Abstract: A new approach is provided to study the growth problems of mode Ⅰand modeⅠ-Ⅱmixed cracks,Split Hopkinson Pressure Bar(SHPB)is used to impact the PMMA USH(Unilateral semicircular hole)specimen containing precast crack. Results of mode Ⅰ cracks and mode Ⅰ-Ⅱmixed cracks are obtained. At the same time,dynamic caustics experiment is used to study the time history of crack growth and the change law of dynamic stress intensity factor at the crack growth tip. Numerical simulation of the test process is performed by using ABAQUS software to study its expansion path. The results show that the mode I and modeⅠ-Ⅱmixed crack trajectories obtained through experiments and the results of numerical simulation are basically similar,which proves the feasibility of using numerical methods to simulate the crack propagation. During the propagation of two types of cracks,the crack tip will be stopped for some time,but they will eventually move towards the central axis of the test piece. Using SHPB test and dynamic caustics experiment with a Unilateral semicircular hole specimen
can effectively obtain the mode Ⅰand modeⅠ-Ⅱmixed cracks,providing ideas for subsequent researches on crack propagation.