Probabilistic approach for prevention of structural failure

A high strength low alloy steel was heat treated to produce two different microstructures. Multiple precracked specimens were tested at a low temperature, and a large scatter in the fracture toughness values was observed. The scatter is attributed to the probabilistic nature of brittle fracture. Based upon the Griffith equation and the 'weakest link' theory, it is derived analytically that the fracture toughness values follow a Weibull distribution, with a Weibull modulus of 4. The experimental data were used to examine the theoretical model, which was found to be applicable only when the fracture is truly controlled by the weakest link. The weakest link theory should be used with caution, although usually it errs on the safe side in a reliability assessment.

Keywords:

• Probabilistic Model
• Weibull Distribution
• Fracture Toughness
• Structural Failure
• High Strength Low Alloy Steel