Weld appearance shape based on line laser scanning and surface defect detection method

Abstract

The invention discloses a weld appearance shape based on line laser scanning and a surface defect detection method. The method comprises the steps of acquiring the actual profile curve of any section of a welded joint by laser; carrying out high-dimensional fitting on the actual profile curve to obtain a fitting profile curve, so as to obtain a first-order derivative curve of the fitting profile curve; determining the addressing ranges of the starting point and the final point of the welded joint by the first-order derivative curve; finding a point which has maximum differential value with the fitting profile curve on the actual profile curve as the starting point and final point of the section of the welded joint to obtain an integrally three-dimensional profile image of the welded joint. The welded joint is deemed to have a defect when a differential value between any point of the profile curve of the welded joint and the fitting profile curve exceeds the preset standard value. According to the detection method provided by the invention, the starting point and the final point of the welded joint can be accurately judged, and various surface defects of the welded joint can be precisely judged.

Description

technical field [0001] The invention belongs to the technical field of weld detection, and relates to a method for detecting the appearance shape and surface defects of welds. Background technique [0002] The quality inspection during the welding process is very important, which determines whether the weld is qualified and meets the requirements for use. At present, the quality inspection of welds mainly includes: weld appearance and surface defect inspection, weld internal defect inspection, and various performance inspections of welds. Among them, the detection of internal defects of welds is mainly realized by non-destructive testing methods such as X-ray and ultrasonic flaw detection, which are mainly used in the detection of welds of pressure vessels and important load-bearing structures, and have perfect and strict quality testing standards. Various performance tests of welds, including mechanical properties, corrosion properties, etc., are used to evaluate welding p...

AI Technical Summary

Problems solved by technology

Existing laser contour recognition methods cannot provide effective contour recognition to accurately determine the starting position of the weld in width, which causes great difficulties for line laser recognition of weld shape and size (such as weld width) information

In addition, the height difference caused by fish scales on the surface of the weld will also bring difficulties to line laser diagnosis

[0007] 2) In the process of welding seam detection, the instability caused by the movement of the line laser sensor, the inclination and angular deformation of the welding plate, the slight fluctuation and change of the detection height, etc. will affect the detection accuracy, and the above factors must be corrected

However, its correction is affected by many factors, and it is necessary to propose a corresponding method through system analysis.

However, in the current industrial inspection of laser profilometry, there is no suitable method for related correction problems, especially problems caused by assembly and thermal deformation in the production process of welds.

[0008] 3) Due to the different types of defects, different positions of surface defects, and differences in defect shapes, more requirements are put forward for the detection of weld surface defects. At the same time, due to the existence of normal fish scales on the welding surface, the detection of normal defects brings In addition to "interference", special judgment methods are required to achieve effective detection

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