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The specimen size effect on R-curve and on crack tip blunting
Mrňa, Tomáš ; Konopík,, Pavel (referee) ; Stratil, Luděk (advisor)
The thesis deals with the determination of fracture toughness using compact tension (CT) test specimens at elevated and high temperatures. The experimental material steel P91 designated for application at temperatures 550650°C was used. The fracture toughness in the ductile fracture region of the steel was characterized by the R curve, which characterises the resistance against crack propagation depending on the crack length. The effect of temperature on the R curve at range 23600°C was evaluated. Next the specimen size effect using three sizes of CT specimens at 23°C and the effect of loading rate (2, 0,2 a 0,02 mm/min) at 600°C was examined. The results showed that the temperature has distinct effect on the R-curve, which yields minimal values at 400°C. Only the smallest test specimen size with thickness 6.25mm showed the specimen size effect giving about 10% lower values of toughness comparing to larger specimens. The effect of loading rate was clearly distinguishable. The values of toughness varied about 20% of the toughness value comparing individual loading rate.
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The specimen size effect on R-curve and on crack tip blunting
Mrňa, Tomáš ; Konopík,, Pavel (referee) ; Stratil, Luděk (advisor)
The thesis deals with the determination of fracture toughness using compact tension (CT) test specimens at elevated and high temperatures. The experimental material steel P91 designated for application at temperatures 550650°C was used. The fracture toughness in the ductile fracture region of the steel was characterized by the R curve, which characterises the resistance against crack propagation depending on the crack length. The effect of temperature on the R curve at range 23600°C was evaluated. Next the specimen size effect using three sizes of CT specimens at 23°C and the effect of loading rate (2, 0,2 a 0,02 mm/min) at 600°C was examined. The results showed that the temperature has distinct effect on the R-curve, which yields minimal values at 400°C. Only the smallest test specimen size with thickness 6.25mm showed the specimen size effect giving about 10% lower values of toughness comparing to larger specimens. The effect of loading rate was clearly distinguishable. The values of toughness varied about 20% of the toughness value comparing individual loading rate.
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