Graphite shape characterisation in cast iron—from visual estimation to fractal dimension
Graphite shape characterisation in cast iron—from visual estimation to fractal dimension
复制标题
铸铁中的石墨形状表征——从视觉估计到分形维数
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
D. Stefanescu
中科院分区：
文献类型：
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作者：
R. Ruxanda;D. Stefanescu
薄壁铸铁件的特点是比普通的商业铸件具有更精细的结构。现有的显微组织标准没有涵盖这一精细的显微组织范围。虽然计算机辅助图像分析可以提供一些答案，但存在局限性。球墨铁和压实石墨铁中的石墨形状对测量方法特别敏感。本文对石墨形状评价常用的各种形状因子进行了讨论。选择的形状因子在它们的能力方面进行比较，以充分描述石墨形状在薄壁铸铁件的整个范围内的石墨形态。虽然可以使用几个形状因素，但球形度似乎比致密度更能描述球形石墨的形状。致密性不能很好地区分爆炸石墨和球形石墨，或形状不良和形状良好的球形石墨。我们的实验数据表明，形状因子方法直观、准确、快速，但它与像素大小有关，不能任意使用。研究了用与像素大小无关的分形维数方法量化石墨形状形态复杂性的可能性。不幸的是，我们发现，对于不同形状的石墨（片状石墨与球形石墨或压实石墨与爆炸石墨），分形维数值存在部分重叠。因此，建议使用形状因子对薄壁铸铁件的石墨形状进行测量。在薄壁球墨铸铁件和压实墨铸铁件中，评价石墨形状的最佳像素尺寸为0.5 ~ 0.6 μm。
Thin wall iron castings are characterised by a much finer structure than that obtained in regular commercial castings. Existing microstructure standards do not cover this fine range of microstructures. Although computer aided image analysis may provide some answers, limitations exist. Graphite shape in spheroidal and compacted graphite iron is particularly sensitive to the measurement method. This paper offers a discussion on the various shape factors commonly used for evaluation of graphite shape. Selected shape factors are compared in terms of their ability to fully describe graphite shape across the whole spectrum of graphite morphologies in thin wall iron castings. While several shape factors can be used, it appears that sphericity is a better descriptor of spheroidal graphite shape than compactness. Compactness cannot distinguish well between exploded and spheroidal graphite, or poorly shaped and well-shaped spheroidal graphite. Our experimental data demonstrate that the shape factor method, otherwise intuitive, accurate and fast, cannot be used indiscriminately, as it is pixel size dependent. The posibility of using the fractal dimension method, which is pixel size independent, to quantify the morphological complexities of graphite shape was also investigated. Unfortunately, it was found that there is partial overlapping of the fractal dimension values for different graphite shapes (flake versus spheroidal graphite or compacted versus exploded graphite). Thus, it is recommended to use shape factors for graphite shape measurement in thin wall iron castings. The optimum pixel size for graphite shape evaluation in thin wall spheroidal and compacted graphite iron castings is 0.5 to 0.6 μm.