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 引用本文: 李静, 佟晓龙, 杨烁, 仇原鹰. 考虑平均应力的同频拉扭多轴高周疲劳寿命评价方法[J]. 力学学报, 2020, 52(5): 1409-1421.
Li Jing, Tong Xiaolong, Yang Shuo, Qiu Yuanying. A MULTIAXIAL HIGH CYCLE FATIGUE LIFE PREDICTION MODEL CONSIDERING THE EFFECT OF MEAN STRESS FOR TENSION-TORSION LOADINGS WITH SAME FREQUENCY[J]. Chinese Journal of Theoretical and Applied Mechanics, 2020, 52(5): 1409-1421.
 Citation: Li Jing, Tong Xiaolong, Yang Shuo, Qiu Yuanying. A MULTIAXIAL HIGH CYCLE FATIGUE LIFE PREDICTION MODEL CONSIDERING THE EFFECT OF MEAN STRESS FOR TENSION-TORSION LOADINGS WITH SAME FREQUENCY[J]. Chinese Journal of Theoretical and Applied Mechanics, 2020, 52(5): 1409-1421.

## A MULTIAXIAL HIGH CYCLE FATIGUE LIFE PREDICTION MODEL CONSIDERING THE EFFECT OF MEAN STRESS FOR TENSION-TORSION LOADINGS WITH SAME FREQUENCY

• 摘要: 目前基于临界平面理论的高周疲劳寿命预测模型, 大都充分考虑了法向平均应力对材料疲劳寿命的影响, 但是没有有效反映剪切平均应力对疲劳寿命的影响. 通过分析7075-T651铝合金的试验数据发现, 与法向拉平均应力类似, 剪切平均应力同样对材料的疲劳寿命产生不利影响. 因此, 如果寿命预测模型中忽略剪切平均应力的影响, 存在明显剪切平均应力加载工况下, 预测寿命可能偏于危险. 由此, 本文定义具有较大法向应力的最大剪应力范围平面为临界平面, 建立了一个能够同时反映法向和剪切平均应力影响的高周疲劳寿命预测模型, 并给出了模型中材料常数的确定方法. 新模型首先将基于应变的Fatemi-Socie准则, 推广到材料的高周疲劳寿命预测, 给出了Fatemi-Socie准则的应力表述形式. 然后, 引入剪切和法向Walker因子, 反映剪切和法向平均应力对材料疲劳寿命的影响. 剪切和法向Walker因子的取值都介于0和1之间, 不同取值反映了材料对剪切和法向平均应力敏感程度的不同. 新模型适用于范围内的金属塑性材料. 利用5种材料在12种存在平均应力加载工况下的试验数据, 对所建模型进行了试验验证, 结果表明预测结果与试验结果吻合良好, 绝大多数寿命预测结果分布在3倍误差带以内.

Abstract: The influence of normal mean stress on fatigue life prediction has been well reflected for most of the critical plane-based high cycle fatigue life prediction models, whereas the effect of shear mean stress isn't well considered in these models. It is found that the fatigue life of 7075-T651 aluminum alloy is substantially reduced due to the existing of the shear mean stress by analyzing the experimental data of this aluminum alloy, which is similar to the effect of tensile mean stress. Therefore, nonconservative predictions maybe obtained under the loading paths with substantial shear mean stresses for these life prediction models ignoring the effect of mean shear stress. In order to estimate the fatigue life better, a new critical plane-based multiaxial high cycle fatigue life prediction model is proposed to take into account the effects of both normal and shear mean stresses. In the proposed model, the strain-based Fatemi-Socie criterion is first extended to the high cycle fatigue life prediction. And then a stress-based Fatemi-Socie criterion is developed. The shear and normal Walker factors are introduced in the developed criterion to consider the effects of shear and normal mean stresses, respectively. Both the shear and normal Walker factors vary from 0 to 1, which reflects the sensitivity of the material to shear and normal mean stresses. Procedures to determine the damage parameters acting on the critical plane and to calculate the constants contained in the proposed model are all presented. The proposed model is valid for the metallic materials with the ratio 0.5<\tau _-1 / \sigma _-1 <0.8. Comparisons between test results of 5 kinds of metallic materials and model predictions under 12 types of loading paths with different mean stress levels showed that the proposed model presents relatively accurate predictions. Most of the predictions are fell within a life factor of \pm 3.

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