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Qualifying indentation fracture toughness testing by ultrasonics

: Bergner, F.; Köhler, B.

Bartos, A.L.; Green, R.E.; Ruud, C.:
Nondestructive characterization of materials VII. Pt.2
Zürich: Trans Tech Publications, 1996
ISBN: 0-87849-730-7
International Symposium on Nondestructive Characterization of Materials <7, 1995, Prag>
Fraunhofer IZFP ()
acoustic; acoustic microscopy; c-mode imaging; cone crack; emission; fracture toughness; Hertzian indentation; soda-lime glass; Vickers indentation

A short review on applications of ultrasonic methods including acoustic emission, scanning acoustic microscopy, and surface wave scattering in the field of indentation fracture toughness testing of brittle materials is given. A problem not solved so far is the nondestructive testing of Hertzian cone cracks in opaque materials. The results of three experimental approaches are discussed: Scanning acoustic microscopy is capable of measuring the local cone angle, but there has been no indication of the crack tip. C-mode scanning permits the determination of the cone diameter, but a calibration is necessary. Time-of-flight measurements have the potential to provide both cone diameter and cone depth simultaneously.