Chapter 49. Welfep: Results from a Round Robin for Weakest-Link Finite Element Postprocessors

  1. John B. Wachtman Jr.
  1. L. Dortmans

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314180.ch49

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

How to Cite

Dortmans, L. (1993) Welfep: Results from a Round Robin for Weakest-Link Finite Element Postprocessors, in Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314180.ch49

Author Information

  1. Centre for Technical Ceramics, P.O. Box 595, 5600 AN Eindhoven, The Netherlands

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780470375266

Online ISBN: 9780470314180

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Keywords:

  • theoretically;
  • experimentally;
  • characterization;
  • probability;
  • questionnaire

Summary

In recent years the description and prediction of the mechanical behavior of modern ceramic materials have been subjects of a number of analyses. Brittle fracture and slow crack growth have been analyzed both experimentally and theoretically with the Weibull statistic distribution used to model the statistical strength distribution of these materials. Experimental data are gathered from a variety of test methods for material characterization and design purposes. Various methods have been proposed to transfer data from one test to another or to use these test data to make strength predictions for more complicated situations that give rise to multiaxial stress systems. To use these mathematical models in a complex body it is usually necessary to use a finite element program. The mathematical models for the failure probability require an integral of stress over a volume or surface, and for this purpose a number of postprocessors have been developed to allow data from the finite element program to be used to evaluate the failure probability.

In 1990, an informal working group was formed to discuss these postprocessors, which in 1991 became part of Technical Committee 6 “Technical Ceramics” of the European Structural Integrity Society. The working group was named WELFEP, which stands for Weakest-Link Failure Probability Prediction By Finite Element Postprocessors and initially focused on two topics: gathering information on the design and structure of the various postprocessors by means of a questionnaire, and comparison of predictions of the postprocessors for a number of selected problems (numerical round robin).

An evaluation has been made of the features and results for selected problems of a number of postprocessors. From the results of the round robin calculations, an indication about the differences between various postprocessors can be obtained. Caution is necessary if there are steep stress gradients and/or high Weibull moduli; in these cases a finer mesh may be required. The need for a standardized notation of the failure probability relation has become clear as the different programs contain a different interpretation of the scale factor.