Further investigation for the macro-microcrack interaction I—in the infinite isotropic body

This work deals with the problems of the macro-microcrack interaction in an infinite isotropic body. On the basis of the continuously distributed edge dislocation technique and the singular integral equation method which was proved to have higher accuracy and less computation than others treated by previous researchers, the shielding or amplification effect and the so-called neutral angle are re-examined and discussed by using the criterion associated with the mode I stress intensity factor (SIF) and the strain energy release rate @ERR). It is found that there is little difference between the shielding or amplification regions and the neutral positions determined by both criteria when the mode II SIF of a macrocrack is much less than the mode I SIF, but the results from the SERR criterion are completely different from those based on the SIF criterion while the pressure acts on the microcrack, or the remote field phase angle diverges from 90” where the remote field is only dependent on mode I SIF. The simple example is that where, on the basis of the SERR criterion, the microcrack whose centre lies just above the microcrack tip does not always shield the macrocrack when considering the remote field phase angle. In fact, the results from both criteria must be considerably different where the mode II SIF is not small compared to the mode I SIF of the macrocrack, and even takes the dominant place. To some extent, the result from the SERR criterion is more convincing than that from the SIF criterion due to the fact that the SERR can fully characterize the state of the crack tip. Copyright 0 1996 Elsevier Science Ltd