On the influence of rubbing fracture surfaces on fatigue crack propagation in mode III

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)29-35
Journal / PublicationInternational Journal of Fatigue
Issue number1
Publication statusPublished - Jan 1983
Externally publishedYes


Fatigue crack growth has been studied under fully reversed torsional loading (R = -1) using AISI 4340 steel, quenched and tempered at 200°, 400° and 650°C. Only at high stress intensity ranges and short crack lengths are all specimens characterized by a microscopically flat Mode III (anti-plane shear) fracture surface. At lower stress intensities and larger crack lengths, fracture surfaces show a local hill-and-valley morphology with Mode I, 45° branch cracks. Since such surfaces are in sliding contact, friction, abrasion and mutual support of parts of the surface can occur readily during Mode III crack advance. Without significant axial loads superimposed on the torsional loading to minimize this interference, Mode III crack growth rates cannot be uniquely characterized by driving force parameters, such as ΔKIII and ΔCTDIII, computed from applied loads and crack length values. However, for short crack lengths (≤0.4 mm), where such crack surface interference is minimal in this steel, it is found that the crack growth rate per cycle in Mode III is only a factor of four smaller than equivalent behaviour in Mode I, for the 650°C temper at ΔKIII = 45 MPa m1/2.

Research Area(s)

  • AISI 4340 steel, fatigue, fatigue crack growth, Mode III fatigue, rubbing fracture surfaces