scholarly journals Dynamic Fracture Experiment of Medium with Defects under Impact Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Chenglong Xiao ◽  
Renshu Yang ◽  
Chenxi Ding ◽  
Cheng Chen ◽  
Yong Zhao ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Dynamic Fracture ◽  
Mode I ◽  
Mode Ii ◽  
Obvious Effect ◽  
Initiation Stage

Defects have a significant effect on the dynamic fracture characteristics of the medium. In this paper, the dynamic fracture experiment of specimens with bias precracks is designed by utilizing the digital laser dynamic caustics system, and the effect of defect eccentricity on the dynamic fracture behavior is studied. Research shows that crack propagation can be divided into four stages: crack initiation stage, attraction stage, repulsion stage, and specimen fracture stage. The change of defect eccentricity has no obvious effect on the crack propagation behavior in the crack initiation stage and penetration stage but has a significant effect on the attraction stage and specimen fracture stage. In the process of the interaction between defect and crack, mode I stress intensity factor decreases at first and then increases. The decrease of mode I stress intensity factor reduces with the increase of defect eccentricity. The value of mode II stress intensity factor changes from negative to positive. With the increase of defect eccentricity, the symbol of mode II stress intensity factor no longer changes. The fractal dimension and the deflection angle of crack trajectory both decrease with the increase of defect eccentricity. In addition, a numerical simulation of the experiment is conducted by ABAQUS, which provides results that are in good agreement with the experimental results.

The effect of friction on crack propagation in the dovetail fixings of compressor discs

1998 ◽  
Vol 212 (3) ◽  
pp. 171-181 ◽  
Author(s):  
R L Burguete ◽  
E A Patterson
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Coefficient Of Friction ◽  
Stress Intensity Factors ◽  
Mode I ◽  
Mode Ii ◽  
Intensity Factors ◽  
The Coefficient Of Friction

Stress frozen photoelasticity has been used to model dovetail compressor blade fixings. During loading a known coefficient of friction was applied and the effect of the variation of this parameter on crack initiation and propagation was investigated. Data were recorded from the specimen using an automated computer aided polariscope based on the method of phase stepping. Isochromatic and isoclinic data were collected and used to determine the stress distribution, the stress intensity factor and the crack propagation direction. The method to predict the direction of crack propagation has been improved so that photoelastic data can be used reliably for this purpose. Three values of the coefficient of friction were used for two different dovetail geometries. It was found that the initial values of the mode II stress intensity factors were higher for a lower friction coefficient. An increase in crack length produced a corresponding decrease in the mode I stress intensity factor and a decrease in the mode II value. It was concluded that the coefficient of friction influenced crack growth at all stages of crack growth because it affects the relative levels of the mode I and mode II stress intensity factors. This has an effect on the direction of the maximum principal stress direction and so on the direction of crack propagation.

scholarly journals A comparative study on stress intensity factor-based criteria for the prediction of mixed mode I-II crack propagation in concrete

2018 ◽  
Vol 197 ◽  
pp. 217-235 ◽  
Author(s):  
Wei Dong ◽  
Zhimin Wu ◽  
Xuchao Tang ◽  
Xiangming Zhou
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Comparative Study ◽  
Crack Propagation ◽  
Mixed Mode ◽  
Mode I

Crack Growth Sensitivity to the Magnitude and Frequency of Load Fluctuation in Stage 1b of High pH Stress Corrosion Cracking

CORROSION ◽  
10.5006/3711 ◽  
2021 ◽  
Author(s):  
Hamid Niazi ◽  
Greg Nelson ◽  
Lyndon Lamborn ◽  
Reg Eadie ◽  
Weixing Chen ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Initiation ◽  
Plastic Zone ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Tip ◽  
Cyclic Plastic Zone ◽  
Secondary Cracks

Pipelines undergo sequential stages before failure caused by High pH Stress Corrosion Cracking (HpHSCC). These sequential stages are incubation stage, intergranular crack initiation (Stage 1a), crack evolution to provide the condition for mechanically driven crack growth (Stage 1b), sustainable mechanically driven crack propagation (Stage 2), and rapid crack propagation to failure (Stage 3). The crack propagation mechanisms in Stage 1b are composed of the nucleation and growth of secondary cracks on the free surface and crack coalescence of secondary cracks with one another and the primary crack. These mechanisms continue until the stress intensity factor (<i>K</i>) at the crack tip reaches a critical value, known as <i>K</i><sub>ISCC</sub>. This investigation took a novel approach to study Stage 1b in using pre-cracked Compact Tension (CT) specimens. Using pre-cracked specimens and maintaining <i>K</i> at less than <i>K</i><sub>ISCC</sub> provided an opportunity to study crack initiation on the surface of the specimen under plane stress conditions in the presence of a pre-existing crack. In the present work, the effects of cyclic loading characteristics on crack growth behavior during Stage 1b were studied. It was observed that the pre-existing cracks during Stage 1b led to the initiation of secondary cracks. The initiation of the secondary cracks at the crack tip depended on loading characteristics, <i>i.e</i>., the amplitude and frequency of load fluctuations. The secondary cracks at the crack tip can be classified into four categories based on their positions with respect to the primary crack. A high density of intergranular cracks formed in the cyclic plastic zone generated by low R-ratio cycles. The higher the frequency of the low <i>R</i>-ratio cycles, the higher the density of the intergranular cracks forming in the cyclic plastic zone. The crack growth rate increased with an increase in either the amplitude or the frequency of the load fluctuations. The minimum and maximum crack growth rates were 8×10<sup>-9</sup> mm/s and 4.2×10<sup>-7</sup> mm/s, respectively, with <i>R</i>-ratio varying between 0.2 and 0.9, frequency varying between 10<sup>-4</sup> Hz and 5×10<sup>-2</sup> Hz, and at a fixed stress intensity factor of 15 MPa.m<sup>0.5</sup>. It was found that avoiding rapid and large load fluctuations slowed down crack geometry evolution and delayed onset of Stage 2. The implication of these results for pipeline operators is that reducing internal pressure fluctuations by reducing the frequency and/or amplitude of the fluctuations can expand Stage 1 and increase the reliable lifetime of operating pipelines.

A comparative study on two stress intensity factor-based criteria for prediction of mode-I crack propagation in concrete

2016 ◽  
Vol 158 ◽  
pp. 39-58 ◽  
Author(s):  
Wei Dong ◽  
Zhimin Wu ◽  
Xiangming Zhou ◽  
Cuijin Wang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Comparative Study ◽  
Crack Propagation ◽  
Mode I ◽  
Mode I Crack

scholarly journals Numerical Investigation on Crack Propagation for a Central Cracked Brazilian Disk Concerning Friction

2021 ◽  
Vol 11 (6) ◽  
pp. 2839
Author(s):  
Jiuzhou Huang ◽  
Xin Pan ◽  
Jianxiong Li ◽  
Shiming Dong ◽  
Wen Hua
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Relative Length ◽  
Mode I ◽  
Brazilian Disk ◽  
Crack Type ◽  
T Stress ◽  
Crack Propagation Angle

This paper concerns the effect of friction on crack propagation for the centrally cracked Brazilian disk under diametric forces by using a modified finite element method. It shows that the mode II stress intensity factor decreases obviously with the increase of friction after the crack is closed, while friction has no influence on the stress intensity factor of mode I and T-stress. Meanwhile, there are some significant influences on the crack propagation due to the change of the friction after the crack is closed with the appropriate loading angle and relative length of the crack. When T-stress is positive, the effect of friction becomes obvious and the crack propagation angle increases with a lager friction coefficient. With increasing the friction, the deviation for the crack propagation trajectory increases and the curvature of path decreases, which may lead to the change of crack type. Additionally, the larger relative crack length can amplify the effect of friction, which is similar to the loading angle.

The plasticity-corrected stress intensity factor for plane stress mode I and mode II cracks

2014 ◽  
Vol 128 ◽  
pp. 231-235 ◽  
Author(s):  
Peng Dai ◽  
Jianda Yang ◽  
Hongyun Li ◽  
Zhonghua Li
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plane Stress ◽  
Mode I ◽  
Mode Ii ◽  
Stress Mode

Crack propagation under mode II loading: An effective stress intensity factor method

1987 ◽  
Vol 28 (1) ◽  
pp. 93-100 ◽  
Author(s):  
Klod Kokini ◽  
Roy D. Marangoni ◽  
George M. Dorogy ◽  
Hesham A. Ezzat
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Effective Stress ◽  
Mode Ii ◽  
Effective Stress Intensity Factor ◽  
Factor Method ◽  
Mode Ii Loading

Intersonic Crack Propagation—Part II: Suddenly Stopping Crack

2001 ◽  
Vol 69 (1) ◽  
pp. 76-80 ◽  
Author(s):  
Y. Huang ◽  
H. Gao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fundamental Solution ◽  
Crack Propagation ◽  
Auxiliary Problem ◽  
Crack Tip ◽  
Mode Ii ◽  
Static Crack ◽  
Intersonic Crack Propagation

In Part I of this series, we have obtained the fundamental solution for a mode II intersonic crack which involves a crack moving uniformly at a velocity between the shear and longitudinal wave speeds while subjected to a pair of concentrated forces suddenly appearing at the crack tip and subsequently acting on the crack faces. The fundamental solution can be used to generate solutions for intersonic crack propagation under arbitrary initial equilibrium fields. In this paper, Part II of this series, we study a mode II crack suddenly stopping after propagating intersonically for a short time. The solution is obtained by superposing the fundamental solution and the auxiliary problem of a static crack emitting dynamic dislocations such that the relative crack face displacement in the fundamental solution is negated ahead of where the crack tip has stopped. We find that, after the crack stops moving, the stress intensity factor rapidly rises to a finite value and then starts to change gradually toward the equilibrium value for a static crack. A most interesting feature is that the static value of stress intensity is reached neither instantaneously like a suddenly stopping subsonic crack nor asymptotically like a suddenly stopping edge dislocation. Rather, the dynamic stress intensity factor changes continuously as the shear and Rayleigh waves catch up with the stopped crack tip from behind, approaches negative infinity when the Rayleigh wave arrives, and then suddenly assumes the equilibrium static value when all the waves have passed by. This study is an important step toward the study of intersonic crack propagation with arbitrary, nonuniform velocities.

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