基于电磁感应特性的钢绞线应力检测试验研究

针对现有技术难以有效检测在役斜拉桥镀锌钢绞线拉索应力状态的问题,结合电磁无损检测技术在检测铁磁性材料应力方面的优势,提出了一种基于电磁感应特性的镀锌钢绞线拉索应力检测方法。设计了8个镀锌钢绞线试件,运用万能试验机对试件进行控制张拉,利用LCR数字电桥采集试件张拉过程中的电磁信号,研究电磁信号的变化特征,分析电磁信号和试件应力之间的关系。研究结果表明:试件相对磁导率μ_r随着应力σ的增加先增大后减小,在应力达到试件抗拉强度f_ptk的73.29%时存在极大值;试件相对磁导率对应力的梯度dμ_r/dσ随着应力的增加先增大后减小,在应力达到试件抗拉强度f_ptk的36.07%时存在极大值,且当梯度dμ_r/dσ≥0时,试件应力处在试件抗拉强度f_ptk的73.29%之内。该试验验证了基于电磁感应特性技术检测钢绞线应力的可行性,可为今后镀锌钢绞线拉索应力检测提供技术参考。

Experimental Study on Stress Detection of Galvanized Steel Strand Based on Electromagnetic Induction Characteristics

The stress state of galvanized steel strand cable for cable-stayed bridge in-service are hard to be detected effectively by existing technologies. In view of this, a method based on electromagnetic non-destructive testing technology was proposed to detect the stress state of galvanized steel strand cable. Controlled tension test was performed on eight galvanized steel strand specimens using universal testing machine. The electromagnetic signals in the tension process were obtained via LCR meter. The variation characteristics of the signals were examined, and the relation between electromagnetic signals and stress state of the specimens was analyzed. Test results illustrated that with the rising of tensile stress σ, the relative magnetic conductivity μ_r of specimens increased at first and then decreased. The peak of μ_r arrived when stress reached 73.29% of tensile strength f_ptk of the specimens. Still with the rising of stress σ, the value of dμ_r/dσ which denotes the gradient of relative magnetic permeability to tensile stress increased at first and then decreased. The peak value of dμ_r/dσ occurred when stress reached 36.07% of tensile strength f_ptk. Besides, while the value of dμ_r/dσ was not less than zero, the stress of specimen was within 73.29% of tensile strength f_ptk. The test verifies the feasibility of detecting the stress of steel strand based on electromagnetic induction technology, and offers a technical reference for future stress detection of galvanized steel strand cable.