Fracture Prediction by Rayleigh Wave Scattering Measurement
An acoustic surface wave NDE technique for predicting the fracture stress of a solid containing a surface crack is described. The normalized stress intensity factor for a crack is determined by measuring the reflection coefficient of Rayleigh waves incident to the crack in the long wave-length limit. An acoustic surface wave wedge transducer was used to excite the incident wave and to measure the reflected wave intensity. The fracture stress of Pyrex glass discs containing the acoustically measured cracks was determined in biaxial flexure. Fracture toughness values obtained through post-fracture examination of the fracture surfaces were in excellent agreement with the values in the literature. The fracture stress predicted from the acoustic measurement of the stress intensity factor correlated very well with the measured value of the fracture stress. For surface cracks with crack radii varying between 50 and 500 microns, the average error between the acoustic prediction of fracture stress and the measured fracture stress is less than 20%.
KeywordsFracture Toughness Stress Intensity Factor Fracture Stress Surface Crack Rayleigh Wave
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