First, the basic structure of the car body. Body damage form 3. Requirements of body surface for body repair. Repair of serious body damage V. Body repair, 1. Thermal shrinkage method The local thermal shrinkage method of sheet metal is a common method for sheet metal repair. When the sheet is damaged and thinned, ji is the tensile deformation of the deformed part, and the original shape can be restored by eliminating the warping stress by thermal shrinkage. The principle of heating deformation of metal plate is shown in Figure 7. The main process of heating cotton picking method is: (1) the midpoint of the depression of Liu sheet metal is heated rapidly locally, and the steel plate expands around the heating point during the heating process, resulting in compressive stress around it. (; Me. (2) When the warm waist continues to rise, the steel plate will burn red locally and become soft. As shown in fig. 7(c), the offset of compression load generated during heating/cold deformation is released and restored to its original shape. (4) In the process of thermal shrinkage, the hammer pad method can also be used to correct and restore large-area deformation. (5) After heating and shrinking, if the first effect is not ideal, it can be shrunk many times. (6) After the heating shrinkage is completed, it needs to be further flattened with a hammer and supporting iron to eliminate the tiny deformation and local wrinkles caused by the shrinkage of the plate. (7) Use grinding wheel or sandpaper to further polish and smooth. (8) Welding repair. Repair welding some concave parts to restore the original shape of sheet metal. 5. Hand hammer and iron support repair method Hand hammer and iron support repair method are traditional sheet metal repair methods. The sheet metal worker holds a hammer in one hand and a supporting iron or other tools in the other hand to tap and reshape the sheet metal. (Article from: China Technician Network)