A correlation of ΔKth-value with the exponent,m, in the equation of fatigue crack growth for various steels

✍ Scribed by K. Tanaka

• Publisher: Springer Netherlands
• Year: 1979
• Tongue: English
• Weight: 681 KB
• Volume: 15
• Category: Article
• ISSN: 1573-2673
• DOI: 10.1007/bf00115909

✦ Synopsis

A B S T R A C T Literature (mainly in Japan) relating to fatigue-crack-growth-data at R = 0 in an air environment for a wide range of steels is reviewed with particular attention to the threshold stress intensity, AKth. The collected data are analyzed in terms of the exponent, m(the slope of the linear portion of the log(da/dN)-logAK relationship) by taking account of microstructure, material strength, fracture toughness and specimen thickness. The mean rate of fatigue crack growth for ductile steels in the range from the intermediate growth rate to threshold level and the relevant threshold values at R = 0, AKth0, can be represented as daldN = 1.700 x 10-4(AK/103.6) m -10 -6 and AKth0 = 103.6(5.88 x 10-3) |/m, where (da/dN) and AK are measured by the units of mm/cycle and kgf/mm 3/2, respectively. Contrary to this, in the case of extremely brittle steels with K~c-Value below 200 kgf/mm m (the fracture occurs by the intergranular separation), the relationships are given by da/dN = 2.893 × 10-~(AK/49.94) m -2.5 x 10 -7 and AKtb0 = 49.94(8.64 × 10-;) lira.