Effect of Residual Stresses on Elastoplastic Properties of SOFC by Nanoindentation Approach

Due to the differences of Young’s modulus and the mismatch of thermal expansion coefficients in the half―cell structure (NiO―YSZ/YSZ), the residual stress, which has effects on the fuel cell’s performance, is aroused during sintering . Taking the residual stress into consideration, a modified reverse analysis model was proposed to calculate the mechanical property of electrolyte thin film in SOFC. Nanoindentation tests were carried out at the points with difference distances from the interface of bilayer, the load―displacement curve was presented. The results of material’s mechanical property from experimental showed that the farther the indentation points was from the interface, the greater was the hardness of film. When the temperature related residual stress field was taken as the initial stress field to simulate the load―displacement curve under nanoindentation, it was found that the load―displacement curve was in agreement with the experiment curve if the residual stress was considered, and also the indentation morphology was much deeper and bigger under the residual stress condition.