[PDF] Fatigue Crack Propagation In Steel Alloys At Elevated Temperatures eBook

Author : HI. McHenry
Publisher :
Page : 10 pages
File Size : 13,46 MB
Release : 1973
Category : Alloy steels
ISBN :

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The fatigue crack propagation characteristics of three steel alloys were evaluated at room and elevated temperatures in an air environment. The alloys and temperature ranges were: A212-B (?YS = 40 ksi) 75 to 800 F, A517-F (?YS = 104 ksi) 75 to 950 F, and 9Ni-4Co-0.30C (?YS = 185 ksi) 75 to 650 F. The compact tension specimen was used for the 9Ni-4Co-0.30C and A517-F tests. A modified compact tension specimen having deep face notches in the crack plane was used for the A212-B tests. Fracture mechanics parameters were used to evaluate the crack propagation data. When plotted as a function of the stress intensity range, ?K, the crack growth rates increased with temperature in A517-F and A212-B; temperature did not influence the 9Ni-4Co-0.30C data. Tests at reduced cyclic frequencies were conducted on A517-F and 9Ni-4Co-0.30C steel. The crack growth rates increased as the frequency was reduced in A517-F at 500 and 950 F. In 9Ni-4Co-0.30C the growth rates at 500 and 650 F were essentially the same for cyclic frequencies of 10 and 0.002 Hz over the range of growth rates investigated.

Author : S. Lesterlin
Publisher :
Page : 23 pages
File Size : 19,36 MB
Release : 1997
Category : Environment
ISBN :

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The fatigue crack propagation behavior of a Ti-6Al-4V alloy has been investigated at room temperature and at 300°C. Tests were run in air, high vacuum, and some other environments with controlled partial pressure of water vapor and oxygen. The enhancement of the fatigue crack growth rates observed in air in comparison to high vacuum, considered as an inert environment, is clearly attributed to the presence of water vapor. Tests in a controlled environment demonstrate that very low partial pressure can accelerate crack propagation. On the basis of previous studies on Al alloys and steels, two controlling mechanisms are considered and discussed, namely, a propagation-assisted water vapor adsorption and a hydrogen-assisted propagation.

Author : O. P. Keifer
Publisher :
Page : 114 pages
File Size : 40,76 MB
Release : 1984
Category :
ISBN :

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Environmental effects in elevated temperature fatigue have been extensively studied and reported in the literature for 2 1/4 Cr-1 Mo steel. The results of cycles to failure (lumped initiation and propagation life) verses strain range have shown drastic reductions in fatigue life with a dwell period at compressive strains in each loading cycle. This thesis has separately examined the crack initiation and propagation stages for several specimens tested in air at 538 deg C without dwell and a single specimen with a five minute compressive dwell. With dwell, the crack initiation stage was severely reduced (by a factor greater than eleven) relative to testing without dwell. The results clearly indicate that oxide cracking is a precursor to crack initiation in the substrate. It is concluded that the fatigue life of this alloy must be estimated based on the crack propagation characteristics alone, since crack initiation can be expected very clearly (i.e., first few cycles) for any practical environment. Originator supplied keywords include: Fatigue, oxide cracking, 2 1/4 Cr - Mo Steel.