Accession Number:

AD0259739

Title:

THE SLOW GROWTH AND RAPID PROPAGATION OF CRACKS

Descriptive Note:

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s):

Report Date:

1961-05-17

Pagination or Media Count:

11.0

Abstract:

The application of fracture mechanics to crackpropagation testing and fracture of high-strength, thin-section materials has been examined in relation to the development of a fracture failure from a small semi-elliptical, surface crack origin. In the absence of environmental influences, slow crack growth will be appreciable only if the ratio of the fracture toughness for the thickness under consideration, K sub c, to the so-called plane strain fracture toughness, K sub Ic, exceeds a certain value. An expression for this lower-bound value has been developed. If the ratio does not exceed the lower bound, direct calculations of fracture stress from the initial crack dimensions and the K sub Ic value can be made. Otherwise, the Irwin criterion that the critical crack length must exceed twice the section thickness applies. Environmental effects are important but are normally a factor only in material selection and not in fracture mechanics calculations. Author

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE