局部应力应变疲劳的能量方法

Energy method of local stress and strain fatigue

应用Neuber准则分析弹塑性材料缺口件时局部应力应变估计过高,因此预测初始寿命常给出过于保守的结论.由于当量应变能密度(Equivalent strain energy density,ESED)准则在Neuber准则的塑性变形项上增加了系数,局部应力应变估计结果更为准确.基于能量方法讨论了循环加载下材料的塑性应变能密度,发现ESED准则相比Neuber准则多考虑了塑性应变能密度,这是ESED准则局部应变场估计值远低于Neuber准则的估计值的能量理论基础.疲劳试验的结果验证了以上结论.

Analysis of notched specimen of elastic-plastic materials by using Neuber rule always lead to over high estimated values of local stress and strain. So conservative initial-life results were usually obtained. Since the coefficient was added to equivalent strain energy density rule on the basis of the plastic deformation item of Neuber rule, the local stress and strain estimation results should be more accurate. According to energy method, elastic-plasticity strain energy density of material in the case of cyclic loading was discussed. It was discovered that the plastic strain density was taken into account by the ESED rule, and this was the energy theory basis for the further lower values of local stresses estimated by ESED rule than those obtained by Neuber rule. The above conclusion agreed well with fatigue test.