Factors affecting the springback of stamped parts
1. Material properties
There are stamped parts of different strengths on the car body, from ordinary plates to high-strength plates. Different plates have different yield strengths. The higher the yield strength of the plate, the more likely it is to rebound.
The material of thick plate parts is generally hot-rolled carbon steel plate or hot-rolled low-alloy high-strength steel plate. Compared with cold-rolled thin plates, hot-rolled thick plates have poor surface quality, large thickness tolerance, unstable material mechanical properties, and low material elongation.
2. Material thickness
During the forming process, the thickness of the plate has a great influence on the bending performance. As the thickness of the plate increases, the springback phenomenon will gradually decrease. This is because as the thickness of the plate increases, the material involved in plastic deformation increases, and then the elastic recovery deformation also increases, so the springback becomes smaller.
With the continuous improvement of the material strength level of thick plate parts, the problem of part dimensional accuracy caused by springback is becoming more and more serious. Mold design and later process debugging require an understanding of the nature and size of part springback in order to take corresponding countermeasures and remedial plans.
For thick sheet parts, the ratio of bending radius to plate thickness is generally very small, and the stress in the plate thickness direction and its stress change cannot be ignored.
3. Part shape
The springback of parts of different shapes varies greatly. Parts with complex shapes generally have an additional order of shaping to prevent springback due to incomplete forming. Some parts with special shapes are more prone to springback, such as U-shaped parts. In the analysis of the forming process, springback compensation must be considered.
4. Part clamping force
The clamping force stamping process is an important process measure. By continuously optimizing the clamping force, the material flow direction can be adjusted and the internal stress distribution of the material can be improved. Increasing the clamping force can make the part more fully drawn, especially at the side wall and R angle of the part. If the forming is sufficient, the internal and external stress difference will be reduced, thereby reducing the springback.
5. Drawbeads
Drawbeads are widely used in today's processes. Reasonable setting of the drawing position can effectively change the material flow direction and effectively distribute the feed resistance on the pressing surface, thereby improving the material formability. Setting drawbeads on parts prone to springback will make the parts more fully formed and the stress distribution more uniform, thereby reducing springback.
