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.

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.

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

1986 ◽  
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.

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

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

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.

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

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

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.

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

Application of the Burnable Poison in the Design of Space Nuclear Reactor

2017 ◽  
Author(s):  
Wang SanBing ◽  
Xie Qilin ◽  
He ChaoHui
Keyword(s):  
Neutron Spectrum ◽  
Nuclear Reactor ◽  
Operation Time ◽  
Life Time ◽  
Stable Operation ◽  
Burnable Poison ◽  
Calculation Results ◽  
Homogeneous Reactor ◽  
In The Beginning ◽  
Criticality Safety

The previous research showed that the application of burnable poison was helpful to improve the criticality safety of space nuclear reactor (SNR). In order to analyze the worth of burnable poison in the SNR’s design, a model of homogeneous reactor had firstly been built based on the design of SAFE400. Comparing its difference with the real design of SAFE400 through criticality calculation, the precise of our model had been verified. Then the influence of the criticality parameters and immersion accident character parameters for this model had been analyzed for the application of the different burnable poisons (such as samarium, europium or gadolinium). The calculation results had shown that the application of the most of the burnable poisons would soften the neutron spectrum and induced a decrement of reactor’s keff in the beginning of life. However, the immersion accident analysis gave out another result that only the reactor using gadolinium could ensure the criticality safety of reactor after it made its initial keff equal with the design value. Meanwhile, compared with the initial design of SAFE400, in one hand, the burn-up results had shown that the decrement of homogeneous reactor’s reactivity using gadolinium as burnable poison was deceased after the 10 years full power operation; in other hand, its neutron spectrum became more softer with the operation time; and what’s more important, the amount of the burnable poison was not decreased with burn-up during its service life-time. These results implied that the application of the burnable poison (especially for gadolinium) could highly ensure the criticality safety and stable operation of SNR.

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