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Visual Feature and Parametric Description during the Process of Defects Forming

Author: PanMingCai
Tutor: WangKeHong；ZhouZuo
School: Nanjing University of Technology and Engineering
Course: Materials Processing Engineering
Keywords: MAG welding Short-circuit transition Pool visual Image procession Shape parameters Welding defects
CLC: TG441.7
Type: Master's thesis
Year: 2009
Downloads: 59
Quote: 2
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Abstract


The real-time detection and extraction of characteristic signals of molten pool in arc welding process is the core problem of intelligent welding.In this article,we extract the visual feature information of forming defects by comparing tests and image processing technology,based on the clear pool image obtained.This can provide related data and models for online control of welding defects.The geometry parameters of short-circuiting pool are proposed and studied and the digital image algorithms of some parameters are designed.The geometry parameters of typical weld pool are extracted,and a quantitative description of the pool is achieved through summing up the numerical range of some parameters.It provides the relevant test data and technical basis for further research about the relationship between the characteristics visual image of weld pool and the process of defects formation.The typical pool images of short-circuit transition(MAG welding) are analyzed. Through extracting the geometry parameters of weld pool under different processes and grooves conditions,the numerical ranges of the geometry parameters are summarized as follows:aspect ratio:TL=0.8～1.4;back angle:a =60～85;relatively symmetric parameter: q=0.95～1.05;pool complexity:e＜2.5,in this range,the probability of defects occurring is low.Also the relationship between visual parameters of pool and standard parameters was given in this paper.Using the simultaneous contrast test,the relationship between the pool geometry parameters(and other features) and the forming process of welding defects(porosity,slag, lack of penetration) is analyzed:the irregular sharp fluctuations of geometry parameters or the protruding or recess in back tail,that is pool complexity increasing,which indicates the increasing probability of porosity and slag.There is high probability of lack of penetration when the pool image is small,the area,perimeter,half length and width of the pool are less than the normal value significantly,the back tail is quasi-circular curve transition,the back angle is greater than 80°.The area,perimeter,half length and width of the pool decreasing rapidly,are characters of declining of the pool heating surface and the penetration probably translated into weld penetration.The features of serious collapse are a large welding wire length,a reducing arc zone and a crescent-shaped arc.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > General approach > Welding defects and quality inspection
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