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Holes have an important influence on dynamic fracture process of brittle materials. In this paper, the influence of the hole offset distance (HOD) on the movement process of the explosive crack is studied. Polymethyl methacrylate (PMMA) is used as the experimental material, and different HOD holes are drilled on the PMMA plate. A new digital laser dynamic caustics system is employed to observe the crack tip dynamic stress intensity factor and crack growth velocity of PMMA plates with different HODs under explosive loading. The results indicate that holes reduce the peak velocity of explosive crack propagation. Moreover, the interaction between the stress wave reflected by the hole and the explosion stress wave is the main cause of crack deflection. Lastly, as the HOD increases, the crack motion trajectory is weakened by the interference of the holes, which gradually decreases corresponding stress intensity factors. With the increase of HOD/d, the crack arrest effect of empty hole decreases gradually.

Using polymethyl methacrylate (PMMA) as the test material, three-point bending tests were carried out on single hole and double hole specimens with prefabricated cracks at the bottom. The fracture ...

In order to study the crack propagation characteristics of the V-shaped energy-storage package at different angles, a new numerical laser caustics test system was used to observe the fracture process of the V-shaped energy-concentrating charge package, the mechanical distribution mechanism around the blast hole of the energy-accumulating charge package is analyzed, and using fractal theory to evaluate the damage degree of the energy-accumulating medicine package. Series of caustics test results show, the main crack has a longer expansion length in the energy-concentrating direction, and the crack expansion length is shorter in the non-energy-concentrating direction, the fractal results of the shaped charge pack show that as the angle of the shaped charge pack increases, the fractal dimension of the binarized picture of the shaped charge pack gradually becomes smaller, and the crack propagation complexity becomes lower and lower, and the main crack is along the energy gathering direction The directivity is becoming less and less obvious, When the energy gathering angle is 120°, the main crack propagation process is similar to that of the circular charge (control group).

A dynamic caustics test system was used, and different moving cracks were analysed to study the interaction between the crack growth rate, stress intensity factor, and curvature of the elliptical end of a moving crack under impact loading. Based on the linear elastic fracture mechanics theory, linearly fitting of the crack tip stress intensity factor and the elliptical curvature were employed to obtain the specific functional expressions. ABAQUS software was used to numerically simulate the moving crack fracture process passing through different elliptical curvatures. The crack tip stress intensity factor was calculated by the stress extrapolation method. The stress intensity factor obtained from the numerical calculation and the caustics test was consistent. The test and numerical simulation results showed that the direction of moving cracks entering and passing through the elliptical defects shows a certain regularity. As the ellipse curvature increased, the moving crack stress intensity factor passing through the ellipse gradually decreased, and the moving crack also passed easily through oval defects.

In this paper, the crack propagation behavior of a polymethyl methacrylate plate with double holes under explosive load is investigated. The propagation process of the explosion crack is recorded using a new digital laser dynamic caustics system, in which a high-speed camera and the explosion loading are employed. Firstly, the interaction process between the explosion stress wave and the empty hole reflected stress wave is analyzed using caustics. Moreover, the deflection law of the explosion crack is discussed. Secondly, the relationship between the propagation distance, velocity, stress intensity factor of the explosion crack tip, and the distance between the two holes is analyzed. Finally, the explosion process is analyzed using numerical simulations. It is concluded that the evolution law of the explosion stress wave in during the simulation process is similar to the caustics diagram. Lastly, the time-varying law of the stress between the double holes is obtained.