Princip koncepce Master křivky, její určování a aplikace

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Conception principle of the Master curve, its specifi cation and application
Mechanical characteristics of ferritic steels are dependent on the temperature and strain rate. From the fracture mechanics viewpoint the most important characteristic is the fracture toughness. The Wallin’s concept [1] of the temperature dependence of the fracture toughness in the transition and lower shelf region, where the micromechanism of the initiation of the unstable fracture is cleavage, is presented. The resulting relation makes it possible to calculate the fracture toughness as dependent on temperature, specimen size and given cumulative probability of the fracture Pf. After setting into the resulting equation the value of Pf = 0,5 and specimen size (thickness) B = 25 mm the relation for Master curve is obtained The infl uence of loading rate on transition temperature is also pointed out. Application of Master curve concept is presented together with the philosophy of the fi ctive defect and also European projects Sintap (Structural INTegrity Assessment Procedure) [2] and Fitnet Fitness-for-Service Procedure [3]. Such approaches can be used at the design stage to provide assurance for new structures and at the operational phase to provide assurance throughout the life of the structure.

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• Ing. Jurášek Ladislav Ph.D.
• Doc. Ing. Holzmann Miloslav CSc.