基于非线性超声混频技术的钢绞线张力识别研究

Identification of steel strand tension based on nonlinear ultrasonic frequency-mixing technology

监测钢绞线应力水平对保证后张混凝土结构、斜拉桥和拱桥的合理结构性能具有重要意义。基于一维入射条件下钢丝接触模型的谐波产生机理,建立钢绞线张力与边频非线性系数之间函数关系;采用有限元仿真和逐级加载试验,计算不同张力水平下边频非线性系数和二次谐波非线性系数;分析激励源输入功率的影响。结果表明,遴选混频激励下钢绞线中产生明显的边频调制谐波和二次谐波;边频非线性系数和二次谐波非线性系数随张力水平变化符合理论模型下降规律;相较而言,边频非线性系数随张力变化规律性更明显,受激励源功率影响更小。

Monitoring stress level of steel strand is of great significance to ensure reasonable structural performance of post tensioned concrete structures,cable-stayed bridges and arch bridges.Based on the harmonic generation mechanism of steel wire contact model under 1-D incidence,the function relationship between steel strand tension and side frequency nonlinear coefficient was established.Finite element simulation and step-by-step loading tests were used to calculate nonlinear coefficients of combined harmonic and second harmonic under different tension levels,and analyze effects of input power of excitation source.The results showed that obvious combined harmonics and second harmonics are generated in steel strand under selected frequency-mixing excitations;the variation of combined harmonic nonlinear coefficient and second harmonic nonlinear coefficient with tension level varying conforms to the decline law of theoretical model;the variation law of combined harmonic nonlinear coefficient with tension varying is more obvious and less affected by excitation source power.