Fatigue thresholds of discontinuously reinforced aluminum alloy correlated to tensile strength

The fatigue strength of reinforced and unreinforced aluminum alloys with silicon carbide particles or whiskers increases in proportion to the ultimate tensile strength. The proportional constant is slightly larger for composites than for unreinforced alloys. The threshold stress intensity range ΔKth tends to decrease with increasing tensile strength. When compared at the same tensile strength, ΔKth tends to be larger for composites than for unreinforced alloys. The effective threshold stress intensity range, ΔKeffth, is fairly constant irrespective of the tensile strength. The characteristic defect sizes, a′0 and a0, tend to be smaller with increasing tensile strength. When compared at the same tensile strength, a′0 is larger for composites, which indicates a low notch sensitivity of composites.