On fracture initiation angle near bi-material notches – Effects of first non-singular stress term

The effect of first non-singular stress term of elastic stress field near bi-material notches (I-stress) on the fracture initiation angle is investigated. A modified maximum tangential stress (MMTS) criterion is suggested for predicting the fracture initiation angles which takes into account the effect of I-stress as well as the singular terms. It is shown that the I-stress can play an important role in fracture initiation behavior adjacent the interface corners and neglecting this term may introduce significant errors in predicting the fracture initiation angle. Then, to evaluate the proposed criterion, a finite element (FE) simulation is done on a typical test specimen and the presented criterion is applied for predicting the fracture initiation direction. It was observed that the MMTS predictions are very close to the results obtained from the FE analysis (which takes into account all stress terms) showing the reasonable accuracy of the MMTS criterion for bi-material notch problems.