Application of crystal plasticity to plastic behavior at notched plate and crack propagation

Strain concentration characteristics of ductile polycrystalline materials are studied experimentally and numerically by considering a notched square segment of material. The micromechanical modeling is performed using the finite element method based on crystal plasticity, while the material sample is taken to be FCC polycrystallline copper segment. The constitutive behavior is taken to be large-strain strain-rate-dependent elastic–plastic material. To effectively simulate polycrystalline behavior, the grain shape is generated from Voronoi tessellation, bearing a different lattice orientation in each grain. Strain concentration patterns around the notched bottom are observed experimentally and numerically, which are enlarged near the notch by accompanying a formation of localized strain accumulation toward an oblique direction. For the sample analyzed, with a relatively small macroscopic strain of 0.10, the notched bottom region experiences plastic strains as large as 1.00, and provides a strong indication that failure will initiate from the corner. Implications of this modeling study to microcracking failure are discussed by considering two fundamental modes of shear and cleavage to provide plausible microcracking examples.