Experimental Investigation of the Differential Combination Resonance

对脉动Reut力作用下悬臂柱的总和和微分组合共振进行了实验研究。通过将来自喷嘴的空气喷流撞击安装在柱子自由端的附着板上来实现Reut力。空气喷射的脉动是通过电磁阀实现的，电磁阀由来自函数发生器的信号控制通断。实现的波形不是一个完整的正弦波形。然而，力的周期性是被实现的。测试柱为长1000 mm、深10 mm、厚2 mm的细长塑料板。该附着板是由橡胶制成的。为了改变作用力的方向，附着体上覆盖了一些材料，比如最粗糙的表面是未编织的材料，或者是最光滑的表面是玻璃板。确定了尼龙无纺布的方向系数为0.006，玻璃板的方向系数为0.9。极小的方向系数导致了第一模和第二模之间的微分组合共振。在方向系数为0.9的情况下，观察到第一和第二模之间的总和组合共振。为了确定共振的类型，每个区域的柱子的实验响应被分解为第一和第二模式，使用切割频率为2.0 Hz的高通和低通滤波器。对参数共振边界的理论预测与实验结果进行了比较。该理论得到了实验的定性支持。

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.