Abstract
The initiation and propagation behavior of short fatigue cracks emanating from a sharp notch in an aluminum alloy (2024-T6) reinforced with 20 volume percent of SiC particles was investigated. The development of crack closure with crack propagation was measured through the compliance method. The propagation rate, dc/dN, of short cracks was higher than that predicted using the dc/dV-ΔK relation for long cracks. For the case of a low stress amplitude, the propagation of short cracks decelerated and finally stopped. The relationship between dc/dN and the effective stress intensity range, ΔKeff, for short cracks at notches was identical to that obtained for long cracks. The relationship between dc/dN and ΔKeff/E(E=Young's modulus) was nearly identical for short and long cracks in reinforced and unreinforced alloys. The roughness of the fatigue fracture surface was determined using a computer image processing method. The roughness of the fracture surface of composites was larger than that of unreinforced aluminum alloy.
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