Study on the interference mechanism and fracture behavior of penetrating parallel double cracks

Abstract

The existence of crack groups in structures is objective and inevitable during the process of manufacture and service. In this paper, the interactions between penetrating parallel double cracks are systematically investigated through finite element methods, experimental studies and theoretical analyses, where both the brittle dominant and ductile materials are taken as the research objects. The interactions between cracks are discussed through the interference factors C based on stress intensity factor K, which is related with the relative distance between crack tips. It is found that the fracture behaviors of multiple cracks are associated with all the interference factors at four crack tips. For the alignment double crack, shielding effects at all the crack tips cause the mutually exclusive crack propagations, and then strengthen the critical load of the specimen. For offset double cracks, the inner crack extension directions are attracted to each other, the outer crack extension directions are repelling each other, the critical loads depend on the degree of the attraction or the repelling effect. There exists a relationship between the comprehensive interference factor with all the crack tips included and the loading capacity. For the specimen with multiple surface cracks, the interference effects are also related with the relative distance between crack tips, through which it can be preliminary obtained that the regulations and the effect to the fracture behaviors are similar to those of penetrating cracked specimen, which will be discussed in detail in our next findings. The interference behaviors and critical loads of multiple cracks discussed above also provide an important basis on the coalescence and evaluation of multiple cracks.