Issue 33

M. Sakane et alii, Frattura ed Integrità Strutturale, 33 (2015) 319-334; DOI: 10.3221/IGF-ESIS.33.36 331 different sections of the columnar grains; the left is the normal section to columnar axes and the right is the parallel section of them. In Case 7, the maximum shear strain direction changed its direction, so that dislocations would easily rearranged to columnar structure by the cross slips. Figure 17 : Correlation of multiaxial LCF lives with maximum principal stress. Figure 18 : Microstructure observed TEM for typical loading paths. Cases 5-10 all have the same maximum shear strain ranges. Cases 8-10 have a rectangular or box strain history. In these strain paths, the maximum shear strain direction rotates continuously, so that many slip systems operate. The additional hardening was most significant in these strain paths. Cases 11-13 are also rectangular strain paths but the phasing of the strain is such that the maximum shear strain range is smaller than Cases 5-10. In Case 9, Fig. 18 (g), cell boundaries are not clear, but many dislocations exist even in the cells. The maximum shear stress direction rotates continuously in Case 9, so many slip planes operate and interact, which results in the significant additional hardening.