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Brittle material usually contains plenty of cracks or micro‐cracks, which raises a question that how a pre‐existing crack affects a running crack as they are approaching. In order to investigate such issue, impact experiments were conducted by using double crack semi‐circle (DCSC) specimens. Polymethyl methacrylate (PMMA) was selected to make the DCSC specimens, and a modified SHPB system was used to perform the impact tests. The finite difference code AUTODYN was employed to simulate the crack propagation behavior and propagation path, and the simulated crack paths agree well with the impact test results. Meanwhile the stresses around the crack tips were analyzed and the crack propagation direction was investigated. To calculate the crack dynamic stress intensity factors (DSIFs), finite element code ABAQUS was employed. The results show that the spacing D between the vertical crack tip and the inclined crack center affects the stress distribution and fracture behavior of the vertical crack largely. As the vertical crack approaches the inclined crack, the crack speed is slow down, and tensile stress appears at the inclined crack tip. As the spacing D is small than 50 mm, the vertical crack connects with the middle area of the inclined crack. As the spacing D is 50 mm, the vertical crack connects with either the middle area or the upper tip of the inclined crack. As the spacing D is larger than 50 mm, the vertical crack coalesces with the upper crack tip. [ABSTRACT FROM AUTHOR]

Highlights • The SCESVB configuration specimen proposed in this paper has the function to arrest crack propagation. • The reflected compressive stress wave confine the outgoing crack propagation. • The angle of V-shaped bottom of SCESVB specimens has effect on crack arrest function. • Propagation toughness is not an independent concrete parameter, and it is related to crack speed. Abstract Concrete structures usually contain cracks or microcracks. Under dynamic loading, such as impacts, blasts and earthquakes, these cracks may initiate and propagate, weakening concrete strength and structure's stability. It is thus necessary to carry out the research on the crack dynamic fracture behavior and to develop crack arresting technique for cracked concrete structures under dynamic loads. In this study, impact tests were performed using a drop-weight impact device. A single crack emanating from a semicircle and a V-shaped bottom (SCESVB) specimen was proposed. The V-shaped bottom has the function of arrest on the propagation of the pre-crack. Crack propagation gauges (CPGs) were used to measure crack propagation parameters. Three angles 120°, 150° and 180° were designed for the V-shaped bottom of the SCESVB specimens. The crack propagation behavior was simulated by the finite difference code AUTODYN, and the dynamic stress intensity factor (DSIF) was calculated by the finite element code ABAQUS. The critical DSIF was determined by the crack initiation time and the propagation time measured by the CPG. The experimental and numerical simulation results show that the SCESVB specimen is suited to studying crack propagation behavior and crack arresting behavior for concrete under dynamic loads. During the crack propagation process, the crack may arrest in a short time, and the critical DSIF at initiation is higher than that at propagation for the concrete. [ABSTRACT FROM AUTHOR]