The 3-Dimension Reconstruction Of Plasma In Laser Welding

Plasma produced in laser welding process has shielding effect to the laser beam It decreases the melting depth on even result in the defect, wastes so much laser energy, affects welding procession and quality due to the plasma, so it is especially necessary to study the laser-induced plasma.The plasma shape in deep penetration laser welding stainless steel is observed using a high-speed synchronous camera system which can get an image including three direction view of plasma, and the change of the brightness are recorded by camera. Based on the laser-induced plasma gray-picture shooted by high-speed camera, we use the theory of Computerized Graphics, to make the result. The main research contents of 3D surface reconstruction include image pre-processing, such as filtering, segmenting and extracting the body, constructing 3D surface models, simplifying of meshes of the models.Accurate segmenting and extracting tissues from plasma images are premises of 3D reconstruction models. In this paper, the 'region growing' method of images segmenting is presented. By this method, the seeds and the tolerances are selected interactively, and segmentations are achieved perfectly. The 3D solids are achieved with Algorithm Reconstruction Technique (ART). By analyzing the 3D model, the characteristic of the plasma is indicated. The surface of the laser-induced plasma is not smooth, and there is some granulation on the photosphere of the plasma. The plasma changs continuously and the volume of the plasma changes acutely. The interior of the laser-induced plasma are devived into three regions. They are the nugget region, the transition region and the periphery region. The temperature is the highest in the nugget region, the volume of this is the smallest, and the radiation of this is the largest. The outskirt of the nugget region is the transition region, the volume of the transition region is the biggest, and there are some hollow in this region. The...