National Repository of Grey Literature 3 records found  Search took 0.00 seconds. 
Růst krátkých trhlin ve feriticko-perliticko-bainitické oceli
Polák, Jaroslav
The initiation and the growth of short cracks were studied in ferritic-pearlitic-bainitic steel. Short cracks initiate preferably in persistent slip markings in areas of proeutectoid ferrite. The kinetics of short crack growth is characterized by exponential growth. Crack growth coefficient was found to be a function of plastic strain amplitude. The comparison of the short crack growth kinetics with Coffin-Manson law allows determining the parameters of the short crack growth law from the low cycle fatigue experiments
Růst krátkých trhlin z vrubů ve dvoufázové austenitcko-feritické oceli
Kotecký, Ondřej ; Degallaix, S. ; Polák, Jaroslav
The effect of microstructure and stress gradient in a two-phase austenitic-ferritic steel in specimens with confined plasticity is studied. Direct optical observations and potential drop technique calibrated via the finite element method are used to measure the surface crack size and its depth and to determine the surface crack growth. The effect of stress and strain gradients on the crack propagation kinetics and crack shape is evaluated and dicussed.
Kinetics of fatigue crack growth under notches in duplex steel
Kotecký, Ondřej ; Degallaix, S. ; Polák, Jaroslav
While under elastic fatigue loading of structural components with a stress concentration the material response is quite well known and the predictions are accurate, under elastic-plastic fatigue loading the predictions are poor and result in over-dimensioning the structure. The present work studies the effect of the stress gradient and the microstructure in an austenitic-ferritic (or duplex) 2507 stainless steel. Fatigue tests were performed on double edge notched specimens. Direct optical observations and potential drop technique calibrated via the finite element method are used to measure the surface crack size and its depth and to determine the in-depth and surface crack growth. The effect of stress and strain gradients on the crack propagation kinetics is evaluated and discussed.

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