Study on Fracture Mode Mixity Under Impact Loading Based on SHTB

Mode mixity plays an essential role in the criteria of mixed mode fracture. In this paper, a novel approach for precisely controlling mode mixity under dynamic loading is proposed. Numerical simulation of all fracture mode (AFM) specimen and modified compact tension shear (MCTS) specimen loaded by split Hopkinson tension bar (SHTB) apparatus is carried out. With a constraint on MOTS specimen on the direction perpendicular to the incident bar, the dynamic stress intensity factor (DSIF) ratio of mode I to mode II remains constant during the loading process. When the constraint is absent, the DSIF ratio varies due to the vibration of clamps and specimen. The DSIF of MCTS specimen under different loading angles is also studied, and the ratio K-1/K-11 approximately equals the tangent of loading angle, which is also proven in experiments. Moreover, numerical results indicate that the influence of the shape of clamps is significantly reduced by applying a constraint on the specimen. It is concluded that AFM specimen is not suitable for dynamic fracture tests owing to over complicated clamps.