基于CT的泡沫铝三维细观模型重建及应用

Reconstruction and application of three-dimensional mesoscopic model of aluminum foam based on CT

为了建立更加真实的闭孔泡沫铝三维细观分析模型,提出了一种基于计算机层析成像(CT)的有限元模型构建新方法。首先,对CT扫描得到的泡沫铝试件的扫描图像进行Otsu算法分析,确定了区分基体材料和空气的灰度最佳阈值。其次,基于映射网格思想直接从扫描图像生成了试件的有限元分析模型,实现了泡沫金属三维细观分析模型的重建。最后,以此为基础进行了泡沫铝试件准静态压缩和动态冲击试验的数值模拟,结果表明,准静态压缩下泡沫铝的内部变形随机分布于整个试件,且与其三维结构密切相关;而动态冲击下变形在冲击端附近首先发生,体现出显著的局部化效应。本文方法能真实地描述泡沫金属内部的细观结构,实现了对泡沫铝试件在准静态压缩和动态冲击作用下的受力、变形与破坏过程更加详细的模拟分析。

In order to obtain a more realistic mesoscopic analysis model of closed-cell aluminum foam, a new methodology for the finite element modeling based on computed tomography （CT） images is presented. First, the optimal threshold between base material and air was developed using Otsu algorithm by analyzing the images obtained from the CT scanning of closed-cell aluminum foam. Then, the mesoscopic finite element model was directly established based on the thought of mapping grid. As a result, the reconstruction of three- dimensional mesoscopic analysis model of metal foams is achieved. Finally, the numerical simulations of qua- si-static compression and dynamic test of closed-cell foam are carried out respectively based on the mesoscopic analysis model. The results demonstrate that the internal deformation of closed-cell aluminum foam distributes throughout the whole specimen, which is closely bound up with their 3D structure under quasi-static compres- sion, while it is close to the loading end and remarkably behaves with localization under dynamic compression. The methodology of modeling can describe mesoscopic structure realistically and provide a more detailed simu- lation analysis on the stress state, deformation and failure of closed-cell aluminum foams under quasi-static and dynamic loading.