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On a reliable equation for the second portion of the fatigue crack growth diagram

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Strength of Materials Aims and scope

Abstract

The fatigue crack growth kinetics on the second portion of the fatigue crack growth diagram is described using an equation that takes into account both the current crack tip opening displacement and the instant when the crack closure in a cycle vanishes and does not appear until the specimen failure. This instant corresponds to the critical effective SIF range, ΔKfcl.

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Abbreviations

da/dN :

fatigue crack growth (FCG) rate

(da/dN) II :

FCG rate on the second portion of the fatigue crack growth diagram (FCGD)

(da/dN) 1′,(da/dN) 2′ :

FCG rate in the first and second parts of the second portion on the FCGD, respectively

ΔK :

stress intensity factor (SIF) range in a cycle

ΔK eff :

effective SIF range in a cycle

ΔK eff1–2 :

effective SIF range in a cycle that corresponds to the beginning of the second portion of the FCGD

ΔK 2–3 :

SIF range in a cycle that corresponds to the end of the second portion of the FCGD

ΔK fcl :

critical effective SIF range of the cyclic loading wherein the effect of crack closure in a cycle vanishes and does not appear until the specimen fracture occurs

K max,K min :

maximum and minimum SIF in a cycle, respectively

K op :

SIF of the crack opening displacement in a cycle

R :

load ratio in a cycle

C,C 1,C 2,n,n 1,n 2 :

material characteristics

arctann 1, arctann 2 :

angles of inclination of the FCG rate curves in the first (second) part of the second portion of the FCGD

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Authors
  1. I. S. Pinyak
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Additional information

Institute of Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 3, pp. 83–87, May–June, 1999.

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Pinyak, I.S. On a reliable equation for the second portion of the fatigue crack growth diagram. Strength Mater 31, 282–285 (1999). https://doi.org/10.1007/BF02511008

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  • DOI: https://doi.org/10.1007/BF02511008

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