A novel online defect detection method based on X-ray images of railway castings

摘要

A digital radiography (DR) image is essentially a projected image of the inspected object. In most cases, the contrast of defects in the inspected object is too low to distinguish easily. Therefore, for X-ray inspection of castings, especially large-scale castings, it is difficult to detect defects in the casting's X-ray images in real time. In this paper, a rapid DR image defect detection method, based on image registration, is proposed using the casting's online DR detection characteristics. Firstly, the DR image of the inspected casting is enhanced using a fusion method to highlight defects. Secondly, the appropriate standard DR image is selected from a library according to a model of the inspected casting. Thirdly, the enhanced DR image and selected standard DR image are registered. Lastly, the difference image method and prior knowledge are used to detect defects in the casting. Experimental results show that the proposed method can effectively detect casting defects at high speed. The method is particularly suitable for the online X-ray inspection of large castings.