T-stress evaluations of mixed mode I/II fracture specimens and T-effects on mixed mode failure of aluminium

By aid of Eshelby's theoretical development, and through the use of a direct line integration procedure for the evaluation of the required path-independent integrals. T-stress calculations have been carried out on a number of mixed mode loading configurations. These involved the obliquely cracked SEN specimen, chosen as a test case, and, from the testing point of view, more suitable Arcan specimen and a version of the CTS specimen. Generally excellent agreement was found between the present results and those of previous investigators. However, results obtained under mixed-mode conditions using direct comparison of field quantities showed large discrepancies, suggesting such methods may be hazardous. A study of the T-stress term in conjunction with mixed-mode failure of aluminium 7075-T6 was also conducted. In applying the numerical results on previously reported experimental data, along with complementary experiments performed under vanishing T-stress conditions it was, however, found that the observed geometry and size dependence could not be explained by this additional term.