Multixial creep life prediction of ceramic structures using continuum damage mechanics and the finite element method

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Journal of Engineering for Gas Turbines and Power

DOI:https://doi.org/10.1115/1.2818511· OSTI ID:20006095

Jadaan, O M; Powers, L M; Gyenkenyesi, J P

High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not take into account the deteriorating state of the material due to creep damage (e.g. cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions. This creep life prediction methodology was preliminarily added to the integrated design code named Ceramics Analysis and Reliability Evaluation of Structures/Creep (CARES/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and CARES/Creep program.

• Research Organization: Univ. of Wisconsin, Platteville, WI (US)
• OSTI ID: 20006095
• Journal Information: Journal of Engineering for Gas Turbines and Power, Journal Name: Journal of Engineering for Gas Turbines and Power Journal Issue: 4 Vol. 121; ISSN JETPEZ; ISSN 0742-4795
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
36 MATERIALS SCIENCE
CERAMICS
CREEP
FINITE ELEMENT METHOD
FORECASTING
MATHEMATICAL MODELS
SERVICE LIFE
SILICON CARBIDES
SILICON NITRIDES