Fracture surface interference in shear. 2: Experimental measurements of crack tip displacement field under Mode II loading in 7075-T6 Al
- Univ. of New Hampshire, Durham, NH (United States). Dept. of Mechanical Engineering
- Limco Manufacturing Corp., Glen Cove, NY (United States)
The in-plane and out-of-plane displacement field around the tip of a crack (produced by Mode I fatigue precracking) loaded in pure, remote Mode II was measured as a function of K{sub IIapp} by electro-optic holographic interferometry. The effective Mode II stress intensity factor and the induced Mode I stress intensity factor were estimated from a fit to the near-tip expressions for the crack face displacement fields. The effective Mode II stress intensity factor was always less than the applied stress intensity factor demonstrating that the fracture surface asperities shield the crack tip. The induced Mode I stress intensity factor was roughly half that of the applied Mode II stress intensity factor, demonstrating that pure Mode II cracks cannot be obtained for cracks with microscopically rough surfaces. Plateaus and jumps in the dependence of the effective Mode II and induced Mode I stress intensity factor on the applied Mode II were correlated further supporting the notion that the fracture surface interference is based on asperity interactions. Analysis of the data shows that force transfer across the crack faces cannot be simply described by a frictional interaction across the asperities. It is suggested that deformation of the asperities must be considered to accurately model the shielding and induced crack face opening under remote Mode II loading.
- DOE Contract Number:
- FG02-90ER45433
- OSTI ID:
- 31709
- Journal Information:
- Acta Metallurgica et Materialia, Vol. 43, Issue 3; Other Information: PBD: Mar 1995
- Country of Publication:
- United States
- Language:
- English
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