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The Influence of Microstructure on the Fatigue Crack Growth Rate in ferrite-pearlite Steels in the Paris Region
  • Victor Igwemezie,
  • Feargal Brennan
Victor Igwemezie
Cranfield University
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Feargal Brennan
University of Strathclyde
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Abstract

This paper presents a study on the effect of microstructure on the fatigue crack growth rate (FCGR) in advanced normalised-rolled (NR) and thermomechanical control process (TMCP) S355 steels in the Paris Region of the da/dN vs. ΔK log-log plot. The environments of study were air and seawater (SW), under constant amplitude sinewave fatigue loading. Discussions were based mainly on the comparison between the crack path in the TMCP and NR steels. Fundamentally, three phenomena: crack-tip diversion, crack-front bifurcation and metal crumb formation were observed to influence the rate of fatigue crack growth (FCG). The prevalence of these phenomena appears to be a function of the nature of the material microstructure, environment and crack-tip loading conditions. The three factors appear to retard the crack growth by reducing or re-distributing the effective driving force at the main active crack tip. A crack path containing extensively the three phenomena was observed to offer strong resistance to FCG. Increase in the FCGR was observed with decrease in the crack-tip diversion angle, branched-crack length and metal crumbs formed. In SW, the degree of the electrochemical dissolution of the microplastic zone (or crack-tip blunting) appears to be an additional factor influencing crack growth in ferrite-pearlite (α-P) steel. This study, generally tends to present microstructural features that strongly influenced FCGR in α-P steels in the Paris Region both in air and SW. This work is very important in the design of fatigue resistant steel.

Peer review status:ACCEPTED

09 Apr 2020Submitted to Fatigue & Fracture of Engineering Materials & Structures
13 Apr 2020Submission Checks Completed
13 Apr 2020Assigned to Editor
18 Apr 2020Reviewer(s) Assigned
08 May 2020Review(s) Completed, Editorial Evaluation Pending
10 May 2020Editorial Decision: Revise Minor
06 Jun 20201st Revision Received
07 Jun 2020Assigned to Editor
07 Jun 2020Submission Checks Completed
07 Jun 2020Reviewer(s) Assigned
20 Jun 2020Review(s) Completed, Editorial Evaluation Pending
24 Jun 2020Editorial Decision: Revise Minor
10 Jul 20202nd Revision Received
14 Jul 2020Assigned to Editor
14 Jul 2020Submission Checks Completed
14 Jul 2020Review(s) Completed, Editorial Evaluation Pending
15 Jul 2020Editorial Decision: Accept