Effects of notch width and loading rate on the dynamic mode II fracture toughness of Ti-6Al-4V.

• An extrapolation method is proposed to assess the DFT of the ideal cracks. • The K plane is used to illustrate the comprehensive sensitivity of the DFT to the two factors. • The influence of notch width on DFT is more pronounced than that of loading rate. • The propagation of cracks is governed by interactions between dynamic shear fracture and ASB. Existing work on size effects in the measurement of dynamic fracture toughness (DFT) has focused mainly on the overall geometric dimensions of the test specimens, while the effects of notch width and loading rate were not explored. In this paper, DFT experiments were conducted using Ti-6Al-4V alloy to study the effects of notch width effect and loading rate effect on its dynamic mode II fracture toughness. An extrapolation method is proposed to estimate the DFT of an ideal sharp crack, and the relationship between DFT, loading rate, and notch width is captured with a 3D spatial plane. Results revealed that the DFT decreases with a reduction of the notch width and increases with loading rate. The effects of notch width on DFT will be shown to be more sensitive compared to loading rate. The failure mode transitional behavior from ductile fracture to adiabatic shearing will be revealed through fractographic analysis of the microstructural evolution, which will elucidate the effects of loading rate on the failure mechanism of the material. [ABSTRACT FROM AUTHOR]