Method for determining size and area of surface defect of bar

Abstract

The invention provides a method for determining the size and the area of a surface defect of a bar, and belongs to the field of machine vision nondestructive testing. The method comprises the steps of acquiring a surface image of a to-be-detected bar by using a 3D line-scan camera and a 2D line-scan digital camera, and detecting a surface defect of the to-be-detected bar in the image acquired by the 2D line-scan digital camera; obtaining multi-point coordinate information on a position curve of the defect from a 3D depth map obtained by the 3D line-scan camera, fitting a curvilinear equation by using the points, performing arc length integration on the curve to obtain an actual length, and realizing a curve expansion algorithm; and decomposing the defect region into a plurality of small rectangles, and calculating the areas of all the small rectangles by using a curve expansion algorithm to obtain the area of the defect region through summation. By adopting the method, the area of the defect region can be accurately determined.

Description

technical field [0001] The invention relates to the field of machine vision non-destructive testing, in particular to a method for determining the size and area of ​​surface defects of rods. Background technique [0002] During the production process of the bar, it is necessary to detect various defects on the surface, analyze the size information of the defect, calculate the area of ​​the defect, and statistically analyze the size and area information of the defect to accurately grade the bar product, and the strip The detection of material products is different. The surface of the bar is not a plane, but an arc surface. It is necessary to accurately expand the arc surface of the bar into the corresponding plane, in order to accurately calculate the real area of ​​various defects and complete the accurate inspection of the product. Grading, most methods will obtain the diameter of the bar from the production management system, and use this diameter as a parameter to develop...

AI Technical Summary

Problems solved by technology

[0002] During the production process of the bar, it is necessary to detect various defects on the surface, analyze the size information of the defects, calculate the area of ​​the defects, and statistically analyze the size and area of ​​the defects Different from the detection of plate and strip products, the surface of the bar is not a plane, but an arc surface. It is necessary to accurately expand the arc surface of the bar into the corresponding plane to be accurate. Calculate the real area of ​​various defects and complete the accurate classification of products. Most methods will obtain the diameter of the bar from the production management system, and use this diameter as a parameter to expand the arc surface of the bar. The defect area calculated by this method is not accurate because:

[0003]1. There may be differences in the diameter of different parts in the length direction of the bar;

[0004]2. There is a situation that the obtained diameter parameter is not consistent with the actual rough rolling diameter;

[0005]3. The cross section of the bar may not be a standard circle, but an ellipse;

[0006]4. The change of the rod diameter leads to the change of the object distance of the camera, which affects the previously calibrated parameters, resulting in calculation errors

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