基于光偏折法的薄板振动变形场测量技术

Measurement technology of thin plate vibration deformation field based on deflectometry

为了研究PMMA薄板在稳态激振作用下的响应,设计了基于光学偏折术的振动实验装置,结合数字图像相关方法,测量带有反射镜面的PMMA薄板发生弯曲时的变形场。利用高速数字摄像机采集采力锤作用下薄板镜面反射的参考散斑图案,基于光学偏折术原理和数字图像相关方法测得薄板沿X、Y轴的转角场分量,通过傅里叶变换得到薄板的前5阶固有频率。基于薄板的固有频率采用激振器对PMMA进行稳态激励,测量得到薄板在一个振动周期内不同时刻的转角场,进而通过二维积分计算得到不同时刻的离面位移场。实验结果表明,随着激振频率的增加,薄板的振幅愈来愈小,光偏折法对薄板的弯曲变形测量有着很高的灵敏度,可用于薄板微小弯曲变形的高精度测量。

In order to study the response of thin plates under steady-state excitation,a vibration testing set-up based on optical deflectometry was designed,combined with the digital image correlation method(DIC).The bending fields of a PMMA vibrating plate with a mirror surface were measured.Excited by hammer impact,the images of speckle patterns reflected by thin plates were acquired by a high-speed camera.The slope fields along axis X and Y were calculated based on the principle of deflectometry and DIC,and then the first 5 orders of natural frequencies were obtained by FFT.A shaker was used to vibrate the thin plate at different frequencies,and the slope fields at different moments in a period were obtained.And the out-of-plane displacement was calculated from the slope components by inverse gradient integration.With the increase of excitation frequency,the vibrating amplitude of the plate decreases.The results show that this technique has high sensitivity in measuring the bending deformation of thin plates,which can be used to measure small bending deformation of thin plates with high-precision.