基于修正Lv模型的低周疲劳寿命预估方法

当材料力学特性不同时,疲劳损伤程度受平均应力的影响不同,于是对Lv模型进行改进.首先,利用材料力学特性系数修正Walker指数,将修正后的指数引入Lv模型.同时,考虑正应变对疲劳寿命造成的影响,修正最大应力.其次,基于M-H模型对材料塑性部分的改进,修正Lv模型塑性变形部分.此外,因为2倍Walker指数对材料特性不敏感,所以引入敏感系数来提高材料受平均应力影响时的反应程度.最后,基于4种航空材料TA11、GH909、FGH96及GH4133合金的低周疲劳试验数据,对SWT模型、M-H模型、Lv模型及改进Lv模型的预估结果进行对比分析.结果表明,相比于其他3种模型,改进Lv模型预测结果具有较好的分散性,在预估精度和适用性等方面均具有较大优势.

Prediction method of low cycle fatigue life based on modified Lv model

The influence of average stress on the fatigue damage is different when the mechanical properties of materials are different, so the influence of material mechanical properties on the fatigue life is considered to improve the Lv model. Firstly, the Walker index is modified by using the material mechanical characteristic coefficient, which is then introduced into the Lv model. At the same time, the maximum stress is modified considering the effect of normal strain on the fatigue life. Secondly, the plastic deformation part of Lv model is modified based on the improvement of the plastic part of M-H model. In addition, the sensitivity coefficient is introduced to improve the response degree of materials under the influence of average stress since double Walker index is insensitive to material properties. Finally, the low cycle fatigue test data of four kinds of aviation materials, i.e. TA11, GH909, FGH96, and GH4133, are used to compare and analyze the prediction results of SWT model, M-H model, Lv model, and improved Lv model. The results show that the improved Lv model has better dispersion and greater advantages in prediction accuracy and applicability compared with the other three models.