疲劳过程中的能量耗散和疲劳寿命的预测

试验测量了A3钢和铝合金LY12CZ在疲劳过程中的耗散能密度与应力幅的关系和破坏时的临界累积耗散能密度。通过一系列不同加载频率和应力比的比较试验，结果表明耗散能密度与应力幅的关系和临界累积耗散能密度在不同加载频率下变化不大，但是受应力比的影响较大。本文还建立了临界累积耗散能密度疲劳寿命预测判据，并用此判据进行了带中心孔板条构件的疲劳寿命预测，取得了较好的结果（误差在25％以内）。这种方法对于构件局部的疲劳主要由一个方向应力控制的工程问题，使用简便有效。

On the Energy Dissipation in Fatigue Process and Fatigue Life Prediction

Relation between the stress amplitude and the dissipated energy density in fatigue process and the critical cumulative dissipated energy density for material damage were studied experimentally on A3 steel and LY12CZ hard aluminium alloy respectively. Different controlling conditions were changed to determine the effect of experimental parameters. A series of experimental result shows that the effect of loading frequency on the relation between stress amplitude and dissipated energy density and the critical cumulative dissipated energy density is small, while the effect of stress ratio is more significant. A criterion was established to predict fatigue life of sheet with center hole under axial cyclic loading based on critical cumulative dissipated energy density. The result can be accepted since the error percentage is less than 25%. This method is simple and effective for some engineering structure with local fatigue damage mainly controlled by one principal stress.