基于半解析模型的花萼状涡流传感器损伤监测灵敏度分析

针对金属螺栓连接结构的孔边疲劳裂纹监测需求,介绍了一种具有柔性平面特点的花萼状涡流传感器,构建其损伤监测半解析模型,并通过半解析模型分析激励频率和传感器结构参数对监测灵敏度的影响,最后利用柔性电路板工艺制备出传感器,并进行2A12铝合金中心孔板试样疲劳损伤监测试验验证花萼状涡流传感器的疲劳裂纹监测能力。损伤监测灵敏度分析结果表明在不同提离距离下传感器具有最优灵敏度频率点,且随提离距离的增大,最优灵敏度值减小,最优频率点降低。传感器线圈厚度越小灵敏度越高,且感应线圈与激励线圈之间的水平间距越大则传感器的损伤监测灵敏度越大,而感应线圈与激励线圈宽度比值对传感器的损伤监测灵敏度影响较小。监测试验表明,除第一个通道以外,传感器其它感应通道归一化跨阻抗幅值随疲劳载荷次数变化曲线的拐点对应的即为裂纹扩展到相应通道下方的疲劳载荷次数,而第一个通道的拐点可以初步确定试件的累积损伤起始点。

Crack Monitoring Sensitivity Analysis of Rosette Eddy Current Sensor Based on Semi-Analytical Model

To monitor the crack damage located at bolt hole of metallic bolted-joint structure, a kind of rosette eddy current sensor with flexible and planar features was introduced, and the effects of driving frequency and sensor geometric parameters on crack monitoring sensitivity of sensor were analyzed based on constructed damage monitoring semi-analytical model. Four-channel rosette eddy current sensor was prepared with flexible printed circuit board technology, and fatigue crack monitoring experiment of 2A12 aluminum alloy specimen with center hole was carried out to verify the fatigue crack monitoring capability of sensor. Analysis results show that optimized driving frequency exists under difference liftoffs and the optimized damage monitoring sensitivity decreases with the increasing of liftoff. Damage monitoring sensitivity increases with decreasing of winding thickness and increasing of distance between driving and sensing winding, while the ratio between driving and sensing winding width has small effect of on monitoring sensitivity. Monitoring experiment result indicate that monitoring curve changing-point of sensing channels could be served as the indication of crack position except channel 1, and monitoring curve changing-point of channel 1 is initiation point of accumulated fatigue damage.