Free-edge stresses and progressive cracking in surface coatings of circular torsion bars

Xiang Fa Wu, Yuris A. Dzenis, Kyle W. Strabala

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of complementary strain energy. Criterion for progressive cracking in the coating layer was established in sense of strain energy conservation, and the crack density is thereby estimated. Effects of external torque, aspect ratio, and elastic properties on the density of progressive cracking were examined numerically. The present study shows that, in the sense of inducing a given crack density, compliant coating layer with lower modulus has much higher critical torque than that of a stiffer one with the same geometries and substrate material, i.e., compliant coating layer has greater cracking tolerance. Meanwhile, the study also indicates that thicker surface coating layer is more pliant to cracking than the thinner ones. The present model can be used for analyzing the damage mechanism and cracking tolerance of surface coatings of torsion shafts and for data reduction of torsional fracture test of brittle surface coatings, etc.

Original languageEnglish (US)
Pages (from-to)2251-2264
Number of pages14
JournalInternational Journal of Solids and Structures
Issue number7-8
StatePublished - Apr 2008


  • Energy release rate (ERR)
  • Fracture criterion
  • Free-edge stress
  • Progressive cracking
  • Surface coatings
  • Torsional shaft bar

ASJC Scopus subject areas

  • Modeling and Simulation
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Applied Mathematics

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