A novel method to determine the mixed mode (I/III) dynamic fracture initiation toughness of materials

Abstract

A novel hybrid experimental-numerical approach is proposed to determine the mixed-mode (I/III) dynamic fracture initiation toughness of engineering materials. To demonstrate the methodology, cylindrical aluminum alloy specimens with V-notch spiral cracks on the surface at spiral inclined angles of $${\beta _{sp}=0}^{\circ }, {11.25}^{\circ }, {22.5}^{\circ }, {33.75}^{\circ }$$ and $${45}^{\circ }$$ are subjected to dynamic torsion load using a torsional Hopkinson bar apparatus. The torque applied at the onset of fracture is measured through strain gages attached to the incident and transmitter bars. Stereo digital image correlation (StereoDIC) is performed to measure the full field deformation and crack mouth opening displacement (CMOD) as a function of loading time. Results are used to estimate the crack initiation time. The dynamic stress intensity factors are extracted numerically based on the dynamic interaction integral method using ABAQUS. The mode-I $$ {(K}_{Id})$$, mode-III $$(K_{IIId})$$, and mixed-Mode ($$K_{(I/III)d})$$ dynamic initiation toughness data as a function of spiral angles are presented and discussed.