变幅载荷下填充型天然橡胶疲劳试验与预测方法研究

以填充天然橡胶哑铃型圆柱试件为研究对象,进行不同应变比R与变幅载荷下的单轴疲劳试验,并分析变幅载荷对疲劳寿命的影响。以应变幅值为损伤参量,建立基于应变比R=0的等效应变幅值统一疲劳寿命预测模型,利用该模型预测所有应变比工况下的疲劳寿命,其预测值与实测寿命的偏差在2倍分散因子以内;对不同应变比R、载荷水平、加载顺序与停顿时间等变幅载荷下的疲劳寿命进行单轴疲劳试验,基于Miner线性损伤法则预测变幅载荷下的疲劳寿命,和实测寿命相比其偏差都落在2倍分散因子以内;对哑铃型试件进行随机载荷疲劳试验,通过雨流统计和不同应变比R下的统一疲劳寿命预测模型计算其总寿命,预测结果和实测结果最大误差在34%以内。验证了Miner线性损伤法则在填充型天然橡胶疲劳寿命预测中的普适性,所建立的不同应变比R下的等效应变幅值统一疲劳寿命预测模型可用于橡胶隔振器的前期耐久评估。

Experiment and Fatigue Life Prediction of Filled Natural Rubber under Variable Amplitude Loading Conditions

Under various strain ratios (R=max/min) loads and variable amplitude loading, uniaxial fatigue experiments are carried out for dumbbell cylindrical specimens of filled natural rubber, and the effect of variable amplitude loading on fatigue life is investigated. Based on the fatigue measurement data, a unified fatigue prediction model with equivalent strain amplitude damage is established. The predicted life of cylindrical specimen is within a factor of two compared to tested life under R>0 and R<0 loading conditions. Variable amplitude loadings are selected to show the effects of R-ratio, load level, load sequence and dwell periods on uniaxial fatigue life test. The predicted life under variable amplitude loading based on Miner linear damage rule and the unified life prediction model is fully within a factor of two compared to measured life. The dumbbell specimens are tested under random loading. The predicted life is calculated based on rain-flow count and unified fatigue prediction model, while the maximum error is less than 34%for tested and predicted life. The proposed unified fatigue life prediction model and Miner linear damage rule can be used to estimate the fatigue life of a filled natural rubber component under variable loading conditions.