scholarly journals Role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures

Composites ◽  
1988 ◽  
Vol 19 (2) ◽  
pp. 170
Keyword(s):  
Fatigue Cracks ◽  
Crack Tip ◽  
Crack Tip Shielding

Crack-Tip Shielding in Metal-Matrix Composites: Modelling Of Crack Bridging by Uncracked Ligaments

1988 ◽  
Vol 120 ◽  
Author(s):  
Jian Ku Shang ◽  
R. O. Ritchie
Keyword(s):  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Crack Tip ◽  
Matrix Composites ◽  
Opening Displacement ◽  
Crack Bridging ◽  
Critical Crack ◽  
Crack Tip Shielding

AbstractAs part of an investigation into the micro-mechanisms of crack-tip shielding associated with the growth of fatigue cracks in metal-matrix composites, simple models are developed for the role of crack bridging in high-strength aluminum alloys reinforced with SiC particulate (AI/SiCp). Based on experimental observations of crack growth, crack-tip shielding and crack-path morphology in these alloys, the bridges are found to be associated with uncracked ligaments in the wake of the crack tip, and are modelled in terms of approaches based on a critical crack-opening displacement or critical tensile strain in the ligament.

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.

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