摘要
In order to evaluate the accumulative of tensile strain in the process of fatigue failure, the digital image correlation（DIC） method was utilized to characterize the tensile strain development of asphalt mixtures in the indirect tensile（IDT）fatigue test. Three typical hot mix asphalt（HMA） mixtures with varying nominal maximum aggregate sizes were tested at four stress levels. During the tests, a digital camera was mounted to capture the displacement/strain fields on the surface of the specimen by recording the real-time change of speckle position. The results indicate that the vertical deformation curve can barely evaluate the fatigue performance accurately due to the non-negligible local deflection near the loading point. However, based on the analysis of strain fields,the optimal fatigue cracking zone is determined as a 40mm×40mm rectangle in the middle of the specimens. Also, a reasonable fatigue model based on the tensile strain curves calculated by DIC is proposed to predict the fatigue lives of asphalt mixtures.
为研究间接拉伸疲劳试验过程中试件中部拉应变的发展规律,选择3种不同最大公称粒径的热拌沥青混合料在4种不同应力比下进行间接拉伸疲劳试验,并采用数字图像相关方法,通过工业相机记录散斑位置随时间的变化,分析疲劳试验过程中试件表面的应变/位移场.试验结果表明,由于压头位置局部应变较大,竖向位移曲线不能准确评价混合料的疲劳性能;基于竖向及横向应变场的分析,定义间接拉伸疲劳试验的最佳疲劳开裂区域为试件中部40 mm×40 mm的方形区域;基于DIC方法可获取试件底部中间的拉应变曲线并建立疲劳方程,从而可以进行沥青混合料疲劳寿命预估.
