| Abstract Scope |
The mechanisms of cyclic crack propagation in ductile metals have been extensively investigated for sixty years. Nevertheless, neither the proposed sketches or sophisticated simulations provided predictions in general agreement with experiments.
Then, new massive molecular dynamics simulations of cyclic propagation in inert environment were carried out, including fifteen million atoms. In fact, the specimen thickness, measured along the crack front line, was increased up to several nanometers to avoid artefacts such as cleavage/voiding. Instead, dislocations could nucleate from crack tips.
Many parameters were investigated: crack plane/front line orientations, load amplitude, temperature, stacking-fault energy (aluminum, nickel, copper, silver) & mode mixity.
Blunting-resharpening is highlighted, including slip irreversibility. The emitted dislocations are indeed more numerous than the re-absorbed ones.
In agreement with experiments, Paris laws with exponents close to four at low amplitudes are predicted, as well as weak temperature effect & strong SFE influence, reducing crack growth rates in planar metals. |