THE EFFECTS OF LATTICE ORIENTATION AND PROXIMITY TO A GRAIN BOUNDARY ON MICROSTRUCTURALLY SHORT CRACKS IN 316L STEEL

The paper presents a finite element crystal plasticity model for microstructurally short cracks. The model is 2D plane strain and consists of 212 randomly shaped and sized grains with different crystallographic orientations. A stationary crack at an angle of 135o is then introduced to a surface grain and the model is monotonically loaded to a macroscopic equivalent strain of 1.45%. The crack tip opening (CTOD) and sliding (CTSD) displacements are then calculated for different crystal orientations in the crack-containing and surrounding grains. The results show that by rotating the crystallographic orientation of a crack-containing grain the CTOD value may vary by a factor of 1.73 and the CTSD by a factor of 1.26. A similar, albeit smaller, effect is observed when the crystallographic orientations of surrounding grains are rotated. Finally, the effect of the vicinity of the crack tip to the grain boundary is studied. No significant decrease in the CTOD/CTSD values is observed if the CTOD/CTSD values are calculated at a distance of 15 % of the average grain size. As the distance is changed to 2.5 % of the average grain size, the CTOD values decrease by 25%.