Observation of Crack Tip Strain Distribution for Brittle Materials by Means of Photoelastic Coating Technique and Non-Linear Fracture Mechanics

Takayuki Fukasawa, Toshiyuki Hashida, Hideaki Takahashi

Research output: Contribution to journalArticlepeer-review

Abstract

Granite, granite and mortar are typical brittle materials. Recently, for evaluating the strength of these materials, a study based on fracture mechanics has been suggested. In general a microcrack process zone at the crack tip of brittle materials is created, which may determine the fracture process. So using the photoelastic coating method with a PLZT (transparent dielectric ceramics) plate (100 -200 μm thickness), the strain field at the crack tip was directly measured. As a result, it was found that the strain field did not show the singularity of γ-1/2, (γ = a distance from crack tip), as the strain field of linear elastic materials. When the strain distributions are normalized by J integral and the tensile stress σull they were expressed by a form of Δɛ=Δɛ0 ((J/ σull/r)m; thus it is found that the strain field within the process zone can be described by the J integral, where Δɛ and m are material constants, and m is near 1. The strain field at the crack tip of the brittle materials is proportional to approximately γ-1. The extension of the process zone, denoted by ω, is closely related to the J integral. The relationship between ω and the J integral can be expressed as a bilinear line. It is shown that the J integral at the knee point is equal to the critical J integral, value determined by AE technique. Thus the J integral can be an important parameter to evaluate the fracture behavior of brittle materials.

Original languageEnglish
Pages (from-to)1553-1558
Number of pages6
JournalTransactions of the Japan Society of Mechanical Engineers Series A
Volume54
Issue number504
DOIs
Publication statusPublished - 1988

Keywords

  • Brittle Material
  • Crack Tip Strain Field
  • Fracture
  • J Integral
  • Photoelastic Coating Technique
  • Process Zone

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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