  In this study, a multi-grid sampling multi-scale (MGSMS) method is proposed
by coupling with finite element (FEM), extended finite element (XFEM) and
molecular dynamics (MD) methods.Crack is studied comprehensively from
microscopic initiations to macroscopic propagation by MGSMS method. In order to
establish the coupling relationship between macroscopic and microscopic model,
multi-grid FEM is used to transmit the macroscopic displacement boundary
conditions to the atomic model and the multi-grid XFEM is used to feedback the
microscopic crack initiations to the macroscopic model. Moreover, an image
recognition based crack extracting method is proposed to extract the crack
coordinate from the MD result files of efficiently and the Latin hypercube
sampling method is used to reduce the computational cost of MD. Numerical
results show that MGSMS method can be used to calculate micro-crack initiations
and transmit it to the macro-crack model. The crack initiation and propagation
simulation of plate under mode I loading is completed.
