总应变寿命方程中疲劳参数的确定和寿命预测

总结分析了多种寿命预测方法,给出了总应变寿命方程的4个材料参数:疲劳强度系数、疲劳延性系数、疲劳强度指数和疲劳延性指数的表达形式,从而提出了一种新的具有很好物理意义、工程意义和普适性的总应变寿命方程,并以6种典型的航空材料光滑试样(TC4(室温)、TC11(室温)、TC11(500℃)、GH901(300℃)、GH901(500℃)和GH4133B(600℃))的对称循环疲劳数据进行验证,获得了很好的疲劳寿命预测结果,其寿命预测结果大都在2倍分散带以内。对比分析了多种寿命预测方法所确定的4个疲劳参数,并且分析了5种断裂真应力表达形式所确定的疲劳强度系数,发现所提出确定断裂真应力的方法获得了较好的精度,与试验值相比,不超过其误差的15%,并且准确确定断裂真应力将会显著提高对中高寿命段的寿命预测精度。 

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.