基于DIC混凝土轨枕和复合轨枕受弯特征分析

Analysis of bending characteristics of FFU composite sleeper and concrete sleeper based on digital image correlation

轨枕是轨道结构重要组成部分,在上部荷载和下部道砟共同作用下处于受弯状态,常产生裂纹,增加维修费用,影响行车舒适性和安全性。采用数字图像相关技术(Digital Image Correlation),通过三点弯曲试验,分析Ⅲ型预应力混凝土轨枕、FFU复合轨枕受弯特征、裂纹发展过程和裂纹开口位移。研究结果表明:数字图像相关技术在位移和裂纹测试中具有高精确性;混凝土轨枕在加载初期处于弹性阶段,刚度大,随荷载增加,裂纹不断发展,刚度逐渐减小,抵抗变形能力下降,裂纹开口位移增加速率逐渐增大;FFU复合轨枕受弯过程中始终处于弹性状态,裂纹产生原因为层间分离,裂纹开口位移增加速率在裂纹开口完全分离时增加,之后保持不变。

The sleeper is an important part of the track structure. Under the combined effect of load and ballast, the sleeper is in the bending state, which often produces cracks. The cracks will increase the maintenance cost, and affect the safety and comfort of passengers. In this paper, digital image correlation is used to analyze the bending characteristics, crack propagation path and CMOD(crack mouth opening displacement) of Ⅲ prestressed concrete sleeper and FFU composite sleeper through three-point bending test. The results show that DIC has high accuracy in displacement and crack measures. The concrete sleeper is in the elastic stage at the initial loading stage with large stiffness. With the increase of load, the crack develops continuously, the stiffness decreases gradually, the resistance to deformation decreases, and the increase rate of CMOD increases. The FFU composite sleeper is always in an elastic state during the bending process, and the crack is caused by inter-layer separation. The increase rate of CMOD increases when the crack opening is completely separated, and then remains unchanged.