Dynamic Crack Propagation and Fracture Behavior of Pre-cracked Specimens under Impact Loading by Split Hopkinson Pressure Bar

Abstract

Deformation and fracture of brittle materials, especially crack propagation, have drawn wide attention in recent years. But dynamic crack propagation under impact loading was not well understood. In this paper, we experimentally tested Brazilian disk (BD) fine sandstone specimens containing pre-cracks under cyclic impact loading by the Φ 74 mm diameter split Hopkinson pressure bar (SHPB) test device. The pre-cracked specimens were named central straight through crack flattened Brazilian disk (CSCFBD). By using the low air-pressure loading conditions (0.1 MPa, equal to the impact velocity of 3.76 m/s), a series of dynamic impact tests were detected successfully, and the effects of pre-cracks on dynamic properties were analyzed. Experimental results show that the multiple cracks mostly initiate at/or near the pre-crack tips and then propagate in different paths and directions varying by inclination angles, leading to the ultimate failure. Compared to static or quasi-static loading, dynamic crack propagation and fracture behavior are obviously different. Furthermore, we characterized the crack propagation paths, directions, and fracture patterns and discussed the influences of the pre-cracks during the breakage process. We concluded that the results obtained are significant in investigating the failure mechanism and mechanical properties of brittle materials under impact loading.

An analysis of impact load and fragmentation dimension to explore energy dissipation patterns in coal crushing

“…where W I , W R , and W T are the incident energy, reflected energy, and transmitted energy, respectively; σ i , σ r , and σ t are the stresses corresponding to the incident, reflected, and transmitted waves on the compression bar, respectively; ε i , ε r , and ε t are the strains corresponding to the stresses of each stress wave on the compression bar; A is the cross-sectional area of the impact bar and the output bar, (i.e., A = πr 2 , where r = 25 mm; E is the compression bar E is the elastic modulus of the material, (210 GPa); C is the wave velocity of the stress wave in (37) www.nature.com/scientificreports/ the one-dimensional state, which can be expressed as C = √ E/ρ , here ρ is the material density of the compression bar and ρ 0 = 7.8 × 10 3 kg/m 3 ; this SHPB experimental system utilizes C value of 5190 m/s.…”

“…Xie 36 ventured into examining the effects of disparate strain rates on the dynamic compression characteristics, energy dissipation, and fragmentation morphology of Basalt Fiber Reinforced Concrete (BFRC). In a foundational study grounded on Separate Hopkins Compression Rod Experiment, Wang 37 , 38 embarked on a meticulous exploration to delineate the critical aspects of energy dynamics involved in coal sample impacts, focusing on both burst-prone and non-burst-prone specimens. The comprehensive analysis encompassed the calculations of various energy parameters including incident, reflected, and transmitted energies, in addition to the scrutinizing of crushing work exerted during the impact load.…”

Experimental Investigation of the Dynamic Tensile Properties of Naturally Saturated Rocks Using the Coupled Static–Dynamic Flattened Brazilian Disc Method

“…Moreover, it is difficult to keep the clamping device and rock specimen axis coincident, which induces bending moments in the specimen and causes measurement deviation. To avoid such fatal defects in direct 2 of 18 tensile tests, some indirect methods have been proposed, and the Brazilian disc (BD) test is recommended by the International Society for Rock Mechanics (ISRM) to gauge the tensile strength of rocks [19][20][21][22][23]. For the BD testing method, the appearance of a central crack is a very eventful factor to validly calculate the tensile strength of rocks [24].…”