scholarly journals Subcritical Crack Growth Life Prediction for Ceramic Components of Advanced Heat Engines

1995 ◽  
Author(s):  
D. C. Wu ◽  
A. D. Peralta ◽  
M. N. Menon ◽  
J. C. Cuccio
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Growth Parameters ◽  
Stress Rupture ◽  
High Strength ◽  
Heat Engines ◽  
Fracture Data ◽  
Ceramic Components ◽  
Data Censoring ◽  
Fast Fracture

Advanced, high-strength ceramics are finding increasing application in advanced heat engines. To ensure the long-term reliability of components made from these materials, subcritical crack growth (SCG) from inherent flaws has to be taken into account, as this has been identified as the primary failure mode under sustained loading. In analyzing fast fracture data, data censoring is necessary to obtain estimates of the inherent strength distributions for competing failure-causing flaw populations. This is particularly important for ceramic designs, where size scaling is a necessary part of the design analysis. While data censoring has become common for fast fracture data, data censoring involving stress rupture data has yet to be widely applied. This paper describes fast fracture and stress rupture tests performed on an advanced silicon nitride ceramic, the test data and fractography results, censored data analysis for both types of data, derivation of the subcritical crack growth parameters, and application of these parameters to verification specimens. Implications of the findings and recommendations for future studies are also presented.

Subcritical Crack Growth Life Prediction for Ceramic Components of Advanced Heat Engines

1996 ◽  
Vol 118 (2) ◽  
pp. 240-245
Author(s):  
D. C. Wu ◽  
A. D. Peralta ◽  
M. N. Menon ◽  
J. C. Cuccio
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Growth Parameters ◽  
Stress Rupture ◽  
High Strength ◽  
Heat Engines ◽  
Fracture Data ◽  
Ceramic Components ◽  
Data Censoring ◽  
Fast Fracture

Advanced, high-strength ceramics are finding increasing application in advanced heat engines. To ensure the long-term reliability of components made from these materials, subcritical crack growth (SCG) from inherent flaws has to be taken into account, as this has been identified as the primary failure mode under sustained loading. In analyzing fast fracture data, data censoring is necessary to obtain estimates of the inherent strength distributions for competing failure-causing flaw populations. This is particularly important for ceramic designs, where size scaling is a necessary part of the design analysis. While data censoring has become common for fast fracture data, data censoring involving stress rupture data has yet to be widely applied. This paper describes fast fracture and stress rupture tests performed on an advanced silicon nitride ceramic, the test data and fractography results, censored data analysis for both types of data, derivation of the subcritical crack growth parameters, and application of these parameters to verification specimens. Implications of the findings and recommendations for future studies are also presented.

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

Subcritical Crack Growth and Ship Structural Design

1976 ◽  
Vol 13 (02) ◽  
pp. 152-160
Author(s):  
Philip H. Francis ◽  
Philip H. Francis ◽  
James Lankford ◽  
Fred F. Lyle
Keyword(s):  
Crack Growth ◽  
Structural Design ◽  
Load Distribution ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Design Criterion ◽  
Low Alloy Steels ◽  
Initiation And Propagation ◽  
Alloy Steels ◽  
Environmental Attack

A review is made of the factors which influence subcritical crack growth in conventional and high-strength, low-alloy steels of the type used in primary and secondary welded ship structures. The types of influencing factors considered are the metallurgical parameters, the fracture mechanics of the crack tip processes, the loading state, and the mechanisms of environmental attack. The fatigue process is separated into the crack initiation and (subcritical) crack propagation stages, and the relative influence of the above factors is discussed for each of these stages. Following this review, a basis for a design criterion is established for safe-life design of welded cargo ship structure. Two specific criteria are advanced: one which utilizes only the endurance strengths of the weldment types employed for constant-amplitude cyclic loading, and the other which sums the initiation and propagation lives each as governed by a spectral load distribution. These two criteria are compared, and existing gaps which need to be closed to elevate the confidence in the criteria are pointed out.

scholarly journals Subcritical crack growth parameters in glass as a function of environmental conditions

2020 ◽  
Author(s):  
Christopher Brokmann ◽  
Stefan Kolling ◽  
Jens Schneider
Keyword(s):  
Crack Growth ◽  
Environmental Conditions ◽  
Subcritical Crack Growth ◽  
Growth Parameters ◽  
Crack Depth ◽  
Indentation Test ◽  
Soda Lime ◽  
Initial Crack ◽  
Chemical Compositions ◽  
Critical Crack

Abstract In the present work, subcritical crack growth in soda–lime silicate glass is investigated under different environmental conditions. Crack growth parameters as a function of temperature and humidity were determined by dynamic fatigue tests, which has been verified by using the in-situ method of filming crack growth during experiments. The specimens were pre-damaged for constant initial crack lengths in all specimens using the Vickers indentation test. The determined parameters were compared with those from literature in order to discuss existing deviations of sub-critical crack growth parameters in literature. These deviations may be caused by environmental conditions and different chemical compositions of the glass. Arrest lines were used to determine the ratio of crack width to crack depth in Vickers indented specimens. For the initial crack depth, images of fracture surfaces were taken using an scanning electron microscope. Furthermore, the influence of humidity and temperature on the failure stress of unindented specimens with a constant initial crack length was simulated.

Lifetime Prediction for Ceramic Gas Turbine Components

1993 ◽  
Vol 115 (1) ◽  
pp. 70-75 ◽  
Author(s):  
G. Stu¨rmer ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Gas Turbine ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Operation Time ◽  
Computer Code ◽  
Experimental Investigations ◽  
Ceramic Components ◽  
Stress States ◽  
Dependent Failure ◽  
Failure Probabilities

At the Institute for Thermal Turbomachinery, University of Karlsruhe (ITS), theoretical and experimental investigations of ceramic gas turbine components are performed. For the reliability analysis by finite element calculations the computer code CERITS has been developed. This code is used to determine the fast fracture reliability of ceramic components subjected to polyaxial stress states with reference to volumetric flaws and was presented at the 1990 IGTI Gas Turbine Conference. CERITS-L now includes subcritical crack growth. With the new code CERITS-L, failure probabilities of ceramic components can be calculated under given load situations versus time. In comparing these time-dependent failure probabilities with a given permissible failure probability, the maximum operation time of a component can be determined. The considerable influence of the subcritical crack growth upon the lifetime of ceramic components is demonstrated at the flame tube segments of the ITS ceramic combustor.

scholarly journals Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete (Vol.58, No.6)

2009 ◽  
Vol 58 (7) ◽  
pp. errata_1
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

Life Time Prediction for Ceramic Gas Turbine Components

1991 ◽  
Author(s):  
G. Stürmer ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Gas Turbine ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Operation Time ◽  
Life Time ◽  
Computer Code ◽  
Experimental Investigations ◽  
Ceramic Components ◽  
Stress States ◽  
Failure Probabilities

At the Institute for Thermal Turbomachinery, University of Karlsruhe (ITS), theoretical and experimental investigations on ceramic gas turbine components are performed. For the reliability analysis by finite element calculations the computer code CERITS has been developed. This code is used to determine the fast fracture reliability of ceramic components subjected to polyaxial stress states with reference to volumetric flaws and was presented at the 1990 IGTI Gas Turbine Conference. CERITS-L now includes subcritical crack growth. With the new code CERITS-L, failure probabilities of ceramic components can be calculated under given load situations versus time. In comparing these time dependent failure probabilities with a given permissible failure probability, the maximum operation time of a component can be determined. The considerable influence of the subcritical crack growth upon the life time of ceramic components is demonstrated at the flame tube segments of the ITS ceramic combustor.

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