Lifetime Prediction for Ceramic Gas Turbine Components

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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Structural Analysis and Life Prediction for Ceramic Gas Turbine Components for the Mercedes-Benz Research Car 2000

Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery ◽

10.1115/86-gt-199 ◽

1986 ◽

Cited By ~ 7

Author(s):

H. Hempel ◽

H. Wiest

Keyword(s):

Gas Turbine ◽

Life Prediction ◽

Subcritical Crack Growth ◽

Time Dependent ◽

Relative Importance ◽

3 Dimensional ◽

Ceramic Components ◽

Dimensional Finite Element ◽

Ceramic Design ◽

Load Conditions

The paper considers the design and the application of ceramic components in a high temperature gas turbine, which is being developed as an alternative for passenger-car propulsion. Silicon nitride turbine wheels were analyzed using 3-dimensional finite element methods. Calculations of temperatures and stresses were carried out for several steady-state and transient load conditions. Time dependent reliability was also computed using the theory of Weibull including subcritical crack growth. The results of these calculations are presented and discussed. The basic theory for ceramic life prediction methodology is reviewed, including the relative importance of various parameters. From the results, conclusions are derived for ceramic design. Finally some operating-experiences of ceramic turbine wheels are reported.

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Effect of Environment and Multiaxial Stress States on Subcritical Crack Growth of Machinable Ceramics.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ◽

10.1299/kikaia.59.319 ◽

1993 ◽

Vol 59 (558) ◽

pp. 319-324

Author(s):

Kiyohiko Ikeda ◽

Toshiya Suzuki ◽

Minoru Tamiaki ◽

Yoshinobu Tanigawa ◽

Hisashi Igaki

Keyword(s):

Crack Growth ◽

Subcritical Crack Growth ◽

Multiaxial Stress ◽

Stress States

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

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award ◽

10.1115/95-gt-236 ◽

1995 ◽

Cited By ~ 2

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.

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Effect of environment and polyaxial stress states on subcritical crack growth in soda-lime glass. Examination based on constant stressing rate technique.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ◽

10.1299/kikaia.55.129 ◽

1989 ◽

Vol 55 (509) ◽

pp. 129-133 ◽

Cited By ~ 2

Author(s):

Kiyohiko IKEDA ◽

Hisashi IGAKI ◽

Koichiro TAGASHIRA

Keyword(s):

Crack Growth ◽

Subcritical Crack Growth ◽

Soda Lime ◽

Soda Lime Glass ◽

Stress States ◽

Stressing Rate

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Effect of environment and polyaxial stress states on subcritical crack growth in glass ceramics.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A ◽

10.1299/kikaia.56.1116 ◽

1990 ◽

Vol 56 (525) ◽

pp. 1116-1122

Author(s):

Kiyohiko IKEDA ◽

Hisashi IGAKI ◽

Yoshinobu TANIGAWA ◽

Koichiro TAGASHIRA

Keyword(s):

Crack Growth ◽

Subcritical Crack Growth ◽

Glass Ceramics ◽

Stress States

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

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2816583 ◽

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.

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Examination of Fracture Interfaces in Silicon Nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113925 ◽

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.

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