Tolerance limit concept was used to construct design curves against the deficiencies of the existing methods. Comparative analysis was implemented to evaluate the safety of the design curve. Experimental result shows that fatigue scatter varies with stress levels. Based on approximate Owen tolerance limit

an improved design curve has been developed to comply with the feature of fatigue scatter that becomes small in high stress levels and large in low stress levels. According to the fatigue test results of Ti-6246

the fatigue life derived from the new method increased by 146% at 925MPa and decreased by 60.2% at 820MPa compared with other methods. Reliability and economy can be improved with the new fatigue design curve.