先進高強度鋼板沖壓模具設計 之有限元素分析

Finite Element Analysis of Stamping Die Design with Advanced High Strength Steel Sheets

江子欣(Tzu-Hsin Chiang)

指導教授 ： 陳復國

國立臺灣大學/工學院/機械工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02934

摘要

由於能源危機、環保問題及碰撞法規的重視，輕量化及強度化為各大汽車廠努力的目標。雖然使用輕金屬，例如鋁合金與鎂合金，可以達成減重的目的，然其價格仍高居不下。而先進高強度鋼板具有高強度及低成本的特性，因此其逐漸應用於車體結構件中。
而先進高強度鋼板在沖壓成形製程中，除成形困難，容易產生破裂與皺褶的缺陷外，其最大的缺點仍在容易產生回彈(springback)與扭曲等幾何形狀與尺寸的變異。雖然過去在使用一般鋼板時亦會產生回彈，然因其強度不高，回彈現象並不十分嚴重，只要在模具方面加以修正後，大多可以解決回彈的問題。可是隨著高強度鋼板之降伏與抗拉強度的增加，回彈現象也愈趨明顯，且更不易解決。使得其模具開發過程中造成時間與成本之耗費。
本研究首先藉由伺服沖床進行V型彎曲、U型彎曲以及U型帽狀基礎彎曲成形實驗，使用材料為270軟鋼、DP590及DP780，探討以不同沖壓速度之成形方式來抑制回彈之可行性。並選取一具有代表性之車體結構件並採用材料為DP590及DP780之裁縫式鋼板，從產品之尺寸外型以引伸成形方式設計餘肉造型，利用電腦模擬分析探討引伸成形設計所造成之成形缺陷包括破裂、皺褶、側壁外開、側壁捲曲及扭曲，探討其成形機制與缺陷成因，並尋求其改善方式，但側壁捲曲之回彈缺陷難以有效改善。以多彎曲成形模式取代引伸成形可避免側壁捲曲之發生。本研究也針對裁縫式鋼板於不同原材拼焊及焊道位置進行模擬分析，以了解其拼焊回彈後互相影響之程度。最後藉由逆向掃描設備與超音波測厚儀來取得實際沖壓板件之幾何外型與厚度，以驗證模擬分析之正確性，而本論文之研究成果可供先進高強度鋼板沖壓成形業者進行製程規劃以及模具設計時之參考。

關鍵字

先進高強度鋼板 ； 沖壓成形 ； 模具設計 ； 回彈 ； 有限元素法伺服沖床 ； 裁縫式鋼板

並列摘要

In order to mitigate the greenhouse effect and promotion of fuel-efficient, how to reduce the weight of vehicle become the new goal for the automotive manufactures. It leads to the fast development and application of advanced high strength steels (AHSS). However, due to the increasing strength, the use of advanced high strength steel has encountered the forming problem just like crack, wrinkle, springback and distortion in the sheet metal forming process. It will consume the cost and times in the die development process.
The V-bending, U-bending, and U-hat bending tests of 270 steel, DP590 and DP780 high strength steels were performed to examine the effects of punch speeds. A servo press was a employed to conduct the bending tests with various punch speeds to investigate the effect of stamping velocity on the springback. Significant springback was found after bending tests, while the stamping velocity has little effect on the occurrence of springback.
The finite element simulations were then performed to examine the die design for structural parts front side which is tailored blank by DP590 and DP780. The multi-forming (bending and re-striking) operations were proposed to produce since the side-wall curl resulted from a draw operation being difficult to be suppressed. The die compensation approach was employed to adjust the amount of springback at each operation systematically to make the dimension of the parts conforming to the design specifications. Stamping die sets were then manufactured according to the finite element analysis. After several tryouts, stable stamping processes of producing front side were established. The accurate dimensions of the production parts validate both the finite element analysis.
Tailored blanks are increasingly used in the automotive industry. A combination of material and position of welding line are discussed. Investigating springback simulation of tailored blanks is the purpose of this study. The results of this study can be reference resources for related academic research and can also be used to develop related products for industry production.

並列關鍵字

advanced high strength steel (AHSS) ； stamping ； springback ； die design ； CAE ； servo press ； tailored blank

參考文獻

[32]劉士維, “先進高強度鋼板沖壓成形之回彈分析”, 國立台灣大學機械工程研究所碩士論文, 2008.

[33] 蘇昱竹, “先進高強度鋼板沖壓成形回彈現象之研究”, 國立台灣大學機械工程研究所碩士論文, 2007.

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