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A nonlinear fracture mechanics approach to the growth of small cracksAn analytical model of crack closure is used to study the crack growth and closure behavior of small cracks in plates and at notches. The calculated crack opening stresses for small and large cracks, together with elastic and elastic plastic fracture mechanics analyses, are used to correlate crack growth rate data. At equivalent elastic stress intensity factor levels, calculations predict that small cracks in plates and at notches should grow faster than large cracks because the applied stress needed to open a small crack is less than that needed to open a large crack. These predictions agree with observed trends in test data. The calculations from the model also imply that many of the stress intensity factor thresholds that are developed in tests with large cracks and with load reduction schemes do not apply to the growth of small cracks. The current calculations are based upon continuum mechanics principles and, thus, some crack size and grain structure exist where the underlying fracture mechanics assumptions become invalid because of material inhomogeneity (grains, inclusions, etc.). Admittedly, much more effort is needed to develop the mechanics of a noncontinuum. Nevertheless, these results indicate the importance of crack closure in predicting the growth of small cracks from large crack data.
Document ID
19830025829
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Newman, J. C., Jr.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 11, 2013
Publication Date
April 1, 1983
Publication Information
Publication: AGARD Behaviour of Short Cracks in Airframe Components
Subject Category
Structural Mechanics
Accession Number
83N34100
Distribution Limits
Public
Copyright
Other
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