封閉式泡沫鋁材料受壓力學響應之數值模擬

Abstract

本研究目的在以數值模擬方式探討封閉式泡沫鋁材料之受壓力學響應。參考實際泡沫材料微觀結構，建立以Kelvin cell為藍本之實體-薄殼以及純薄殼兩類數值模型。配合特徵單元法模擬泡沫材料之相對楊氏模數與局部最大應力。與實驗相比後，模擬結果不論在相對楊氏模數或局部最大應力均存在相當程度高估。接著於真實泡沫材料微觀結構中辨識出各式幾何特徵，包含曲面、曲邊…等，建立了修正數值模型。幾何特徵之加入大幅提昇了數模型在楊氏模數與局部最大應力之模擬表現。最後以有限尺寸之修正數值模型，模擬泡沫材料之完整受壓力學響應。除整體應力-位移曲線，在變形機制與變形演進等方面，皆能有效重現實驗結果。

The present study aims to investigate the mechanical response of closed-cell aluminum foam under uniaxial compressive loading by means of numerical simulation efforts. Motivated by the measurements conducted on real foam microstructure, two kinds of numerical models, including shell-solid and purely shell models, based on perfect Kelvin structure have been developed. The characteristic cell homogenization approach was then incorporated to simulate the Young’s modulus as well as the initiation stress of the foam compressive response. Numerical results on both parameters were seen to overestimate the experimental ones by a large margin. Additional geometric features of the foam microstructure such as the cell wall curvature, the cell edge curvature…etc. were characterized through the comparison drawn between the perfect Kelvin numerical models and the real foam microstructure. Modified Kelvin models were then developed subsequently based upon the implementations of the newly characterized real foam geometric features and the effect of each of the features was examined accordingly. The resulting modified Kelvin models outperformed the perfect Kelvin ones greatly on the simulation of Young's modulus and the initiation stress. Finally, the finite-sized modified numerical models were used to simulate the complete mechanical response of closed-cell foam under compressive loading. Using the modified models, the overall mechanical response, the deformation patterns as well as the deformation evolution were reproduced successfully.