Mapping the cyclic plastic zone to elucidate the mechanisms of crack tip deformation in bulk metallic glasses

2017 ◽  
Vol 110 (8) ◽  
pp. 081903 ◽  
Author(s):  
S. Scudino ◽  
R. N. Shahid ◽  
B. Escher ◽  
M. Stoica ◽  
B. S. Li ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Crack Tip ◽  
Cyclic Plastic ◽  
Cyclic Plastic Zone

A Model of Fatigue Crack Growth Based on Damage Accumulation

2004 ◽  
Author(s):  
Satish Chand ◽  
K. N. Pandey
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Plastic Zone ◽  
Crack Growth ◽  
Damage Accumulation ◽  
Process Zone ◽  
Crack Tip ◽  
Cyclic Plastic ◽  
Cyclic Plastic Zone ◽  
Material Element

A fatigue crack growth model based on cumulative damage is presented, when a material element ahead of the crack tip, is approached by the tip of the crack. The cyclic plastic zone and process zone ahead of the crack tip are taken as the area where damage accumulation takes place when the material element, first, enters into the cyclic plastic zone and then into the process zone. During this period, the Coffin-Manson damage law in conjunction with Miner’s linear damage accumulation is used to determine the damage in the material element. A constant strain gradient was assumed along the process zone ahead of the crack tip and the size of process zone was taken to be variable and dependent on the range of stress intensity factor. For a cyclic loading, the effective crack driving force takes into consideration the crack tip blunting process. The model results are in good agreement with experimental data available in literature for a number of materials.

scholarly journals Using DIC techniques to measure strain ranges inside the cyclic plastic zone ahead of a fatigue crack tip

2019 ◽  
Vol 13 (49) ◽  
pp. 74-81 ◽  
Author(s):  
Giancarlo Gonzáles ◽  
Julián González ◽  
Jaime Castro ◽  
José Freire
Keyword(s):  
Fatigue Crack ◽  
Plastic Zone ◽  
Crack Tip ◽  
Cyclic Plastic ◽  
Cyclic Plastic Zone

A Study on the Cyclic Plastic Zone Size Method, ω*, for Digital Fatigue Life Prediction of Arc-Welded Joints

2003 ◽  
Author(s):  
Tomohiro Hirata ◽  
Toshiaki Nakamaru ◽  
Keisuke Toyama ◽  
Shuichi Magara ◽  
Hiroshi Watanabe ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Plastic Zone ◽  
Welded Joints ◽  
Life Prediction ◽  
Plastic Zone Size ◽  
Fatigue Life Prediction ◽  
Zone Size ◽  
Cyclic Plastic ◽  
Cyclic Plastic Zone

Plastic Strain Distribution at the Tips of Propagating Fatigue Cracks

1976 ◽  
Vol 98 (1) ◽  
pp. 24-29 ◽  
Author(s):  
D. L. Davidson ◽  
J. Lankford
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Plastic Strain ◽  
Plastic Zone ◽  
Strain Distribution ◽  
Dimensionless Parameter ◽  
Fatigue Cracks ◽  
Crack Tip ◽  
Cyclic Plastic Zone ◽  
Plastic Zones

The techniques of selected area electron channeling and positive replica examination have been used to study the plastic zones attending fatigue crack propagation in 304 SS, 6061-T6 aluminum alloy, and Fe-3Si steel. These observations allowed the strain distribution at the crack tip to be determined. The results indicate that the concepts of a monotonic and a cyclic plastic zone are essentially correct, with the strains at demarcation between these two zones being 3 to 6 percent. Strain distribution varies as r−1/2 in the cyclic zone and as ln r in the monotonic plastic zone. The strain distributions for all materials studied may be made approximately coincident by using a dimensionless parameter related to distance from the crack tip.

Cyclic plastic zone modified critical distance theory for notch fatigue analysis of metals

2021 ◽  
Vol 121 ◽  
pp. 105163
Author(s):  
Anteneh Tilahun Taddesse ◽  
Shun-Peng Zhu ◽  
Ding Liao ◽  
Hong-Zhong Huang
Keyword(s):  
Plastic Zone ◽  
Fatigue Analysis ◽  
Critical Distance ◽  
Cyclic Plastic ◽  
Cyclic Plastic Zone

Plastic zone at crack tip: A nanolab for formation and study of metallic glassy nanostructures

2009 ◽  
Vol 24 (9) ◽  
pp. 2986-2992 ◽  
Author(s):  
X.X. Xia ◽  
Wei H. Wang ◽  
A. Lindsay Greer
Keyword(s):  
Fracture Surface ◽  
Plastic Zone ◽  
Metallic Glasses ◽  
Room Temperature ◽  
Crack Tip ◽  
Plastic Zone Size ◽  
Fracture Mechanisms ◽  
Clear Correlation ◽  
Zone Size ◽  
Deformation And Fracture

We report that various metallic glassy nanostructures including nanoridges, nanocones, nanowires, nanospheres, and nanoscale-striped patterns are spontaneously formed on the fracture surface of bulk metallic glasses at room temperature. A clear correlation between the dimensions of these nanostructures and the size of the plastic zone at the crack tip has been found, providing a way to control nanostructure sizes by controlling the plastic zone size intrinsically or extrinsically. This approach to forming metallic glassy nanostructures also has implications for understanding the deformation and fracture mechanisms of metallic glasses.

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.

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