基于疲劳驱动力能量损伤参数修正的非线性疲劳寿命预测

针对疲劳驱动力能量模型中变幅载荷间交互因子难以确定的问题,考虑载荷大小次序、载荷间的干涉以及疲劳损伤程度等因素对变幅载荷作用下损伤累积规律的影响,在引入能量准则确定损伤参数的基础上,将变幅载荷应力比、载荷循环比、疲劳损伤程度引入载荷间交互因子的计算,建立分别采用载荷循环次数比和实时疲劳损伤对交互因子进行修正的改进非线性疲劳寿命预测模型。根据Q235B和铝合金2种常用材料的焊接接头在多级变幅载荷作用下的试验数据,对改进的疲劳寿命预测模型的预测能力进行验证。结果表明:在变幅载荷作用下,改进的疲劳寿命预测模型能有效地对焊接结构的疲劳寿命进行预测,相比其他模型更接近于试验结果,且模型中仅含有2个比较容易通过试验确定的常规参数,无需引入其他参数,便于应用于实际工程结构的分析及设计。

Nonlinear Fatigue Life Prediction Based on Energy Damage Parameter Correction of Fatigue Driving Force

In view of the difficulty in determining the interaction factors between variable amplitude loadings in the fatigue driving force energy model,an improved nonlinear fatigue life prediction model was established,in which the interaction factors were modified by cyclic loading ratio and real-time fatigue damage degree respectively,considering the influence of loading sequence,loading interaction and fatigue damage degree on the damage accumulation rule under variable amplitude loading.Based on the energy criterion to determine the damage parameters,the variable amplitude loading stress ratio,loading cycle ratio and fatigue damage degree were introduced into the calculation of the interaction factor between loads.According to the test data of the welded joints of Q235 Band aluminum alloy under multi-stage variable amplitude load,the predictive ability of the improved fatigue life prediction model was verified.Numerical results show that,under the action of variable amplitude load,the improved fatigue life prediction model can effectively predict the fatigue life of welded structures,which is closer to the test results than other models.The model contains only two conventional parameters that can be easily determined by experiments,and no additional parameters need to be introduced to facilitate the analysis and design of practical engineering structures.