The Effects of Load Ratio, Interstitial Content, and Grain Size on Low-Stress Fatigue-Crack Propagation in α-Titanium

1973 ◽  
Vol 7 (1) ◽  
pp. 153-159 ◽  
Author(s):  
J. L. Robinson ◽  
C. J. Beevers
Keyword(s):  
Grain Size ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Load Ratio ◽  
Interstitial Content ◽  
Stress Fatigue

50-Fold Difference in Region-II Fatigue Crack Propagation Resistance of Titanium Alloys: A Grain-Size Effect

1979 ◽  
Vol 101 (1) ◽  
pp. 86-90 ◽  
Author(s):  
G. R. Yoder ◽  
L. A. Cooley ◽  
T. W. Crooker
Keyword(s):  
Grain Size ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Load Ratio ◽  
Plastic Zone Size ◽  
Crack Propagation Resistance ◽  
Order Of Magnitude ◽  
Region Ii

Fatigue crack growth rates (da/dN) in ambient laboratory air have been determined for a wide variety of materials from four basic α + β titanium alloy systems. Each material was cyclically loaded with a haversine waveform and a load ratio, R = 0.10. The results indicate that, at a constant value of stress-intensity range (ΔK), the width of the da/dN data band exceeds an order of magnitude. For example, at ΔK = 21 MPa·m1/2, a 50-fold difference in fatigue crack propagation rates is observed. Analysis of the crack growth rate data at this point indicates a systematic dependence on grain size (l), viz. that da/dN decreases with increasing l. An interpretation of this effect is offered in terms of reversed (cyclic) plastic zone size considerations.

scholarly journals Near-Threshold Fatigue Crack Propagation in an ECAP-Processed Ultrafine-Grained Aluminium Alloy

2010 ◽  
Vol 667-669 ◽  
pp. 873-878 ◽  
Author(s):  
Kristin Hockauf ◽  
T. Halle ◽  
Matthias Hockauf ◽  
Martin F.X. Wagner ◽  
Thomas Lampke
Keyword(s):  
Grain Size ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Aluminium Alloy ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Load Ratio ◽  
Angular Pressing ◽  
Growth Properties ◽  
Near Threshold

In the present work, the near-threshold fatigue crack propagation (FCP) at different load ratios is studied for an aluminium alloy processed by equal-channel angular pressing (ECAP). The conditions under investigation represent different stages of microstructural refinement as well as a ductility-optimized condition with superior crack growth properties, obtained by a combination of ECAP and aging. The results show a strong dependency of the threshold and its load ratio sensitivity on the grain size and grain size distribution. These observations can be rationalized on the basis of crack path tortuosity and the contribution of (roughness-induced) crack closure. Moreover, the experimental data is evaluated using the two-parametric concept of Vasudevan and Sadananda, which employs two necessary minimum conditions for crack growth, namely a critical cyclic K*th, and a critical maximum stress intensity K*max. The application of this concept shows a strong interaction of both parameters for all ECAP-processed conditions, where the ductility-optimized condition reveals superior FCP properties compared to the “as-processed” conditions.

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