基于激光干涉测量的冲击损伤程度表征

Characterization of impact damage degrees based on laser interferometry

传统的压电传感器用于板结构表面的冲击监测时,受到其接触式测量方式和窄带宽的影响,从而降低了监测过程的准确性,而外差干涉测量的系统设计结构复杂、成本较高,因此研究了一套基于零差干涉原理的激光测振方法来进行板结构表面的冲击监测。分析了激光零差干涉测振方法原理,研究了冲击损伤机理和损伤程度表征方法,最后设计了激光零差干涉测量系统,并进行了板结构的冲击损伤监测实验。实验研究中,分别采集了在板结构上不同位置的冲击损伤响应信号,利用快速傅里叶变换和小波分解提取了瞬时冲击损伤响应信号中的多个损伤特征参数,通过对比损伤特征与损伤程度之间的关系,得出了表征冲击损伤程度的最优特征参数。研究结果表明,用该方法来表征冲击损伤程度一定程度上消除了仅信号强度单一评价损伤程度的局限性。

Traditional piezoelectric sensors are used to monitor the impact on surfaces of the plate structures,but their contact measurement method and narrow bandwidth reduce the monitoring accuracy.Plus,the design of heterodyne interferometry is complicated and costly.Therefore,a set of laser vibration measurement methods based on the principle of homodyne interference is proposed to investigate the impact of the surface of the plate structure.First,the principle of the laser homodyne interferometer vibration measurement method is analyzed.Second,the impact damage mechanism and the damage degree characterization method are studied.Third,the laser homodyne interferometer measurement system is designed,and the impact damage monitoring experiment of the plate structure is carried out.In the experiment,the impact damage response signals at different positions on the plate structure are collected,and multiple damage characteristic parameters in the instantaneous impact damage response signal are extracted by fast Fourier transform and wavelet decomposition.By comparing the damage features with the degrees of damage,we obtain the optimal characteristic parameters that can reflect the degree of impact damage.The proposed method can characterize the degree of impact damage and to some extent counteract the limitation of evaluating damage degrees only by the signal strength.