Dynamic Propagation of a Kinked or Bifurcated Crack in Antiplane Strain

1982 ◽  
Vol 49 (2) ◽  
pp. 371-376 ◽  
Author(s):  
P. Burgers
Keyword(s):  
Constant Velocity ◽  
Crack Tip ◽  
Crack Initiation And Propagation ◽  
Crack Line ◽  
Kinked Crack ◽  
Dynamic Propagation ◽  
Straight Line ◽  
Initiation And Propagation ◽  
Cauchy Singular Integral ◽  
Cauchy Singular Integral Equation

An initially unloaded, semi-infinite, stationary crack is assumed to kink or bifurcate at time t=0 and the new crack tip(s) propagate out along a straight line at a constant velocity vCT. A Green’s function, consisting of a dislocation whose Burgers vector is growing linearly with time, that is suddenly emitted from the tip of a stress-free semi-infinite crack and propagates out along the kinked crack line at constant velocity u, is used to form a Cauchy singular integral equation. This equation is solved using standard numerical techniques and the stress-intensity factor is obtained as a function of crack-tip speed vCT and kink angle δ. The bifurcation case is treated in a similar manner. Finally, some conclusions concerning crack initiation and propagation are drawn.

On the Topology Update of the Numerical Manifold Method for Multiple Crack Propagation

2021 ◽  
pp. 2150030
Author(s):  
Jun He ◽  
Shuling Huang ◽  
Xiuli Ding ◽  
Yuting Zhang ◽  
Dengxue Liu
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Numerical Method ◽  
Crack Tip ◽  
Search Method ◽  
Numerical Manifold Method ◽  
Crack Initiation And Propagation ◽  
Multiple Crack ◽  
Initiation And Propagation ◽  
Numerical Manifold

Crack initiation and propagation are the two key issues of concern in the geotechnical engineering. In this study, the numerical manifold method (NMM) is applied to simulate crack propagation and the topology update of the NMM for multiple crack propagation is studied. The crack-tip asymptotic interpolation function is incorporated into the NMM to increase the accuracy of the crack-tip stress field. In addition, the Mohr-Coulomb criterion with tensile cut off is adopted to be the crack propagation criterion to judge the direction of crack initiation and propagation. Then a crack tip searching method is developed to automatically update the position of the crack tips. The inapplicability of the original loop search method in the NMM is also illustrated and a novel loop search method based on manifold elements is developed for physical loop updating. Moreover, methods for the manifold element updating and physical cover updating are provided. Based on the above study, the developed numerical method is capable to simulate multiple crack propagation. At last, typical rock rupture problems are numerically simulated to manifest the effectiveness of the developed numerical method.

scholarly journals First Steps of Crack Initiation and Propagation in Fatigue of FCC Crystals Studied by Dislocation Dynamics

2012 ◽  
Author(s):  
C. Déprés ◽  
G. V. Prasad Reddy ◽  
L. Tabourot ◽  
R. Sandhya ◽  
S. Sankaran
Keyword(s):  
Stress Field ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Crack Tip ◽  
Dislocation Dynamics ◽  
Crack Initiation And Propagation ◽  
Dislocation Dynamic ◽  
Discrete Dislocation ◽  
Initiation And Propagation

3D discrete dislocation dynamic (DDD) simulations are performed to simulate stage-I fatigue crack initiation and propagation along the surface, in the primary grain and its neighbouring grain, in 316L stainless steel. The scenario of crack propagation in primary grain and the evolution of dislocation structure ahead of crack tip are discussed, and in addition crack tip sliding displacement is estimated. Probable mechanisms of crack propagation from primary grain to neighbouring grain are evaluated. In this process, surface relief in the neighbouring-grain under the influence of crack stress field in the primary grain is studied for varying neighbouring-grain orientations. An enhanced evolution of surface extrusions in the neighbouring grain, are observed in the presence of heterogeneous stress field (i.e., in the presence of crack in the primary grain), compared to that in the case of homogeneous stress field. In addition, influence of crack stress field on prior cyclic-deformed substructure is presented.

Local Crack-Tip Strain Concept for Fatigue Crack Initiation and Propagation

1987 ◽  
Vol 109 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Heihachi Shimada ◽  
Yasubumi Furuya
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Notch Root ◽  
Fatigue Crack Initiation ◽  
Crack Tip ◽  
Local Strain ◽  
Strain History ◽  
Crack Initiation And Propagation ◽  
Fine Grid ◽  
Initiation And Propagation

The existence of the unified local strain field where we can substantially combine the two fatigue stages, crack initiation and propagation, was experimentally confirmed. Using the fine-grid-method, the changes of local notch-root or crack-tip strain and these histories were investigated until the small elemental block of material was broken by crack initiation and propagation. It became clear that the crack-tip strain behavior and its fracture process showed the similarity with local strain damage accumulation on crack initiation process. Especially, when the local strain history in the “elemental size, ρ*” adjacent to the crack-tip was taken into account, very good agreement of two stages could be obtained, ρ* depended on the kind of material. Based on this result, we have proposed a new idea termed “local crack-tip strain concept” that has the possibility for more simple, one parameter approach for future fatigue life analysis. It qualitatively differs from the currently used macroscopic, two parameters approach by combining the gross-strain (Δεtotal) fatigue life curve and fracture mechanics parameter (ΔK).

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