The influence of a duplex microstructure in steels on fatigue crack growth in the near-threshold region

1982 ◽  
Vol 13 (3) ◽  
pp. 439-445 ◽  
Author(s):  
K. Minakawa ◽  
Y. Matsuo ◽  
A. J. McEVILY
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Threshold Region ◽  
Duplex Microstructure ◽  
Near Threshold

Effects of Different Microstructure on Resistance of EA4T Railway Axle Steel of Equal Strength to Fatigue Crack Growth

2013 ◽  
Vol 592-593 ◽  
pp. 631-634 ◽  
Author(s):  
Ivo Černý ◽  
Václav Linhart
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Experimental Methodology ◽  
Threshold Region ◽  
Railway Axle ◽  
Heat Treated ◽  
Crack Growth Rates ◽  
Steel Heat ◽  
Near Threshold

Fatigue crack growth (FCG) rates in an EA4T railway axle steel heat treated by two different methods in near threshold and stable regions of growth were evaluated. Quite significant differences were observed, when the obtained results were compared with those published in the literature. Participation of the laboratory in an Exova (GE Aviation) FCG measurement qualification round robin programme with very good results practically excluded errors in the experimental methodology used. Strength of the two different evaluated series of the experimental material was equivalent. Nevertheless, there were substantial differences in fatigue crack growth rates, about 5-times in stable FCG region and even more than 10-times in the near threshold region, when oil quenching and air hardening treatments were compared. The differences were explained by different microstructures of the two groups of materials. Some minor differences between the character of the FCG curve in the threshold region evaluated using SEN(B) and M(T) specimens, published in the literature, are discussed considering crack closure phenomenon.

Evaluation of Fatigue Crack Growth Curves in Existing Codes and a Proposed Modification Based on Experimental Data of Cr-Ni-Mo-V Steel Welded Joints

2016 ◽  
Author(s):  
Yan-Nan Du ◽  
Ming-Liang Zhu ◽  
Fu-Zhen Xuan ◽  
Shan-Tung Tu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Welded Joints ◽  
Growth Curves ◽  
Crack Growth Behavior ◽  
Fatigue Assessment ◽  
Crack Growth Model ◽  
Threshold Regime ◽  
Near Threshold

A comparison of currently available codes for assessment of fatigue crack growth, including ASME (America Society of Mechanical Engineers) SEC. XI, FKM (Forchungskuratorium Maschinenbau) guideline, WES (Japan Welding Engineering Society) 2805, BS7910 and JSME (The Japan Society of Mechanical Engineers), was carried out by paying attention to the suitability of application and the easiness to obtain the parameters, based on fatigue crack growth data of Cr-Ni-Mo-V steel welded joints. Results showed that fatigue crack growth curves provided by the FKM or WES were good choice when few inputs were at hand while the curves in the BS7910, JSME and ASME were recommended for precise estimation. It was indicated that the assessment of welded joints solely by fatigue crack growth behavior at base metal part and the assessment of fatigue crack growth for the aged condition by as-received one both resulted in non-conservativeness, albeit dependent on the range of stress ratios, R. A new bilinear form of fatigue crack growth model independent of R was developed based on transition point occurred in the near-threshold regime. This constituted the bilinear approach to fatigue assessment, and thus contributed to the optimization of fatigue assessment in the near-threshold regime.

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