behavior for A Hiped Silicon Nitride at Elevated Temperatures

1992 ◽  
Vol 287 ◽  
Author(s):  
Chih-Kuang Jack Lin ◽  
Michael G. Jenkins ◽  
Matitison K. Ferber
Keyword(s):  
Silicon Nitride ◽  
Cyclic Loading ◽  
Crack Growth ◽  
Failure Mechanism ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Cyclic Fatigue ◽  
Creep Rupture ◽  
Static Fatigue ◽  
Dynamic Fatigue

ABSTRACTTensile fatigue behavior of a hot-isostatically-pressed (HIPed) silicon nitride was investigated over ranges of constant stresses, constant stress rates, and cyclic loading at 1150-1370°C. At 1150°C, static and dynamic fatigue failures were governed by a slow crack growth mechanism. Creep rupture was the dominant failure mechanism in static fatigue at 1260 and 1370°C. A transition of failure mechanism from slow crack growth to creep rupture appeared at stress rates ≤10−2 MPa/s for dynamic fatigue at 1260 and 1370°C. At 1 150-1370°C, cyclic loading appeared to be less damaging than static loading as cyclic fatigue specimens displayed greater failure times than static fatigue specimens under the same maximum stresses.

Prediction of Lifetime in Static Fatigue at High Temperatures for Ceramic Matrix Composites

2010 ◽  
Vol 112 ◽  
pp. 129-140 ◽  
Author(s):  
O. Loseille ◽  
Jacques Lamon
Keyword(s):  
Crack Growth ◽  
High Temperatures ◽  
Slow Crack Growth ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Woven Composites ◽  
Static Fatigue ◽  
Matrix Composites ◽  
Random Load ◽  
Delayed Failure

Previous works have shown that ceramic matrix composites are sensitive to delayed failure during fatigue in oxidizing environments. The phenomenon of slow crack growth has been deeply investigated on single fibers and multifilament tows in previous papers. The present paper proposes a multiscale model of failure driven by slow crack growth in fibers, for 2D woven composites under a constant load. The model is based on the delayed failure of longitudinal tows. Additional phenomena involved in the failure of tows have been identified using fractographic examination of 2D woven SiC/SiC composite testspecimens after fatigue tests at high temperatures. Stochastic features including random load sharing, fiber overloading, fiber characteristics and fiber arrangement within the tows have been introduced using appropriate density functions. Rupture time predictions are compared to experimental data.

scholarly journals Statistical-Probabilistic Approach to the Lifetime and Strength Degradation of E-Glass Filaments and Bundles under Constant Tensile Loading in Water

2019 ◽  
Vol 3 (3) ◽  
pp. 78
Author(s):  
Jacques Lamon ◽  
Mohamed R’Mili
Keyword(s):  
Crack Growth ◽  
Slow Crack Growth ◽  
Probabilistic Approach ◽  
Tensile Tests ◽  
Fatigue Behaviour ◽  
Strength Degradation ◽  
Tensile Behaviour ◽  
Static Fatigue ◽  
Statistical Parameters ◽  
Pertinent Data

The present paper discusses the statistical features of static fatigue for E-glass multifilament tows in water. In such an aggressive environment, the glass fibres are sensitive to slow crack propagation from micron-sized flaws. Rupture and interrupted static fatigue tests under constant deformation in water, as well as tensile tests in inert environments on tows after fatigue were carried out on E-glass fibre tows that comprised around 2000 single filaments. The slow crack growth constants and the fast fracture statistical parameters for filaments were extracted from the outcome of experiments on tows, i.e., the load relaxation curves during fatigue and stress-strain curves during the tensile tests. These parameters provide a pertinent data base for the prediction of several characteristics in various conditions of fatigue for filaments and tows including statistical distributions of lifetimes and residual strengths, strength degradation during fatigue, size effects on lifetime and tow residual behaviour. Equations for calculation of filament lifetime and residual strength, and tow tensile behaviour were based on the model of slow crack growth and Weibull statistical distribution. Calculations using strength-probability-time relations provided insight into static fatigue behaviour of tows in water. Validity of the approach was assessed by the comparison of experimental and predicted tow residual behaviours.

Slow Crack Growth of a Pyroceram Glass Ceramic Under Static Fatigue Loading: Commonality of Slow Crack Growth in Advanced Ceramics

2014 ◽  
Author(s):  
Sung R. Choi ◽  
D. Calvin Faucett ◽  
Brenna Skelley
Keyword(s):  
Crack Growth ◽  
Glass Ceramic ◽  
Life Prediction ◽  
Elevated Temperatures ◽  
Slow Crack Growth ◽  
Static Fatigue ◽  
Fatigue Data ◽  
Prediction Approach ◽  
Applied Stresses ◽  
Dynamic Fatigue

An extensive experimental work for Pyroceram™ 9606 glass-ceramic was conducted to determine static fatigue at ambient temperature in distilled water. This work was an extension and companion of the previous work conducted in dynamic fatigue. Four different applied stresses ranging from 120 to 170 MPa was incorporated with a total of 20–23 test specimens used at each of four applied stresses. The slow crack growth parameters n and D were found to be n = 19 and D = 45 with a coefficient of correlation of rcoef = 0.9653. The Weibull modulus of time to failure was in a range of msf = 1.6 to 1.9 with an average of msf = 1.7±0.2. A life prediction using the previously-determined dynamic fatigue data was in excellent agreement with the static fatigue data. The life prediction approach was also applied to advanced monolithic ceramics and ceramic matrix composites based on their dynamic and static fatigue data determined at elevated temperatures. All of these results indicated that a SCG mechanism governed by a power-law crack-growth formulation was operative, a commonality of slow crack growth in these materials systems.

Slow Crack Growth of a Pyroceram Glass Ceramic Under Static Fatigue Loading—Commonality of Slow Crack Growth in Advanced Ceramics

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Sung R. Choi ◽  
D. Calvin Faucett ◽  
Brenna Skelley
Keyword(s):  
Crack Growth ◽  
Glass Ceramic ◽  
Life Prediction ◽  
Elevated Temperatures ◽  
Slow Crack Growth ◽  
Static Fatigue ◽  
Fatigue Data ◽  
Prediction Approach ◽  
Applied Stresses ◽  
Dynamic Fatigue

An extensive experimental work for Pyroceram™ 9606 glass–ceramic was conducted to determine static fatigue at ambient temperature in distilled water. This work was an extension and companion of the previous work conducted in dynamic fatigue. Four different applied stresses ranging from 120 to 170 MPa was incorporated with a total of 20–23 test specimens used at each of four applied stresses. The slow crack growth (SCG) parameters n and D were found to be n = 19 and D = 45 with a coefficient of correlation of rcoef = 0.9653. The Weibull modulus of time to failure was in a range of msf = 1.6–1.9 with an average of msf = 1.7 ± 0.2. A life prediction using the previously determined dynamic fatigue data was in excellent agreement with the static fatigue data. The life prediction approach was also applied to advanced monolithic ceramics and ceramic matrix composites (CMCs) based on their dynamic and static fatigue data determined at elevated temperatures. All of these results indicated that a SCG mechanism governed by a power-law crack growth formulation was operative, a commonality of SCG in these materials systems.

Methodology to Predict Delayed Failure Due to Slow Crack Growth in Ceramic Tubular Components Using Data From Simple Specimens

1993 ◽  
Vol 115 (2) ◽  
pp. 204-210 ◽  
Author(s):  
O. M. Jadaan ◽  
R. E. Tressler
Keyword(s):  
Crack Growth ◽  
Fatigue Testing ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Scaling Analysis ◽  
Rupture Data ◽  
Threshold Stress Intensity Factor ◽  
Using Data ◽  
Tubular Components

The methodology to predict the liftime of sintered α-silicon carbide (SASC) tubes subjected to slow crack growth (SCG) conditions involved the experimental determination of the SCG parameters of that material and the scaling analysis to project the stress rupture data from small specimens to large components. Dynamic fatigue testing, taking into account the effect of threshold stress intensity factor, of O-ring and compressed C-ring specimens was used to obtain the SCG parameters. These SCG parameters were in excellent agreement with those published in the literature and extracted from stress rupture tests of tensile and bend specimens. Two methods were used to predict the lifetimes of internally heated and pressurized SASC tubes. The first is a fracture mechanics approach that is well known in the literature. The second method used a scaling analysis in which the stress rupture distribution (lifetime) of any specimen configuration can be predicted from stress rupture data of another.

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