封閉式泡沫鋁材料之動態力學行為

Abstract

本研究主要目的為探討封閉式泡沫鋁材料之動態力學行為。內容包括霍普金森桿之建立、動態衝擊實驗與數值模擬。實驗設備方面，以壓克力桿件為主體，設計出滿足一維波傳理論、可測試泡沫鋁材料動態性質之霍普金森桿。接著進行動態衝擊實驗，以探討試體幾何形狀、相對密度與應變率對泡沫鋁材料力學行為之影響。實驗結果發現，整體力學反應受試體幾何形狀影響不大，但隨相對密度之增加而提高，此二結論皆與擬靜態力學實驗結果相同。另外動態力學反應明顯高於擬靜態實驗結果，但在測試範圍內不同應變率之影響並不明顯。數值模擬方面，利用有限元素軟體ABAQUS建立霍普金森桿與泡沫材料試體數值模型，其中桿件材料假設為線彈性，泡沫材料組成律則假設為ABAQUS內建之可壓縮泡沫模型。配合適當邊界條件，該數值模型可成功模擬各項實驗結果。最後並以所建之數值模型進行參數分析，以預測各可能實驗參數對泡沫材料力學行為之影響。

This study aims to investigate the dynamic response of APORAS closed-cell aluminum foam by means of experiments and numerical simulations. Toward this end, a PMMA based split Hopkinson pressure bar (SHPB) has first been established. A series of dynamic crushing experiments are subsequently conducted in an effort to access the effects of the specimen geometry, the relative density as well as the strain rate on the mechanical response of APORAS closed-cell foam studied. It is found that mechanical response is not sensitive to the specimen geometry while becomes increasingly higher as the specimen relative density increases. These two conclusions agree with results obtained from quasi-static crushing experiments. Also the dynamic response is seen to be higher than the quasi-static one, although the effect of strain rate is not significant in the tested strain rate range. Regarding the simulations, numerical models mimicking experimental set-up have been developed using the commercial FE package ABAQUS. The bars are assumed to be linearly elastic while the constitutive relation for the foam specimen is chosen to be the crushable foam which has been built in ABAQUS. Along with appropriate boundary conditions, the developed numerical models are bale to reproduce the experimental results successfully. Furthermore, the developed numerical models are utilized to perform parametric studies on the influences of bar lengths and strain rates.