Parametric study of notch geometry in standardized chevron notched fracture test specimens for advanced ceramics

摘要

The purpose of this study was to determine the relative influences of selected geometric parameters on the resulting stress intensity factor geometry correction factor, Y, for chevron notched fracture test specimens, stable crack propagation during the test and stability of the resulting fracture process. Finite element analysis (FEA) was used to model test specimen geometries specialized in American Society for Testing and Materials (ASTM) Standard Test Method C 1421 [1]. Geometric parameters studied include notch thickness, notch corner radius, notch symmetry, notch centering, test specimen width and test specimen thickness. The results showed that the allowed notch thickness should not be increased. The assumption that the influence of the test specimen width is small is correct. The calculations showed that the eccentricity of the notch has no influence on Y. The results for the symmetry were good for the lower limits, and the difference to the ASTM values was less than two percent. The biggest differences were for the changes in the specimen height. The differences of the FEA results compared to the ASTM values were up to five percent. The study of the crack stability showed that the notch can not be modeled ideal with a sharp notch and that the importance of the crack initiation.