多轴载荷下结构细节疲劳强度额定值确定方法

目的提出一种在多轴载荷下确定结构细节疲劳强度额定值的方法。方法基于单轴双点法细节疲劳强度额定值(DFR)确定方法,在多轴载荷下,首先利用高周多轴疲劳损伤模型求出其等效应力幅(等效拉伸应力幅或等效剪应力幅),结合Goodman方程,把等效应力幅转换为应力比R=0.06时的最大正应力,最终确定多轴条件下的细节疲劳强度额定值。通过7075-T651铝合金薄壁管进行单轴疲劳试验,确定单轴细节疲劳强度额定值,并进行多轴疲劳试验,包括比例加载和非比例加载。结果采用该方法预测多轴载荷下的DFR值,对比单轴试验的DFR值,相对误差的绝对值在10%左右。结论该方法确定多轴条件下的结构细节疲劳强度额定值具有较好的效果。

Determination of Detail Fatigue Rating of structure under Multiaxial Loading

Objective To propose a method for determining Detail Fatigue Rating (DFR) of structure under multiaxial loading. Methods Based on the two-point method for uniaxial loading (DFR), the high-cycle multiaxial fatigue test model was adopted to obtainthe equivalent stress (equivalent tensile stress or equivalent shearing strength). The equivalent stress was transferred to the equivalent tension stress under R=0.06 through the Goodman equation, to determine the detail fatigue rating under multiaxial loading. The equivalent stress was determined by employing a multiaxial high-cycle fatigue model. According to the uniaxial fatigue tests for 7075-T651 aluminum alloy under R=0.06, the DFR for uniaxial loading was determined. Then, the multiaxial fatigue tests were conducted, including the proportional and non-proportional loadings. Results From the comparisons between the predicted DFR for multiaxial loading and the experimental DFR for uniaixal loading, the absolute value of the relative errors was about 10%. Conclusion The proposed method, for the determination of the DFR under multiaxial, has a good predictive capability.