1. Scope

1.1 This practice covers the evaluation and reporting of uniaxial strength data and the estimation of Weibull probability distribution parameters for advanced ceramics that fail in a brittle fashion (see Fig. 1). The estimated Weibull distribution parameters are used for statistical comparison of the relative quality of two or more test data sets and for the prediction of the probability of failure (or, alternatively, the fracture strength) for a structure of interest. In addition, this practice encourages the integration of mechanical property data and fractographic analysis.

1.2 The failure strength of advanced ceramics is treated as a continuous random variable determined by the flaw population. Typically, a number of test specimens with well-defined geometry are failed under isothermal, well-defined displacement and/or force-application conditions. The force at which each test specimen fails is recorded. The resulting failure stress data are used to obtain Weibull parameter estimates associated with the underlying flaw population distribution.

1.3 This practice is restricted to the assumption that the distribution underlying the failure strengths is the two-parameter Weibull distribution with size scaling. Furthermore, this practice is restricted to test specimens (tensile, flexural, pressurized ring, etc.) that are primarily subjected to uniaxial stress states. The practice also assumes that the flaw population is stable with time and that no slow crack growth is occurring.

1.4 The practice outlines methods to correct for bias errors in the estimated Weibull parameters and to calculate confidence bounds on those estimates from data sets where all failures originate from a single flaw population (that is, a single failure mode). In samples where failures originate from multiple independent flaw populations (for example, competing failure modes), the methods outlined in Section 9 for bias correction and confidence bounds are not applicable.

1.5 This practice includes the following:

1.6 The values stated in SI units are to be regarded as the standard per IEEE/ASTM SI 10.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

C1145 Terminology of Advanced Ceramics

C1322 Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics

E6 Terminology Relating to Methods of Mechanical Testing

E178 Practice for Dealing With Outlying Observations

E456 Terminology Relating to Quality and Statistics

IEEE/ASTM?SI?10 American National Standard for Use of the International System of Units (SI): The Modern Metric System

Keywords

advanced ceramics; censored data; confidence bounds; fractography; fracture origin; maximum likelihood; strength; unbiasing factors; Weibull characteristic strength; Weibull modulus; Weibull scale parameter; Weibull statistics;

ICS Code

ICS Number Code 81.060.99 (Other standards related to ceramics)

DOI: 10.1520/C1239-07

ASTM International is a member of CrossRef.