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Research Papers

Elastic Brittle Damage Model of Ni-YSZ and Predicted Stress–Strain Relations as a Function of Temperature and Porosity

[+] Author and Article Information
Gulfam Iqbal1

Bruce Kang

 Mechanical and Aerospace Engineering, Department West Virginia University, Mechanical and Aerospace Engineering Building, G-70 Morgantown, WV 26506-6106Bruce.Kang@mail.wvu.edu

1

Corresponding author.

J. Fuel Cell Sci. Technol 8(5), 051002 (Jun 13, 2011) (5 pages) doi:10.1115/1.4003751 History: Received December 22, 2009; Revised February 09, 2011; Published June 13, 2011; Online June 13, 2011

Nickel-yttria stabilized zirconia (Ni-YSZ) is the most widely used material for solid oxide fuel cell (SOFC) anodes. Anode-supported SOFCs rely on the anode to provide mechanical strength to the positive–electrolyte–negative (PEN) structure. The stresses generated in the anode can result in the formation of microcracks that degrade its structural properties and electrochemical performance. In this paper, a brittle elastic damage model is developed for Ni-YSZ and implemented in finite element analysis with the help of a user-defined subroutine. The model is exploited to predict Ni-YSZ stress–strain relations at temperatures and porosities that are difficult to generate experimentally. It is observed that the anode material degradation depends on the level of strain regardless of the temperature at the same porosity: at higher temperature, lower load is required to produce a specified level of strain than at lower temperature. Conversely, the anode material degrades and fails at a lower level of strain at higher porosity at the same temperature. The information obtained from this research will be useful to establish material parameters to achieve optimal robustness of SOFC stacks.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Stress–strain relation of a brittle elastic material under uniaxial compression

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Figure 2

Strain–damage relation of high strength concrete under uniaxial stress

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Figure 3

Predicted degradation of Young’s modulus under uniaxial compression

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Figure 4

Predicted stress–strain curve of Ni-YSZ at room temperature

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Figure 5

Predicted stress–strain curves of Ni-YSZ at (a) room temperature and (b) 1073 K, as a function of porosity

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Figure 6

Predicted stress–strain curves of Ni-YSZ at p = 30% as a function of temperature

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