Effects of mixed mode I/II loading and grain orientation on crack initiation and stable tearing in 2024-T3 aluminum

Conference · Mon Dec 01 04:00:00 EST 1997

OSTI ID:544221

Amstutz, B E; Sutton, M A; Boone, M L ^[1]; Dawicke, D S ^[2]

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1. Univ. of South Carolina, Columbia, SC (United States). Dept. of Mechanical Engineering
2. AS and M, Inc., Hampton, VA (United States)

The effects of material grain orientation and mixed mode I/II loading on crack initiation and stable tearing in 2.3-mm-thick, unclad 2024-T3 aluminum is experimentally investigated. Mode I experiments were performed on center-cracked specimens with the crack being oriented at various angles relative to the rolling direction. Defining {theta} to be the angle between the normal to the initial crack plane and the loading direction, Mode I/II experiments were performed using an Arcan test fixture for 0{degree} {le} {theta} {le} 90{degree} [corresponding to 90{degree} {ge} {beta} {ge} 0{degree}, where {beta} = atan (K{sub II}/K{sub I})] with the crack oriented either along the rolling direction (T-L) or perpendicular to the rolling direction (L-T). Results indicate that: 1. The Mode I crack tip opening displacement (CTOD) is a strong function of the orientation of the crack relative to the rolling direction; CTOD for a T-L specimen is 0.84 mm, increasing linearly with orientation angle to 1.05 mm for an L-T case. 2. The Mode I/II CTOD increases rapidly during initial increments of crack growth and then decreases towards a constant value as crack growth continues. 3. For {theta} < 68{degree} ({beta} > 29{degree}), all cracks kinked and the Mode I/II plastic zones are similar to rotated Mode I plastic zones throughout the crack growth process. 4. J{sub II} = 0 reasonably predicts the direction of tension-dominated crack growth, but does not predict the transition to shear crack growth which occurs for {theta} {ge} 75{degree}. 5. K{sub II} {ge} K{sub I} for {theta} {approx} 58{degree} ({beta} = 45{degree}) does not quantitatively predict the transition to shear crack growth for {theta} {ge} 75{degree} ({beta} {le} 22{degree}), but does provide an indication of changing conditions in the crack tip region.

• OSTI ID: 544221
• Report Number(s): CONF-950618--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AIRCRAFT
ALUMINIUM BASE ALLOYS
CRACK PROPAGATION
FORECASTING
GRAIN ORIENTATION
MECHANICAL TESTS
SERVICE LIFE