Probabilistic fracture mechanics

Bloom, J. M. (ed.) 1983 Probabilistic Fracture Mechanics and Fatigue Methods Applications for Structural Design and Maintenance. American Society for Testing and Materials. 

Both deterministic and probabilistic fracture mechanics methodologies are being development for the integrity assessment of flawed or cracked structure. 

Probabilistic fracture mechanics risk analysis of reactor pressure vessel (RPV) integrity... 

Key words reactor pressure vessel integrity, probabilistic fracture mechanics, risk-based safety goals, through-wall cracking frequency. 

The event frequencies and conditional failure probabilities used to evaluate vessel integrity in the USA are distributions. Probabilistic fracture mechanics computations generate distributions of conditional probability of initial flaw extension (CPI) and conditional probability of vessel failure (CPF) for each transient event and a number of statistically sampled trial pressure vessels. The CPF distributions and the frequency distributions for each transient event are combined to generate a TWCF distribution for the population of trial vessels and events. The individual TWCF values in the distribution are ... 

The sequences of events that may lead to vessel failure and their frequencies are determined from probabilistic risk assessment (PRA) analyses. The pressure, temperature and heat transfer coefficient time histories at the vessel inner surface are determined from thermal hydraulic analyses for the events identified by the PRA analyses. These time histories are used together with probabilistic fracture mechanics (PFM) analysis to calculate the conditional probability of RPV failure. Discussion of the methodology used to perform the PRA analyses and define the transient events and associated frequencies, and the thermal hydraulic analyses used to define the event pressure and temperature time histories are outside the scope of this chapter. Consequently, the remainder of this chapter focuses on the PFM evaluation assumptions and procedures. 

This section presents some example calculations and results from licensing criteria and ASME Code guidelines that have been developed using risk-based safety goals and probabilistic fracture mechanics computational... 

Probabilistic fracture mechanics risk analysis 389 Table 12.2 Vessel dimensions and material RTndj... 

Probabilistic fracture mechanics risk analysis 391 Table 12.3 Frequency distribution for a postulated PTS transient... 

BROCKNER, a.. Numerical Methods in Probabilistic Fracture Mechanics, Primarbericht, Kernforschungszentrum Karlsruhe, June 1985. 

The statistics of test results and measured data might be critical to part reliability analysis in machine design and reverse engineering. In some cases the method of probabilistic fracture mechanics along with the statistical data is preferred over deterministic fracture mechanics in failure prevention analysis. However, a simple average value, that is, 250 mm for the shaft length in the above example, is usually sufficient in most calculations... 

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