Proposal for an engineering definition of a fatigue crack initiation unit for evaluating the fatigue limit on the basis of crystallographic analysis of pearlitic steel

Tomoya Fujisawa, Shigeru Hamada, Norimitsu Koga, Daisuke Sasaki, Toshihiro Tsuchiyama, Nobuo Nakada, Kazuki Takashima, Masaharu Ueda, Hiroshi Noguchi

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4 Citations (Scopus)

Abstract

In this study, in order to define a fatigue crack initiation unit, the relationship between the fatigue crack initiation process and the crystal structure in the pearlitic steel used for railroad rails was examined and fatigue tests, focusing on crack initiation, were performed. The fracture surfaces were analyzed using a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The crystal structure of the pearlitic steel is composed of "pearlitic colonies" that have the same lamellar structure direction and "pearlitic blocks" that have the same ferrite crystal direction. The SEM and EBSD results revealed that the crack initiation depends on the pearlitic colonies. Therefore, we defined the characteristic dimension for fatigue crack initiation as the pearlitic colony size. However, for safety purposes, the pearlitic block size should be considered the engineering definition of the fatigue crack initiation unit, since decreasing the pearlitic block size should cause an improvement in the fatigue limit of pearlitic steel.

Original languageEnglish
Pages (from-to)17-29
Number of pages13
JournalInternational Journal of Fracture
Volume185
Issue number1-2
DOIs
Publication statusPublished - Jan 1 2014

All Science Journal Classification (ASJC) codes

  • Computational Mechanics
  • Modelling and Simulation
  • Mechanics of Materials

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