The Simulation Study Of Effect Of Hrdrogen On Crack Propagation Mechanism

Molecular dynamics simulation can directly present the experimental result by atomic structure geometry,thus it is possible to perform the detailed motion of atoms.Therefore molecular dynamics simulation plays an important role in the study of micro mechanism of materials.In this paper,molecular dynamics simulation was used to study the effect of hydrogen on the alpha iron crack propagation.The propagation mechanism of alpha iron crack with two different crystal orientations and different hydrogen concentration was studied.The results showed that the yield stress decreased with the increase of hydrogen concentration in these two kinds of crystal orientations models,because the introduction of hydrogen induced lattice distortion,it caused dislocation to nucleate easily.In addition,the effect of hydrogen accumulation area on crack propagation was also studied.It discovered that when the hydrogen accumulating at the front of the crack tip,these hydrogen atoms can prevent crack propagating,but the hydrogen atoms adsorbing on crack surface can promote the crack propagation.A extensive analysis was performed about the displacement trajectory of the hydrogen atom under gradient stress.In this paper,the effect of temperature and grain size on the mechanical properties of alpha iron crack with hydrogenation was also studied,it indicated that,at 100 k and 400 k alpha iron crack's flow stress is lower than at 200 K and300K,this is because of atomic activity is different under different temperatures,it results in the different degree of impeding the emission of partial dislocation by hydrogen.Finally,this paper studied the effect of grain size on the mechanical properties of alpha iron crack.