EN 843-5:2006

Foreword
1 Scope
2 Normative references
3 Terms and definitions
  3.1 Flaws
  3.2 Flaw distributions
  3.3 Mechanical evaluation
  3.4 Statistical terms
  3.5 The Weibull distribution
4 Symbols
5 Significance and use
6 Principle of calculation
  6.1 Maximum likelihood method
  6.2 Bias correction
  6.3 Confidence interval
7 Procedure
  7.1 Graphical representation of data
  7.2 Determination of Weibull parameters
      by maximum likelihood method
  7.3 Determination of limits of the confidence
      interval
8 Test report
Annex A (informative) Relationship between
        characteristic strengths of test pieces
        or components of different size or
        shape, or with different stress fields
        applied
Annex B (informative) FORTRAN program for
        calculating Weibull parameters
Annex C (informative) PASCAL program for
        calculating Weibull parameters
Annex D (informative) BASIC program for
        calculating Weibull parameters
Annex E (normative) Unbiasing factors for
        estimation of Weibull modulus, m
Annex F (normative) Confidence factors for
        characteristic strength, sigma[0]
Annex G (normative) Confidence factors for
        Weibull modulus, m
Annex H (informative) Worked examples
Annex I (informative) Example test report
Bibliography

This part of EN 843 specifies a method for statistical analysis of ceramic strength data in terms of a two-parameter Weibull distribution using a maximum likelihood estimation technique. It assumes that the data set has been obtained from a series of tests under nominally identical conditions.NOTE 1In principle, Weibull analysis is considered to be strictly valid for the case of linear elastic fracture behaviour to the point of failure, i.e. for a perfectly brittle material, and under conditions in which strength limiting flaws do not interact and in which there is only a single strength-limiting flaw population.If subcritical crack growth or creep deformation preceding fracture occurs, Weibull analysis can still be applied if the results fit a Weibull distribution, but numerical parameters may change depending on the magnitude of these effects. Since it is impossible to be certain of the degree to which subcritical crack growth or creep deformation has occurred, this European Standard permits the analysis of the general situation where crack growth or creep may have occurred, provided that it is recognized that the parameters derived from the analysis may not be the same as those derived from data with no subcritical crack growth or creep.NOTE 2This European Standard employs the same calculation procedures as method A of ISO 20501:2003, but does not provide a method for dealing with censored data (method B of ISO 20501).