含宏观孔泡沫铝阻尼行为研究

本文采用空气加压渗流技术制备了含宏观孔开孔泡沫铝材料。宏观孔的直径大小为0.8毫米和1.4毫米,宏观孔体积分数为69%和76%。通过多功能内耗仪采用内耗技术测试了泡沫铝在不同温度、不同频率和不同振幅下的内耗谱特征,利用内耗技术研究了宏观孔开孔泡沫铝的阻尼行为。泡沫铝的阻尼能力比致密工业纯铝的阻尼能力得到了很大的提高,泡沫铝的内耗随着测量频率的增加而增加。同时,内耗也随着应变振幅的增加而增大。运用透射电子显微镜对材料的微观结构进行了观察,发现在晶界附近存在有大量的位错亚结构。根据内耗测量和微观观察提出了泡沫铝中可能的阻尼机制：孔周围的应力集中和模式转换、孔洞/金属基体界面处由于动力学模量相差很大而使机械能转化为热能和孔洞发生不均匀的膨胀或畸变使外加应变能耗散为热能。

Study on Damping Behavior of Foamed Aluminum with Macroscopic Pores

Experiments have been carried out to study the effects of macroscopic open - pores on the damping behavior of foamed commercially pure aluminum （FA）. The damping characterization was conducted on a multifunction internal friction apparatus （MFIFA）. The FA specimens were prepared by air pressure infihration process. The size of macro- scopic pores is on the order of a millimeter （0. 8 and 1. 4 ram） and in large proportions, typically up to 76 vol. %. The internal friction （IF） of the FA specimen was measured at different temperatures, different frequencies, and different amplitude dependences. The measured IF shows that FA has a damping capacity which is enhanced in comparison with bulk commercially pure aluminum, increases with increasing porosity, increases with decreasing macropore size, increases with increasing frequency and increases with increasing strain amplitude. The mierostruetural analysis was performed using transmission electron microscopy （TEM）. TEM observations show that moderate density of dislocation substructures exist near the grain boundaries in the FA. In light of IF measurements and mierostruetural observations, the possible operative damping mechanisms in the FA are the stress concentration and mode conversion around macroscopic pores, the elastic modulus difference between the matrix and the macroscopic pores that results in a marked inhomngeneous stress, inhomogeneons expansion deformation around macroscopic pores.