Method for detecting type of FSW welding seam defect by using ultrasonic phased array

Abstract

The invention provides a method for detecting the type of an FSW (Friction Stir Welding) welding seam defect by using an ultrasonic phased array, and belongs to the technical field of nondestructive detection of a welding joint. The method is characterized by taking aluminum alloy as a raw material, obtaining butt welding seams by using FSW, for incomplete-penetration and tunnel hole defects in different shapes in the welding seam, detecting the shapes of the interfaces of the defects by means of the ultrasonic phased array, detailedly researching the characteristics of phased array sector scanning modes in different directions of the interfaces of the tunnel holes, and finally identifying the different shapes of the incomplete-penetration and tunnel hole defects by combining texture analysis. The method of the invention has the advantages that: (1) the detection is convenient and easy to operate; (2) The detection efficiency is high and the reliability is strong; in conclusion, the ultrasonic phased array technology has obvious advantages on FSW welding seam detection, is accurate in tunnel hole positioning, and has good detectable rate even if the orientation of a defect interface is complex in the aspect of detection of fine size defects.

Description

technical field [0001] The invention belongs to the technical field of non-destructive testing of welded joints, and in particular relates to a detection method for ultrasonic phased array detection of friction stir welding seam defect types. Background technique [0002] Since the advent of Friction Stir Welding (FSW) technology in the early 1990s, it has been considered the most eye-catching welding method since laser welding. Its appearance has brought about a major change in the joining technology of non-ferrous metals such as aluminum alloys. Some high-strength aluminum alloy materials that were previously considered unweldable can basically be welded by friction stir welding. It is used in aerospace, ships, and high-speed railways. Numerous examples of successful applications have emerged in fields such as train manufacturing. [0003] In practical applications, due to the influence of welding process parameter deviation, clamping conditions, material surface conditio...

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Problems solved by technology

[0003] In practical applications, due to the influence of welding process parameter deviation, clamping conditions, material surface conditions, operators and other factors, friction stir welding workpieces may also have defects, which will affect the performance of the joints, and friction stir welding defects are relatively more than conventional fusion welding defects. It has the characteristics of closeness, subtlety and complex orientation, which increases the difficulty of detection, affects its popularization and application to a certain extent, and also makes it of great practical significance for the efficiency, accuracy and convenience of its defect detection

At present, the non-destructive testing technologies for friction stir welding seam defects mainly include X-ray and ultrasonic testing. X-ray images are clear and can be stored for a long time, but the detection sensitivity is relatively low, while ultrasonic testing has strong applicability and high detection sensitivity, but At present, the ultrasonic testing research mainly focuses on the regular defects on the incident surface, and there is little research on the defect interface with variable curvature and variable orientation. In the FSW process, the plastic metal flow caused by the stirring effect easily changes the interface shape, which is different from the flat interface. The detection is different. The curved interface will enhance the ultrasonic focusing and scattering characteristics, making it difficult to detect defects. For the detection of incomplete penetration defects, oblique incidence is usually used, and the uncertainty of orientation makes it difficult to choose the detection angle.

[0004] However, the ultrasonic phased array technology can realize the focus and deflection of the acoustic beam by controlling the time difference of chip excitation. The detection method is used for the detection of FSW defects. It is found that the phased array has a good detection rate and accurate positioning ability for defects with complex orientations, but it is difficult to accurately determine the type of defects. Therefore, many researchers combine image processing technology with The combination of ultrasonic phased arrays has realized feature extraction and recognition of different defect images through methods such as threshold segmentation, boundary extraction and texture analysis. However, this research method is relatively rare in the field of FSW, and the correlation between defect interface morphology and interface texture powerful

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