[PDF] Fatigue Reliability Predictions In Silicon Nitride Ceramics Based On Fatigue Behavior Bridging Stresses And Fracture Data eBook

Author : Rawley Brandon Greene
Publisher :
Page : 118 pages
File Size : 42,49 MB
Release : 2013
Category : Silicon nitride
ISBN :

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Because of its attractive material properties like high hardness, high toughness, and excellent high temperature strength, materials like silicon nitride are becoming more common for use in high performance applications. However, there have been limited studies of the fatigue behavior of small cracks in silicon nitride and other materials toughened by grain bridging mechanisms. This study explores using micro Raman spectroscopy, fatigue crack growth data and results from static fracture experiments to determine a bridging stress profile for silicon nitride doped with MgO and Y2O3 as sintering additives. These bridging stress profiles allow for the creation of a geometry specific fatigue threshold R-curve which can be used to develop a fatigue endurance strength prediction tool to aid in the design of products using the material. Cyclical fatigue experiments conducted on bend beams with induced semi-elliptical surface cracks were conducted to verify the prediction tool. The results show that no bend beams with this crack geometry failed below the predicted endurance level. It is expected that this method can be extended to create fatigue endurance strength predictions for other materials similarly toughened by grain bridging and other mechanisms.

Author : Hidehiro Kishimoto
Publisher : Elsevier Science & Technology
Page : 304 pages
File Size : 20,28 MB
Release : 1995
Category : Technology & Engineering
ISBN :

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Hardbound. Structural ceramics, such as silicon nitride, silicon carbide, alumina and zirconia have more potential than metallic materials for practical applications to various kinds of engineering components, especially for high temperature applications. For example, automotive engine parts, such as turbocharger rotors and swirl chambers, and ball bearing systems have been produced on a commercial basis using these materials for the last ten years. These industrial motivations have stimulated extensive progress in the research on evaluation of the strength properties of ceramics. In particular, cyclic fatigue has been investigated as one of the major concerns in the design of reliable ceramic components, and many researchers have been engaged in the field of cyclic fatigue in ceramics. As a result, new aspects such as crack bridging, R-curve behavior and fracture morphology have been clarified in the last decade.This book presents in three se

Author : Sarah Gallops
Publisher :
Page : 90 pages
File Size : 30,36 MB
Release : 2011
Category :
ISBN :

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Toughened ceramics, or bridging ceramics, are being developed in an attempt to widen the application base of traditional ceramics, which are brittle and have low resistance to crack extension. The crack growth resistance of these extrinsically toughened ceramics has been shown to increase with crack length, and unlike traditional ceramics, toughened ceramics are susceptible to fatigue failure (failure below fracture strength after repeated loading and unloading). Many ceramic applications, especially those in the aerospace or automotive industries, require components to be designed for infinite life since fatigue crack growth can lead rapid failure. The current methods for predicting and preventing fatigue failures are unsuitable; most were developed for metal alloys, which behave very differently than toughened ceramics. Damage tolerant design takes into account that most engineering structures are inherently flawed, thus a method is needed that ensures an existing flaw will not propagate to failure within foreseen in-service lifetimes. Such a method has been proposed for making fatigue reliability predictions in bridging ceramics. Fatigue crack growth experiments were performed on 99.5% pure polycrystalline alumina. The fatigue behavior was characterized as a function of crack size using a fatigue threshold R-curve, similar in principal to a fracture toughness Rcurve. A bridging stress profile, the relevant material property, was both calculated using the R-curve and measured directly with fluorescence spectroscopy. The fatigue threshold R-curve was used to make predictions of fatigue endurance strength based on an initial minimum detectable flaw size. These endurance strength predictions were validated with small crack fatigue failure experiments.

Author : R. Badaliance
Publisher :
Page : 14 pages
File Size : 10,64 MB
Release : 1976
Category : Crack propagation
ISBN :

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The thermal fatigue behavior of a soda-lime-silica glass subjected to water quench and silicon-nitride subjected to thermal environment of a turbine engine was predicted from data of slow (subcritical) crack growth. A numerical integration technique was developed to calculate the extent of slow crack growth for each thermal cycle over the total duration of the transient thermal stress and temperature, as well as the total number of cycles required for catastrophic failure to occur. Good agreement between the predicted and experimental data was found. The results indicate that, for reliable prediction of thermal fatigue resistance, an estimate of critical flaw-depth based on a statistical (such as the Weibull) theory of brittle fracture is necessary.

Author : J. B. Wachtman
Publisher : Wiley-Interscience
Page : 478 pages
File Size : 48,24 MB
Release : 1996-05-25
Category : Science
ISBN :

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The competing roles of microstructure in weakening and toughening ceramics are explored and interpreted in terms of reliability improvement through processing for controlled and tailored microstructures.

Author :
Publisher :
Page : 105 pages
File Size : 39,29 MB
Release : 1986
Category :
ISBN :

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The objective of this program was to establish a method for predicting the lifetime reliability of structural ceramic materials in high temperature applications. Fast fracture and stress rupture data were collected on two materials, a sintered silicon nitride and a lithium-aluminum-silicate. The fast fracture data was presented graphically in the form of Weibull plots of percent failed versus failure stress. Stress rupture results were presented in tabular form. Photo micrographs were presented to illustrate the fracture surfaces of fast fracture and stress rupture failures. A program of specimen development was conducted. The objective of the program was to develop processing techniques to make it possible to fabricate integral shaft spin disks suitable for hot spin testing as stress rupture specimens. The hot spin disk stress rupture results were to be used to correlate experimental time dependent failure results with analytical time dependent failure results.