| The control of weld quality is an important research project in the field of welding,and the excellent quality of welding is an important factor to ensure the performance of the welding structure.During the welding process,on account of the uneven temperature field of welded joints,the distribution of stress and strain on welded structures is uneven.The welding residual stresses form further deformation during the use of materials,which brings potential safety risks to production.The stress and strain measurement of the welded structure can be used to characterize the deformation of the material,thus further controlling the deformation of the material.In addition,the weld forming is an important factor for the structural integrity of welding,and the shape of liquid metal flow state of the molten pool in the welding process determines the weld forming state.The processing and analysis of welding pool image during the welding process is instructive for the welding quality control.Firstly,a robotic arc welding test system was set up and a set of liquid visual sensing unit suitable for TIG welding of stainless steel robots and the on-line high temperature strain measurement and characterization sensing unit were developed.The 304 stainless steel TIG welding multilayer multi-channel Welding process test was conducted,the state of liquid welding pool and on-line measurement and characterization of full-field high-temperature strain in HAZ was analyzed.According to the on-line high temperature strain measurement and characterization in HAZ,the preparation algorithm of welding high temperature speckle in HAZ is optimized and a high temperature speckle with geometric diversity and randomness is generated.Based on the principle of digital image correlation method,an algorithm for online measurement and processing of high temperature strain in the welding field was developed by the efficient IC-GN iterative algorithm,the simplified bicubic interpolation method,the optimized sampling size and frequency,to improve the strain calculation speed and achieve strain on-line measurement.Combined with 304 stainless steel robot multi-layer multi-pass welding process,the liquid pool image acquisition of backing,filling and cosmetic welding was carried out.In view of the integrity and high efficiency of welding pool image processing,ASM algorithm was developed,and the geometrical parameters of the weld pool were obtained.The characteristics of the weld pool under the different penetration conditions were compared,and the quantitative and qualitative evaluation methods were given.The images of welding pool under different penetration states and the corresponding relation of strain in HAZ were studied.The surface shape of weld pool with penetration was not smooth and the contour of the front of weld pool was obviously concave and the strain value is lower than that of the incomplete-penetration backing welding adjacent the weld.However,the surface of weld pool without penetration welding is smooth,the contour of welding pool front is smooth and gentle,and the strain value near weld zone is higher.Finally,according to the characteristics of the welding pool in TIG multi-pass welding of 304 stainless steel,combined with the high temperature strain in the heat-affected zone of the joint,the monitoring method and evaluation mechanism of the welded joint are established,conducting a useful exploration for the follow-up welding morphology and performance control. |
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