AIMS Mathematics, 2020, 5(4): 3256-3273. doi: 10.3934/math.2020209

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Mathematical morphology approach to internal defect analysis of A356 aluminum alloy wheel hubs

1 Science and Technology on Electronic Test and Measurement Laboratory, North University of China,Taiyuan 030051, China
2 Department of Electronic engineering, Taiyuan Institute of Technology, Taiyuan 030008, China

A356 aluminum alloy is a material widely used in the production of automobile wheels. Internal defects such as gas holes and shrinkage cavities are likely to develop in the process of low pressure casting. X-ray images of the hub are able to provide some information on such defects. This paper proposes a defect extraction method which is built on mathematical morphology. It involves three operations, i.e., the top-hat transform, the top-hat reconstruction transform and the dilation reconstruction. A larger square structuring element and a small threshold are used firstly to obtain all potential defect areas of the hub. A structuring element of a suitable size are applied to different defect areas in subsequent extraction. A new threshold is then decided to get the final defect extraction results. The experimental results show that the above defect extraction method not only works on X-ray hub images, but is robust against the interference caused by noises and hub geometry, and hence can potentially be extensively applied to X-ray detection of hubs.
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