镁合金低周疲劳寿命预测模型探讨

Discussion of Low Cycle Fatigue Life Prediction Models for Magnesium Alloys

通过铸造镁合金AZ91D和变形镁合金AZ31B室温环境下应力控制的低周疲劳试验,采用Basquin模型、SWT模型、应变能-寿命模型等模型进行了镁合金低周疲劳的寿命预测。在此基础上,基于连续介质损伤力学的不可逆热力学理论,将镁合金的低周疲劳损伤视为一个不可逆的耗散过程,用熵来反映系统的耗散过程,并以每一次循环的平均应变增量来反映平均应力对材料的影响,提出了一种新的镁合金低周疲劳寿命预测模型。用该模型进行了镁合金的低周疲劳寿命预测,预测结果与实测结果符合较好,同时相比上述其他模型,该模型具有较好的预测效果。

Through low cycle fatigue experiments of the cast magnesium alloy AZ91D and the wrought magnesium alloy AZ3IB at room temperature under stress control, the fatigue life prediction was conducted by the Basquin model, the SWT model and the strain energy-life model. Then, regard- ing the low cycle fatigue damage of magnesium alloys as an irreversible dissipation process that might be described by the entropy according to the irreversible thermodynamics theory of continuum damage mechanics, and using the mean strain increment per cycle to reflect the effects of the mean stress, a new model for the low cycle fatigue life prediction of magnesium alloys was developed. By this model, the low cycle fatigue life prediction of magnesium alloys was carried out through the experiments men- tioned above. Results show that the predicted results are in good agreement with the experimental re- suits. And compared with the other life prediction models, the new model for the low cycle fatigue life prediction of magnesium alloys has a better effectiveness.