| With the increasing requirements for environmental protection and vehicle safety as well as fuel economy, there are some serious issues on safety characteristics and exhausting emission for automobile. Advanced high strength steel (AHSS) offers a great opportunity to make vehicles lighter and stronger as well as to make the environment better due to its excellent combination of strength and ductility, and it has been widely applied to the manufacturing of important parts in automobile, such as vehicle structures and reinforcements. However, with the higher yield strength of AHSS, it requires more forming force, and may make stamping die in a much worse condition simultaneously. Therefore, the tooling elastic deflection (TED) should be considered during the AHSS forming process.Traditionally, in order to solve the above problems, there are some approaches, such as increasing the thickness and volume of die structure or using the high-hardness materials, are employed. Unfortunately, the manufacturing cost of die and the energy consumption during the production are increased. For the above shortcomings, under the supports from the National Science and Technology Major Project of the Ministry of Science and Technology of China (2010ZX04014-072) and National Natural Science Foundation of China (51075269), multi-optimizations of process and die structure are studied, considering the effect of TED. The research results are summarized as follows.According to some key locations for binder elastic deflection (BED), the distribution and variation of BED during the forming process are studied, and the effects of BED on the distribution of blank holder force (BHF) and springback of the part are analyzed respectively. Through doing the study on the BED with different drawbead geometrical parameters, the relationship between BED and springback is revealed.Considering the BED, a finite element model is created by using Hypermesh, and the effects of difference process parameters, such as drawbead and BHF, on the springback of DP780 are analyzed by LS-DYNA. A surrogate model based on Kriging algorithm is built, and the optimal result involving the relationship between drawbead parameters and springback is obtained by employing a self-adaptive simulated annealing algorithm. Comparisond with the initial springback, the amount of springback along Z-direction on the optimized model is decreased by 13% from 2.217mm to 1.933mm.The structure analysis of binder is discussed. It can improve the robustness and efficiency of structure to use the methodology proposed bellow. For one hand, the structural analysis of binder is discussed by selecting the key load step of the forming load, according to the load variation of binder during forming process; on the other hand, the contact forces obtained from stamping simulation are mapped to the binder structure analysis model as force boundary conditions based on the developed load mapping algorithm.A methodology to control the springback and optimize the topology of binder based on sheet metal forming simulation and die structure analysis is proposed considering TED. Firstly, get an optimal result by process optimization, using the initial binder structure; secondly, proceed the binder structure topology optimization, using the force boundary conditions, which is obtained in the optimal process; Finally, Adjust the threshold of element density in the topology result, then proceed the forming process to gain a better forming quality and realize the multi-object optimization of blank springback control and die volume reduction. It is shown by optimization that the results of springback and binder weight are optimal when the threshold of topology is 0.783. The binder weight decreased by 52.2%, and the amount of springback along Z-direction on the optimized model is decreased by 4.0%. |
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