Three-dimensional crack growth assessment by microtopographic examination

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

OSTI ID:597679

Lloyd, W R ^[1]; Piascik, R S ^[2]

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1. Idaho National Engineering Lab., Idaho Falls, ID (United States)
2. National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center

The initial stage of the stable tearing process in two 2.3 mm sheet 2024-T3 aluminum alloy M(T) specimens are analyzed using fracture surface microtopography reconstruction techniques. The local crack tip opening angles (CTOA) in the interior of the specimens are determined relative to both crack extension and through-thickness position. The microtopographic analysis of cracks grown in the L-T and T-L orientations reveal that interior CTOA is comparable to those measured on the surface using standard optical analysis methods. Similar to surface CTOA results, interior (mid-thickness) CTOA exhibit a transient behavior; CTOA transitions from high angles, at near crack initiation, to a lower steady-state value of 5 deg. and 4.2 deg. for L-T and T-L, respectively, at crack lengths greater than 1.5mm. Fracture surface topographic projection maps are used to study the evolution of crack front tunneling during the initial stage of the fracture process. Stable tearing initiates at mid-thickness followed by a crack front tunneling process to a depth of approximately 2mm. A brief discussion of the basis of the fracture process reconstruction method is provided and comments on the general utility of microtopographic fracture surface examination for general assessment of elastic-plastic and fully-plastic fracture processes are made.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• OSTI ID: 597679
• Report Number(s): CONF-9406335--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
CALCULATION METHODS
CRACK PROPAGATION
FRACTURE MECHANICS
MAPPING
SHEETS
SURFACE PROPERTIES