Surface Flaw Reliability Analysis of Ceramic Components With the SCARE Finite Element Postprocessor Program

Abstract

The SCARE (Structural Ceramics Analysis and Reliability Evaluation) computer program on statistical fast fracture reliability analysis with quadratic elements for volume-distributed imperfections is enhanced to include the use of linear finite elements and the capability of designing against concurrent surface flaw-induced ceramic component failure. The SCARE code is presently coupled as a postprocessor to the MSC/NASTRAN general purpose, finite element analysis program. The improved version now includes the Weibull and Batdorf statistical failure theories for both surface and volume flaw-based reliability analysis. The program uses the two-parameter Weibull fracture strength cumulative failure probability distribution model with the principle of independent action for polyaxial stress states, and Batdorf’s shear-sensitive as well as shear-insensitive statistical theories. The shear-sensitive surface crack configurations include the Griffith crack and Griffith notch geometries, using the total critical coplanar strain energy release rate criterion to predict mixed-mode fracture. Weibull material parameters based on both surface and volume flaw-induced fracture can also be calculated from modulus of rupture bar tests, using the least-squares method with known specimen geometry and grouped fracture data. The surface flaw reliability prediction uses MSC/NASTRAN stress, temperature, and external boundary area output, obtained from the use of linear or quadratic shell and three-dimensional isoparametric finite elements. The statistical fast fracture theories for surface flaw-induced failure, along with selected input and output formats and options, are summarized. A sample problem to demonstrate various features of the program is included.