Stress intensity factor extraction using moiré interferometry based on a two-parameter displacement eigenfunction: Validity criteria and comparison with ASTM E-399 KIC plane strain test methods

Abstract Validity criteria are presented for use of moire interferometry as a means to obtain near tip crack data combined with the use of a truncated two parameter, displacement based, KIC eigenfunction extraction method. Comparison is made with standard ASTM plane strain fracture toughness test methods for a three point bend specimen of 15V-3Cr titanium. Agreement between the experimental and ASTM plane strain KIC is found even though surface data were used. Quantitative explanations of this agreement are postulated, based on extreme near tip data extraction, the theoretical three-dimensional free surface crack tip eigenvalue for a relatively low Poisson ratio material and a direct measurement of this eigenvalue based on measured displacement.

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