Accession Number : ADA016933

Title :   Dynamic Fracture Toughness Measurement.

Descriptive Note : Final technical rept. May 74-Apr 75,

Corporate Author : NEWCASTLE-UPON-TYNE UNIV (ENGLAND) DEPT OF METALLURGY AND ENGINEERING MATERIALS

Personal Author(s) : Congleton,J. ; Denton,B. K.

Report Date : JUL 1975

Pagination or Media Count : 84

Abstract : An improved crack velocity monitoring procedure able to cope with irregular crack initiation and crack acceleration in ceramics has been developed and used to obtain KId measurements for silicon nitride, polycrystalline alumina and magnesia. The system allowed extended recording times at fast sweep rates for open-camera single shot oscilloscope work. Velocity data was obtained for three point bend tests on PMMA using surface resistance grids to monitor crack growth and an auto-resistance technique was used for velocity measurements during bend tests on tool steels. For the latter, the data was interpreted using an iterative procedure based on an empirical estimate of the functional dependence of the dynamic potential output. Consistent and reproducible data was obtained using auto-resistive crack length measurements for fast fracture in bending, tension and combined impact-tension tests but the interpretation of the resulting data requires further clarification.

Descriptors :   *FRACTURE(MECHANICS), *DYNAMIC TESTS, TEST METHODS, CRACK PROPAGATION, SILICON NITRIDES, ALUMINA, MAGNESIUM OXIDES, BENDING STRESS, CERAMIC MATERIALS, GLASS, POLYMETHYL METHACRYLATE, STEEL, TENSION, IMPACT TESTS, PHOTOGRAPHY, GREAT BRITAIN

Subject Categories : Ceramics, Refractories and Glass
      Metallurgy and Metallography
      Plastics

Distribution Statement : APPROVED FOR PUBLIC RELEASE