基于扫描式激光多普勒测振仪的叶片工作变形研究

Operational Deflection Shape of a Blade Based on Scanning Laser Doppler Velocimeter

目的保证叶片结构的完整性。方法采用结构工作变形分析理论,借助扫描式激光多普勒测振仪多点、非接触、高精度测量的优点,搭建了一套发动机叶片工作变形分析试验系统。通过振动台对叶片施加快速正弦扫频的基础激励,用测振仪测量叶片表面55个测点的速度响应,然后用工作变形分析方法得到该叶片的前6阶固有频率和振型,用模态置信准则评估上述6阶振型之间的相关性。结果该叶片振型由低阶到高阶依次是一阶弯曲、两种不同节线的一阶扭转、二阶弯曲、二阶扭转、弯扭耦合,不同阶次振型的MAC值都小于或等于0.2。结论不同模态振型之间的相关性很低,证明了工作变形分析结果的正确性。

Objective To keep integrity of the blade.Methods The theory of structural operational deflection shape was applied.The operational deflection shape test system of aeroengine blade was established with a scanning laser Doppler velocimeter which has advantages of measurement multi-points,non-contact and high precision.A fast sine sweep base excitation was applied to the blade by a vibration table.The velocity response of 55 points on the blade was measured with the laser velocimeter.The front six natural frequencies and vibration modes of the blade were obtained through the operational deflection shape analysis method.The correlation between the above 6 modes of vibration was s evaluated according to the modal assurance criteria(MAC).Results The front six modes are first bending,two kinds of first twist,second bending,second twist and bending-twist coupling.The MAC of different modes was all smaller or equal to 0.2.Conclusion The correlation of different mode shapes is very small.The result correctness of operational deflection shape analysis is validated.