Experimental Investigation of the Differential Combination Resonance

总结和差分组合共振，引起的悬臂柱受到脉动罗伊特力，实验研究。Reut力是通过从喷嘴将空气射流撞击到安装在柱上的自由端附着板来实现的。射流的脉动是通过一个电磁阀来实现的，电磁阀由一个函数发生器发出的信号来控制开关。所实现的波形不是一个完整的正弦波形。但实现了力的周期性。试验柱为长1000mm，深10mm，厚2mm的细长塑料板。连接板是由轻木制成的。为了改变作用力作用线的方向，连接件上覆盖了一些材料，比如最粗糙的表面是无纺布材料，最光滑的表面是玻璃板。确定尼龙无纺布材料的方向系数为0.006，玻璃板的方向系数为0.90。极小的方向系数导致第一模态和第二模态之间的组合共振存在差异。当方向系数为0.9时，观察到第一模态和第二模态的总和共振。为了确定共振类型，使用切割频率为2.0Hz的高通和低通滤波器将每个区域柱的实验响应分解为第一和第二模式。对参数共振边界的理论预测与实验结果进行了比较。实验定性地支持了这一理论。

Summed and differential combination resonances, caused in cantilevered columns subjected to a pulsating Reut force, are experimentally investigated. Reut force is realized by impinging an air jet from the nozzle onto the attachment-plate mounted to the column at the free end. Pulsation of the air jet is carried out by means of an electromagnetic valve which is on-off-controlled by the signal from a function generator. The realized wave form is not a complete sinusoidal form. However, the periodicity of force is realized. The test column is a slender plastic plate of length 1000mm, depth 10mm and thickness 2mm. The attachment-plate is made of balsa. To change the direction of the line of action of an applied force, the attachment was covered with materials such as unwoven material for the roughest surface or a glass plate for the smoothest surface. It was confirmed that the direction coefficient was 0.006 for the case of nylon unwoven material and 0.90 for the case of glass plate. The vanishingly small direction coefficient resulted in differential combination resonances between the first and second mode. Summed combination resonance between the first and second modes was observed for the direction coefficient of 0.9. To confirm the type of resonances, experimental responses of the columns in each region were resolved into the first and second modes, using high-pass and low-pass filters with the cutting frequency 2.0Hz. Theoretical predictions of boundaries of parametric resonances are compared with the experimental results. The theory is supported qualitatively by the experiment.