悬臂闭孔泡沫铝板的非线性振动实验研究

Experimental study on nonlinear vibration of cantilever closed-cell aluminum foam plates

为了研究闭孔泡沫铝板的非线性振动特性,首先采用电子散斑干涉技术对3个孔隙率相同的悬臂闭孔泡沫铝板共振模态进行了测量,获得了前14阶离面共振激励频率和相应的模态振型,并基于欧拉-伯努利梁模型及1阶弯振频率测量值计算得到闭孔泡沫铝的动态弹性模量.然后对相同孔隙率的闭孔泡沫铝静态单轴压缩力学行为进行了实验研究,测得了其静态压缩弹性模量.实验结果表明:由于闭孔泡沫铝存在大量不规则孔洞结构,导致其振动响应具有明显的非线性,表现为同一振动模态对应于数个谐振激励频率,是典型的超谐振.另外,基于振动分析得到的泡沫铝动态弹性模量是静态压缩弹性模量值的2倍多,这与泡沫铝是拉压双弹性模量材料有关.

In order to analyze the nonlinear vibration behaviour of the aluminum foam plate,first 14 order flexural vibrating mode shapes and driving frequencies of three cantilever closed-cell aluminum foam specimens with the same porosity under harmonic excitation were measured by the the electronic speckle pattern interferometry（ ESPI）. The dynamic Young＇s modulus of closed-cell aluminum foam is obtained based on the Euler-Bernoulli beam model and the measured frequency value of the first order resonant mode. Meanwhile,the mechanical behavior of closed-cell aluminum foams under quasi-static uniaxial compression was investigated experimentally and the static Young＇s modulus was obtained accordingly. Experimental results show that the dynamic response of forced vibration of aluminum foam is nonlinear due to its cellular structure. One resonant mode shape corresponds to several driving frequencies,which is a typical characteristic of super-harmonic vibration. The dynamic Young＇s modulus of the closed-cell aluminum foam is greater than two times of its static Young＇s modulus,which is related to the fact that the aluminum foam is a type of bi-modulus material with different elastic moduli in tension and compression.