坑蚀钢筋疲劳与其压磁效应演化试验研究

EXPERIMENTAL STUDY ON EVOLUTION OF FATIGUE AND PIEZOMAGNETIC EFFECT OF CORROSION PITTED STEEL BARS

海洋环境下混凝土结构内钢筋的锈蚀多为坑蚀,反复荷载作用下极易发生疲劳断裂。文中通过外加电流加速锈蚀方法制作了11根带蚀坑的钢筋试件并进行轴向拉伸疲劳试验,分析坑蚀钢筋疲劳过程中的压磁效应演化规律。研究结果表明,压磁滞回曲线在不同疲劳阶段存在差异,疲劳破坏之前磁感应强度时变曲线发生了显著畸变,可以预警疲劳破坏;试验得到的法向压磁信号演变符合疲劳三阶段规律;蚀坑较深的试件,应力集中效应更加显著,其应力幅值Δσ与磁感应强度幅值ΔB值也较大,疲劳寿命也较低,ΔB可作为评估坑蚀钢筋疲劳损伤程度和疲劳寿命的定量指标。

In the marine environment,the corrosion of steel bars in concrete structures is mostly pit corrosion,which is prone to fatigue fracture under repeated loading.In this paper,11 steel bars with corrosion pits were made by the method of accelerated corrosion with applied current,and the axial tensile fatigue tests were carried out to analyze the evolution law of piezomagnetic effect during the fatigue process of corroded steel bars.The results show that the piezomagnetic hysteresis curves varied in different fatigue stages,and the time-varying curve of magnetic induction intensity is significantly distorted before fatigue failure,which can be used to warn the fatigue failure.Moreover,the evolution of normal piezomagnetic signal obtained from the tests conforms to the three-stage fatigue law.The results show that in the specimens with deeper corrosion pits,the effect of stress concentration is more significant with the lower fatigue life and the larger stress amplitude valueΔσand magnetic induction amplitudeΔB value which can be used as a quantitative index to evaluate the fatigue damage degree and fatigue life of corroded reinforcement.