NASA Logo

NTRS - NASA Technical Reports Server

Back to Results
An Evaluation of the Plasticity-Induced Crack-Closure Concept and Measurement MethodsAn assessment of the plasticity-induced crack-closure concept is made, in light of some of the questions that have been raised on the validity of the concept, and the assumptions that have been made concerning crack-dp damage below the crack-opening stress. The impact of using other crack-tip parameters, such as the cyclic crack-tip displacement, to model crack-growth rate behavior was studied. Crack-growth simulations, using a crack-closure model, showed a close relation between traditional Delta K eff, and the cyclic crack-tip displacement (Delta eff) for an aluminum alloy and a steel. Evaluations of the cyclic hysteresis energy demonstrated that the cyclic plastic damage below the crack-opening stress was negligible in the Paris crack-growth regime. Some of the standard and newly proposed remote measurement methods to determine the 'effective' crack-tip driving parameter were evaluated on middle-crack tension specimens. A potential source of the Kmax effect on crack-growth rates was studied on an aluminum alloy. Results showed that the ratio of Kmax to Kc had a strong effect on crack-growth rates at high stress ratios and at low stress ratios for very high stress levels. The crack-closure concept and the traditional crack-growth rate equations were able to correlate and predict crack-growth rates under these extreme conditions.
Document ID
19980234244
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
Authors
Newman, James C., Jr. (NASA Langley Research Center Hampton, VA United States)
Date Acquired
September 6, 2013
Publication Date
August 1, 1998
Subject Category
Composite Materials
Report/Patent Number
NAS 1.15:208430
NASA/TM-1998-208430
L-17748
Report Number: NAS 1.15:208430
Report Number: NASA/TM-1998-208430
Report Number: L-17748
Meeting Information
Meeting: Advances in Crack Closure Measurement and Analysis
Location: San Diego, CA
Country: United States
Start Date: November 13, 1997
End Date: November 14, 1997
Sponsors: American Society for Testing and Materials
Funding Number(s)
PROJECT: RTOP 538-02-10-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available