A new testing method for mode Ⅰ crack initiation fracture toughness under middle-low speed impacts

In this work, we proposed a specimen with a new configuration specimen, i.e.double inclined bottom central cracked specimen (DIBCC) to explore a more suitable configuration specimen for the study of the behavior of Mode Ⅰ crack under impacts, by conducting tests using a middle-low speed drop hammer impact test device, and by driving the initiation and propagation of the prefabricated crack inside the DIBCC specimens using stress waves.Meanwhile, we measured the crack initiation time using a strain gauge test system and carried out the corresponding numerical simulation using the AUTODYN finite difference code.Then we calculated the dynamic stress intensity factors and determined the initiation toughness of the specimens using the initiation time measured from the experiments.The results show that, under the action of the reflected tensile waves, the prefabricated crack surfaces have outward displacements perpendicular to the crack surface, making the prefabricated crack expand and thus induce the crack to initiate, and that the numerical result of the crack propagation path agrees well with the test result, indicating that the DIBCC configuration specimen proposed is effective and can be used to test the fracture toughness under impacts.