壁板结构热屈曲后模态特性试验

高速飞行器在服役期间面临着严酷的气动加热效应,热载荷会引起材料性能变化,会在结构内部产生热应力、热变形及热屈曲,从而改变结构的有效刚度,影响其动力学特性。针对铝合金壁板结构开展热屈曲后模态特性的试验,采用石英灯辐射加热方法模拟气动加热,利用热应变与温度的关系,获得了壁板结构热屈曲临近温度,进而选取屈曲前、屈曲后一系列温度状态开展热模态试验。试验结果表明,模态频率随加热温度的增加先降低,在临近屈曲温度附近达到最低值,热屈曲后随着温度增加又逐渐增加。由于不同阶模态对热载荷的敏感程度不一样,第3阶和第4阶模态在加热过程中发生交换,而模态阻尼随着加热温度的增加呈现增加的趋势。

Experimental Research on Modal Characteristics of a Thermal Post-Buckling Panel

High speed vehicles are exposed to severe aerodynamic heating during flight. The thermal load can affect material properties and induce thermal stress, thermal deformation, even thermal buckling. Therefore, the dynamic stiffness and modal characteristics change. Experiments are carried out on an aluminum alloy panel to investigate the thermal modal characteristics pre-and post-buckling. The panel is heated using a quartz lamp heating system. The thermal buckling characteristics are first experimentally tested, and the critical buckled temperature is obtained. Then, a series of high temperature modal surveys are carried out. The modal frequency, damping and shape are identified at each temperature distribution. It is shown that the modal frequencies reduce firstly as the temperature increases. However, after the critical buckled temperature, the modal frequencies increase with the augment of the temperature. Since the sensitivities of different modal parameters with the same thermal loads are different, the 3dr and 4th modal shape are swapped during the heating process. The modal damping increases with the raise of temperature.