3D atomistic simulation of fatigue behaviour of cracked single crystal of bcc iron loaded in mode III

We present new results of 3D molecular dynamic (MD) simulations of a mechanical behaviour of an edge crack (1¯10) [1 1 0] (crack plane/crack front) in a single crystal of bcc iron cyclically loaded in mode III at room temperature. Our previous 3D molecular dynamic simulations showed that this crack under monotonic uniaxial tension loading in mode I emitted blunting dislocations in the inclined 〈11¯1〉{1¯12} slip systems and it was stable up to very high loads, in qualitative agreement with experiments and continuum predictions. Our question is how the cyclic loading in mode III changes the crack behaviour and its stability. The paper also brings information on how the distribution of external forces in mode III influences the fatigue crack behaviour and how the defects generated by the crack can produce experimentally observed advances of the crack front in local modes I, II, I + II and II + III.

► 3D molecular dynamic simulations of crack growth in the iron single crystal. ► Crystal with (1¯10)[110] edge crack is loaded cyclically in mode III. ► Value of crack growth threshold ΔKIIIth lies below mode I threshold. ► Crack emits dislocations in oblique systems 〈111〉{112¯}, 〈111¯〉{011} and 〈111¯〉{123}. ► Plastic failure along the crack front occurs in mixed modes II + III and I + II.