scholarly journals Influence of microstructure on near-threshold fatigue-crack propagation in ultra-high strength steel

Metal Science ◽  
1977 ◽  
Vol 11 (8-9) ◽  
pp. 368-381 ◽  
Author(s):  
R. O. Ritchie
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
High Strength Steel ◽  
High Strength ◽  
Ultra High Strength Steel ◽  
Near Threshold

scholarly journals Effects of Crack Size, Stress Ratio and Hydrogen on the Near Threshold Fatigue Crack Propagation of High Strength Steel

2005 ◽  
Vol 54 (12) ◽  
pp. 1237-1243 ◽  
Author(s):  
Kazutoshi YANAGIHARA ◽  
Satoshi OHYANAGI ◽  
Masanobu KUBOTA ◽  
Chu SAKAE ◽  
Yoshiyuki KONDO
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
High Strength Steel ◽  
Stress Ratio ◽  
High Strength ◽  
Crack Size ◽  
Near Threshold

scholarly journals Near-Threshold Fatigue Crack Propagation in Ultra-High Strength Steel: Influence of Load Ratio and Cyclic Strength

1977 ◽  
Vol 99 (3) ◽  
pp. 195-204 ◽  
Author(s):  
R. O. Ritchie
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Growth Rates ◽  
Threshold Stress ◽  
Load Ratio ◽  
High Strength ◽  
Threshold Stress Intensity ◽  
Ultra High Strength Steel ◽  
Near Threshold

Fatigue crack propagation behavior of an ultra-high strength steel (300-M) has been investigated in humid air over a very wide spectrum of growth rates from 10−8 to 10−1 mm/cycle. Particular emphasis has been devoted to the influence of mean stress (or load ratio R = Kmin/Kmax) and microstructure on fatigue crack growth near the threshold stress intensity for crack propagation, ΔK0. Increasing the load ratio from R = 0.05 to 0.70 was found to lead to increased near-threshold growth rates, and a decrease in the threshold stress intensity. Similarly, increasing material strength, by varying the microstructure through quench and tempering and isothermal transformation, resulted in higher near-threshold growth rates, and a marked reduction of ΔK0. These effects are contrasted with behavior at higher growth rates. The influence of strength on ΔK0 is rationalized in terms of the cyclic hardening or softening response of the material, and hence it is shown that cyclic softening can be beneficial to fatigue crack propagation resistance at very low growth rates. The results are discussed in the light of crack closure and environmental contributions to fatigue crack growth at low stress intensities.

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