Prediction of ductile crack formation in uncracked bodies

One of the important challenges facing the scientific and engineering community is the development of a reliable computational tool for predicting failure of structures under extreme and/or accidental loads. Considered in the present thesis is the process of formation of ductile cracks, which may be responsible for a catastrophic structural failure. Experimental, numerical and analytical studies are carried out on the prediction of ductile crack formation in uncracked bodies on an example of 2024-T351 aluminum alloy. A methodology for ductile crack formation suitable in industrial applications is developed through the introduction of different weighting functions for different stress triaxiality ranges where different ductile crack formation mechanisms occur ("shear fracture" in negative stress triaxialities, void nucleation, growth, and linkage in high stress triaxialities, a transition mode in intermediate stress triaxialities). A cut off value at the stress triaxiality of -1/3 is discovered. Effects of stress and strain ratios, specimen size and anisotropy are also quantified. It is found that the stress triaxiality and the equivalent strain are the two most important parameters governing ductile crack formation while other parameters are probably of secondary importance. A modification to the criterion is introduced to predict crack formation in a single reversal of straining. A case study of a solid aluminum 2024-T351 beam with a smooth round notch under 3-point bending is conducted.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Ocean Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Bao, Yingbin, 1972-

Advisor dc:contributor.advisor

• Tomasz Wierzbicki.

• Ocean Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/17634

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/17634