Stress Intensity Factors for Cracks Emanating from a Notch under Shear-Mode Loading

2018 ◽  
Vol 774 ◽  
pp. 48-53
Author(s):  
Jana Horníková ◽  
Pavel Šandera ◽  
Stanislav Žák ◽  
Jaroslav Pokluda
Keyword(s):  
Stress Intensity ◽  
Critical Length ◽  
Shear Mode ◽  
Mode I ◽  
Mode Ii ◽  
Mode Iii ◽  
Loading Mode ◽  
Notch Stress ◽  
Notch Geometry ◽  
Mode Ii Loading

The influence of the notch geometry on the stress intensity factor at the front of the emanating cracks is well known for the opening loading mode. The critical length of the crack corresponding to a vanishing of the influence of the notch stress concentration can be approximately expressed by the formula aI,c = 0.5ρ(d/ρ)1/3, where d and ρ are the depth and radius of the notch, respectively. The aim of the paper was to find out if this formula could be, at least nearly, applicable also to the case of shear mode loading. The related numerical calculations for mode II and III loading were performed using the ANSYS code for various combinations of notch depths and crack lengths in a cylindrical specimen with a circumferential U-notch. The results revealed that, for mode II loading, the critical length was much higher than that predicted by the formula for mode I loading. On the other hand, the critical lengths for mode I and mode III were found to be nearly equal.

Study on Generalization of Lefort’s Approach to Critical Crack Length

2019 ◽  
Vol 827 ◽  
pp. 153-158
Author(s):  
Jana Horníková ◽  
Pavel Šandera ◽  
Stanislav Žák ◽  
Jaroslav Pokluda
Keyword(s):  
Crack Length ◽  
Critical Length ◽  
Shear Mode ◽  
Mode I ◽  
Critical Crack ◽  
Relative Level ◽  
Critical Crack Length ◽  
Transformation Procedure ◽  
Notch Stress ◽  
Analytical Formulae

The critical length aIc of a mode I crack that corresponds to a vanishing of the influence of the notch stress concentration can be approximately expressed by a formula reported by Lefort. This study aimed to generalize his approach to shear mode cracks by finding a criterion for a statistical compatibility of formulae for critical lengths of cracks. It revealed that the Lefort ́s formula describes the critical crack length aIc at which the relative level of the notch effect on the mode I SIF is less than 1%. Based on this criterion, a mathematically similar formula for the critical length aIIIc was found. A part of this study was also a development of a transformation procedure suitable for fitting the obtained SIF data by simple analytical formulae and for clear related illustrative plots of results.

Three-Dimensional Mode Separation to Obtain Stress Intensity Factors

2006 ◽  
Author(s):  
Pei Gu ◽  
R. J. Asaro
Keyword(s):  
Stress Intensity ◽  
Crack Propagation ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Integral Approach ◽  
Mode I ◽  
Mode Ii ◽  
Intensity Factors ◽  
Mode Iii ◽  
Mode Separation

For mixed-mode loading at a crack tip under small-scale yielding condition, mode I, mode II and mode III stress intensity factors control the crack propagation. This paper discusses three-dimensional mode separation to obtain the three stress intensity factors using the interaction integral approach. The 2D interaction integral approach to obtain mode I and mode II stress intensity factors is derived to 3D arbitrary crack configuration for mode I, mode II and mode III stress intensity factors. The method is implemented in a finite element code using domain integral method and numerical examples show good convergence for the domains around the crack tip. A complete solution for the three stress intensity factors is obtained for a bar with inclined crack face to the cross-section from numerical calculations. The solution for the bar is plotted into curves in terms of a set of non-dimensional parameters for practical engineering purpose. From the solution, mode mixity along the crack front and its implication to the direction of crack propagation is discussed.

Stress Intensity Factors for Rough Cracks Loaded in Mode II

2016 ◽  
Vol 258 ◽  
pp. 310-313 ◽  
Author(s):  
Stanislav Žák ◽  
Jana Horníková ◽  
Pavel Šandera
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Local Stress ◽  
Compact Tension ◽  
Shear Mode ◽  
Mode Ii ◽  
Intensity Factors ◽  
Mechanical Models ◽  
Related Stress ◽  
Mode Ii Loading

Most fracture mechanical models do not take the materials microstructure into account and use averaged material properties although the real crack flanks and fronts exhibit microstructurally induced tortuous shapes. These influences the stress-strain field at the crack front as well as the related stress intensity factors. This phenomenon was investigated by some authors only for remote mode I loading and was named geometrically induced shielding. This study is focused on the analysis of the stress intensity factors for rough cracks loaded in the shear mode II by modelling the Compact-Tension-Shear (CTS) specimen containing cracks of various roughness. The study revealed that, in accordance with our previous study, already small changes in the crack roughness have a rather high influence on the local field of stress intensity factors. The local stress intensity factor KII decreases with increasing roughness and, for its higher levels, it converges to a constant value that is significantly lower than that of the remote mode II loading associated with the planar crack of the same length.

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