X線CT画像を用いたダイカスト内鋳巣面積分布に対するフラクタル解析 Fractal Analysis of Porosity Area Distribution in Die Casting Using X-ray CT Image
Pores in pressure die castings are generated by entrapped gases or solidification shrinkage. To determine the pore formation mechanism and prevent the formation of pores, the morphology of pores, such as their shape and spatial distribution, should be quantitatively evaluated, and the cause of pores, such as gas or shrinkage, must be quantitatively specified. The accurate identification of pores requires a huge amount of knowledge about the die casting process, the lack of which may lead to misjudgment. We previously introduced a fractal dimension to quantitatively identify the cause of pores and verified the validity of using the fractal dimension <i>D<sub>a</sub><sup>M</sup></i>, calculated by the spatial distribution of the areas of pores from optical micrograph images. This fractal dimension can also be calculated from an X-ray CT image, which allows nondestructive inspection. However, X-ray CT images generally have lower resolution than optical micrographs. In this study, we examined the validity of identifying the cause of pore formation using the fractal dimension <i>D<sub>a</sub><sup>X</sup></i>, calculated from X-ray CT images, by comparison with <i>D<sub>a</sub><sup>M</sup></i>. In aluminum alloy die castings, <i>D<sub>a</sub><sup>X</sup></i> was found to have a lower value inside the samples than on the surface. This result showed that the effect of shrinkage increases in the inner area, which is consistent with the behavior of <i>D<sub>a</sub><sup>M</sup></i> Therefore, the evaluation of <i>D<sub>a</sub><sup>X</sup></i> is also expected to provide sufficient information to identify the cause of pore formation.
- 鋳造工学 = Journal of Japan Foundry Engineering Society
鋳造工学 = Journal of Japan Foundry Engineering Society 80(5), 284-289, 2008-05-25