Determination of fatigue parameters in total strain life equation and life prediction

Several prediction methods were summarized and evaluated, and the expressions of fatigue strength coefficient, fatigue ductility coefficient, fatigue strength exponent, fatigue ductility exponent were given, then an equation having both good physical and mechanical significance and universal utility was proposed, with which good fatigue life prediction results within a scatter band of 2 for six typical aeroengine materials(TC4(room temperature), TC11(room temperature), TC11(500℃), GH901(300℃), GH901(500℃) and GH4133B(600℃)) were gained; four fatigue parameters acquired from several prediction methods were compared and analyzed, and five forms of true fracture stress were proposed, helping to derive the fatigue strength coefficient accordingly. It was found that the true fracture stress proposed gained more accurate results compared with the test having an error not more than 15%, then a conclusion was made that applying true fracture stress could realize high accuracy in midhigh life prediction.