Three-dimensional CTOA and constraint effects during stable tearing in a thin-sheet material

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:597670

Dawicke, D S ^[1]; Newman, Jr, J C ^[2]; Bigelow, C A ^[3]

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1. Analytical Services and Materials, Inc., Hampton, VA (United States)
2. National Aeronautics and Space Administration, Hampton, VA (United States)
3. FAA Technical Center, Atlantic, City, NJ (United States)

A small strain theory, three-dimensional elastic-plastic finite element analysis was used to simulate fracture in thin sheet 2024-T3 aluminum alloy in the T-L orientation. Both straight and tunneled cracks were modeled. The tunneled crack front shapes as a function of applied stress were obtained from the fracture surface of tested specimens. The stable crack growth behavior was measured at the specimen surface as a function of applied stress. The fracture simulation modeled the crack tunneling and extension as a function of applied stress. The results indicated that the global constrain factor, {alpha}{sub g}, initially dropped during stable crack growth. After peak applied stress was achieved, {alpha}{sub g}, initially dropped during stable crack growth. After peak applied stress was achieved, {alpha}{sub g}, began to increase slightly. The effect of crack front shape on {alpha}{sub g} was small, but the crack front shape did greatly influence the local constraint and through-thickness crack-tip opening angle (CTOA) behavior. The surface values of CTOA for the tunneled crack front model agreed well with experimental measurements, showing the same initial decrease from high values during the initial 3 mm of crack growth at the specimen`s surface. At the same time, the interior CTOA values increased from low angles. After the initial stable tearing region, the CTOA was constant through the thickness. The three-dimensional analysis appears to confirm the potential of CTOA as a two-dimensional fracture criterion.

• OSTI ID: 597670
• Report Number(s): CONF-9406335--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
CRACK PROPAGATION
CRACKS
MATHEMATICAL MODELS
MECHANICAL TESTS
STRESSES
THREE-DIMENSIONAL CALCULATIONS