激励对柔性结构上设备振动传递率的影响

对机载仪器设备进行振动控制是提高其精度和寿命的重要手段。发动机、其它设备或者外部环境振动通过机体结构传递到机载设备。从这一实际出发,将机体结构建模为弹性梁,认为外部激励直接作用于梁结构,并通过隔振器传递到机载设备。运用子结构导纳法建立基础-隔振器-刚体系统动力学模型,推导出由基础结构通过隔振器传递到机器设备的速度传递率表达式,分析速度传递率随激励频率和激励施加位置变化规律,并通过试验进行验证。结果表明,基础梁的横向共振是导致传递率增大的主要原因;相对于基础梁非对称激励能激发更多基础结构弯曲共振模态;高频激励会引起隔振器纵向与弯曲共振产生驻波效应;推导出公式在100 Hz~1 000 Hz之间能够比较准确地反映传递率的变化。

Effect of Excitation on Vibration Transmission Characteristics of Mechanical Equipment on Flexible Structures

It is important for devices and equipments on board to isolate the vibration from base structure because of the dependency of accuracy and lifespan on vibration. The excitation comes from base structure directly for the devices, so a dynamic system that consists of a flexible base, vibration isolators and a rigid body is considered in this paper. Based on sub-structures method and the concept of admittance, the model of the dynamic system is constructed, and the expression of transmitted vibration from base to equipment is deduced. The effects of frequency and allocation on vibration are analyzed by simulation and tests. The result shows that the transverse resonance of the beam is the main reason of the high vibration transmissibility; the nonsymmetrical excitation can arouse more bending resonant modes of the foundation architecture; excitation with higher frequency will cause longitudinal and bend vibration of the vibration isolator that result in standing wave effect; the expressions given can reflect the vibration transmissibility accurately at the range of 100-1000Hz.