引伸件筒壁差溫沖孔之研究

A study of thermal differential piercing on cylindrical wall of drawn cup

王蕾勤(Lei-Chin Wang)

指導教授 ： 許源泉

國立虎尾科技大學/工程學院/創意工程與精密科技研究所/碩士(2010年)

https://doi.org/10.6827/NFU.2010.00053

摘要

由於引伸件筒壁進行沖孔並無壓料板，導致沖孔面的品質不高，因此本研究利用差溫的方式，使引伸件筒壁強度降低及增加延性。
本研究利用有限元素法及Normalized Cockcroft-Latham延性破壞準則來分析AISI 1045中碳鋼之引伸件筒壁差溫沖孔，以了解差溫沖孔的沖孔面演變過程、溫度、應力、應變及速度場分佈，探討差溫沖孔溫度、沖頭圓角、間隙及心軸孔圓角之相關參數，以了解參數對沖孔面之影響。
依據沖模設計理論，利用VISI模具設計軟體設計一組引伸件筒壁差溫沖孔之模具，經由沖孔面檢測以驗證有限元素模擬與實驗之可靠性。為了解不同溫度差溫沖孔的材料流線、晶粒大小及硬度分佈等，本研究亦進行微觀組織分析。
本研究經由拉伸試驗建構出AISI1045板材完整的資料庫。經由研究各參數之結果顯示，在差溫沖孔方面，當差溫沖孔溫度越高時，圓弧面、光亮面及毛邊尺寸值會越高，而撕裂面尺寸值則越小。當沖頭圓角越大時，圓弧面、光亮面及毛邊尺寸值會越大，而撕裂面尺寸值則越小。當模具間隙及心軸孔圓角越大時，圓弧面、撕裂面及毛邊尺寸值會越大，而光亮面尺寸值則越小。
本研究藉由實際差溫沖孔實驗來驗證有限元素模擬之可行性，並檢測引伸件筒壁沖孔面之情形，實驗所量測之數據與模擬結果互相比對後，研究結果顯示，有限元素模擬與實驗的沖孔面尺寸值是相當接近，更加驗證有限元素模擬軟體應用於差溫沖孔之可行性與可靠性。
本研究利用顯微鏡及維氏硬度試驗機觀察沖孔面之微觀組織及硬度分佈。研究結果顯示，隨著差溫沖孔溫度越高時，引伸件筒壁的強度降低造成塑性變形更容易，因此在越接近沖孔面的流線越直。在硬度分析上，研究結果顯示，越接近沖孔面的位置其硬度值越高。
藉由差溫成形技術可用於其他高強度之材料或是複雜化之零件，以局部加熱方式進行塑性加工，則不需再做二次加工，便提昇成品的品質與強度，因此可以節省模具開發時間及成本。透過本文對於差溫沖孔之開發與研究，有助於提供學術界與產業界之參考。

關鍵字

引伸件 ； 差溫 ； 沖孔 ； 有限元素分析 ； 微觀組織

並列摘要

Due to lack of a blank holder in the die for the piercing on cylindrical wall of the drawn cup, the surface quality of piercing edge is lower. Therefore, the thermal differential technique was applied in the current study to reduce the strength and enhance the ductility on the cylindrical wall of the drawn cup.
In this study, the finite element method and the normalized Cockcroft-Latham ductile fracture criterion were used to analyze the thermal differential piercing on AISI 1045 medium carbon steel cylindrical wall of the drawn cup. The piercing edge, temperature, stress, strain, and velocity distribution were further investigated. The influences of related parameters, such as thermal differential piercing temperature, punch radii, die clearance, and mandrel holes radii on the piercing surface were also explored.
Based on the die design theories, a die set for the thermal differential piercing on cylindrical wall of drawn cup was developed employing the VISI die design software. Through the measurement of piercing surface, the reliability of finite element method and the experimental results were verified. To understand the distribution of flow line, grain size, and hardness in cylindrical wall of drawn cup, the microstructure of thermal differential piercing at different temperatures was also analyzed in this study.
In this study, a complete database for the AISI 1045 sheets metal detail properties was also constructed through the tensile test. Results of the study showed that the size values of the rollover depth, the burnish depth, and the burr height increased as the thermal differential piercing temperature increased, but the fracture depth decreased as the thermal differential piercing temperature increased. However, when the punch radii increased, the size values of the rollover depth, the burnish depth and the burr height increased, and the size values of the fracture depth decreased as the punch radii increased. In addition, when the die clearance and the mandrel hole radii increased, the size values of the rollover depth, the fracture depth, and the burr height increased, but the size values of the burnish depth decreased as the die clearance and the mandrel hole radii increased.
The feasibility of the finite element simulation was confirmed by thermal differential piercing experiment. Furthermore, the piercing edge on cylindrical wall of the drawn cup was examined. This study showed that the FEM simulation values agreed with the experiment results with a reasonable accuracy, which further confirmed the feasibility and reliability of the application of FEM software for the thermal differential piercing.
In this study, the microstructure and the hardness distribution of the piercing edge were observed by the microscope and Vickers hardness testing machine. Results showed that with the increase in the thermal differential piercing temperature, the strength on cylindrical wall of the drawn cup decreased, resulting in easier plastic deformation. Therefore, the flow line closer to the piercing edge is straighter. The hardness analysis showed that the hardness value is higher in the position closer to piercing edge.
In conclusion, the current study shows that the thermal differential forming technique could be used to manufacture high strength materials or complicated components. The product quality and strength could be improved, and the die delivery time and cost could be saved too, through the local heating and plastic working, without the secondary process. The results found in the study will shed some light on the research and development of thermal differential piercing process for the academia and the industry.

並列關鍵字

Drawn cup, Thermal differential ； Piercing ； Finite element analysis ； Microstructure

參考文獻

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