scholarly journals Phase Field Modeling of Anisotropic Tension Failure of Rock-Like Materials

2021 ◽  
Vol 9 ◽  
Author(s):  
Susheng Wang ◽  
Jiuchang Zhang ◽  
Lunyang Zhao ◽  
Wanlu Zhang

The tensile fracture is a widespread feature in rock excavation engineering, such as spalling around an opened tunnel. The phase field method (PFD) is a non-local theory to effectively simulate the quasi-brittle fracture of materials, especially for the propagation of a tensile crack. This work is dedicated to study the tensile failure characteristics of rock-like materials by the PFD simulation of the Brazilian test of the intact and fissure disk samples. The numerical results indicate that the tensile strength of the disk sample is anisotropic due to the influence of pre-existing cracks. The peak load decreases at first and then increases with the increase of the inclination angle, following the U-shaped trend. The simulation results also indicate that the wing crack growth is the main failure characteristic. Moreover, the crack propagation path initiates at the tip of the pre-existing crack when the inclination angle is less than 60°. Crack propagation initiates near the tip of the pre-existing crack when the angle is 75°, and it initiates at the middle of the pre-existing crack when the angle is 90°. Finally, all cracks extend to the loading position and approximately parallel to the loading direction. This process is in agreement with the Brazilian test of pre-existing cracks in the laboratory, which can validate the effectiveness of the PFD in simulating the tensile fracture of rock-like materials. This study can provide a reference for the fracture mechanism of the surrounding rock in the underground excavation.

Author(s):  
Shuwei Zhou

The crack propagation in the Brazilian discs with multiple pre-existing notches is investigated by using a phase field method. The phase field modeling is verified by applying a direct tension test and an indirect splitting test on a Brazilian specimen with no pre-existing notches where the simulated results are in good agreement with previous numerical and experimental results. The influence of the notch number and spacing on the crack propagation in the Brazilian discs with multiple vertically and horizontally arranged notches is studied. Outer cracks initiate from the notch tips and propagate at a small angle with the vertical direction, finally coalescing with the ends of the discs. The strength of the specimen decreases as the notches increases. The Brazilian discs with horizontally arranged pre-existing notches only have outer cracks when the notch number is 1, 3, and 5 and have both outer and inner cracks for two and four notches. The peak load of the Brazilian discs with horizontally arranged notches increases as the notch spacing increases. The final crack patterns obtained by the phase field modeling are consistent with those by previous numerical simulations and experimental tests.


Author(s):  
Xunjian Hu ◽  
Xiaonan Gong ◽  
Ni Xie ◽  
Qizhi Zhu ◽  
Panpan Guo ◽  
...  

2020 ◽  
Vol 10 (16) ◽  
pp. 5513
Author(s):  
Diyuan Li ◽  
Bang Li ◽  
Zhenyu Han ◽  
Quanqi Zhu

The fracture behavior of the disc specimens in the Brazilian test is closely related to the reliability and accuracy of the experimental results. To comprehensively investigate the effect of various loading methods and rock material types on the failure mechanism of the Brazilian discs, five different rock types tested with three typical loading methods were employed in this work. The digital image correlation (DIC) method was applied to record and analyze the strain and displacement field of the specimens during the loading process. Experimental results indicate that the peak load and deformation characteristics of the Brazilian discs are strongly affected by the loading types. The Brazilian test with the Chinese standard is evidently not suitable for measuring the tensile strength of rocks, and the other two testing methods may lead to an invalid failure mode for rock materials with high stiffness and tensile to compressive strength ratio. Furthermore, it revealed that the maximum equivalent stress point of a disc specimen is co-controlled by the material stiffness and its tensile–compression ratio. The present work shows that it is necessary to select a suitable loading configuration for each rock type in the Brazilian test.


2019 ◽  
Vol 9 (6) ◽  
pp. 339-352 ◽  
Author(s):  
Xingxue Lu ◽  
Cheng Li ◽  
Ying Tie ◽  
Yuliang Hou ◽  
Chuanzeng Zhang

2009 ◽  
Vol 79-82 ◽  
pp. 1029-1033 ◽  
Author(s):  
Jia Yu ◽  
Yi Zhuo Liu ◽  
Rong Rong Shi

Unidirectional carbon fibre reinforced resin matrix composite (CFRP) with different fibre volume fraction are stretched dynamically under static load in SEM, initiation and propagation mechanism of crack is in-situ observed, and tensile fracture of specimens is also observed. The results show that: Microscopic cracks are mainly originated from fracture of fibre, numerous fibre cracks transfixion each other in form of matrix or interface cracking, and cause failure of CFRP. Microscopic crack propagation path is related to the thickness of matrix layer between fibres. Propagation of single fibre crack at interface accord with description of microscopic crack deflection criterion for fibre reinforced composite, but the crack deflection criterion cannot descript microscopic crack propagation mechanism of unidirectional CFRP effectively, because distribution discreteness of fibre and its strength are not considered.


2018 ◽  
Vol 116 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Rudy J. M. Geelen ◽  
Yingjie Liu ◽  
John E. Dolbow ◽  
Antonio Rodríguez-Ferran

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