The Stress Field And Plastic Deformation Of Mode I Crack In Magnesium

:Magnesium and its alloys are widely used in aerospace, automotive and other industrial fields due to their low density, high specific strength, specific stiffness, good castability and shock absorption, etc. However, due to the hcp structure, the fracture toughness of magnesium is very lower. Especially when there are cracks and crack initiation in magnesium and its alloys, stress concentration at the crack tip will lead to plastic deformation and crack propagation, and finally cause a serious security problems. So it is very important for the study of the crack in magnesium.This paper is based on ABAQUS, the extended finite element method is applied to calculate the elastic stress field and the elastic strain energy density distribution at the crack tip of five different orientation type I cracks in magnesium. The calculated results are also compared with the results of molecular dynamics simulations. We aim to discuss the relation between the crack tip field and the micro structure evolution. The results indicate that the microstructure evolution at the crack tip is closely related with the elastic strain energy density distribution. The high elastic energy can be released by the plastic deformation at the crack tip. The main deformation mechanisms for the basal crack are void formation and π3twin. For the prismatic crack, the deformation mechanisms are void formation and basal slip.Furthermore, using the XFEM simulation of mode I crack, the relationship between the plastic deformation at the crack tip and the crack propagation behavior are discussed. It is found that the distribution of stress and strain energy density on the slip plane are different in the different stages of loading. There exist a stress plateau on the slip plane during the plastic deformation. Crack propagation and the plastic deformation compete with each other, and compensate each other.