Research On Reconstruction Of Molten Pool Temperature Field For Laser Welding

In the laser welding process, the status and quality of welding are greatly influenced by the molten pool temperature and its variation. Based on the digital image processing technology, the three-dimensional temperature field of molten pool is reconstructed by using the pictures of both-side of the molten pool and the contours of weld joints, which provides reference for the research on the mechanism of laser welding.Firstly, a reconstruction method of surface molten pool was explored based on the laser welding mechanism and radiation temperature measurement theory. According to analysis on laser welding temperature field, put forward an algorithm on the basis of gray average to obtain several isotherms of surface molten pool; used conic correction way to avoid the influence of laser-induced plasma and spray droplet; utilized prior information of molten pool isotherms, denoted standard molten pool isotherms used geometric curves;, rebuilt surface temperature field used a filling method based on polar coordination, and also acquired characteristic parameters of isothermal surfaces. Secondly, used the slice-based three-dimensional reconstruction method, made use of obverse and inverse surface isotherms acquired before, together with welding joint tissue contours, obtained information of each sections; and reconstructed three-dimensional molten pool according to oblique secondary auxiliary drawing method. Lastly, developed the Three-Dimensional Reconstruction Software System of Laser Welding Molten Pool Temperature Field based on LabWindows/CVI development platform. The software can achieve the following purposes: image pre-processing, surface molten pool isotherms acquisition, surface molten pool temperature field reconstruction, rebuilding and displaying three-dimensional temperature field.The molten pool photographs actually acquired were analyzed and processed under the software system, the result acquired reflected the shape of molten pool and the distribution of temperature field well.