Analysis and Elimination of Forming Defects in the Stamping Process of Automotive Parts
| Autor: | Meng-Syun Tsai, 蔡孟勳 |
|---|---|
| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 Energy conservation and carbon reduction have become a major issue in the face of increasing global warming. Therefore, all major international automotive industries aim for lightweight. In order to achieve the goal of lightweight, major automakers mainly use Advanced High Strength Steel (AHSS) to reduce the weight of the car. However, advanced high strength steels are subject to forming defects such as crack, wrinkle and springback, which are more serious than mild steel. The advanced high-strength steel forming is difficult, and it takes a lot of money and time cost to test the mold. Therefore, Computer Aided Engineering (CAE) analysis technology is introduced, and it is hoped that CAE analysis can achieve more accurate mold design. Significantly reduce the cost of mold opening. The material model is also a very important part of its CAE analysis. The advanced high-strength steel has a significant Bauschinger effect, the work hardening rule considering the Bauschinger effect and the yield criterion of considering the biaxial force. Understand the plastic deformation behavior of materials, improve the forming characteristics analysis and springback prediction ability of advanced high-strength steel. This paper first discuss the commonly used yield criteria such as Hill48, Hill90, Barlat89, Barlat91 and Yld2000-2d, and explore the Yoshida-Uemori material model which can describe the material Bausching effect, and implement the establishment of the yield criterion and the work hardening rule. The required experiments include uniaxial tensile experiments, tensile-compression experiments, and plastic strain ratio experiments to establish the parameters of the Hill48 and Barlat91 yield criteria and the work hardening rule material model required for finite element analysis. With reference to the side sills of the automotive, this paper proposes a basic shape and two special-shaped U-hat shape to discuss the forming defects of the side sill parts. The main forming defects are wrinkle defects and springback defects, using variable holder force and drawbead. Variable holder force and drawbead can effectively improve wrinkle defects and springback defects. In order to improve the springback part of drawbead, a set of experimental molds is designed. The drawbead height can be adjusted by changing the gasket. The drawbead design has been used in the U-hat shape drawing die. The isotropic work hardening rule and the Yoshida-Uemori material model were simulated with Hill48 and Barlat91 yield criteria. The thickness and springback results of the experiment were compared. The results show that the Barlat91 yield criterion combined with the Yoshida-Uemori material model is the closest to the experimental results. And use the mechanism to design an adjustable drawbead to quickly adjust the height of the strip. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|