Subcritical Crack Growth Models for Static Fatigue of Hi‐Nicalon TM ‐S SiC Fiber in Air and Steam

2021 ◽  
Author(s):  
R.S. Hay ◽  
S.J. Robertson ◽  
M.B. Ruggles‐Wrenn ◽  
M. Piper ◽  
T. Shillig ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Growth Models ◽  
Static Fatigue ◽  
Sic Fiber

scholarly journals Cyclical fatigue of annealed and of thermally tempered soda-lime-silica glass

2018 ◽  
Vol 165 ◽  
pp. 18003
Author(s):  
Jens Schneider ◽  
Jonas Hilcken
Keyword(s):  
Crack Growth ◽  
Silica Glass ◽  
Subcritical Crack Growth ◽  
Soda Lime ◽  
Cyclic Fatigue ◽  
Growth Exponent ◽  
Static Fatigue ◽  
Strength Increase ◽  
Soda Lime Silica Glass ◽  
Number Of Cycles

We present experimental and theoretical investigations on the cyclic fatigue of annealed and of thermally tempered soda-lime-silica glass. Static fatigue due to subcritical crack growth at micro cracks significantly decreases the macroscopic strength of soda-lime-silica glass and causes a time-dependent strength reduction. A subsequent thermal tempering process is typically used to induce residual surface compression stresses, which inhibit the crack growth of surface cracks, and corresponding bulk tension stresses. From the experimental results we show that the existing models for static fatigue used in linear elastic fracture mechanics can be used for the lifetime prediction of cyclically loaded annealed glass and thermally tempered glass, although the (static) crack growth exponent slightly decreases in cyclic loading. The equivalent duration of tensile stress at the crack tip of a micro crack governs the crack growths and not the number of cycles. The threshold for subcritical crack growth determined from the cyclic experiments was found to be in good agreement with data from literature. But unlike in strength tests with singular and quasi-static re-loading, it could be found that periodic loading with load free intervals does not lead to a strength increase by crack healing effects. Based on the results, an engineering design concept for cyclically loaded glass is presented.

Subcritical Crack Growth of α/β-Sialon Ceramics in Distilled Water

2008 ◽  
Vol 403 ◽  
pp. 129-132
Author(s):  
Marco Riva ◽  
Rainer Oberacker ◽  
Michael J. Hoffmann ◽  
Theo Fett
Keyword(s):  
High Pressure ◽  
Life Cycle ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Testing Procedure ◽  
Fatigue Tests ◽  
Static Fatigue ◽  
Distilled Water

Environmental-assisted subcritical crack growth on two different /-sialon ceramics is determined in static fatigue tests. The goal of these investigations was to determine the influence of delivering medium of high pressure pumps on their durability (life cycle). Therefore 4-point-bending bars were statically loaded in distilled water and subcritical crack growth was analyzed. The large number of spontaneous failure and survivals made the development of a modified testing procedure necessary in order to obtain a significant database.

The Static Fatigue Limit in the Thermal Activation Approach to Subcritical Crack Growth

1979 ◽  
Vol 62 (9-10) ◽  
pp. 536-537 ◽  
Author(s):  
D. K. SHETTY ◽  
A. R. ROSENFIELD ◽  
W. H. DUCKWORTH ◽  
G. K. BANSAL
Keyword(s):  
Crack Growth ◽  
Fatigue Limit ◽  
Thermal Activation ◽  
Subcritical Crack Growth ◽  
Static Fatigue

Subcritical Crack Growth in Cementitious Materials Subject to Chemomechanical Deterioration—Experimental Test Using Specimens of Negative Geometry

2017 ◽  
Vol 84 (4) ◽  
Author(s):  
Weijin Wang ◽  
Teng Tong ◽  
Susheng Tan ◽  
Qiang Yu
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Crack Tip ◽  
Cementitious Materials ◽  
Hardened Cement ◽  
Static Fatigue ◽  
Cement Pastes ◽  
Stable Crack Propagation ◽  
Hardened Cement Pastes ◽  
Physical And Chemical

Knowledge of the subcritical crack growth (SCG) in cement-based materials subject to concurrent physical and chemical attacks is of great importance for understanding and mitigating the chemomechanical deterioration in concrete structural members. In this study, the SCG in hardened cement pastes is investigated experimentally by a novel test approach aided with microcharacterization. In the test, specimens of negative geometry are designed, which enable the use of load control to trigger stable crack propagation in hardened cement pastes. Multiple specimens, cast from the same batch of mixture, are exposed to the same chemical condition and loaded at the same age. With the aid of a high-resolution microscopy system, which is used to trace the crack tip, the average trend and the associated variation of the dependence of crack velocity v on the stress intensity factor K at the crack tip are obtained. Different from static fatigue, three distinctive regions are captured in the K–v curves of specimens experiencing chemomechanical deterioration. With the help of advanced techniques including scanning electron microscopy (SEM), atomic-force microscopy (AFM), and Raman spectroscopy, the microstructure destruction and chemical composition change induced by the imposed chemomechanical attack are characterized at different stages. In addition to the physical insights for deeper understanding of the coupled effect of chemomechanical attack, these experimental results provide important macro- and microscopic benchmarks for the theoretical modeling and numerical investigation in the future studies.

Fracture, Fatigue and Indentation Behavior of Pyrolytic Carbon for Biomedical Applications

1995 ◽  
Vol 383 ◽  
Author(s):  
R. O. Ritchie ◽  
R. H. Dauskardt ◽  
W. W. Gerberich ◽  
A. Strojny ◽  
E. Lilleodden
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Mechanical Heart Valve ◽  
Pyrolytic Carbon ◽  
Cyclic Fatigue ◽  
Graphite Substrate ◽  
Static Fatigue ◽  
Small Surface ◽  
Biomedical Implant ◽  
Valve Prostheses

ABSTRACTThe fracture, fatigue and indentation properties of pyrolytic carbon, both as a monolithic material and as a coating on a graphite substrate, are described in light of its use for biomedical implant applications, specifically for the manufacture of mechanical heart valve prostheses. From the perspective of determining properties that are important for the prediction of safe structural lifetimes in such prostheses, it is found that by traditional engineering standards, pyrolytic carbon has low damage tolerance, i.e., fracture toughness values between 1 and 3 MPa√m and susceptibility to subcritical crack growth by both cyclic fatigue and stress-corrosion cracking (static fatigue). Subcritical crack-growth rates are evaluated in simulated physiological environments for both through-thickness “long” cracks, and for physically “small” surface cracks, the latter measurements being performed for cracks initiated at hardness indents. The unusual deformation characteristics of indentation in pyrolytic carbon are described based on instrumented microhardness indentation and scanning probe microscopy (AFM/STM) studies.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength

Effective Modeling of Fatigue Crack Growth in Pipelines

2012 ◽  
Author(s):  
Steven J. Polasik ◽  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Models ◽  
Critical Parameters ◽  
Operating Pressure ◽  
Mechanics Model ◽  
Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

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