Investigator: prof. RNDr. Jaroslav Polák, DrSc., dr. h. c.
Number of Project: 101/07/1500
Agency: Czech Science Foundation
Duration: 01. 01. 2007 - 31. 12. 2009

Existing methods for life prediction of components are often not reliable and high safety factors must be used.
Recent research into fatigue damage of structural materials revealed new possibilities to evaluate the fatigue
life based not only on the stress amplitude but on the plastic strain amplitude. It is important to use a
differential characteristic, the growth rate of short cracks Within a proposed project new findings concerning
the effect of plastic strain amplitude and mean stress will be obtained. The rates of short cracks will be
measured and the kinetics of short crack growth for various values of plastic strain amplitudes and mean
stresses will be established. Simultaneously the fatigue life of smooth specimens cycled with various plastic
strain amplitudes and mean stresses will be determined and correlated with the rates of short crack in order to
propose more simple evaluation of relevant parameters.

WEIDNER A, MAN J, TIRSCHLER W, KLAPETEK P, BLOCHWITZ C, POLÁK J, SKROTZKI W: The half-cycle slip activity of persistent slip bands at different stages of fatigue life of cyclically strained polycrystalline nickel. Mater. Sci. Eng. A 492 (2008) 118–127.

MAN J, OBRTLÍK K, POLÁK J: Extrusions and intrusions in fatigued metals. Part 1. State of the art and history. Phil. Mag. 89 (2009) 1295–1336.

MAN J, KLAPETEK P, MAN O, WEIDNER A, OBRTLÍK K, POLÁK J: Extrusions and intrusions in fatigued metals. Part 2. AFM and EBSD study of the early growth of extrusions and intrusions in 316L steel fatigued at room temperature. Phil. Mag. 89 (2009) 1337–1372.

ZAPLETAL J, VĚCHET S, KOHOUT J, OBRTLÍK K: Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit. Strength of Materials 40 (2008) 32–35.

POLÁK J, MAN J, VYSTAVĚL T, ZOUHAR L: Fatigue crack initiation in crystalline materials – experimental evidence and models. Key Eng. Mater. 345–346 (2007) 379–382.

KOTECKÝ O, DEGALLAIX S, POLÁK J: Growth of short fatigue cracks emanating from notches in an austenitic-ferritic stainless steel. Key Eng. Mater. 348–349 (2007) 117–120.

POLÁK J, SAUZAY M: Growth of extrusions in localized cyclic plastic straining. Mater. Sci. Eng. A 500 (2009) 122–129.

POLÁK J, MAN J, VYSTAVĚL T, PETRENEC M: The shape of extrusions and intrusions and initiation of stage I fatigue cracks. Mater. Sci. Eng. A 517 (2009) 204–211.

POLÁK J, PETRENEC M, KRUML T: Cyclic plastic response and fatigue life in superduplex 2507 stainless steel. Int. J. Fatigue 32 (2010) 279–287.