Abstract
To design and evaluate the analytical crack propagation of a specimen under dynamic load, measurement of dynamic fracture parameters is necessary. However, analytical methods have significant complexity, and experimental methods are also time-consuming that require high precision and considerable funding. Therefore, numerical methods can be used to solve these problems. The Extended Finite Element Method (X-FEM) as a powerful and efficient tool can be used for this purpose. In this paper, X-FEM code in ABAQUS software was used in order to simulate crack growth in a semi-circular specimen with pre-existed crack and also intact specimen to determine dynamic stress intensity factor (DSIF) using displacement extrapolation method. To verify the numerical modeling output, the curve of crack surface opening displacement (CSOD) in X-FEM model has been compared with the experimental curve. Moreover, concrete damage plastic (CDP) model was used to validate X-FEM simulation results. The results show that the DSIF for a cracked sample under a maximum dynamic load 3000 N is equal to 0.5 Mpa . Comparison between the CDP and X-FEM results showed that in both approaches, the same area for crack propagation was also determined.
Highlights
I n most civil or mining projects such as blasting, road tunnels excavation, flying rocks and support systems, the type of the forces applied are dynamic
While a dynamic load distribution model increases the level of complexity and the existing analytical solutions are mainly suitable for simple problems, numerical modeling is considered as a suitable tool for solving these problems
There are a variety of numerical methods for cracking process modeling such as NMM (Numerical Manifold Method) [2], DDA (Discontinuous Deformation Analysis) [3], BEM (Boundary Element Method) [ 4], RFPA (Rock Failure Process Analysis) [5], PFC (Particle Flaw Code) [6], X-FEM [7, 8], and several other in-house codes based on the LEFM Criteria [9]
Summary
I n most civil or mining projects such as blasting, road tunnels excavation, flying rocks and support systems, the type of the forces applied are dynamic. The ISRM has proposed two standard methods for determining static fracture toughness in rocks They suggest that core-based prototypes experiments be performed on a typical laboratory compression or tension load frame [16]. The benefits of semi-circular sample (SCB) instead of CB (Chevron Bend), SR (Short Rod) & CCNBD (Crack Chevron Notched Brazilian Disc) in determining of static fracture toughness are the low requirement of material per each specimen (for meeting the requirements in linear elastic fracture mechanics (LEFM)), simple test setup, and the synchronization of the maximum compressive load with initiation cracking[16]. The maximum principal stress failure criterion is selected for damage initiation and an energy-based damage evolution law based on a power-law fracture criterion is chosen for damage propagation These criteria have been described in the previous section. The impact loads applied to the specimen are shown in (Fig. 2)
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