高強度汽車結構件造型參數對成形缺陷之研究

A Parametric Study of Forming Defects for High-Strength Automotive Structural Parts

陳冠杰(Kuan-Chieh Chen)

指導教授 ： 李貫銘

國立臺灣大學/工學院/機械工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.10444

摘要

先進高強度鋼板相較於傳統鋼板具有強度上之優勢，但也因為強度大幅提升，於沖壓成形方面容易產生破裂與回彈缺陷。產學研各界為深入研究高強度鋼板之沖壓成形問題，除了從模具設計角度分析外，均廣泛使用有限元素分析軟體作為工具，以探討成形缺陷之產生機制。然而在鋼板強度逐漸提升之趨勢下，有限元素法目前於成形回彈分析之準確性仍有所不足。故本研究當中，除針對模擬參數進行收斂性分析測試外，為進一步提升回彈分析之準確性，也將針對有限元素模擬所需之材料模型進行研究及比較。
為使有限元素軟體分析之結果接近於實際情況，本論文亦針對實際汽車結構件－橫樑件，進行開發設計，並藉由成形性分析了解成形狀況。回彈現象方面，提供回彈補償方法與建議，以改善成品之回彈量。最後在驗證方面，本研究利用逆向掃描取得實際沖壓成品之外型尺寸，並與採用不同材料模型之分析結果進行比較，可知使用Y-U model分析1180級鋼材回彈量之模擬準確率達80%以上。
本論文同時歸納目前各國車廠使用高強度鋼板於車體之相關資訊，包含使用高強度鋼板之結構件歸納、最常應用之鋼板強度等級以及目前冷沖壓鋼板應用於結構件之最高等級。在汽車結構件造型方面，本論文分析主要汽車結構件之造型參數且找出共通特徵，利用簡化造型探討特徵造型參數對成形性以及回彈現象之影響性，並比較材料強度提升時之差異，最後利用實際結構件模擬驗證，簡化造型與實際造型除了成形缺陷處皆相同外，且回彈準確率可達90%左右。本論文之研究成果可提供模具相關工作者於汽車結構件開發設計時之參考。

關鍵字

先進高強度鋼板 ； 有限元素分析 ； 汽車結構件 ； 成形缺陷 ； 回彈分析

並列摘要

Advanced high strength steels (AHSS) have higher strength than conventional steel sheets. However, the occurrence of stamping defect and springback are more difficult to be solved. In order to study the stamping problems of AHSS, the researchers not only make use of mold design but also finite element analysis software to investigate the mechanism of forming defects. The efforts were endeavored to establish the optimum simulation parameters, such as element size, number of integration point, and punch velocity. However, the accuracy for the prediction of springback still needs to be improved even with the optimum simulation parameters adopted. Hence, the material model, including the yield criteria and the work hardening rules, has been considered as the other possible reasons that may cause the inaccuracy of the finite element simulations in the sheet forming of advanced high strength steel.
With the use of the Yoshida-Uemori model, this thesis examined the springback occurred in the stamping of advanced high strength steel sheets. After stamping, the finished part was scanned by a coordinate measuring machine for the actual dimensions. Compared with the experimental data, the finite element simulation results with the use of the Yoshida-Uemori model display an error of less than 20% in predicting the springback of AHSS of grade DP1180.
This thesis aims to establish the database of advanced high strength steel stampongs for automotive structural parts. This thesis first summarized the information of the applications for automotive parts made of advanced high strength steels in the world recently.

Side sill, A-pillar and B-pillar were investigated in this study. The key geometric parameters for those structural parts, which affect the formability of AHSS sheets, were studied with simplified model, different grades of AHSS and sheet thickness were also included in this database. Finally, case studies for different actural automotive structure parts were presented. It is proved that the database can served as a reference for die design of advanced high strength steel stampings.

並列關鍵字

advanced high strength steel ； finite element simulation ； automotive parts ； formability ； springback predicting

參考文獻

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