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

Abstract

The SCARE (S tructural C eramics A nalysis and R eliability E valuation) 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.